On 10/13/2010 02:32 PM, J. Clarke wrote:
In ,
says...

On 10/13/10 9:43 AM, J. Clarke wrote:
In , says...

J. Clarke wrote:
In , says...

J. Clarke wrote:
In ,
says...

On Mon, 11 Oct 2010 19:59:30 -0400, wrote:

J. Clarke wrote:
In , says...

I would think that an emergency stop mechanism would be a whole different
magnitude than a scheduled, everyday, stop.

For a finger saver an emergency stop mechanism would have to stop the blade
in a few teeth passings. For everyday usage a couple dozen blade rotations
would be OK too. These two situations would require different tactics.

A dynamic electronic brake could vary the intensity for the two different
scenarios and we could add the caliper to the emerg stop. A caliper probably
wouldn't last long in everyday usage and would need to be adjusted and/or
replaced frequently.

So how much power do you have to put into that electronic brake to stop
the blade as fast as Sawstop's physical block?

And why would a caliper not last long? A set of brake pads on a car
with 10" rotors lasts 40,000 miles or so, and they're getting a Hell of
a lot more of a workout that they would stopping a little bitty saw
blade that masses less than 1/1000 as much.

The physics on that seem interesting. A little like stopping a speeding
bullet on a dime--it challenges my imagination. Probably not quite as
difficult as stopping a lightning bolt, but I wouldn't want to try that
either.

Bill
No way a caliper could stop the blade in even 4X the time the
saw-stop does. And keeping dust out of the gap between tha "pad" and
the blade would be quite problematic - with dust decreasing the
stopping efficiency by a very large margin.

I suspect that a small pyrotechnic pressurizing one of the calipers off
my '76 Lincoln might surprise you.


When it snapped (seriously)? I'm not an engineer, so I don't know for
sure. I just wouldn't be surprised. Maybe someone else can opine.

Why would something that can stop a 4000 pound car "snap" when called on
to stop a 3 pound saw blade?

"Pyrotechnics" rather than a master cylinder with brake fluid?

To stop the saw in a fraction of a revolution, you need rapid
application. A pyro will build pressure rapidly.

I didn't think we were talking about an emergency stop.
AFAIK, we're discussing a convenience stop which, in my opinion, would
be satisfactorily done in a couple seconds, not milliseconds.

Well, geez, for that a bicycle brake will work fine.

Another reality check for all the people taking this thread off into the wild blue yonder is
the issue of getting the blade onto the arbor in the presence of calipers that grip either
side of the blade. My interest (and Mike's as well, I think) in using a bicycle brake was
simply a matter of "how can I retrofit my existing table saw with a simple convenience
brake?" I think the wide-opening jaws of a bicycle brake (maybe along with some kind of
front-side cable disconnect to allow the calipers to drop out of the way) would allow enough
clearance to get the blade on the arbor without too much trouble. This heavy-duty
automotive caliber Saw-Stop alternative that everybody else is talking about would also have
to provide a similar mechanism, which would of course add to the complexity.

--
So will there ever be a day, throughout the rest of my life, that I
won't encounter in the written word a case of somebody not understanding
the difference between the meanings of the words "to" and "too"?
To reply, eat the taco.
http://www.flickr.com/photos/bbqboyee/