Motor Reversing

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"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."
http://www.homemetalshopclub.org/news/sep01/sep01.html#reversing
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Why did you find it???????????????
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EXT wrote:

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).
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A boil on the bum then :-)
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wrote:

Sounded like election-time talk to me. <shrug>
-- 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
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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.
--

Bill
In Hamptonburgh, NY
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On 10/10/10 11:35 AM, willshak wrote:

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

-MIKE-

"Playing is not something I do at night, it's my function in life"
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wrote:

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
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On 10/10/10 4:51 PM, Larry Jaques wrote:

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

-MIKE-

"Playing is not something I do at night, it's my function in life"
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wrote:

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
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On 10/10/10 9:22 PM, Larry Jaques wrote:

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?
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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snipped-for-privacy@mikedrumsDOT.com says...

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.
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On 10/11/10 12:13 AM, J. Clarke wrote:

Especially since it's apples and oranges. SawStop is a safety brake that only stops when contact with flesh is made, and it's instantaneous. I'm talking about a gradual brake that occurs as part of normal operation.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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wrote:

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
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On 10/11/10 9:01 AM, Larry Jaques wrote:

I understand and it is certainly frustrating. But, if we let that deter us, not one would ever invent anything.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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On 10/10/2010 11:54 AM, -MIKE- wrote:

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.
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The now common disk brakes might be a great match - their designed to grab a thin metal disk instead of a wide rim. Kerry
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On 10/10/10 7:51 PM, Steve Turner wrote:

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.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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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.
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.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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