Motor Reversing

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).

A boil on the bum then :-)

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

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.

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

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

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

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.

thin metal disk instead of a wide rim. Kerry

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

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.

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?

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.

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.

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.

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

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