Grinder Motor Question

Joined
Oct 13, 2004
Messages
474
I've decided, after much soul searching and ruminating, to upgrade the grinder I currently have (Log Cabin Forge and Electric) with some better rollers (anyone familiar with this machine will understand what I'm talking about) , platen wheels, and especially a variable speed motor. Can anybody suggest a good variable speed motor (with speed control)? I'm looking for 11/2 hp variable speed TEFC, 110V. I really kinda want a KMG, but I already have this grinder that I kinda like, and it does almost everything I want it to. Also, the upper wheels on the platen disintegrate with the large drive wheel on the motor (1hp Marathon, 3450rpm) pretty quickly so I want some new upper (mainly) wheels for the platen. Any suggestions on where to get some?
 

Stacy E. Apelt - Bladesmith

ilmarinen - MODERATOR
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Knifemaker / Craftsman / Service Provider
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Aug 20, 2004
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34,836
Just bouncing your own comments back to you.
You have a grinder that needs wheels,motor,and platen.The mounting plate must be all that is still OK.If it is this shot,perhaps a KMG would be money well spent.
Not badmouthing your machine,just playing echo.
Stacy
 
Joined
Oct 13, 2004
Messages
474
They're not shot. They still work fine, I just want to upgrade. The small wheels above the platen are fine with the small drive wheel. With the large, the small bearings in them get too hot after extended grinding sessions, and the urethane melts off the center. I almost never use the large drive wheel for that reason. The guy who built it died, so replacement parts from him are obviously out of the question. Actually, my platen is the best I've ever used. I just want to put a few parts on it that are more easily replaceable.
 
Joined
Dec 17, 2005
Messages
633
If you are going to go variable speed I would suggest using an AC variable frequency drive and a three phase ac motor. Ac has the advantage of less loss of torque at low speeds than encountered with DC motors.

Here is a link to the place I bought mine from. You can usually use a three phase ac drive and run it off two phase power up to a three horse power unit. You have to derate the drive by a third to make up for the lost phase. It will still produce a three phase output.

You can usually pick up surplus three phase motors fairly cheap. Get the TEFC (totally enclosed fan cooled) motor. The big differences (as far as I can tell from my research) between the regular three phase motor and a digital (made specifically to operate from an ac drive) is the cooling fan on the digital motors doesn't run off the motor shaft, but has its own motor which runs at a set speed despite the motor speed. This keeps the motor cool even at slow speeds. You can add a wisper fan running off a separate power source to a regular 3 phase motor to acheive this. The secon big difference is the windings on the digital motor are wound slightly different to accept a waveform which isn't exactly a sine wave.

Jim A.
 
Joined
Dec 17, 2005
Messages
633
DAMNENG said:
If you are going to go variable speed I would suggest using an AC variable frequency drive and a three phase ac motor. Ac has the advantage of less loss of torque at low speeds than encountered with DC motors.

Here is a link to the place I bought mine from. You can usually use a three phase ac drive and run it off two phase power up to a three horse power unit. You have to derate the drive by a third to make up for the lost phase. It will still produce a three phase output.

You can usually pick up surplus three phase motors fairly cheap. Get the TEFC (totally enclosed fan cooled) motor. The big differences (as far as I can tell from my research) between the regular three phase motor and a digital (made specifically to operate from an ac drive) is the cooling fan on the digital motors doesn't run off the motor shaft, but has its own motor which runs at a set speed despite the motor speed. This keeps the motor cool even at slow speeds. You can add a wisper fan running off a separate power source to a regular 3 phase motor to acheive this. The secon big difference is the windings on the digital motor are wound slightly different to accept a waveform which isn't exactly a sine wave.

Jim A.

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