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pntrbl
07-10-2007, 02:17 AM
I casually mentioned treadmill motors to a buddy and he already turned up a free one. Wants to put it on his 10" Atlas.

Says 2HP on it but it's only 3 1/2" in dia and about 8" long which seems a little small for 2 horses. Labeled 5,000 rpm. Got a flywheel on it.

2 boards. One's up top in the control/console and the other is at the motor. I have a small amount of electronic knowledge from college transistor days and he knows less than me .... so it's a clear case of the blind leading the blind!

I'm suspecting we only need the speed pot off of the console board but any advice is welcome.

SP

darryl
07-10-2007, 03:37 AM
I think you'll pretty much need both boards as is, since that will be the power in, power out, power control device whether scr, triac, or mosfet, and speed control circuitry, including that control itself. You don't really need the display circuitry, but that may not be separable from the control electronics.

Doc Nickel
07-10-2007, 06:55 AM
I have two ex-treadmill motors that I've had various plans for. I am not yet convinced they're accurately rated, but they do work.

Both had, as you say, two boards- typically the one down by the motor is the actual speed controller, which is in turn controlled by the upper board, which is little more than a timer, speed display, and typically an entirely seperate heart monitor or clock or what have you.

I asked about the same thing over a year ago (http://bbs.homeshopmachinist.net/showthread.php?t=15491) and I got some great answers and details. I currently have that motor mounted to a powered threading mill I built to attach to my Logan lathe. Plenty of power, though I have no idea where the top speed is. Pretty quick though; clearly faster than my vertical mill's 2,780 rpm top speed. 4K maybe?

I have another that "says" it's a whole 2-1/2 HP and seven thousand RPM, despite appearing almost identical in construction and size as this 1HP 4K motor. Same deal- speed controller, seperate board, big board up for the displays and whatnot.

For this one I've been playing with the idea of adapting it to my bandsaw (old Craftsman woodcutting, vertical only) because the current homebrew system (the thing was sold as a bare saw, you provided the motor and mounting) is too fast even for wood. I figure a hefty jackshaft setup to knock that 7K rpm down to between 1,100 and 1,700 rpm, and use the speed control to be able to turn it down to perhaps as little as 500 rpm (saw wheel speed.)

Problem is, as these guys have mentioned, these motors generate most of their power due to the high RPM. I can easily see these two motors being fucntionally identical, with one "rated" at 1HP when driven to 4,000 rpm, and the other 'rated" for 2.5HP when driven to 7000 rpm.

Which makes me wonder if the saw would have any power at all when turned down low. For the same reason, I haven't spent too much time pondering one of my earlier plans which was similar to yours- to swap out the 3/4HP motor in my Logan with the 2-1/2 HP. More power, higher top speed, electronically variable speed...

'Course, won't do me any good if the motor has to struggle to give me half a horse at the low speeds I'd usually be running it at. Makes me think it'd be easier to just buy a surplus 1-1/2HP of the same frame and shaft size and just swap it in.

Won't have to worry about jackshaft bearings being capable of surviving sustained 7K rpm, either. :D

But I digress.

Doc.

Bill Pace
07-10-2007, 09:55 AM
Those treadmill motors are great things to have ---- It'll probably work alright-- (a bit of maybe?)-- a 10" lathe is probably about the limit. I've got one on my 9x20 chinee import and it does very well. Youll need the lower control board and the pot. and its very simple to hook up. Some of the control boards are set up to require you to rotate the pot to the full off position before it will restart, just flipping a switch wont start/restart.

Keep and eye out for these things,--- I picked up a what looked like brand new one in the trash dump, another 2 at the thrift store for $10 and $15 each. Got them on 2 drill presses and a small sander also......

Forrest Addy
07-10-2007, 11:52 AM
Fast as that motor is you'll need to install a jackshaft to reduce the motor speed to something the lathe's built in reduction can safely handle. The pulley ratio would depend on the proposed motor's RPM and the reccommended motors. You sat 5L RPM? I imagine the reccommended motor would be a 1750. That's 2.8:1 or so. I suggest a toothed belt drive.

Is the motor skeletonized or does it have a full housing. One that's open will attract chips and magnetic dust and debris so it will have to be protected. A drill chip wound up in the wrong place can sure make a mess.

Outside of these concerns - and separating the electrical parts needed from those that aren't - some very satisfactory light machine tool drives have been made from exercise equipment motors.

darryl
07-11-2007, 04:12 AM
I use a treadmill motor on my 8x18, and it's been fine. I do use a jackshaft and speed reduction prior to the spindle pulley, at about 2 to 1. It should be more like 3 to 1, closer to what Forrest suggested, The drawback for me is that the low speed torque is lacking, but an advantage is that the motor doesn't have to be run at such a high speed. This lathe has a micro vee belt drive as original equipment, and though I've broken it once (don't recall why) it does very well as a drive belt. I can't say the same for the appliance type vee belt that' I got to go between the motor and the jackshaft. I should have used a higher quality belt there too.

My speed control is a simple variac/rectifier/filter capacitor set-up. It does ok, but an electronic control would be better to maintain torque at lower rpms and regulate speed better.

Back to the two circuit boards that are with your motor, SP. If the lower board does have the power controlling circuitry, it's entirely possible that the speed control pot is merely wired through the upper board to the lower one, and if so it could just as easily be rewired to go directly to the lower board. I do suspect though that the upper board contains an IC that's essential to making it all work. I wonder if there's a hack that can be found for your particular model. Might be worth trying to google it up.

Kernbigo
08-11-2007, 07:05 PM
I have a 10' atlas lathe that I did that conversion and it works great,email me if you have any guestions.
kernbigo@yahoo.com