mcfay

I need to change out my motor on my Singer 1191 d300a. It now has a 12v, 3500 rpm on it. It's getting hot, my husband would like to change it over to an ac motor. He thinks a regular sewing machine motor will work because it is a 7000 rpm. I think it won't because it is a smaller motor.

Here is the question, would the 7000 rpm, ac motor, be equivelant to a 3500 rpm, 12 volt.

I know it will have to be rewired and some rigging it up so I can use a foot peddle.

oldsewnsew

If that tiny little home sewing motor were able to reach its 7000 peak rpm, it would be running your machine head at twice the speed. That would be outside of its design parameters. So by changing relative pulley sizes you could reduce the speed of the head back down to where it should be. Now if you were to look at the rating plate on the motor that was designed to be used with this head, you can multiply amps x volts and get an idea of the power. Now do the same for the little home sewing motor, likely 120v x 1 amp=120volt amps which is close to the wattage. I'm sure the commercial machine motor was considerably more than this. It would be like trying to replace the Cummins diesel engine in your big Dodge pickup with a little 4 cylinder motor from a Pinto. It would be asking too much, resulting in, at least, overheating the motor. Maybe there is some point I'm missing here...

Rodney

Do you have an owner's manual to see what the motor should be for your machine? One reason why the motor could be over heating is if it's too small and working too hard to power the machine. A smaller motor will only make matters worse if that's the case.

Do you have a HP rating or the amps used shown on the motors? Volts x Amps equals power in Watts. That will give you at least a rough estimate of the difference in power between the two. You will want them equal or the new motor to be a little more powerful.

If your new motor is twice as fast you want it's pulley to be 1/2 the diameter of the original pulley to keep machine speeds the same.

It won't hurt to try it and see if you already have the motor laying around but I think you would be better off finding a closer match to your current motor.

Rodney

*Jim beat me to it*

oldsewnsew

OTOH, looking at your earlier post, you said it had a 90vdc, 70 watt motor. So a home sewing motor could replace it, but you probably want to change pulley sizes to a ratio that will slow down the max speed of the head, if it's in danger of exceeding the 4000 to 4500 stitches per minute rating. Was the original motor 90 or 12vdc, and what amperage?
hope I'm not just obfuscating the situation!

mlmack

Are you wanting to use a tiny motor from a household sewing machine on an industrial sewing machine?

If so, that probably won't alleviate your overheating motor problem.

Can you post some photos of the motors in question?

mcfay

I will try and get a photo of the motors today. I don't think it will work, my husband is the one that says he thinks it will.