Ok, I Wat To Play Dc Motor Swap On My Lathe!

[blaser.306]

As the title implies, I wish to modify my 10x22 gearhead lathe from a 1 HP ( 1725 rpm ) AC motor to a 2.5 HP (4000 ) rpm DC treadmill motor. The mill I picked up today was operational except for the display for speed and distance etc. So the control board should be good. I did take close up pics of the wiring as it was originally installed. To those that have done the mod, are you driving the spindle pulley stack direct from the motor or using a different arrangement. I am all ears! Any and all help / suggestions are both welcome and appreciated.

 

[TomS]

As the title implies, I wish to modify my 10x22 gearhead lathe from a 1 HP ( 1725 rpm ) AC motor to a 2.5 HP (4000 ) rpm DC treadmill motor. The mill I picked up today was operational except for the display for speed and distance etc. So the control board should be good. I did take close up pics of the wiring as it was originally installed. To those that have done the mod, are you driving the spindle pulley stack direct from the motor or using a different arrangement. I am all ears! Any and all help / suggestions are both welcome and appreciated.

When I had my G4000 (9 x 20) lathe I put a 2-1/4 HP treadmill motor on it to replace the 3/4 HP AC motor. It worked OK but at low speeds there wasn't much torque. I did some follow up reading and learned that most treadmill motors are rated higher than their actual output. You may be disappointed with the results.

For info I used the pulleys, drive belt and controller from the treadmill.

Tom S.

 

[Chipper5783]

Try to keep the motor in its' torque range for normal turning. Do you have a torque and power curve at different speeds? 4000 rpm is probably the top speed. You probably don't really want to operate much below 3000 rpm. If there is room, for a smaller motor pulley and larger gearbox input pulley? Set up a counter shaft, then you could put a couple 2 step pulleys and really cover the bases.

 

[John Hasler]

Treadmill motors can deliver the power they are rated at but not for very long (and they need forced-air cooling). The torque delivered by a shunt-wound or PM DC motor is directly proportional to the armature current. The controller will have current limiting that will prevent it from exceeding the treadmill's rated current. A good closed-loop controller can deliver full torque over a 10:1 speed range but many treadmill controllers are open-loop. A motor with a 2.5HP treadmill rating should be able to deliver 1HP without difficulty. I replaced a 1/3 HP Leeson with a 1.5HP GE treadmill motor (series-wound) and I couldn't ask for better performance.

 

[blaser.306]

So far from what I am hearing , the mod really isn't even worth the hassle! Should I just stick with a mod like Fabrikator did using a second jack shaft and a extra set of pulley's to gain ( reduce ) my spindle speed? I am looking for a low end speed of 50-60 rpm for reaming use and now I am stuck with 150 ( ish ) as supplied by the factory.

 

[John Hasler]

So far from what I am hearing , the mod really isn't even worth the hassle!

I have found it very worthwhile but I have a closed-loop controller. I directly replaced the induction motor on my Logan 400 with a 1.5HP treadmill motor with a smaller pulley than the induction motor had, keeping the jackshaft. The usable speed range (with backgears) is now 5-1000RPM without moving the belt. I can get 2000RPM by moving the belt down one pulley. The smallest pulley is useless now: I won't run this lathe that fast.

The controller is the most important factor. Figure that the motor is good for about half of what the label says.

 

[rwm]

Does the de-rating of HP only apply to treadmill motors? If I were to buy a Baldor shunt wound DC motor would the label HP be more accurate?
Robert

 

[John Hasler]

Does the de-rating of HP only apply to treadmill motors? If I were to buy a Baldor shunt wound DC motor would the label HP be more accurate?
Robert

The Baldor motor will have a real NEMA nameplate with real NEMA ratings. If it says 1HP, Service Factor 1.15 it will put out 1HP 24 hours a day continuously.

[Edit] I bought a 1/3HP 100VDC shunt-wound Baldor at an auction last week. $4.00. Runs fine.

 

[rwm]

Hey John- What do you think about using a PM type motor on a lathe? Will it always have chips of steel stuck to it? Would I fare better with a wound field motor?
Great purchase!
Robert

 

[John Hasler]

Hey John- What do you think about using a PM type motor on a lathe? Will it always have chips of steel stuck to it? Would I fare better with a wound field motor?
Great purchase!
Robert

Good DC motors have very little external field whether PM or wound. Note that induction motors use magnetic fields: they also keep the field inside. You do have to make sure no chips get inside, though.