# penn state variable speed motor RPM?



## geep (Jan 25, 2011)

Has anyone tried playing around with the 3 potentiometers located in the control box in order to slow the minimum speed down? I am using the PSI motor/controller on a Taig lathe for both metal and pen turning. I formerly had a treadmill motor/controller on this lathe and real enjoyed the 0 RPM+ that was available with that setup.
If anyone has pot settings I would be interested, since I hate re inventing the wheel....


----------



## fishlux (Jan 25, 2011)

Mine is slowed to a low of 400.  A friend with a bench full of scopes and meters did it and it hasn't caused a problem yet.  

The motor is dependent on the fan for cooling.  The fan speed is the motor speed.  I fully expect it to overheat the motor eventually.  I don't run it long at low speeds, and it's in the garage (which is plenty cold now).


----------



## ssajn (Jan 25, 2011)

I talked to a PSI tech person a while back and was told you can adjust the speed down as far as you wanted but it also decreases the top speed. For me that was not a problem. 
I was also informed in doing so you would void the warranty.


----------



## bloughrey23 (Jan 26, 2011)

*Variable Speeds for Lathe*

I have a Grizzley bench lather with a step-down spindle for changing speeds. I have considered placing the belt on top speed and placing a "dimmer" switch between the motor and the outlet to use as a variable speed device. Has anybody tried this? Will it work? 

Thanks,

BL


----------



## Robert Taylor (Jan 26, 2011)

bloughrey23 said:


> I have a Grizzley bench lather with a step-down spindle for changing speeds. I have considered placing the belt on top speed and placing a "dimmer" switch between the motor and the outlet to use as a variable speed device. Has anybody tried this? Will it work?
> 
> Thanks,
> 
> BL



no, we all wish it were that simple/easy. but it is not.


----------



## bloughrey23 (Jan 26, 2011)

bettyt44720 said:


> bloughrey23 said:
> 
> 
> > I have a Grizzley bench lather with a step-down spindle for changing speeds. I have considered placing the belt on top speed and placing a "dimmer" switch between the motor and the outlet to use as a variable speed device. Has anybody tried this? Will it work?
> ...


 

Wow....what an informative post! Glad you took the time.


----------



## ldb2000 (Jan 26, 2011)

The motors on single speed lathes are AC motors which require 110 volts 60 Hz AC power . Router speed controls and Dimmer controls are for universal (DC) motors or light bulbs and vary the voltage and will cause an AC motor to overheat and burn out , if it runs at all . AC motors require variable frequency controls to vary the speed . While these types of devices are available , they cost more then a new variable speed lathe . 
This question has been asked over and over so if someone just says " no , it won't work" it's because it has been explained before and the poster might not have understood the theory behind it but knows that it won't work .


----------



## KenV (Jan 26, 2011)

I have one of those motors -- for a Taig -  

The electric motor game is nothing for nothing -- no magic tricks that do it all.  

The simple DC permanent magnet motors in 1/2 nominal HP lose power significantly as the speed is slowed down.   The treadmill motors are nominal 1.5 HP or so and the effect on power loss is less because they start with more capacity.

I use the pulleys to slow the speed and the motor controls to vary the speed within the range provided by the pulleys.   (Machining out the motor pulley to 15 mm is a neat challenge).  

Below a motor speed of about 400-600 rpm the power drop off is too much for what I do.

Next step up is the sherline motor and controller and it has a lower speed capacity with power (for more money).


----------



## geep (Jan 27, 2011)

KenV said:


> I have one of those motors -- for a Taig -
> 
> 
> I use the pulleys to slow the speed and the motor controls to vary the speed within the range provided by the pulleys.   (Machining out the motor pulley to 15 mm is a neat challenge).



HaHa...I thought about boring out the pulley myself so I put the stock 1/2" bore Taig sheave on a bolt in the chuck of my electric drill to power the lathe to do the boring.....still with me?......well it turned out that I took the sheave to a machine shop.....best intentions poor execution:redface:


----------



## ctubbs (Jan 27, 2011)

If you must take the small motors to a lower speed than factory set, I would highly recommend placing a fan at the fan end of the motor to aid in cooling.  It will eventually over heat and then you will be able to replace it with a larger motor.  What I am putting on my old lathe is a 3 phase motor with VFD that accepts single phase 230V power.  It will output power to the 1hp 3phase 230v motor from 0hz to 1000hz.  The range will be reduced to 0 to 75 hz to protect the motor.  The motor is a regular 3 phase motor and there is an additional fan for low speed use.
Any time you reduce the speed of a motor below its design speed, the air flow across the motor is greatly reduced.  With reduce air flow, the heat is not removed as efficiently and insulation damage occurs.  Failure most likely will not happen instantly the first time but the damage has started and will continue each time the motor is abused.  Eventually it will fail.  Guaranteed.
Charles


----------

