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caddy
05-31-2008, 06:57 PM
Howdy boys
I went to a garage sale today and a used treadmill followed me home. I stripped it out and now have a 2.5 hp DC moter that turns 7900 rpm and all the brains that run it. Varible speed etc. I'm coming up a bit short on how to best use it. I know there are a zillion ways but at the moment I blank. I'm sure all/some of you have run across this. What can this be used for?
Thanks
Caddy

macona
05-31-2008, 07:03 PM
The motors are usually rated "Treadmill duty" which is something like 20 minutes on 1 hour off. So you may need to add cooling to make it more usable.

Some issues of treadmill systems is they will not start at a predetermined speed. The ramp up from the bottom for obvious reasons. There have been some people who have figured out how to get around that though.

Mike Burdick
05-31-2008, 07:20 PM
How about a grinder with a diamond wheel?

Get a diamond wheel and fit is such that it is flat (facing upward) and submerge the entire wheel in a water bath - this will require a "pump" seal. Then run the grinder at slow speed. This way, everything is kept cool and one can sharpen HSS or carbide tool bits to perfection...and NO abrasive dust to breath or harm tools!

I have made one similar to this but the "power" is provided by the foot - like a potters wheel. It works great, especially for sharpening my scraping tools.

Liger Zero
05-31-2008, 07:36 PM
How about some sort of device that stimulates the economy? Something involving a sharp pointed stick that jabs people when they make poor decisions like trying to pay for a $500,000 home with a $22,500 a year job six kids and a car payment and credit-card debt.

Bill Pace
05-31-2008, 08:08 PM
I've been using them for 15-20 years in various applications.... They come is many, many sizes, ratings, rpms, HP, etc. Yours rated at 7900rpm is one I havent run across, thats pretty high -- the 2.5hp is common. And the controls come all sorts of ways... as mentioned, and probably the most common is on the less expensive models, is one that requires you to back off the pot to get a restart (really, its not THAT big a deal), then some of the more fancy units have quite sophisticated controllers.

I've got one on a Chinese floor drill press (I have to back the pot off on it) that I have had for some 15 yrs, use it primarily for drum sanding polishing/cleaning up metal pieces. I never put the little fan on it and run it a quite high speeds and for some pretty lengthy runs and it just keeps going, --hey, if the smoke comes out of it , just get another! Built a couple belt sanders, --have one on one of the 9x20 (I DONT have to back off the pot on it) lathes giving it variable speed -- that made a nice addition to it. Then I adapted one of the more "robust" models to a wood bandsaw in order to get the rpms down and be able to use it on metal, ---AND its got variable speed!

I bet you can come up with something to use it on..........

jcarter
05-31-2008, 08:16 PM
I want to make a KMG style belt grinder. A treadmill motor would be ideal for a belt grinder.

caddy
05-31-2008, 09:12 PM
Thanks for the ideas so far. more more more
This particular unit must have been a spendier one in that the controls have a set series of pre programmed routines that include incline, speed etc and of course the ever popular heart rate AND blood pressure!! cool huh?
the good news being that it also has a manual position for people like me
Keep 'em coming
Thanks again
Caddy

JRouche
05-31-2008, 10:26 PM
I really like the belt grinder use. Make up a nice single phase Burr-King.... JR

Doc Nickel
05-31-2008, 10:46 PM
One of the drawbacks is that it really only makes that (largely theoretical) horsepower at top speed. Torque drops off sharply as you start to dial back the speed.

The built-in speed controller is not terribly sophisticated, and will NOT give you good power at the low end.

Your best bet is to use pulleys and jackshafts to reduce the top speed to a normal working range, and then use the speed control to dial in a small adjustment band from there.

Doc.

Forrest Addy
05-31-2008, 11:16 PM
That DC motor is made to order to run a drill press. Variable speed in a drill press is a real plus. You need the full range of the mechanical reduction however so don't dispose of the step pulleys or other means of mechanical ratio changing. Most drilling is low duty cycle so the even the inflated HP rating of that treadmill motor won't pose a problem.

You will also need a countershaft and a 3.9 to 1 belt reduction from the treadmill motor to the counter shaft. Mount the original step pulley on the countershaft.

The design of the motor mount, the countershaft etc and their manufacture and installation isn't rocket science but if it's well executed it will be a real project. Goods luck with it.

By the way, motors are constant torque devices. They don't lose "torque" at lower RPM. HP is a function of RPM and torque. A HP is a HP at rated motor RPM. Halve the RPM and you halve the motor HP but the torque stays almost constant - all the way to single digit revs - but the HP drops in proportion. Lower the RPM and you have to raise the torque vua mechanical reduction to hold the HP constant. So it's not a "loss of torque" that stalls a motor when a dufus operator attempts to drive a 4" hole saw from a motor electronically slowed to 100 RPM. The motor is working fine. It's the demand for constant HP as RPM varies that causes confusion and draws careless assessments from from the physics challenged.

Because larger tool diameters require lower RPM's to function properly and because shade tree engineers usually slept through their high school physics classes they usually blame their faulty motor engineering to derive from "loss of torque".

TGTool
05-31-2008, 11:36 PM
Because larger tool diameters require lower RPM's to function properly and because shade tree engineers usually slept through their high school physics classes they usually blame their faulty motor engineering to derive from "loss of torque".

Forrest, I get pretty torqued when things aren't working the way they should. And spinning my wheels must be the loss of horsepower. Does that count?

Maybe I'm just a little loopy from spending an extra day on a road trip installing a wifi system that wasn't working as intended and expected. Today I figure out that the wireless adapter on the laptop is out to lunch (thank you Dell) so a lot of that time it might have been working perfectly well. Somebody turn my pot up, will you?