repair or replacing motor on old Rockwell Delta lathe

[mark ahlenius]

Its hard to tell if a motor like this one would be "inverter-ready" -

https://www.ebay.com/itm/MARATHON-1-...IAAOSwHIlZzUU9

Was hoping to find something a little more powerful due to the lower torque on lower speeds when using a VFD.

thoughts on a motor like above?

thank you

'mark

[Jim Barkelew]

I bought my VFD for my home-built lathe from Automation Direct. It was easy to set the parameters for the motor. Good documentation. I used a Dayton motor that is about 50 years old and came off my bandsaw. To help with low speed torque I used a small pulley on the motor. Wood lathes are generally intermittent low power use so overheating should not be a problem.

[Curt Harms]

<p>
Bill and rest, since I am new to VFD's - should I only be looking for "inverter-rated" 3-phase motors? Searching around eBay this afternoon, but don't want to order something which is not going to work. Also been reading up a little on the kinds of VFD units. If any of you have done this (Bill, Jim or others) could you share a little more detail on the kind of motor and VFD model you used? Anything to be aware of as far as brands or specifics? I can easily add a new 220 volt outlet for a VFD unit, if I cannot find 120 VAC unit. thanks again everyone, this help has been great! 'mark

I would recommend taking a look at Dealer's Electric for VFDs and 3 phase motors. I just bought a VFD & 1/2 h.p. motor from them for a drill press. I went with an open box VFD & new surplus motor. I went with a 230 volt VFD but Dealer's Electric has several 115 volt VFDs available. Their prices seem competitive and they're sorta local to me. They also offer motors with synchronous speeds of 1200 r.p.m. Using one of those should help with the higher torque at low r.p.m. when using a VFD. Running an 1800 r.p.m. motor at 30 Hz. would yield a motor speed of 900 r.p.m. Running a 1200 r.p.m. motor at 30 Hz. would yield 600 r.p.m. if my understanding and math are correct.

http://dealerselectric.com/115V-single-phase-input.asp

[mark ahlenius]

So I think I'm going down the 230 VAC - 3 ph motor with VFD route. Looking at motors running 1800 RPM which was similar to my old Delta motor at 1725 RPM.

Would it make sense with the VFD to use a 1.5:1 or 2:1 pulley ratio (motor to headstock) so that my highest speed on the lathe at full motor speed on the VFD is 2700 or 3600? I'd normally run my lathe at a lower speed but try to not sacrifice the torque?

I'm assuming that the VFD drive does not spin the motor faster than its nominal RPM and if it does, I was not planning on running the motor faster than what it was designed for. I hope this makes sense.

thanks

[Geoff Crimmins]

You should go over to owwm.org, join the forums, and offer the Delta motor for sale in the classifieds. Someone there would probably like to buy it, fix it, and put it to use. Most lathes that use a VFD have pullies with at least two steps, one for slower speeds and more torque, the other for higher speeds with less torque. Just keep the 4-step pullies that came with the lathe. A VFD can run a motor faster than its nominal RPM, but you're correct that it's not a good idea to do so.

--Geoff

[mark ahlenius]

Great idea. Thanks very much Geoff.

'mark

[Olaf Vogel]

So I think I'm going down the 230 VAC - 3 ph motor with VFD route. Looking at motors running 1800 RPM which was similar to my old Delta motor at 1725 RPM.

Would it make sense with the VFD to use a 1.5:1 or 2:1 pulley ratio (motor to headstock) so that my highest speed on the lathe at full motor speed on the VFD is 2700 or 3600? I'd normally run my lathe at a lower speed but try to not sacrifice the torque?

I'm assuming that the VFD drive does not spin the motor faster than its nominal RPM and if it does, I was not planning on running the motor faster than what it was designed for. I hope this makes sense.

thanks

Assuming you do bowls.....

If you are going 3 PH, then set up your gearing for the lower speeds.
You can use the VFD to raise the hertz above 60 and generate the higher speeds. So a 1800 rpm motor can run at 3600, when the VFD provides 120 Hz.
Yes, 3PH motors will do that. Its just that no utility company delivers electricity at 120 hz...

And you will get better torque at low speeds

How do I know? I have have an 8 pole motor, that runs at 880 rpm, so I get the torgue.
If I want higher speeds, I use my VFD to run at 120 Hz.

[mark ahlenius]

<p>
Hey everyone. Thanks for your help and advice on this project of mine. I purchased a Marathon 1 HP 200 VAC (not a typo) 3 phase motor from Dealer&#39;s Industrial Equipment along with a Teco VFD. THey came as a package (preprogrammed as well) deal which is what I could afford right now. I still need to order a step pulley with a 7/8&quot; bore which does not seem that common. My question is that i want to make a hinge plate type belt tensioner for this motor so I can still adjust between the pulley steps easily. Since I don&#39;t have access to a welder, I was thinking of making it from 2 pieces 3/4 high density baltic birch plywood and use a couple of heavy duty hinges I picked up. The motor hinges I see online are metal for the most part but not seeing any for sale. I may cover the motor side of one of the pieces of wood with ~12 ga steel from an electrical box cover. &nbsp;I could also make the wood plates which extend the hinge out of hard maple. &nbsp; Wondering your thoughts on this approach. &#39;mark</p>

[Olaf Vogel]

I've used door hinges without issues. Its a fairly light motor
Baltic birch works well. Did that on a 5 hp motor.

The hinge idea is good, you just need to figure out the pivot point, so that you get the right amount of tension.
2 options I know:
- spreadsheets and some trigonometry, or
- trial and error - I'd use cheap plywood for this route.


The problem with this is that under load, the motor tends to come up and reduce tension. That can be a good thing, if have a catch.
But its really hard to tune.

The other option is a sliding motor mount. With horizontal tension applied by toggle clamps
I like this solution because its really easy to set accurately.

[mark ahlenius]

<p>
ok I was planning on using a couple of springs to apply additional tension on the motor pulling it downwards. Right on the trig for the distance to select for the motor on the hypotenuse of the movable tension arm. Have you or anyone else found a good source for step pulleys with a 7/8 inch bore?</p>
<p>
best &#39;mark</p>

[Curt Harms]

<p>
ok I was planning on using a couple of springs to apply additional tension on the motor pulling it downwards. Right on the trig for the distance to select for the motor on the hypotenuse of the movable tension arm. Have you or anyone else found a good source for step pulleys with a 7/8 inch bore?</p>
best 'mark

Here's a source, don't know how good it is.

http://www.wttool.com/index/page/pro...e+Step+Pulleys

[Perry Hilbert Jr]

nearly every machine in dad's shop that had multiple speed pulleys had a motor mounted on a board and the board on hinges. I did the same for a cement mixer I bought for $15.00. The hotor was on a pice of pywood hanging under the hopper. Only instead of hinges, I just used electric fence wire to wire one end to the frame. It worked fine like that through several "projects" over a span of 12 years. Just don't leave it out in the weather.

Almost every farmer I know, has a box or bin somewhere with spare electric motors for various pieces of equipment. Corn grinders, hay elevators, etc. I am getting low, there are only three out there right now. a half, a 3/4 and a fill hp.

[David L Morse]

ok I was planning on using a couple of springs to apply additional tension on the motor pulling it downwards...

I used a bungee cord for that purpose on a saw I once had. My daughter would always tell me that I should add some duct tape to complete the look.

[mark ahlenius]

or you could probably use duct tape in a pinch for a v-belt.

;-}

[Don Bunce]

I bought that same VFD/motor combo a few months ago for my South Bend lathe. A good source for 7/8" bore pulleys is Amazon.com