Shopsmith Forums

prmindartmouth wrote:Well, I set up that aux. motor drive]10544[/ATTACH]
I used a McMillan Electric Model 2716 dc treadmill motor, 120v, 6 amp, fed by a rectifier hooked to a router speed control. The router speed control is good for up to 2hp routers so handles this load ok. I run it at near slowest setting and am not hearing any strange noises from the SS (yet?). The treadmill motor runs very smoothly. SS is left on slow and unplugged. Here is a closeup of the motor and rectifier:
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The motor base plate has a slot where the two thumb knobs are, to allow belt tensioning. There seems to be plenty of power with these pulleys. I am using a 3" and 10" pulley but want to get one smaller than the 3"when I can (or maybe bigger than the 10") to get even lower speed. I had to bore the 3" out on my metal lathe to suit the odd shaft diameter on the treadmill motor. At slowest speed it seems to be turning the SS at under 200rpm, a guess since I have not measured it yet.
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The big pulley had to go on the upper shaft. I used the base I made for the 7" grinder and drill sharpener and can easily reuse it for those again (see this post https://forum.shopsmith.com/viewtopic.php?t=5672 )
Here it is running.
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I want to use it first to polish the tubes off that old greenie I am slowly refurbing. Safety would suggest I should make some guards next.

prmindartmouth wrote:Good question jpg and thank you for it. Reasons in favor of fast were well covered above, but I am mildly concerned about robinson's point about the centrifigal start switch if not rotated fast enough, plus I know I won't overspeed the SS motor since I intend to run at or below 200 rpm, which causes the SS motor to turn at 2/7 of normal, well within it's capability.
I did try running the speed control up to fast and back to slow while running the aux. motor and could not hear much difference in the noise made by the headstock.
In use as opposed to the test runs done so far, I will however likely leave the speed set somewhere in the middle. I think in reality, it does not matter one way or the other so long as the big pulley stays below 700 rpm.

prmindartmouth wrote: . . .
I am going to get a lighter belt, this one is a bit too stiff and I want to pretty up that wood spacer block. . . .

JPG40504 wrote:FWIW, the condition of the 'start switch' is irrelevant in this setup(I am assuming you do not intend to 'start' the 'normal' motor while using this external motor setup:D:eek:).

robinson46176 wrote:I'm afraid that that statement is incorrect and that you missed my point...
My concern has nothing to do with current at all. Flip on any motor that uses a centrifugal start switch then flip it back off. Do you hear that switch drop back into contact as it slows down? Do you hear the centrifugal mechanism dragging until the motor comes to a complete stop. That switch activation mechanism is NOT designed to be dragging full time. If you run it that way it WILL wear out that mechanism quite quickly. It is only designed to be in that physical contact position for a few seconds at start up and at shut down (and while the motor is not turning). If his "normal" motor is spinning fast enough to kick the start switch he is OK. If it sits and spins too slowly to kick that switch regardless of power to that motor or not, that centrifugal mechanism will not hold up for long run times. It becomes a constant mechanical wear point.

robinson46176 wrote:I'm afraid that that statement is incorrect and that you missed my point...
My concern has nothing to do with current at all. Flip on any motor that uses a centrifugal start switch then flip it back off. Do you hear that switch drop back into contact as it slows down? Do you hear the centrifugal mechanism dragging until the motor comes to a complete stop. That switch activation mechanism is NOT designed to be dragging full time. If you run it that way it WILL wear out that mechanism quite quickly. It is only designed to be in that physical contact position for a few seconds at start up and at shut down (and while the motor is not turning). If his "normal" motor is spinning fast enough to kick the start switch he is OK. If it sits and spins too slowly to kick that switch regardless of power to that motor or not, that centrifugal mechanism will not hold up for long run times. It becomes a constant mechanical wear point.

curtisgeorge wrote:Hello
Why dont you just make your own speed reducer ? by hooking up pullieys and belts to the head stock.

I would think a block of wood mounted to the rails, with two bearings (or bushings) with four pullieys on it. large to small, and then small to large. I have not done the math, but something like a 4x1 ratio should do.
I hope this makes since. Im at work now (that is Im not on the books yet, but I am at work) so I cant pull up any info. but I would suggest to look at any old lathe book on reduceing speed. I would not think that it would be all that hard to make a speed reducer.

Good luck.

C.A.G.