I was watching This Old House and Ask This Old House tonight, and at the end of the hour where they give a preview of next week’s show I noticed that Tom Silva will be demonstrating the Sawstop table saw on the upcoming episode.
It’s been talked about a lot in woodworking magazines and on the Internet, but I don’t think I’ve ever seen anything about the Sawstop on television. I wonder what this will do for their sales.
Replies
Stuart,
Is that the deal that they run a hot dog into the blade and it stops? I can't figure how the saw knows the difference between a piece of flesh and basswood or sugar pine.
Chuck S
Yup, that's the one. There's an explanation on their website.
http://www.sawstop.com/how-it-works-overview.htm
Stuart, I'll stick with my push sticks. I have been eating dust for over 30 years and can still count to 10. Hope you can too.Chuck Slive, work, build, ...better with wood
"I can't figure how the saw knows the difference between a piece of flesh or basswood or sugar pine."....
I don't own a Saw Stop, but from what I've read and heard about the saw, the saw blade is set up to detect electrical current...I'm talking milli-amps....and the human body is so electrically charged so that the blade can detect this....and wood is a bad conductor and so the saw blade does not detect any current from the wood when wood is being cut.
When the saw blade does detect a charge, this triggers it's immediate shut-down
I've seen the hot dog demonstration on a video, and the dog is barely scratched....but I still say if you really believe in your product and you claim that the worst cut you can receive is just a scratch, then throw out the hotdog and lay down your finger! Put up or shut-up. Still, the Saw stop is a novel idea and I definately think it is a worthwile tool; especially in technical training schools and such.
Davo
Edited 1/26/2007 12:16 am ET by Davo 304
Davo,You are right. They should do a video with their finger, not yours or mine.Chuck Slive, work, build, ...better with wood
Edited 1/26/2007 7:55 pm ET by stevent1
>>..but I still say if you really believe in your product and you claim that the worst cut you can receive is just a scratch, then throw out the hotdog and lay down your finger! Bad idea.
Some hot dog (pun pun) would show off to his buddies
after monkeying with the set-up, and cut his whole hand off.
Then sue the company claiming he didn't do anything he didn't see on the video.
I wonder what the electrical charge in a hot dog is...
I actually just watched that episode of Watch TOH and they did show the SawStop system in use - Tommy used a hotdog as well, can't blame him there I guess. All I can say is WOW, that is impressive. Still not 100% sure that I'd trust it, but man that sure is nice insurance. I'd need a change of pants and a long pull of Jameson's afterwards though...
Nick
I don't think I would trust it either. BUT it is nice to have one more thing in your corner. How are the reviews of the saw itself?
Think ya used enough dynamite there, Butch?
wonder how it behave with wet wood???
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
Edited 1/26/2007 2:56 am by IMERC
Good question.
Think ya used enough dynamite there, Butch?
Think ya used enough dynamite there, Butch?
got the answer to yur ringing ears....Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
Yea that's an ironic tagline for that isn't it? LOL
Think ya used enough dynamite there, Butch?
I was wondering about that pond-dried ACQ. Copper is a better conductor...The other thing I trhink I read once is that some really expensive part has to be replaced if the saw does it's saviour thing, so if it miss-fired on a simple PT wood cut, you are out a couple hundred and time.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
You have to replace the cartridge and the blade. The stop function can be shut off if you are cutting something that will (may) trigger it. Have to shut it off if cutting metals, or would that may have nails in it. Not sure how wet wood would have to be to trigger it. I beleive they go into that on their website.
It is reported to be a very nice saw even without considering the stop device.
Yeah, the saw is quite nice, and has some other nice features you don't find on most North American saws.
I've seen it demonstrated live, in person (with the hot dog)....it definitely works. Trashes your blade I believe, and you need to buy a new panel for the mechanism, but better than losing a finger.Cabinetmaker/college woodworking instructor. Cape Breton, Nova Scotia.
<< wonder how it behave with wet wood??? >>I haven't yet read this entire thread, and maybe somebody already answered your question. The stop cartridge will trigger if the wood is damp, as in pressure treated stock.However, there is switch so you can disable the mechanism if you suspect this will be a problem.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
I know what it feels like to suddenly find one finger shorter than God intended it to be, so I would need a long pull of Jamessins BEFORE making a demonstration like that!;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
that bottle must be just about empty..
must be time for a return trip to the auld sodMike Smith Rhode Island : Design / Build / Repair / Restore
"I wonder what the electrical charge in a hot dog is..."When you're holding it with bare fingers, the same as you. What I think Sawstop is measuring though is capacitance, same as those touch-on touch-off lamps.
BruceT
"I wonder what the electrical charge in the hot dog is..."
Yeah...now you know why they are called "hot" dogs. LOL
Actually the hot dog is relaying the electrical charge from the person's hand that is holding the hot dog.
Davo
Yep. And Chili Dogs have greater potential.
;)
Especially the habenero variety...they are downright SHOCKING!
Brilliant.
When I hear something will happen in so many thousandths of a second, I tend to think of it happening instantly. Actually, a lot can happen in just a few thousandths of a second. My gut feeling is that the saw stop will prevent loss of a digit if you put your hand in at a certain speed. I can envision several scenarios where my hand could be pulled in faster than the saw stop could save a finger.
Sixteen years ago, my radial arm saw hit a knot. The 2X4 came out smashed up and hit my hand pretty hard, nearly pulling me into the blade. This took only about two milliseconds. I was stunned and lost feeling in my hand for about a minute. It was another minute before I was sure I had not lost anything.
Another point is that someone who has a shop full of dangerous whirring and spinning tools like me needs to respect the tools at all times. Having one piece of equipment that makes you think you are safe could affect your alertness. I am a creature of habit. I have three table saws and sometimes use somebody else's, such as when I have worked for Habitat. I think the safest position is to treat every saw as a dangerous. I am typing with ten fingers, and want to keep it that way!
This took only about two milliseconds.
How do you know? Human perception is measured in hundreds of milleseconds:
"while a reaction time of 150 milliseconds lies beyond the capability of even the Michael Johnsons and Carl Lewises of the world"
http://mednews.stanford.edu/releases/1999/sepreleases/reaction.html
I thought someone might challenge me on that. Let's just say it was very fast and much less than a second, closer to an instant than to 1/10th of a second. Now, a person can estimate 1/10th of a second. I can easily count to ten within the space of one second. I'm sure you can too. Here I mean verbally count very fast. I can perceive much smaller periods of time. You can too.
If you think my comment is BS, you might consider slamming your hand into a moving blade on a saw-stop-equipped table saw as fast as you can. Considering that pitchers can pitch a ball at about 100 mph, I will use that figure for calculations. The end of the pitcher's arm has to be moving at that speed for the ball to leave his arm at that speed.
That comes to 100 miles in 60 minutes, or ten miles in six minutes, or one mile in six tenths of a minute, or 36 seconds.
That is 5280 feet in 36 seconds as the velocity possible for a human hand. This is 63360 inches in 36 seconds, or 1760 inches in one second.
Note that this speed is well within the reach of humans.
Now, to continue, this is 1.76" in 1/1000 of a second. So in two milliseconds, you could conceivably put your finger into the blade at a depth of 3.52 inches.
Of course, by then, you would not have a finger tip.
My point is not the actual time. This is an area which I believe has not been accurately measured. My point is that in that zone where accidents with moving and spinning objects take place, or even in projectile accidents such as with a nail gun, a human being is out of the element of control. The actions and decisions that you take immediately prior to such an accident will determine the outcome. A device that will stop a blade in a few thousandths of a second will not always be fast enough, even if your hand is not moving at 100 mph. If it is moving at only 10 mph, the finger can move into the blade approximately 1/3" in two milliseconds.
This discussion only considers a perfectly-working saw-stop. My computer works well at these speeds, but whenever you have a mechanical reaction responding to a digital signal, your digital signal speed will not determine the final speed. It will be the mechanical brake, which can be no better than other mechanical systems.
Ultimately, I am saying that we should not think "instant stop" in a case like this.
Finally, if you slam your hand into a sharp saw blade that is stationary, you can still do some real damage to yourself. When a piece of wood catches and pulls your hand into the blade, it will be over before you know it. I would rather rely on good habits and respect for the danger than on a technical device that will save me after I have done something dumb.
To clearly answer your question, I don't know. I just took a guess. I think it was a pretty good guess. You can focus on that and disagree or you can think about what I am saying, which is designed to heighten awareness. I admire the saw-stop people for what they are doing, but would never test it with my finger. I understand that they think they have a good thing and it is ok that they want this good thing to apply to everyone, even if they make a well-deserved profit. I just don't think that it should be considered the complete solution, since that can only reside in your attitude and habits.
Thank you for your comment, since it allowed me to focus a bit more on what I wanted to say.
Edited 1/26/2007 8:27 pm ET by Sasquatch
My friend, I am in complete agreement with what I think you are trying to say.
I am in no way trying to undermine or discredit the validity of the saw stop or what they are trying to accomplish. what I am saying is that this device should in no way be any sort of a substitute for good, safe working habits and techniques.
This issue is not unlike the whole airbag/safety thing with new cars. Has anybody else noticed that the general attitude with automobile industry seems to have accepted it as a forgone conclusion that you are going to be involved in an accident and therefore you need to buy "our" vehicle because it has all these safety features which makes it better than the other guy's vehicle? What ever happened to just plain old defensive driving? I've driven for over 25 years and I have yet to have a wreck! I know plenty of people who have driven for more than twice as long as I have and also never been involved in a wreck! Pay attention to yiour surroundings and you should never have to find out how good the airbags in your car are!
The table saw finger safety issue and the auto acident issue can best be settled by the immortal words of mr. Miagi from Karate kid...
"Mr. Miagi, what's the best defense against a punch?"
"Best defense against punch.... not be there when it come."" If I were a carpenter"
And I too think we agree.
There is a slight difference in the airbag situation, which is why I didn't bring it up.
I was going to say that airbags are good up to a certain speed. I would not want to depend on the timely deployment of an airbag when hitting a bridge abutment at 100 mph.
Some people work with tools, dangerous tools. Almost everyone drives a car. On a vehicle that costs about $20k, with an airbag system that costs a few hundred, and with all kinds of other people out there driving, I think it is a good investment. Additionally, there is the factor of not necessarily being in control, such as when someone else makes a mistake and runs into your vehicle.
With a table saw, the operator should have a great deal of control, without someone unexpectedly running into the shop and slamming into the operator, for instance.
I also agree with the dearly departed Mr M. This is good thinking for tool users. I don't think that most automobile users are at that level.
The first time I used a table saw, I instinctively understood the danger.
When I got my first car, I could not see the danger.
I have seen the hot dog test on the saw stop, impressive, if your a hot dog!
What I wonder though is what happens if the palm of your hand slips off of a board and lands directly on top of the spinning blade? Thats the test I want to see!
I dont think most saw accidents are as simple as someone slidding their finger across the blade as though they wanted to slice a piece off. Without digging into all the accident reports on table saw injuries I'm assuming that a majority of them happen with the injured person slipping and landing a large portion of their hand/finger across the blade, and at a very fast pace.
I say we take a prisoner, preferable someone that committed a heinous crime, or bilked their investors out of all their life savings, either way.... and have them test this thing out once and for all!
I have heard good things about the saw though, supposedly it has a very good riving knife, something that American table saw manufacturers dont have.
Doug
you realize that it will now take several days for my blood to thaw out...Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
One of the safety features of the SawStop is that the blade drops BELOW the table surface when the electronics go off, at the same time the cartridge stops the blade.
I'm not saying your palm won't get cut, but both features will minimize the injury.
"I dont think most saw accidents are as simple as someone slidding their finger across the blade as though they wanted to slice a piece off. Without digging into all the accident reports on table saw injuries I'm assuming that a majority of them happen with the injured person slipping and landing a large portion of their hand/finger across the blade, and at a very fast pace."
I agree with your conjecture, and I'd be interested in seeing the stats on tablesaw accidents. My guess is that quite a few tablesaw injuries are related to kick-backs - second only to rectal-cranial insertions.
I had an accident a few decades ago that forever changed my tablesaw practices. Today, I operate a sawmill and teach woodworking to college students who, thankfully, have very few significant accidents. Under the conditions in which our students operate, the situations that seem to cause the greatest number of accidents continue to be (in no particular order) inattention, immaturity, fatigue, arrogance and stupidity. In post-accident interviews, students usually say: "It happened so fast!" and "I had a bad feeling about this before it happened."
Although machine malfuctions and freak accidents do happen, I believe the vast majority of accidents we fallible humans have stem from mental errors. IMHO, if we can employ simple devices like push sticks, zero-clearance throat plates, and riving knives or splitters, we should be held culpable if we choose not to use them.
-Jazzdogg-
"Don't ask yourself what the world needs. Ask yourself what makes you come alive, and go do that, because what the world needs is people who have come alive." Gil Bailie
Yes, but............Steven Gass is a patent attorney and a PhD Physist, the inventor of this technology, and now the owner of SawStop. And he knows that TS accidents send 60,000 people to the ER every year (according to some esitmates), with about 3000 finger amputations. The problem is, he offered the technology to the industry at what amounted to extortionate rates (8% royalty), and when manufacturers resisted, he took the issue to the Consumer Product Safety Commission, in an effort to mandate (coerce) the industry to accept (buy) his technology. So, not only was the industry faced with paying him the royalty, but it would also have to add the cost of producing the cartridge to the price of every TS. Moreover, by offering an "injury proof" TS, the manufacturer would now face litigation in the event of any injury. And Gass flatly refused to indeminify the manufacturers against any such suits. Remember, the SawStop system should prevent amputations, but it is still possible to incur a serious injury, depending on the circumstances of the accident. So the potential for litigation is substantial, and Gass is apparently not confident enough in his device to indemnify other manufacturers against failure. Personally, I think it is a great invention.But I disagreed with Gass' strategy to take it to the CPSC, since I think it is high time the government curbs its penchant for "protecting us against ourselves."Furthermore, I am delighted the technology is available to anyone who wishes to spend $2800 for the SawStop cabinet saw.Rather than being mandated, the market will determine the validity and value of Gass' invention. And that, I think, is as it should be. ********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
<<<Rather than being mandated, the market will determine the validity and value of Gass' invention. And that, I think, is as it should be. >>>
If the cabinet model shows up in Norm's shop and Tommy Silva or Mike Smith end up with the contractor's version then you know SawStop is "accepted". ;0)...The unspoken word is capital. We can invest it or we can squander it. -Mark Twain...
Be kind to your children....they will choose your nursing home.
If the cabinet model shows up in Norm's shop and Tommy Silva or Mike Smith end up with the contractor's version then you know SawStop is "accepted".
Norm and Tommy will hawk any tool that pays them, cant speak for Mike!
I'll buy one when I see that Tommy has enough confidence to put his own hand into the spinning saw blade! That'll convince me that he's really sincere about the saw and not just picking up another check! <G>
Doug
I respect them all for their talent and commitment to quality. I simply made the comment in jest, hence the wink. [ ;0) ]
edit to add: We all have to make a buck somehow.
...The unspoken word is capital. We can invest it or we can squander it. -Mark Twain...
Be kind to your children....they will choose your nursing home.
Edited 1/27/2007 1:18 pm by oldbeachbum
OBB
I knew you meant the comments in jest.....I meant mine in the same vein.
I don't care if Tommy and Norm pick up a little dough for hawking someone's product, hell I wish I could! But unfortunately I'm not getting any offers, dammit.
Doug
I'll buy one when I see that Tommy has enough confidence to put his own hand into the spinning saw blade! That'll convince me that he's really sincere about the saw and not just picking up another check!
I wanna see 'em invite Bob Vila back on the show and use Bob's finger (or other body parts) to demo the saw.
I wanna see 'em invite Bob Vila back ...
I think we'd all like to see that! And the funny part is, Bob never could keep is damn fingers off of anything.
Doug
The problem is, he offered the technology to the industry at what amounted to extortionate rates (8% royalty),
That's typical - the "going rate" is 5% to 10% for royalties, so it's a fair price.
By not adopting it, the manufacturers ARE exposing themselves to risk. THere is technology available that they could have added to their saws for 8% of manufacturing cost - say $80 on a unisaw. That's really, really cheap, compared to the consequences. It's just a matter of time before someone sues them for NOT adding this safety feature - by not adding it, that person will argue that they knowingly produced a less safe product, to increase their profits. That person will likely win.
I'd say a simple, relatively safe way to test the SawStop brake with a human finger is to raise the blade all the way up and touch the side of the blade.Woodturner9, a baseball only looses velocity after it leaves the pitcher's hand; except for gravity, there's no way it can gain energy/speed. The snap a pitcher puts onto the baseball comes from the wrist, so when Nolan Ryan was throwing 100+ MPH, his fingers and hand were moving at least at that velocity.
"I'd say a simple, relatively safe way to test the SawStop brake with a human finger is to raise the blade all the way up and touch the side of the blade."To test WHAT?Yes it test the logic of the mechism.But it does to show that it will prevent damage is some of the common accidents.I am wait for the inventor to slam the palm of his had down on a spinning blade.But here is a test that could better simulate an accident.It would take some work to get the right sizes, but get a something like a small ham and attach it to an arm that pivots on the ceiling.Then with the saw running pull it way back and let it swing into a running blade..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
You've touched on one of the big unanswered questions about this device.As you say, it's one thing to "touch" a hot dog to a spinning blade, but what happens if your finger or palm is driven into the blade with some force?The swinging ham is a great idea. EDIT: The only consistent problems I have heard about with false stops is if you hit a nail or you're sawing damp stock -- like pressure treated wood. I would imagine the SawStop people are working on this, but for now, you can switch the device off -- but that works only if you can anticipate a problem. Otherwise, the device has been very reliable (from what I've heard). And the rumor is that Sawstop has been outstanding about replacing any cartridge (free) that does a false fire.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
Edited 1/27/2007 10:52 am by nikkiwood
The question is if a human hand has the same conductivity as a hot dog. We know that the SawStop will work for Reggie Jackson <grin> but what about the rest of us?Agreed, how fast a hand is moving into a blade is a big uncontrollable variable, with hugely significant consequences.
a baseball only looses velocity after it leaves the pitcher's hand; except for gravity, there's no way it can gain energy/speed
OK, but it does - simply physics and biomechanics. Application of energy causes acceleration.
Simple experiment - drop a ball from your hand. Velocity is 0 when it starts, higher when it hits the ground.
QED
Application of energy causes acceleration - correct; however, after the ball leaves the pitcher's hand, the only energy being applied is gravity. The ball is moving roughly horizontally. Air resistance is having the greatest effect on the ball. The ball is continually slowing as it approaches the batter.Simple experiment - drop a ball from your hand. Velocity is 0 when it starts, higher when it hits the ground - correct again, but you're talking about a ball dropping vertically. What does this have to do with pitching?We're hijacking this post - shame on us :-)
Simple experiment - drop a ball from your hand. Velocity is 0 when it starts, higher when it hits the ground - correct again, but you're talking about a ball dropping vertically. What does this have to do with pitching?
Just a sneaky attempt to get people thinking....
Most people seem to be making the assumption that acceleration requires ADDITIONAL energy application "during flight" - which is not accurate. Stored energy is still energy, whether kinetic or potential.
Consider the case of a rocket - which is a better analogy. The rocket motor burns for a short period of time, but the rocket continues to accelerate after the motor burns out - just like the baseball.
Edited 1/29/2007 9:08 am ET by woodturner9
"Most people seem to be making the assumption that acceleration requires ADDITIONAL energy application "during flight" - which is not accurate. Stored energy is still energy, whether kinetic or potential."
Hmm. That's contrary to what I learned in Physics class. When the rocket engine stops, the rocket will continue to travel at it's attained velocity at that point (and not faster or slower), unless it is acted upon by external forces, such as gravity. It will not accelerate after the engine is stopped. Yes the rocket has stored kinetic energy -- that's why it doesn't stop when the engine stops, but keeps moving at the same speed. Exactly how could energy be stored in the rocket after the engine stops to enable the rocket to use that "stored enegy" to accelerate? The only way I can think of is compression of the rocket along the axis of thrust, to be released when the engine stops, like a spring. I can't believe that is a significant factor, though. Ref. Isaac Newton: Objects in motion will remain in motion, in a straight line, at a constant velocity, unless force is applied. (Still a valid law of nature, last I checked.)
Regarding the pitched ball (assuming the ball is pitched in a perfectly dark vacuum): Yes the ball will accelerate after release, but not in the direction of the throw. Rather, acceleration will occur due to the pull of gravity towards the earth, resulting in curving the path of the ball towards the ground. This additional acceleration is indeed the result of stored potential energy, which was imparted to the ball when the pitcher lifted it from the ground to pitch it. The instant the ball leaves the pitcher's fingertips, it has reached its maximum velocity on the horizontal vector. And yes, the pitcher's fingertips have indeed achieved that same velocity, resulting from an accumulation of force applied sequentially through the various joints in the pitcher's body, shoulder, elbow, wrist, hand and fingers.
That's my story, and I'm stickin' to it!
This sounds like a case for Mythbusters!
Mike HennessyPittsburgh, PA
Woodturner9, you're outnumbered here... :-)It would be an amazing rocket engine that continued accelerating after it was turned off.Sorry, it just doesn't happen this way.
go back and do high school physics again.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
"go back and do high school physics again."He also needs to read the chapters on electricity also.He is the frenchy of physics..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
--- Consider the case of a rocket - which is a better analogy. The rocket motor burns for a short period of time, but the rocket continues to accelerate after the motor burns out - just like the baseball. ---No, it continues to travel after the motor burns out - just like the baseball. Any acceleration after that point is due to forces other than those generated by the burning fuel - such as gravity of nearby heavenly bodies.F=ma. Acceleration is proportional to to the applied force (as well as inversely proportional to the mass).Rebeccah
As far as litigation is concerned, right now Sawstop is selling briskly to schools and commercial shops for that very reason. If a student/worker gets injured on a saw that was purchased after SawStop was available, I would think any liability lawyer would love to take the case. With such a case the school/shop might have considerable exposure, but I am guessing the manufacturer would not, since historically, they have never been culpable in cases where accidents were due to human error.Ironically, the device itself opens the door to litigation, according to some of the opinions I have read. The theory is that the device presumably makes the TS "injury proof" -- and yet, depending on circumstances (say your fingers or palm are driven hard into the blade), there is still considerable potential for serious injury. And that's why the manufacturers asked Gass to indemnify them against such suits, but he refused. My point is simply that the issue is not quite as clear as it may seem to be on the surface.But one thing is clear: you can bet that every manufacturer is laboring to come up with their own safety device. Thanks to Gass, it's an idea whose time has come. ********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
absolutely. Very well said."The nearest thing to eternal life we will ever see on this earth is a governmental program" -Ronald Reagan
Let's just say it was very fast and much less than a second, closer to an instant than to 1/10th of a second. Now, a person can estimate 1/10th of a second.
Considering that pitchers can pitch a ball at about 100 mph, I will use that figure for calculations. The end of the pitcher's arm has to be moving at that speed for the ball to leave his arm at that speed.
Hmm. Seems to me some significant misunderstandings here.
Among others:
1/10th of a second is 100 ms, not 10 ms.
A person cannot move at 100 mph - and a pitcher does not need to move his arm at that rate to produce a speedball of that speed. You appear to be assuming that the ball leaves the arm at that speed and travels at constant velocity. In fact, it is the "snap" as it leaves the pitcher's hand that provides the additional energy needed accelerate the ball as it travels, so that it has attained 100 mph speeds by the time it reaches the plate.
As a point of reference, motion pictures change images at 30 frames per second. TV changes images at 30 images per second. The latency of the human eye is about 30 ms. Basically, you can't see anything if it lasts less than 30 ms - so humans cannot directly observe events shorter than 30 ms, so you can't measure 2 ms.
Regarding sawstop, they have tested and published numbers regarding the time to stop the blade. Without looking up the numbers, my recollection is about 20 ms. At any achievable human movement speed. that stops the blade in less time than you can advance 1/16" of an inch, even if you are being pulled into the blade.
They can make it as fast as they want - it's just time, cost, and energy. They could make it stop in 100 us - no reason you can't build a mechanical system to do that, and the electronics can easily response in 10 ns (i.e. 100,000 times faster than 1 ms), so it's not a problem.
So they have built the system to minimize cost while ensuring that the blade will stop before it can do any damage to anyone.
So they have built the system to minimize cost while ensuring that the blade will stop before it can do any damage to anyone.
I'm not dissing the saw because everything I've read about it is good. Those reviews are based solely on the preformance of the saw though, had nothing to do with the saw blade stoping when it hits your finger. Problem was they couldnt get enough people to sign up for the test that were willing to potentially loose a didgit!
Its my opinion that your quote above lacks validity, I dont know that your assertion has been proven. What has been proven is that when the inventer moved his finger, or the hot dog, into the blade at a fairly slow rate the saw did in fact stop! Thats all that has been proven so far. Thats not enough for me to be convinced that this is the end all to table saw injuries.
The inventer did as Nikkiwood suggested, went to all the committies involved and did his best to extort, pretty plain and simple. If his saw stop should be implemented in all table saws as you and the inventer are suggesting then whats next? Because I'm sure there will be a next, there always is.
I think the saw is a good idea, I'm not buying one though and I dont think I should be forced to.
The example that the shop teacher gave is probably a very good reason to buy one, and I hope some high school kid has his fingers saved because of this invention. Anybody else that thinks that they would like the added benifit of the saw stop should also get one, but thats it!
Doug
Where did I say 1/10th of a second is 100 ms?
You appear to be assuming that the ball leaves the arm at that speed and travels at constant velocity.
I make no assumptions here. The ball leaves the arm at the highest speed and immediately (upon release) begins to slow down (due to friction from the air it must pass through). The propulsion comes completely from the body and can be no faster than the hand that snaps it. This is because the ball has no internal engine, such as a rocket.
The ball does NOT increase speed after leaving the hand.
What the eye can see is irrelevant. We can sense events faster than we can see them. You can feel a bullet whizzing by your ear even though you cannot see it. You'll no doubt remember the old magician's saying: "The hand is quicker than the eye." This is absolutely true.
Once again, I didn't "measure" two milliseconds. I just used it as a point of illustration. It was to get those who were interested in my argument to shift their minds to the realm of milliseconds, which is where hands usually get hurt.
Actually, I don't believe they can make the blade stop in microseconds. It is not just a matter of more money and better technology. Although the digital signals of the control unit may travel near the speed of light, there is quite a lot that happens beyond the signals themselves. The algorithm that determines the moisture in the finger, or the charge level, or whatever, takes time. So does the reaction of the mechanical brake.
As we get into a discussion of the speed of light and smaller and smaller units of time and mass, or in other words, the micro or nano-world, mass and energy and time as we know them completely change their meaning. They no longer mean the same things at that level. In fact, I would argue that physicists around the world are focusing on this very area and have been ever since Einstein's theories of general and special relativity and Max Planck's quantum theory. At this level time bends or changes, objects can be in more than one place at the same time, and the world as we know it does not apply.
Your 1/16th inch number is incorrect. I stand by my calculations.
To put these numbers in perspective, Navy Top Gun fighter pilots typically score between 200 and 225 milliseconds, while a reaction time of 150 milliseconds lies beyond the capability of even the Michael Johnsons and Carl Lewises of the world. For that reason, response times of less than 150 milliseconds were not counted, Powell explained.
Typical scientists. "Oh, those are impossible, so we ignore them." Even when they see them quite often.SamT
Guys that don't do things correctly the first time.....then argue that they did nothing wrong.....if made to agree to fix the problem, rarely put the time and effort into truely doing it properly. they'll just look for the quickest fix to appease you and get their money. JDRHI <!----><!----> 84310.51
After 30+ years in the trades, I still have all 10 fingers, too.
But I only use 2 of them to type.
Andy Rooney wrote a lot of good columns just that way.
"'my gut feeling is that the Saw Stop will prevent the loss of a digit if you put your hand in at a certain speed..."
I'm 100 % with you on that! The video demonstration I saw was of course using a hot dog...the person was talking to the group as he was using the table saw to "cross cut" the hot dog..and he was going at a very slow, deliberate pace when the saw blade finally hit the dog. It still was spectacular to see that saw shut down the way it did...but I can't help but wonder.
About 10 years ago I was ripping a board on a Craftsman tablesaw without a blade guard. I had just finished the rip when it looked like the offcut was going to hit the blade and fly back at me...this particular saw had a bad vibration...anyway, I reached over the blade to flip the offcut away using my thumb. I thought my hand had cleared the spinning blade but I was wrong.
In the matter of a split second, the spinning blade nicked my thumb at the tip. That nano second resulted in my having plastic surgery to replace the missing tip. I was lucky..blade missed my thumbnail, just removed some of the fleshy part at the inside edge. Still, it required surgery, and to this day, I have no feeling in that tip.
That was a nano second..and the blade barely clipped me...it's hard to think if a person is ripping a board at regular speed and somehow gets his hand in contact with a Saw Stop blade that his hand won't get anymore damge to it than a small scratch. I sincerely hope in just that situation that that is all anyone ever gets is a scratch...I hope my hunches are dead wrong...but my gut still tells me to be wary of all the claims.
Davo
I think this is getting way too complicated.
Instead of touching the saw with a dog, why don't they drop a 1 lb T-bone steak on the blade from a height of one foot? That should be well within normal expectations of accident situations.
I don't believe we'll ever see that demo. The result would be a ruined blade, a ruined brake unit, and two steaks.
Instead of touching the saw with a dog, why don't they drop a 1 lb T-bone steak on the blade from a height of one foot? That should be well within normal expectations of accident situations.
Interesting question - and I wonder why some of the magazine reviews haven't tried that.
If you go to their website (sawstop.com) they say that the device " stops and retracts the blade (within 5 milliseconds) upon accidental contact" - it doesn't just stop the blade, it retracts it, BTW.
Anyway, let's explore your example. Dropping 1 lb a distance of one foot, and knowing that the rate of acceleration due to gravity is 32 feet per second^2, we can say that the speed at the time the steak hits the blade is about 1/32 feet per second, or about 12 inches per second (assuming linear acceleration, which is an approximation). Using their 5 ms number, the steak will advance about 0.06 inches in the time it takes the blade to stop and retract, around 1/16" of an inch (12 inch/second *5s/5000ms=0.06)
So, for that example, the damage to the steak would a small cut, ASSUMING that the stated 5 ms number is accurate. That also assumes that dropping a steak is a valid test - if your hand was pulled into a saw, it could be moving faster than the rate due to gravity, and the cut could be deeper. In addition, as the saw is slowing down and retracting, that might result in a smaller cut than calculated.
Makes you wonder why they don't do this demo - it would be rather compelling. But it does seem that sawstop will do what they claim - or at least, what they claim is physically achievable.
Let's say 1 ft above the blade for the sake of argument.
I think the formula for starting with zero velocity at normal gravitational attraction of 32.2 ft/(sec squared) is Distance = 1/2 (a x (t squared)), or, with a 1 ft distance, the steak will travel to the table in .25 seconds. It would be traveling at a velocity of about 8 ft/sec at that point, or about 96 in/sec. Say 100 in/sec for ease of calculation. This comes out to .1 in/.001 sec., or about 1/2" of movement into the blade in 5 milliseconds.
The blade, assuming 10" diameter, is about 31.4" in circumference.
At 3000 rpm, the teeth are moving at 94,200 in/sec, or 7,850 ft/sec. This would be a constant speed. That's enough to do a lot of damage quickly.
Dropping a hot dog would be no different than dropping a steak since it will fall at exactly the same speed as any other object, neglecting the minimal air friction. We have all heard about dropping a feather and a heavy, solid object in a vacuum.
I think it would be naive to assume that someone at Sawstop has not tried this. If it had turned out well, they would have certainly used the information in their promotions.
For a more graphic test, which would convince me that this device should be on every saw, maybe we could get a condemned prisoner volunteer to crouch with his body centered over a spinning blade and pull his feet out from under him. He could be doped up and be offered freedom if he survived intact.
I have no objection to safety devices like saw stop. I hope they do well, but do not support any kind of mandated configuration. I especially like the idea of having the saw stop in high schools; however, I would not let the students know that the device is installed. After all, we do not inform students that the electrical circuit has a GFCI breaker. Let them remain respectful of the saw and let the Sawstop give them as much protection as it can when disaster strikes. This logic applieas also to shapers and lathes and many other devices which were present in my junior high school shop class back in '65.
I, like others, am a bundle of contradictions to the untrained observer, since I always us a seat belt, but do not use a blade guard on any of my table saws. I do believe in using a modified guard to create a riving knife, although I have not yet gotten to this project.
Yes, I was approximating for simplicity.
Here is a link that describes the equations
http://hyperphysics.phy-astr.gsu.edu/hbase/mot.html
So, more precisely, after travelling the one foot (assuming we mean the distance from drop point to blade is 1 foot):
1foot=1/2(32)t^2 ==> t=.25s
v=v0+at=32*.25=8 fps
Now, where is it and how fast is it going 5 ms later?
x=v0t+1/2at^2=8 fps*.005s+1/2(32fps)*.005^2 = 0.0404 feet = 0.48 inches
So my "rule of thumb" approximations were misleading and too imprecise for this example.
However, we have not accounted for the slowing blade, which will limit the depth of cut to some extent. I don't see a good way to calculate that, but it seems reasonable to estimate that the steak might receive a 1/4" cut. That's more than I would prefer, but probably still not enough to be unrepairable or cause loss of a finger.
And again, there are a number of factors we have not considere, such as the reflexive reaction to withdraw the limb, assuming that "oh *****" feeling happens in time to start a reaction.
Thankfully a great many accidents happen at slower speeds, where the sawstop can clearly react in time.
FWIW, a friend cut off the tip of his finger over the weekend on a tablesaw. I bet he wishes he had a sawstop - and he will pay more in copays for the reconstruction than the cost of the sawstop.
Just a question to anyone from one who is completely ignorant of this saw's operation.
Is there a conductivity issue about jamming something into the blade that is not touching the table? Are the electronics measuring current between table and blade and material being cut? Or, just between blade and material?
Could this change or delay "recognition" by the system?
Just wondering. Maybe I did not understand or I missed something.
bum...The unspoken word is capital. We can invest it or we can squander it. -Mark Twain...
Be kind to your children....they will choose your nursing home.
Is there a conductivity issue about jamming something into the blade that is not touching the table? Are the electronics measuring current between table and blade and material being cut? Or, just between blade and material?
The information on the website is limited, so it's hard to say for certain. However, as an electrical engineer, I would infer from their description that they are using a tank circuit that detects when unbalanced. It is very similar to the "touch on" lamps. The return in the circuit is not the tablesaw table, but essentially the earth. So even if a person had no contact with the saw other than to touch the blade, the device should activate (assuming my inferences about their method are accurate).
The sawstop technology works by the fact that the human body has a larger inherent electrical capacitance than wood does. The body stores, absorbs and emits electricity. A small electric charge / signal is applied to blade which is constantly monitored by a microprocessor inside the brake cartridge which mounted under the blade. The signal is only three volts so you can't feel it if you touch the blade.
If you touch the blade while it is spinning, your body absorbs some of that charge and drops the signal. That drop in signal is what starts the process of firing the the brake. The blade stops and drops below the table surface. From the time you touch the blade to the time the blade drops is less than 5/1000's of a second or 5 milliseconds. Wood, having an inherently small electrical capacitance, does not conduct nearly electricty to change the signal.
So, all that said, you have to touch the blade to fire the brake. If you throw meat at the blade, it will cut the meat. The reason you see a person holding the hot dog in the video and during live demonstrations is that the hot dog acts as an extension of your body. It senses your electrical capacitance. If you were to tape the hot dog to a board and push it through the blade, it would cut through the hot dog. You have to hold it.
BTW: Over 5000 sawstop saws have been sold over he past 24 months. More than 120 instances or "finger saves" have been documented where people in real work environments have accidentally come in contact with the blade and the saw did what it was designed to do.
Simple enough, stick a wire in the meat, and hold onto the other end of the wire, continuity should be continued through the meat.
Msr. Clous, Merci et bienvenu a' Breaktime !
Woodturner9, Thanks
Now I understand better as to what should happen and why.
...The unspoken word is capital. We can invest it or we can squander it. -Mark Twain...
Be kind to your children....they will choose your nursing home.
More than 120 instances or "finger saves" have been documented
Do we really know that 120 fingers were saved?
My first interpretation of that statistic is that the answer is no, we dont know that. I need to see more then the testimonys on a web site for the product to come to that conclusion.
Dont get me wrong, I like the idea of the saw, I've heard good things about its quality/features and so on...........but..........
I'm not conviced that the damage will be minimal if ones hand is projected towards the saw blade from a slip or fall. The hot dog test may be nice for the naive but I'd have to see a more "real world" experience to be convinced.
I hope the saw turns out to be the answer to all table saw injuries, or at least a good percentage of them. I believe the SawStop has gone a long way towards achiving that goal, but they need to stay out of the "mandate" end of it.
Doug
A cabinet building homeowner buddy of mine bought that saw a couple weeks ago. Damn expensive but he used a length of salami and the mitre gauge and says it works so fast it is more impressive in person than the video shows. With moving the salami at a normal cutting speed on the saw it was just a nick on it.
It looks like a very good saw despite the extra price for the safety.
Yeah but somebody is going to question wether he used a sharp blade or if the skin on that salami is thicker or more resilient than human skin. :>|
ANDYSZ2WHY DO I HAVE TO EXPLAIN TO FRIENDS AND FAMILY THAT BEING A SOLE PROPRIETOR IS A REAL JOB?
REMODELER/PUNCHOUT SPECIALIST
"or if the skin on that salami is thicker or more resilient than human skin. :>|
ANDYSZ2"
Yeah, probably some old dried up salami he found on sale! lol
He is a school teacher so how much could we value his opinion?!!
DougU,
I am a marketing manager at SawStop. I am responsible for tracking what we call "finger saves". The first one that we documented was in March of 2005. It was a cabinet shop in Arkansas. The shop called and told us just how thrilled they were. Most of the saves come from phone calls. Let me preface the rest of this writing with one thing.
In the early days of the SawStop technology, before SawStop made saws, the inventors had devised a way to visually capture, via the computer, what a finger save looks like. On a computer graph, you can see the dip in the signal which looks different depending on whether it was a finger or say a staple scraping along the side of the blade. The only way to establish this initial benchmark was to have someone touch the blade. This test was performed a couple of times with a finger but never since.
That said, we hear about finger saves mostly by phone, some from email, some simply send their cartridges in and many have sent photos. When we receive the cartridges, we can hook them up to the computer and read the data. I many cases, someone may have thought that they experienced a finger save but the data proved otherwise (such as an aluminum tape measure touching the blade or cutting some kind of conductive material such as wood with laminated carbon fiber paper, etc.)
To date, we have identified 121 finger saves. 77 of those from industry shops, 36 from schools and 8 from individuals. In all cases, we either have proof from the cartridges, photos, testimonials, emails or a completed incident report. These finger saves have ranged anywhere from full-on contact with dado sets to flicking away scrap material on coast down. (Many serious injuries and even amputations have occurred during coast down) Some of the people have been willing to give testimonials or have authorized us to use their stories in our marketing efforts. Many wish to remain anonymous.
We are confident that with more than 5000 SawStop saws being used in real working environments and given the statistics, it is likely that there are upwards of 100-200 more finger save incidents that we don't know about. We have heard about many situations, either at trade shows or through our dealer grapevine, where business have had finger saves but kept in on the down low. Some people are embarrassed that it happened. Some don't report the incident because they didn't feel that the end result was an "incident" because nothing tragic had happened...which is exactly what the saw was designed to do!
I hope this was helpful.
NailsClous:
It's great to have someone on here who can speak with some authority and answer the questions that come up. So much of the discussion here about the topic is based on wild speculation and personal preferences. Information from the manufacturer, as opposed to ranting by posters (which NEVER happens here, right? <G>), will be a welcome addition!
Mike HennessyPittsburgh, PA
Thank you for participating and your explanations.
The information you post will be questioned by many figuring that marketing will drive your responses but anything that can be done to eliminate rumors and urban legend is welcomed by me.
I am waiting to see your 10" Contractor Saw. Overall cost and size being my reasons since I have a very small shop and my work is recreational. (I'm retired)
Again, thanks for your input and welcome to Breaktime.
Jim
...The unspoken word is capital. We can invest it or we can squander it. -Mark Twain...
Be kind to your children....they will choose your nursing home.
Thanks for the comments Jim.
To help put your mind at ease, we are all extremely dedicated to ethics here... (and therefore, believe or not, none of us are getting rich quick ;). We are very cautious about saying or printing anything that can't be backed up. I don't use anything but facts that I can personally back up in our marketing efforts. The seriousness of our product does not allow us to twist data or bend the truth. The consequences are far too great.
My favorite quote from myself (as far as I know) is: Truth makes for lasting products...propaganda is merely a gimmick.
Thank you for allowing me to participate.
I would add my thanks for your participation here. Your saw represents a marvelous, and needed advancement in technology.What resistence there is, I think, comes in large part from Mr. Gass' efforts to force the technology on the industry (through the CPSC).This did not sit well in a marketplace with many people who think the government already spends too much effort on laws to "save us from ourselves."But it is clear the technology is proving itself out everyday in the market, and the bad taste some of us have because of Mr. Gass' PR misstep will soon be a distant memory.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
Nails
Thank you very much - very informative and I'm glad to hear that the SawStop has actually preformed as it was intended.
I would still like to see some sort of test with a more "real world" mishap, dont discount my prisoner/guinne pig experiment! I'm sure there are plenty of possible canditates. :)
Again, thank you for taking the time to come on here and give some first hand experience/knowledge with the saw.
Doug
I considered addressing the conductivity issue along with a few others. I thought that it might be better not to get too deep into the ramifications. For one thing, I do not have a definitive understanding of how the manufacturer of Sawstop controls the safety mechanism.
I did wonder whether it would make a difference if I had rubber shoes or leather shoes on a damp floor. I strongly believe questions of this type are of huge importance. It is not a matter of false hits and a few bucks for replacement parts. It is more about whether the device will work reliably under conditions that we understand. After all, nobody wants to hear that they have lost a finger or two because they did not understand the limitations of the device. This information should be available up front, and subject to liability questions, if the device is truly what it is presented to be.
My original post was to increase awareness that the zone where injury takes place is beyond any means of control. I wanted to offer up the idea that what we do before we reach this zone has a significant impact on our safety. This boils down to safe habits, attitudes, techniques, and a very good understanding of the dangers. I do not claim this to be a comprehensive list of important factors. I do not doubt that there are many more important things to contemplate.
The safety mechanism is made up of a soft aluminum brake pawl, a micro processor, a heavy duty spring, a capacitor and a fuse wire. When a person comes into contact with he blade, the microprocessor recognizes the incident by the drop in signal on the blade.
Then, a capacitor, also inside the cartridge housing, sends a quick burst of electricity to the fuse wire which burns it. The fuse wire is holding back the spring, which is under about 150lbs. of compression. The spring releases and pushes the brake pawl into the teeth of the spinning blade. The angular momentum and the sheer force of the blade digging into the brake triggers a release device that breaks- free and forces the blade down below the table surface. This happens because the arbor assembly is built into a heavy pivot arm which swings down from the force.
In terms of conductivity, the body acts independently, It doesn't matter if you are standing on a rubber mat or wearing any kind of shoes. You could be, if it were possible, hovering in the air and it would still work from your body's capacitance.
In terms of the liability, it's never not worked because if that day ever comes, you can be sure you'll hear about it. One thing is for sure, if you slammed your hand down on a sawstop, you will probably need a bandage, perhaps a stitch or two. If you did the same thing on any other saw, your hand will cease to exist.
Nailsclous are you the inventor of the Sawstop?
Could you cut aluminum if you were wearing gloves without tripping the device?
No
I usually wear gloves to protect my hands when working with wood. Does that have any effect on the timing or sensing Mechanism?
No. The blade will first cut through the glove and when it touches your skin, it will react just as if you weren't wearing gloves.
Actually the inventor did put his finger to the test. Said it was one of the hardest things he ever did.
What irks me though is he is trying to get OSHA or some such jurisdiction to mandate his invention on all table saws. I think it is a great idea but he has ulterior motives ie;$
THis is the 2nd or 3rd time that show has been on. The concept is great....but it is developed by lawyers. And they want laws changed to REQUIRE all table saws to have this!! talk about a hidden agenda. It's scarry to me that it has gotten as far as it has!...keep watch, it's not going away."The nearest thing to eternal life we will ever see on this earth is a governmental program" -Ronald Reagan
the guy behind this saw is actually a lawyer <G>. He fought hard to get his technology mandated by the guvmint, but he lost. So I think that battle is over. However, the saw seems to be selling briskly in schools and some commercial shops, largely because of the liability issue. That is, if some kid gets hurt because the school was too cheap to buy this saw, you can imagine what the lawyers will do with that.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
Nikki
And I dont have to tell you that over at knots this subject ellicits the same reaction as Festool/EZ!
BTW, are allowed back in yet.
Doug
Just wondering about our ts safety habits...
Could we draw up a list of do's and dont's that would help any of us improve our personal safety at the ts?
I use a builder's saw (portable jobsite saw) not a full-blown shop ts like the SawStop.
Here's what I'm doing wrong: I have yet to modify the table so as to accept a zero-clearance throat insert like Luka advised last year. I do not use the saw guard. There is no riving knife. I don't use featherboards.
Here's what I do that's right: Keep hands in front of the blade, use a push-stick, stand slightly to the side, make sure the fence is parallel to blade, do not rip crooked lumber, make sure there is nothing on the ground to trip on, screw the saw down, use a sharp blade, do not rip diagonals unless work is fastened to a square plywood edge that runs against the fence, do not cut full plywood sheets .... So I feel pretty safe.
What kind of chances do you guys take or don't take?
Edited 1/26/2007 9:49 pm ET by Pierre1
I was kicked out for about 2 weeks. It's kind of dumb though, since all you have to do is register with another screen name, and you're back in.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
"He fought hard to get his technology mandated by the guvmint, but he lost.
So I think that battle is over."
Although I am neither for or against SawStop, it has been intriguing to watch developments related to it unfurl over the past few years.
Thirty-plus years in business have taught me that these kinds of issues are often treated as financial decisions. For example, insurance companies routinely examine a company's willingness to adopt business practices that will reduce risk and save the insurance company money, including the equipment they buy and use (fall restraint systems for roofers spring to mind).
As courts begin to award larger judgements against businesses and their insurers for injuries that "could have been" prevented if tools like the SawStop had been used, insurers will start rewriting policies and adjusting premiums.
Regulations and laws will doubtless be enacted, but trial attorneys, the courts, and insurance premiums are likely to have a greater and more immediate, effect - IMO.
-Jazzdogg-
"Don't ask yourself what the world needs. Ask yourself what makes you come alive, and go do that, because what the world needs is people who have come alive." Gil Bailie
Edited 1/27/2007 11:06 pm by jazzdogg
<<< Regulations and laws will doubtless be enacted, but trial attorneys, the courts, and insurance premiums are likely to have a greater and more immediate, effect - IMO.>>>I think you are absolutely right. There's no question that the saw does prevent at least some TS injuries, and I suspect it won't be long before business insurance carriers will, at a minimum, offer discounts to commercial shops equipped with the SawStop. And, I would bet my last dollar that other saw manufacturers are currently beating the bushes to come up with a similar device.What kind of discussions have there been about buying the SawStop for the school where you teach?********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
"I suspect it won't be long before business insurance carriers will, at a minimum, offer discounts to commercial shops equipped with the SawStop."
"What kind of discussions have there been about buying the SawStop for the school where you teach."
Hi Nikkiwood,
I agree that insurance carriers would be smart to offer discounts to get the ball rolling, but I'd be willing to bet that, after a few years, the inverse will be the rule: an increase in premiums for everyone who hasn't invested in a comparable safety mechanism.
I feel very comfortable saying that safety is of the utmost importance to everyone involved in the woodworking program at my school. However, I am not representing our woodworking program here, and I don't feel comfortable making any statements that someone might attribute to the public institution that employs me.
-Jazzdogg-
"Don't ask yourself what the world needs. Ask yourself what makes you come alive, and go do that, because what the world needs is people who have come alive." Gil Bailie
Edited 1/28/2007 1:44 am by jazzdogg
I was just wondering if there had been any discussions about buying a SawStop................. but I don't wanna getcha in any trouble <G>.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
It should be osha mandated on all saws: table saws, sawzalls, power saws, hand saws. All of them!
blue"...if you just do what you think is best testing those limits... it's pretty easy to find exactly where the line is...."
From the best of TauntonU.
This comming from the guy that takes his guard off of his circular saws!
Thats just plain funny.
Doug
As Ron White sez "you can't fix stupid".
I haven't read all the posts, I don't know if someone already answered you, But, Sawstop was designed by a lawyer, from what I'm told--or at least originally marketed by one. And in the original demonstration, he did shove his hand into the blade. However, being a reasonably bright chap, he figured doing it once was enough, and a hot dog would suffice from that point on. Also, it does have an override switch for cutting wet lumber, but you lose the benefits of the technology. And when it trips, you better hope you have a new blade and cartridge lying around, because the saw becomes worthless. Neat tool, I guess the guy tried to use litigation to have all the manufacturers put it on their saws, and when that didn't work, made one himself.
I don't know who designed it..and though you and others say the designer didi place his hand in it then I say..ARE YOU NUTS?...
Actually, if the guy did do this, then, I say, All right..he truly believes in his product.
The only demonstration I ever witnessed was a video clip and the demonstrator was using a hot dog.
As for trying to get all the companies to market his design...Yes, I heard about this...the other companies refused...partly infact because they would be possibly opening themselves up to litigation on the grounds that they knowingly built "defective" machinery and were acknowling this fact by totaly revamping to a new (Saw Stop) system...or at least this is the arguement I've heard in the past.
I also heard the designer wanted the U.S. to declare that from here on, all companies MUST build the Saw Stop type table saw. The fact that a lawyer was involved in this doesn't surprise me one bit... The best thing that can happen is to let Saw Stop manufacture their table saw, and let everyone else manufacture their own designs, and let the consumer buy whatever saw he/she so chooses.
I'm sick and tired of all these government regulations that are crammed at us for OUR safety. Its time to let Joe Consumer be responsible for his own actions and let Joe decide what is and/or isn't safe for Joe.
As for lawyers...let them be dammned.
Davo
Yeah, I agree. It takes a true act of faith to shove your own hand in your saw. That's faith I just don't have. More power to him, and I don't blame him for never doing it again. It's an act of lunacy.
I help a friend run a custom furniture shop. We hire young guys that after a year or two move on to better things. Means we always have some green guys around. I got really nervous, even with our training and over the shoulder eyeball, that someone would lose a hand. So we got the Sawstop.
Its really heavy duty because it needs to survive the force of an instant stop. Good saw. Pain in the #### to switch to dado though
I teach woodworking and construction to high school students. Last year I talked my school into buying one. We have had it since September. The machine is very well made. The saw shuts off in the middle of a cut occasionally when cutting PT. But the carrtrage did not deploy. We have had the saw "stop" once. A student was ripping a piece of pine, and for no reason it went off. Not only do you replace the cartrage but the blade also. It can get expensive. But with kids using it, it is worth it. The computer only will let the saw turn on if everything is just so. And the dado blade set up is a real pain. We actually use the old one for this. I don't think I would get one for my shop, but again with all the kids using it, it is worth the expense and the few small headaces.
Mike
If I got a Sawstop I'd have to cut my hotdogs on the bandsaw.
Stash
Go over to Knots and search their archives but just don't mention the saw in a thread, last sawstop thread I saw turned into a street riot. Those people have strong opinions about everything. A couple of the guys over there have the saw and several have been hit by the blade and none have gotten badly injured IIRC. Yes you do have to bypass the break to cut wet stuff, PT anything, and metal. According the the Knots users sometimes a blade is still usable after break activation but it is kind of a hit or miss thing. I would love to have one when I set up a real shop. I will pony up $200 to $250 for a new cartridge and blade without compliant if and when I hit the blade and activate the break rather than the pain, hospital bill, insurance rate jump, and lost work time of losing a finger(s).As far as safety around other equipment is concerned, I don't think that it is a matter of forgetting that a workshop is dangerous if you are using a Sawstop. While the point about complacency is valid, I think there are other factors at work. 85% of the accidents I have seen involve a distracted worker, being tired, unusual cutting situations or the "I have gone 10 years without an accident on any equipment" and it really just being a matter of luck rather than safety on the mind. An ER doctor told me last time I was getting stiches that pros who work with power tools and the trades average a major accident once every 7 years. If you do not make an effort everyday to think safety than it is only a matter of luck and time before you have an injury.
I would gladly accept the hundred dollar blade and a couple bills for the saw parts for saving a finger.
Digits are up to about a grand or so now, plus pain and time off. My last one was only about six hundred bucks to put back togehter.I just flinch at the idea of spending all those dollars for a false stop on PT or finding a nail in wood....
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Man, you must be getting discount fingers. Three stitches in my wrist after a minor chisel incident Christmas eve was $550...did<!---->Cure Diabetes - Whitefish, Montana, 2007!<!---->
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They saw you coming! Jeff Buck would have taken care of that for you for only a hundred;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
On the plus side, since I had to have stitches, they waived the normal medi-center copay. Woohoo, free injuries!did<!---->Cure Diabetes - Whitefish, Montana, 2007!<!---->
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"Jeff Buck would have taken care of that for you for only a hundred"
Whatever happened to Jeff? He don't come 'round here no mo.
Mike HennessyPittsburgh, PA
His PC died and unlike constant acceleration rocketry, only his reputation remains on trajectory...He has stopped in a couple of times from the library and has had another new kid. Who would want to hang here when you canchange diapers and stuff?;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
It's been around for awile now. Supposedly, the guy who developed it approached the Deltas and Powermatics and Grizzlys of the world but no one was willing to use it because of the added cost.
Given the fact that so much policy is driven by lawyers and litigation, I'm actually surprised it hasn't been mandated yet. Mind you, I'm not necessarily saying it should or shouldn't, but I'll bet sooner or later, it will be.
Here's to keeping all ten to count on!
Yup, I know it's been on the market for some time now. The thing I was thinking about is that having it on This Old House may be the first (or at least one of the first) times it's been put on television where the general population will see it.
I seem to recall some info about their cartidge. About $50.00 plus blade (if the blade is damaged). Even at twice that cost, it is still a bargain compared to an appendage, emergency travel, emergency room, all that goes with it and time lost all over.
I've been in touch with them about the 10" contractor saw they are about to release. We may see it in the next 3 months....no price yet but guessing at around $1100.00 for this version.
They are working on using this technology in other power tools. (planers, jointers,bandsaws,mitersaws)
You cannot idiot proof everything but the technology can't hurt. It seems we accept other new technologies faster than we do for tools of the trade. Costs not withstanding, I wonder why. Same goes for site built vs factory/manufactured environment. But, those two questions can lead to whole new threads, if they haven't already.
...The unspoken word is capital. We can invest it or we can squander it. -Mark Twain...
Be kind to your children....they will choose your nursing home.
According to their web site, the standard cartridge sells for $69; but they also sell a separate cartridge ($89) for an 8" dado. I intuit that you have to switch out the cartridges when you use the dado.Apparently, when the cartridge fires, it usually also destroys the blade. I also read recently that the cost of reattaching a severed finger ranges from $10,000 to $25,000 -- depending on the extent of the nerve damage.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
I also read recently that the cost of reattaching a severed finger ranges from $10,000 to $25,000 -- depending on the extent of the nerve damage.
In '64 I lost one digit to a razor sharp knife. $14,000 to reattach.
In '87,it was 4 to a SkilSaw. $14,000 for all 4 then.SamT
Guys that don't do things correctly the first time.....then argue that they did nothing wrong.....if made to agree to fix the problem, rarely put the time and effort into truely doing it properly. they'll just look for the quickest fix to appease you and get their money. JDRHI <!----><!----> 84310.51
Your numbers for hospital treatment (probably 20% higher every year) should put to rest any claims that Sawstop is "too expensive". A neighbor laughed when I told him we paid a tree service $350 to take down some dead limbs. He thought we should just get our extension ladder, climb up 12 feet, and do it ourselves. Last year my wife fell off a step ladder and broke her wrist. She's OK now but the hospital bills totaled $7K just for that simple injury. It taught us both a lesson and we don't take needless risks anymore.Paying $200 to save a finger is a bargain.
If the price keeps going down like that, pretty soon finger reattachment will be a bargain <G>.********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
"If the price keeps going down like that, pretty soon finger reattachment will be a bargain <G>."
I'm concerned that the SawStop will cause the price of reattachments to rise.
You see, fewer amputations will lead to fewer hand surgeons. And those few will lack the expertise that comes from performing reattachments on a daily basis. ;)
Nailsclous, bienvenue to the forum. The SawStop website is great, and the product looks and sounds awesome.
"I seem to recall some info about their cartidge. About $50.00 plus blade (if the blade is damaged). Even at twice that cost, it is still a bargain compared to an appendage, emergency travel, emergency room, all that goes with it and time lost all over."What is the cost benifit ratio if you have a 1000 false trips , but the only real trip was when you had hard push into the blade, as several have mention, and still did real damage.Comparing the cost of a single fix to a single incident is never valid. Because life it not like that. It works out to tens of thousands, hundreds of thousand, even millions of fixes to one incident..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
--"Sorry, simple physics, the ball does accelerate."
You are the one who needs a basic physics class. I taught high school physics in my first career, and I can assure you that you are quite definately wrong, in this case.
"Sorry, simple physics, the ball does accelerate."
I just got off the phone with my brother who has a PHD in physics, told him the gist of this thread and he said BS. He did grudgingly give in and say technically you are correct because of gravity, but it was going to be a big stretch because the ball is basically thrown horizontally and at roughly 100 mph (ie very little time from the time the ball is released till it reaches the batter for gravity to have much effect) air friction is going to be the major problem.
So I guess you are right, but really wrong.
My 2 cents. the average if you are a tradesmen you don't want a stop say yet. our wood shop has had a few miss fires and they are costly at $75. for the break and a new blade. but for high school students age 13-16 they don't pay attention all the time and accidents do happen so i just hope if will save a finger someday.
>>>>"Sorry, simple physics, the ball does accelerate.">>I just got off the phone with my brother who has a PHD in physics, told him the gist of this thread and he said BS. He did grudgingly give in and say technically you are correct because of gravity, but it was going to be a big stretch because the ball is basically thrown horizontally and at roughly 100 mph (ie very little time from the time the ball is released till it reaches the batter for gravity to have much effect) air friction is going to be the major problem.So I guess you are right, but really wrong.Okay. Basic two-dimensional kinematics.One COULD speak of acceleration acting upon the ball from the moment it leaves the pitcher's hand. You would have force of gravity accelerating the ball in the y-direction at 32.17 ft/s^2, and you would have friction acting upon the ball in the x-direction, which you could for all practical purposes call a negative acceleration.The ball will gain some energy from the pull of gravity, but will probably lose more energy due to air friction, so the ball would probably have less net energy when it reached the batter than when it left the pitcher's hand. So, no, the ball does not magically speed up after it leaves the pitcher's hand. Sir Isaac Newton summed this up pretty well in the 17th century.It is categorically wrong to say that gravity will not have much effect on the ball because it is thrown horizontally. First of all, here on planet Earth, it would be impossible to throw any object horizontally. Somewhere in space, beyond the gravitational effects of other masses, you could perhaps do it, but on this planet objects with an initial horizontal velocity travel in parabolic trajectories.The effect of gravity upon the ball is evidenced by the fact that baseball diamonds include a raised pitcher's mound--raising the pitcher up 10.5 inches to compensate for the vertical distance the ball will travel before it reaches the batter.I haven't cracked my physics books in a few months, but I can try to spitball this. The distance between the pitcher and batter is approximately 60 ft. 100mph converts to about 146.667 ft/s, so it would take the ball approximately 0.41 seconds to travel the 60 ft.y-final=[y-initial]+[(v-initial)(t)]+[(1/2)(a)(t^2)]y-final=unknown
y-initial=0
v-initial=0 (remember, the 100mph is in the x-direction, not the y)
t=0.41 seconds
a=-32.17 ft/s^2 (negative because of where I located y-initial)
t=0.41 secondsThe first two terms zero out, leaving us with the third term: (1/2)(32.17 ft/s^2)(0.41s)^2I solve and get -2.70 ft. Due to gravity, the ball falls more than 32 inches in the time it takes it to travel from pitcher to batter. My numbers may be off, and I welcome any corrections, but the idea is clear--I don't think a fall of over 2 1/2 feet is insignificant.Watch a pitcher closely, or pay attention to your own actions when throwing the ball--the pitcher doesn't throw the ball straight out horizontall, he throws it slightly upwards, and it arcs back down to the batter.
Kinematics are easy. Let me chew on linear momentum for a bit later on tonight and get back to the concept of the pitcher and the ball. There's an interaction going on there with the masses and velocities, but I don't recall the equations off the top of my head.Er, or angular momentum, since when the pitcher actually winds the ball through an arc before releasing it.
Edited 1/29/2007 1:47 am ET by tuffy
The Hot dog demonstration shows so really great technology. Not at all fool proof, but an outstanding step in the right direction.
So let's talk about real life accidents, for example:
You had a kick back, your push stick slipped, lost your footing on some scraps, doing something dumb, working tired………..
Your hand hits the blade at a high speed, ( faster than the hot dog - not as fast as a baseball ).
Would you have serious injury even WITH Sawstop? Yeah your probably going to the emergency room.
In this situation the Sawstop may be the difference between a few hours in the E.R. and getting a complete rebuild from the resident Orthopedic Surgeon.
Bill
OK I am getting way out of league, but help me understand your statement:
Watch a pitcher closely, or pay attention to your own actions when throwing the ball--the pitcher doesn't throw the ball straight out horizontall, he throws it slightly upwards, and it arcs back down to the batter.
wouldn't throwing the ball in an upward arch be fighting gravity causing the ball to decelerate?
I think we are on the same page, just not sure of the fine details.
>>"wouldn't throwing the ball in an upward arch be fighting gravity causing the ball to decelerate?"Yup. Absolutely. Until it hit the apex of the parabolic arc along which it is travelling, at which point it starts to accelerate towards the earth again.
He's right in saying it accelerates - just not in the same direction it's being thrown. Gravity makes it accelerate downwards, which is almost exactly 90 degrees to the direction we're interested in. Semantics, really. And if you really want to play that game, the deceleration induced by air friction IS an acceleration - just in a direction opposite to the motion.
The root premise that for any meaningful purposes the ball will be at maximum speed at the instant it leaves the pitcher's hand is pretty clear.
Now what was this thread about?
Don
I'm with you on that. You are right on the gravity and the decelaration, if my judgment is worth anything. I think the reason I got into this saw stop conversation in the first place was to clarify (give my opinion and firm belief) that the claims of preventing amputations could not be verified. I felt that they could only apply to certain situations. People who operate table saws are exposed to many more complicated situations than can be addressed by any technical solution. I wanted to show that things that hurt us happen in a gray zone where time and perception are not clear even to the best of us.
I wanted to put out a word of caution. "If it sounds too good to be true, it probably is."
I would only respectfully say that your statement about the speed of the object leaving the arm/hand/finger is much more than a premise. It is virtually beyond discussion - firmly established by science long before any of us were born.
Sorry to hi-jack in but you know there are so many issues that haven't been addressed with this saw and obvious ones at that. So far I haven't heard of an accident with this saw where someones finger or other part was saved from a more serious damage. I have heard of many misfires though. If the saw could misfire when it's not supposed to why is it safe to assume that it will work when it needs to? The saw is advertised as a safe saw, or safer saw. There needs to be an independent psycological study of how people address certain situations in their lives. Are they more aware when they feel they are in a dangerous situation or do they tend to let their gaurd down if they feel safer? The greatest amount of damage done with a table saw accident is not the actual cut but the impact or shock of the blade hitting the bone. there have been cases where a persons whole forearm up to the elbow have been shattered because of the shock. Slaming a bolt into a blade will still send a shock wave capable of doing damage. They should put a bone in that hot dog and see what it does. Personally I'm in the camp of "there are no safe saws only safe users". 30+ years at my saw and still got all 10. I'm not bragging, I'm scared to death that one day I might be the next statistic, so I address my tools with the respect that they deserve. On the other hand I have heard that they are good saws and I guess if someone gave me one I would use it, but only after I removed all of the safety features.
Boy, when I started this thread I didn't know it was going to turn into such a debate...I thought all this stuff had been hashed out already.
I was just thinking about how this saw hasn't had much mainstream exposure up till now.
Like I said before you should go read some of the SawStop brawls/threads over at Knots. As for exposure of the SawStop, I doubt if public TV help their sales at all, the people who are likely going to drop $3000 on a TS probably already know about the saw through community reading materials. The SawStop debate plays into a bigger safety in general debate. The question of safety and safety devices and what works, what doesn't, what is likely to be used or not used by guys in the field and all the other issues involved have always been and always will be strongly debated in the trades. It is the same with all new building technologies or techniques; tradespeople are like the general population, some will always adopt the latest ideas and some will only change if it is forced upon them.
There are some in the trades who will even bypass safety in favor of some other perceived benefit. How many guys out there have disabled the safety nose on their nail guns? I haven't, but I have been around more than a few carps who have.
I think if one were to do a study of accidents involving tradespeople and or power tool accidents as a whole, I think you would find that the majority of them involve the victim being A)distracted, B)tired, C)doing something despite a known danger, or D)lack of situational awareness.
Last summer I saw a young roofer nail his hand to the deck because he had been working 9 hours in 100 deg heat and was talking to his buddy while still nailing down shingles (A,B,D). Let's face it not a single one of us works totally safely 100% of the time and those who have not gotten hurt are just lucky. Some of us work safer than others and their chances of injury are less but they are still there. Watch New Yankee, Norm does not always use push sticks on the TS or the router. Last time I got hurt I had picked up 5" discs instead of 4 1/4" discs for my grinder and in a time pinch I removed the guard and started working, my hand slipped forward and I ended up needing 3 stitches (C). I know 6 guys who are missing fingers due to TS accidents, only one was from kick back. Four of them were push through injuries, shop phone rang, they looked up at the boss as he walked by, poor light at the end of the day, exhausted from four 12 hour days and was just going through the motions. The last one was a tripping accident on a cluttered jobsite. They were all human error IMHO. The first and sixth may have been prevented by a riving knife and an in place guard. Who knows, the other four may have been lessened if they had been on a SawStop, I bet those guys would have loved to have found out if the saw works. Sorry bout the long post but those are my 2 cents.
-day
I agree with you for the most part but... Seatbelts are there to save (or reduce) you from major injury. You can be a safe driver and stil get in an accident. Also if you dont use the seat belt it's not gona help.
If you look at the SawStop site, they are starting to accumulate testimonials:http://www.sawstop.com/why-sawstop-testimonials.htmBut both you and Jazzdog make very good points. Far as I know, the saw has not been "tested" by an accident in the real world where the operator's hand was slammed forcefully into the blade, as might happen with a kickback. I don't think there is any question though, that running your finger into the blade will result in just a minor gash with this device. Still, there are no shortage of boneheads out there, and that's why schools and commercial shops are buying the saw. The question remains, however, whether users will consider the machine to be "injury proof" and therefore take foolish risks they might not dream of taking with an ordinary saw. Time will tell.Finally, I want to say again, I think this saw is a great advancement in safety. If I were buying a TS today, I think I would probably buy one.I just resent Gass' efforts to force the device on the industry. ********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
Read the testimonials and frankly felt that they were quite convinceing and sincere, for just myself in the shop I could probably get by without one, but with two employees I could honestly say that as soon as I'm up the 3500 big ones I will probably invest in one. I saw the light, thanks for shareing that post.
WT,
I'm going to have to jump in and take issue w/ your statements, too. (a) Biomechanics has nothing at all to do w/ what happens to the ball after it leaves the pitcher's hand. (b) Physics is how the world works. Period. (c) Ignoring quantum physics, everything in the universe is constantly being accelerated by gravitational forces: the planets, the stars, the black holes, even the nerds sitting at their computers. We are all in orbit about something. (d) That said, there are only two accelerations that are important in the baseball analogy. The acceleration due to gravity which is causing the ball to drop and the acceleration (deceleration) caused by the aerodynamic forces. There are no other forces acting on the ball after it leaves the pitcher's hand. In the absence of a force, no acceleration occurs. The velocity of the ball toward the batter starts diminishing immediately after it leaves the pitcher's hand, and continues to do so until it is hit or caught. The velocity of the ball towards the ground starts increasing after it leaves the pitcher's hand & continues to do so until it is hit or caught.
Momentum is not an issue until the ball is hit or hits the catcher's glove.
So I guess you were right
Woodturner, If you desire to quote somebody please use an entire sentance or paragraph. Your use of a partial sentance of mine changed the context of my statement completly. Here is the complete thread to help you remember:
"Sorry, simple physics, the ball does accelerate."
I just got off the phone with my brother who has a PHD in physics, told him the gist of this thread and he said BS. He did grudgingly give in and say technically you are correct because of gravity, but it was going to be a big stretch because the ball is basically thrown horizontally and at roughly 100 mph (ie very little time from the time the ball is released till it reaches the batter for gravity to have much effect) air friction is going to be the major problem.
So I guess you are right, but really wrong. (bold added)
And where did I say my brother was confused?
If your brother's experience is limited to Physics, that would explain some of his confusion - biomechanics is a factor here, and physics deals primarily with mechanical rather than biological forces.
Where does the boimechanics come from? I thought it was "simple physics".
>>"Most people seem to be making the assumption that acceleration requires ADDITIONAL energy application "during flight" - which is not accurate. Stored energy is still energy, whether kinetic or potential.
Consider the case of a rocket - which is a better analogy. The rocket motor burns for a short period of time, but the rocket continues to accelerate after the motor burns out - just like the baseball."
-Nope.
From Newton's second law we get:
Net force = (mass)(acceleration). So acceleration = (F-net)/(mass). You don't get acceleration without the application of a force. The only forces acting upon a baseball after it's left the pitcher's hand are gravity and drag, so it's not acclerating. It's not gaining velocity in the x-direction, anyway.
The same goes for the rocket--once it has spent its fuel, the only forces still acting upon it are friction and gravity. Unless the rocket happens to be falling towards a planetary body or something, it's not going to magically continue to speed up.
In its purest definition, acceleration is the rate of change of velocity with time, which is why we can speak of a negative acceleration when something is slowing down. One could say that the baseball does accelerate when it leaves the pitcher's hand, but only negatively.
If Newton's second law isn't enough, from Newton's first law we understand that if the net force on an object is zero, then its velocity is constant. That velocity is only going to change with the application of an outside force.
>>>"If your brother's experience is limited to Physics, that would explain some of his confusion - biomechanics is a factor here, and physics deals primarily with mechanical rather than biological forces."
If that were actually true, then every physics textbook ever published would have to be rewritten, because they all make no distinction in their examples between "mechanical" and "biological" forces. Unless you're working at the quantum scale, Newton's three laws apply to all things equally.
>>>>Check out an introductory college physics textbook - the rocket example is typically covered in the first chapter or two.
I suggest you do the same, but maybe pay closer attention this time around. Newton's laws are typically covered in the first chapter or two.
If a rocket, or any object, was able to continue accelerating after a force was no longer applied to it....well, what? It would just continue to accelerate until it approached the speed of light? Well, intergalactic travel would be a snap. You wouldn't even need rocket fuel, would you? You'd just give an object a good shove, and it would keep speeding up, speeding up, speeding up, until it finally got up to a velocity great enough to overcome earth's gravity.
Well said.
I'm sure I'm just being obnoxious by this point--rudely hijacking a thread. :-)
If a rocket, or any object, was able to continue accelerating after a force was no longer applied to it....well, what? It would just continue to accelerate until it approached the speed of light?
Of course they don't - the acceleration stops when the acceleration due to the stored energy has been achieved. Put another way, when the energy (force) stops, the acceleration stops.
>>>"Of course they don't - the acceleration stops when the acceleration due to the stored energy has been achieved. Put another way, when the energy (force) stops, the acceleration stops."The acceleration stops when the applied force stops: a=F/m When F=0, a=0. Basic algebra.To put Newton's first law very succinctly: When the net force on an object is zero, its velocity is constant.I think somehow you're confusing the concepts of inertia and acceleration.
Edited 1/29/2007 4:59 pm ET by tuffy
>>Of course they don't - the acceleration stops when the acceleration due to the stored energy has been achieved. Put another way, when the energy (force) stops, the acceleration stops.The rocket fuel, whether it's as simple as compressed gas or as complex and liquid hydrogen and liquid oxygen, IS the stored energy. Once it's all burned and blasted out the back, there is no more acceleration. The energy that was stored in the fuel has been converted into kinetic energy - the speed of the rocket. You cannot use the kinetic energy of an object to make that object go faster - that would be a perpetual motion machine.did<!---->Cure Diabetes - Whitefish, Montana, 2007!<!---->
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>>>>"You cannot use the kinetic energy of an object to make that object go faster - that would be a perpetual motion machine."Maybe he's found a loophole in classical physics and unwittingly solved the world's energy crisis.
Of course they have - but - they reached their maximum velocity at the moment the engine shuts down. Unless they're being pulled by a gravitational force, they do not continue to accelerate without a rocket engine pushing them.
Of course they have - but - they reached their maximum velocity at the moment the engine shuts down.
OK. Then how would you explain how rockets are able to leave the gravitational pull of the earth? Keeping in mind, of course, that mass-energy can neither be created or stored - so it's essentially impossible to carry enough (non-nuclear) fuel to overcome the earth's gravitational pull (unless you can store the energy as energy, thus accelerating the rocket after the mass of the rocket fuel is converted to energy, and the resulting lower mass can be accelerated by the greater force, due to the consumed mass, and over come the gravitational force...).
Who would have thought we would start with sawstop and end up with rocket science :-)
This is certainly an interesting discussion, but I make a motion that if we want to continue this, we start a new thread and stop hijacking Stuart's thread.Anyone care to second the motion?
Coincidentally enough I used to be a rocket scientist, but I'm staying out of this one. :-)
Well, sorry about the hijack of your thread.
Are you kidding .......... <G>Where else could you see a single thread devoted to table saws and physics -- all at the same time?Moreover, the physics part sounds pretty sophisticated, but it's way over my head.........********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
This is certainly an interesting discussion, but I make a motion that if we want to continue this, we start a new thread and stop hijacking Stuart's thread.
second :-)
I'm still waiting for those scientific papers.
--- If your brother's experience is limited to Physics, that would explain some of his confusion - biomechanics is a factor here, and physics deals primarily with mechanical rather than biological forces. ---
Physics deals with a lot of different kinds of forces, and biomechanics is the application of physics to the study of certain aspects of biological systems. The physics doesn't change just because a human hand is applying the force to the ball. It certainly doesn't change after the human had has released the ball.
Rebeccah
--- http://www.howstuffworks.com/framed.htm?parent=rocket.htm&url=http://library.thinkquest.org/12145/propul3.htm ---
I wasn't aware that baseballs used propellant. This article is about impulse drive, in which propellant is expelled from the rocket and changes its mass. You still need to burn fuel in order to generate the force that accelerates the propellant away from the rocket -- it just happens that in so doing, Newton's third law comes into play and the rocket (minus the expelled propellant) itself accelerates in the opposite direction.
The net acceleration of rocket plus propellant is 0, since the force involved is internal to the rocket-propellant system (generated by the fuel burning within the rocket's impulse engine). But the two subsystems, rocket and propellant, are accelerating in opposite directions.
Rebeccah
I don't think that anyone has the nerve to acturally use their own body parts to demonstrate it's abilities to actually work. Right now I have one in my shop. It has triggered on several occasions. No one has ever been hurt and we lost about two hours or more in each occasion. It always a shop stopper because it is so amazing that other than the saw stopping it hasn't hurt anyone yet. So far the triggering has been because of the blade touching the splitter.
Ken