# Logan 400 Treadmill Motor Conversion --lashup Test



## John Hasler (Mar 7, 2016)

Got a lashup of my DC motor conversion working well enough to test.  Very satisfied.  Good stability over a 20: 1 speed range, enough torque at 10 RPM (back gear and large pulley) to take a .020" cut on a 7.5" diameter piece of steel.  800RPM top speed in direct drive with large pulley.  I'm going to have to spring for some Power-Twist belt, though.  I robbed one of the three belts off my mill to test with and it sort of works but is too big.  It measures 9/16" wide, hits the gearbox cover if I close it, and cannot be shifted to a different pulley without disassembly.  The belt looks like Power Twist but has brass rivets instead of tabs.

And, of course, I'll need to kludge up a tach.


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## 47convertible (Mar 7, 2016)

John, as another Logan owner who converted to DC variable speed using treadmill motor I'd like to get more information on the motor and controller you used as my conversion has not proven to have the necessary torque to take decent cuts on mild steel at SFPM recommended spindle rpm. If I use the back gear its difficult to get it up to those recommended spindle rpm though I can take a heavier cut including .020 but do not get a good finish on the work piece.  I know it could have to do with other factors including tool of choice, sharpness of tool, rigidity of tool post etc. I'm still sorting through all of this as the lathe is very recently restored and operating. But still I think the 10 inch Logan should be able to make .020 or deeper cuts without going to back gears. Perhaps I expect too much and learning on 16 to 20 inch lathes at the college has spoiled me?

I salvaged a 60M controller and a DC motor rated at  2 hp "treadmill duty" and 6000 rpm for the initial power source. What others have told me since doing that is that the rating is basically misleading and the motor can only make its  2 hp at the relatively useless 6000 rpm and then only for a fraction of the time it is running.  At useful motor rpm of  2 to 3 thousand rpm it probably makes about 1/2 hp or maybe less.  Well, live and learn. This lesson didn't cost much as the treadmill was free. I included a photo of the label on my treadmill motor.  In the meantime I'm looking at other DC motors designed for around 1750 to 2000 rpm and with continuous duty rating not "treadmill rating" whatever that is. I hope to be able to use my 60M controller on that new motor but don't know if it has the oomph to do that.

Some feedback on your motor and controller specs would help me in my search. I know there are better DC motors out there including treadmill motors more suitable to lathe use.
Jerry


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## John Hasler (Mar 7, 2016)

I have a 9 amp 120VDC GE series motor and a GE thyristor controller but the important thing is that the motor has a tachometer generator that connects to the controller so that I have closed-loop control.  For closed-loop control to work properly the controller must be matched to the motor, of course.

You also have to select pulleys so as to allow your motor to operate over its full speed range.  Thus with a 6000RPM motor if you want a top spindle speed of 1500RPM you need a 4:1 reduction.  Your lathe was probably designed for a 1750RPM induction motor so you need to make changes.


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## Kernbigo (Mar 8, 2016)

I have a treadmill motor on my 9"south bend wide bed, My motor pulley is 1 1/2" and running most of the time on the spindle middle pulley which is 4", also running through the indeterminate pulley system, never ran out of power yet with a 1 hp, slipped the polley v belt a couple times.


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## 47convertible (Mar 9, 2016)

John and Kernbigo, Thanks for your information. I do think the 10 inch Logan was designed for a much slower fixed rpm. I have read that Logan recommended motors but did not ship with a motor and the same for Montgomery Ward which is what my "Logan" lathe started out life being. I've also read Logan did ship with motors. It doesn't make much difference and is off the point which is the gear train was likely designed for around 1750 rpm. I could easily be wrong about that and if so, someone please correct me.

My lathe became something of a Frankenlathe somewhere along  the way since its 1947 beginning and now has a two inch spindle with four V belt pulleys. Likewise four pulleys on the counter shaft.   *(Photo of spindle and counter shaft below.)*   So I do have a choice of alternating speeds with belt/pulley combinations, back gears or with the variable speed motor or by using a combination of both whereby the number of choices becomes dizzying.  I hit on the idea of a variable speed motor as I don't particularly like the stop, adjust, restart of adjusting belts.  To be able to operate with minimal changing of belts I need useful power across most of the rpm range. I didn't get that with the first try described above. So now am looking for more power at the lower rpms and the ability to keep that power up to higher rpms. Just how much higher one can go and keep good torque I do not know but intend to find out as I pursue this. My knowledge of electricity and particularly motors is very basic so I read, watch you tube and ask questions. Thanks again for your responses.
Jerry


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## wa5cab (Mar 9, 2016)

You're correct about it being designed originally for a motor RPM in the 1725 to 1750 range.  The most common FHP single phase motors are 4-pole, which is where that came from.

Also, it was apparently common with a number of vendors in the "old" days for the motor to not be included with a lathe.


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## Kernbigo (Mar 9, 2016)

Here is a picture of my 9" setup , you have more pulley selections than i do, i can't see why it wont work for you , try the  1 1/2" pulley on the motor. You can't be out much the price of a pulley at ace hardware.


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