(semi-OT) SawStop : Hard Information

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Frank Ketchum wrote:

The purpose of the bypass switch is stated repeatedly in their literature. They never say anything about using it to change blades.
As to a sensor, I have never seen a photo or illustration that shows enough detail to be able to tell. They may be assuming that nobody would have his hands near the blade after he turns off the saw--not necessarily a valid assumption. But there are other circumstances under which you can get hurt with a Sawstop-equipped saw so they have clearly made _some_ assumptions about its use.

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--John
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On Fri, 17 Dec 2004 18:26:44 -0500, "J. Clarke"

There's a lot more detail in the CPSC filings, if you're willing to wade through thoses.
--RC
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On Fri, 17 Dec 2004 22:06:55 GMT, "Frank Ketchum"

IIRC there is a spinning blade sensor, a Hall effect thing. This is discussed in some of the reports in the CPSC filings.
One of the reservations expressed by several of the testers was the design and programming of the system. Apparently it's not up to the standards expected of safety equipment.
(I was wrong, btw, to say that SawStop hadn't been tested. It was tested by two engineering companies whose reports were attached to the petition by SawStop, by the CPSC staff and by the manufacturers.)
What all the groups that tested SawStop agreed on -- with varying degrees of vehemence -- is that it is a long way from being a deployable product. The general consensus was that in its present state it can't even be completely tested because so many of the details haven't been reduced to production status.
After reading the descriptions I'd say what we've got here is closer to a late-stage proof-of-principle device than a fully developed prototype. I suspect this is the reason the manufacturers are so unenthusasistic about putting it on table saws, although the very high royalty doesn't help.
--RC

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On Fri, 17 Dec 2004 07:15:03 GMT, snipped-for-privacy@TAKEOUTmindspring.com wrote:

Thanks, that's good stuff. Not so good for SawStop :-)
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In wrote:

You must have landed at tyhe wrong address
--
Ted Harris
http://www.tedharris.com
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On Fri, 17 Dec 2004 16:17:05 -0800, "ted harris"

Why do you say that? Having read through all the CPSC information, I'd say it's painfully obvious this isn't a fully developed product. Read the information, especially the engineering reports and you'll see what I mean.
--RC
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While browsing through this document, one thing in the petition jumped out at me.
"2) .... so that a person will be cut no deeper than 1/8th of an inch when contacting or approaching the blade at any point above the table and from any direction at a rate of one foot per second"
I take this to be the spec that the device performs at, or close to it. One foot per second is a very slow hand movement. When industrial OEMs install light screens on dangerous equipment such as presses, they must do a safe distance calculation to determine how far away from the hazard point the light screen must be installed. The reaction time of the machine must be taken into consideration as well as the speed that a person's hand can move. The constant value that is used for such calculations is 2000 mm/second. This is equal to 6.56 feet/second. Think about it. Move your hand at about one foot per second. Slow isn't it? Is that the speed that you move around the workshop? No.
It appears that the spec of 1/8" cut at 1 ft/second is off by a factor of 6.5. To me is seems that in a real situation, a person could get cut 1/8x6.5 or a little more than 3/4". This obviously does not really do a whole lot to protect you.
The more I read about this thing, the more I am convinced it is a POS. That being said, it may eventually lead to something worthwhile.
Frank
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In

Do you feed your wood throught the saw at one foot per second? I think not.
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Ted Harris
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On Fri, 17 Dec 2004 17:58:30 -0800, "ted harris"

do all saw injuries occur while feeding wood? I think not.
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Bridger:

I came within a red cubic hair of severing the itty-bitty tendon (tenon in wreckspeak) running up my middle finger and not only was the saw unplugged the blade was off.
And that's about all I say of the matter except that saw maintenance can get a wee bit hairy at times.
UA100
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I sure don't. That is obviously the speed in which the device is designed around. What percentage of amputations do you suppose are from people feeding the stock through the blade and continuing on right into their fingers? The more I think about this the more I think that the hand speed constant of 2000 mm/sec is inadequate. That is a hand moving under it's own power. Many injuries happen from kickback which can "throw" a persons hand into the blade.
Frank
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Does that have anything to do with how fast one moves ones hands over the blade when it is running? What makes you think the only time tablesaw accidents happen is while one is feeding a board through?
scott
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If your hand slips? Which, of course, is an incident where you really need the protection.
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On Fri, 17 Dec 2004 16:15:49 -0800, "ted harris"

Maybe there are some US companies that one would qualify. I do not know. But I do know that BMW, Saab, Mercedes Benz, Volvo would qualify. I think it is BMW that designed and is selling this incredible instant roll bar in its sports-style cars convertibles. When the sensors sense that a roll is happening, the roll bar deploys -- it hinges up, 90 degrees. I saw a video taken by an autobahn monitor camera of a guy flipping his car and being saved by this technology. Overall, I do not think that any US federal car safety requirement in the last 40 years that did not involve a technology already on the market -- so someone went first w/o prodding. FWIW. -- Igor
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Well, let's see. How about four-wheel brakes? More crash-resistant body designs of welded steel? How about 12 Volt electricial systems with concomittant brighter headlights?
Or, closer to home, how about guards on table saws?
I could go on at some length.

In fact American automobile manufacturers had been making progressively safer cars for decades before the government even got involved in safety regulations. As shown by the declining death rates in auto accidents. And also by declining death rates in industrial accidents.
--RC
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On Sat, 18 Dec 2004 04:21:35 GMT, snipped-for-privacy@TAKEOUTmindspring.com wrote:

I think that our road infrastructure had a lot to do with this. And until spurred by competition from overseas. US manufacturers did precious little other than to change body design
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GregP responds:

Simply not true.
The list of improvements start with body changes and design, and, unfortunately, the annual model change, which we all have now come to expect.
But among non-mandated changes, U.S. manufacturers made intensive improvements in straight line performance year-after-year. As a kid, I saw Chevy finally introduce a V8, the small block 265, that is still, nearly 50 years later, one helluva popular engine. Engine technology didn't pace the Europeans, but neither did gasoline prices, so getting sufficient power out of small engines was left for the motorcycle manufacturers, none of which by the '60s and '70s, was based in the U.S. (I know, I know, Hardly-Ableson, but that's currently a government construct that keeps overall motorcycle prices up, and it is working primarily on '30s engine technology).
But auto development has been spotty, in response to demand too often, with U.S. manufacturers not taking the lead, though they did on occasion do so, so stating that body changes were the only things going on is wrong.
Charlie Self "Absolute faith corrupts as absolutely as absolute power." Eric Hoffer
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On 18 Dec 2004 10:46:11 GMT, snipped-for-privacy@aol.comnotforme (Charlie Self) wrote:

Actually I'd say that's incorrect. Where the Americans excelled was at producing engines which were not only more powerful, but much more reliable than the European engines. The Europeans not only had an incentive to produce high-output and low gasoline consumption out of small displacement, but they didn't have anything like our incentive to produce extremely reliable engines that could sustain very high speeds day after day.
A number of sports car designers realized this early on and the result was the marriage of American engines with European chassis in vehicles like the Cad-Allard, the Sunbeam Tiger and, most famously, the Ford-AC Cobra.

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snipped-for-privacy@TAKEOUTmindspring.com wrote:

American engines got their power from large displacement, which let them run in an incredibly mild state of tune, leading to the remarkably dependability they exhibit. Take that same 427 that's in grandma's station wagon and tune it to the same level as a Ferrari and watch out because it's going to be putting out 600+ reliable horsepower. As Enzo found to his dismay after he made the mistake of ticking off some yahoo named Henry Ford II. But that's just the beginning. There's another thousand or two in there if you look hard enough for it.
The potential of those old 50's vintage American engine designs even today is quite remarkable. The fastest gasoline powered wheel-driven car in the world, at well over 400 MPH, is powered by one GM 454, basically a bored and stroked version of the Chevy 427 that was competing against Ford in Nascar in the early '60s. There's a street-legal TransAm tooling around southern California that was clocked at 268 mph for the two-way average and 277 through the traps at Bonneville (and, no-Eurofans, that is _not_ kilometers). The same guy who built that one used to carry parts around in a 6-cylinder S-15 pickup truck that had been clocked at 210, and lately he's been driving a diesel pickup that also has been proven to be able to exceed 200.

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wrote:

Improved road design definitely contributed to the decreasing death rate as well.

Well, no. Overseas competition didn't begin to be noticed until the 1960s. The safety improvements I cited pre-dated that.
It seems to me that as a general rule safety does sell -- as long as the safety advantages are obvious or, if unobvious, can be effectively and dramatically explained.
And for most of the history of the automobile you're incorrect that manufacturers did little except change body design. The change-the-body-annually school of design was a phenomenon that began in the early-to-mid 50s.
It followed a huge surge in improvements to car design that started when passenger car production resumed after World War II. Cars had been improved steadly since their introduction, but after 1946 there was a backlog of technical innovation that was either ready for market or almost ready for market. The manufacturers went to a schedule of yearly models as a compromise between manufacturing economics and getting these new innovations to customers who were clamoring for them.
Which was fine until, say, 1954, at which time the innovation curve leveled off and the auto makers were hooked on the big sales that came with new models every year.
--RC
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