Motor Reversing

[Josepi]

Can we drink beer in court?

[Josepi]

You must be a controls or P&C guy with WNH!

[Josepi]

The electornic way would be so much gentler and easier to implement. They work like a charm.

Maybe only because of the background of the guys proposing it.

15" wheel.

[clare]

This is all assuming a clean blade for the proper high co-efficient of friction. Dust od sap build-up on the blade can change that very quickly.

[clare]

Nope, just an ex-mechanic wire-head.

[clare]

You want to put that monstrosity on a tilting arbour saw, mounted under the saw table and in the path of the saw-dust and have it work reliably??? Not going to happen - guaranteed.

[Josepi]

As I stated posters seem to lean towards the technology they are comfortable with.

The mechanics would be a nightmare to me, also. To others the electronics would be a nightmare.

Contactor and resistor?...way too complicated.

[J. Clarke]

But we don't know which way it changes. Brake pad material isn't all that high-friction you know.

[J. Clarke]

If it "works like a charm" then why can't it slow a dado fast enough to meet EU regulations?

[J. Clarke]

It works reliably on a tilting Lincoln wheel in the path of rain, road dust, and whatever else mother nature can throw at it, so why does a nice, dry saw cabinet present such problems?

Do yourself a favor, pull a wheel off your car and _look_ at the mechanism.

[J. Clarke]

So tell us how to wire an induction motor to make the "contactor and resistor" work.

[HeyBub]

Consider what a disk brake caliper has to overcome: dirt, water, oil, pigeons. It still does a pretty good job.

[HeyBub]

You want to put that goober under a car where it has to contend with dirt, water, oil, ice, salt, road-kill entrails, and have it work reliably???

Common sense says it won't work and can't be made to work. Don't believe your lyin' eyes.

[clare]

It's BECAUSE I was a mechanic for several decades that I would NOT use a brake caliper for the application.

[clare]

On an induction motor the process is a bit different. Instead of a resistor across the motor to stop it you use "DC Injection" - in other words throw about 40 volts DC across the winding for about 2 seconds.

[clare]

I've been doing it for over 45 years I've also rebuilt a few tilting arbour saws - both belt drive, gear drive, and direct drive..

[clare]

It's the clearance issues around a tilting arbour more than the dirt and sawdust. A purpose built caliper could be used on the opposite end of the motor on a direct drive saw - but a drum would be just as effective and smaller for the same stopping power. You don't need the fade resistance of a disk brake for the application, nor the thermal mass of a Lincoln car caliper.

[Steve Turner]

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.

[J. Clarke]

caliper probably

And yet you see a problem.

[J. Clarke]

So now you have to add a power supply and controls.