Motor Reversing

Found this article...

"Single-phase induction motors drive many arbor-mounted cutting tools in the home workshop. Stationary grinders, table and radial arm circular saws frequently turn abrasive or cutting disks that are directly mounted on the motor's spindle. These disks have large inertial moments that allow them to free wheel for a long time after the power is turned off. A lengthy coast to complete stop often amounts to a major inconvenience."

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Reply to
HeyBub
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I was looking for a home remedy for a festering, fulminating, giant red mass on my, er, never mind. Just say I stumbled across it and thought it might be interesting to some (the motor business, not my, um, temporary disability).

Reply to
HeyBub

A boil on the bum then :-)

Reply to
Stuart

Sounded like election-time talk to me.

-- Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive. -- Howard Thurman

Reply to
Larry Jaques

WW wrote the following:

If I need to stop a spinning table saw blade in a hurry to change or reset something, I find that a scrap piece of lumber makes a great blade brake. Turn the saw off and slide the scrap up to the still spinning blade. Blade stops in a couple of seconds. No extra parts needed.

Reply to
willshak

Someone could make some money by developing an aftermarket saw brake, under the table.... pads or rollers or whatever, that would squeeze the blade.

Reply to
-MIKE-

Lawsuits from the arse with the SawStop patents notwithstanding, I think he went with the positive stop style because it's the only one which would keep from taking a finger off. The rest spin just enough to do serious damage.

-- Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive. -- Howard Thurman

Reply to
Larry Jaques

A saw blade brake wouldn't infringe on SawStop's patent at all.

Reply to
-MIKE-

I've always wondered if a set of good quality bicycle brakes couldn't be safely mounted on the trunnion to perform that very task. Route the cable to the front of the saw to a hand or foot operated lever and there ya go.

Reply to
Steve Turner

thin metal disk instead of a wide rim. Kerry

Reply to
Kerry Montgomery

WTF does that have to do with lawsuits? People sue to keep their product on top whether they have a case or not. REAL WORLD, Mike.

-- Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive. -- Howard Thurman

Reply to
Larry Jaques

Interesting. There is certainly a lot for force against a bike brake than a coasting saw blade/motor. I think a simple spring and electromagnet/solenoid would do the trick in the same way an electric door bell works. No electric current: spring holds brakes closed. Electric current: solenoid pulls brakes open. A manual cable or secondary electric source could be added for manual brake release.

Reply to
-MIKE-

In the "REAL WORLD" (relax, man), patent infringement law suits get thrown out in the first hearing, too, Larry. What, you're a patent attorney, too?

Reply to
-MIKE-

For fast stops a powered brake on may be preferred to normally brake on with a spring setting the speed and strength to be held open all the time.

Reply to
Josepi

I would prefer powered off/normal on, because the operator would get used to the blade always braking and in the case of a solenoid failure, the blade would not coast.

I would also think an assembly with wheels applying just a little pressure to the sides of the blade would make a decent passive system. It would be just enough pressure to slow down the blade in a second or two and not enough pressure for the motor to even register the resistance.

Think about how little pressure it takes with a scrap piece of wood to stop a coasting blade.

Reply to
-MIKE-

In any case, since EU law requires brakes already (indirectly, with an allowed spindown time IIRC), Sawstop would have an uphill battle claiming that they infringe its patents.

Reply to
J. Clarke

Isn't there an old Indian trick about a spinning piece of wood and starting a fire?

Reply to
HeyBub

No, I've just been horrified at how many frivolous lawsuits make it into court, including patent infringement suits. Check it out.

-- Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive. -- Howard Thurman

Reply to
Larry Jaques

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