Hello there!


I am trying to fix my grandmother's sewing machine, replacing the old motor with a new one. The old motor worked at 4.500 rpm, so I figured I would try and find a similar one. Thus I did, but I was sent a different motor than the one I ordered and this one works at 10.000 rpm. It's too fast for the sewing machine so I figured I would try to reduce, besides the pedal itself, the output rpm (I am trying not to do it using pulleys or gears because of space). I have basic knowledge of electrics and electronics and I am ready to learn and investigate to fulfil this project, but I don't really know how to start.

I will attach some pictures of the motor and the pedal as well as extra information about the motor.


GOAL:

Reduce the rpm of the motor in half and be able to still use the pedal to control the velocity of the motor. The maximum rpm being reduced to half of the initial 10.000. Basically I want to use the pedal to control the motor's velocity being able to make it spin at a max. velocity of 5000 rpm


I want to thank you for taking your time reading the thread, I hope you will be able to help me!

Manex

 

Ar that RPM and the fact it appears to have brushes, most likely the same kind of Universal motor, a simple ceiling fan 'dimmer' could be used, if you insert a series resistor in the dimmer pot you could restrict the rpm range.
The other way is to use a larger pulley.
There is also many dimmer circuits out there if wishing to build one.
Max.

 

The other way is to use a larger pulley.

Larger pulley on the machine, but probably easier, a smaller pulley on the motor.

 

Most sewing machine foot pedals are resistance controlled, in series with the motor. You could be better off with a simple light dimmer or fan controller.

 

Larger pulley on the machine, but probably easier, a smaller pulley on the motor.

By the dia of the present motor pulley, there is not much room for reduction.
Max.

 

. You could be better off with a simple light dimmer or fan controller.

As per #2.
Max.

 

By the dia of the present motor pulley, there is not much room for reduction.
Max.

May be able to use just the bare motor spindle.

 

Another way would be to restrict the pedal travel.
Max.

 

If a 'dimmer' is used to halve the speed, hopefully the available motor torque doesn't suffer too much.

 

If a 'dimmer' is used to halve the speed, hopefully the available motor torque doesn't suffer too much.

Although no more than the original variable resistance!
Max.

 

It looks like there is a controller that came with the motor, which may not be just a variable resistor. Thus I also am going to suggest that the best choice will be to either reduce the diameter of the driving portion of that pulley to a half of what it is now, or what is more likely to be simple to do, is add an external 2:1 pulley reduction stage close to the motor. If the machine is a conversion of an older treadle type there would be plenty of room for that , otherwise it may get tight.
Reducing the voltage a lot will also reduce the torque and make the system harder to use, since it will slow a lot as the load increases.But the simple way to experiment without modifying the motor or controls is to locate a step-down transformer, possibly one such as used to allow the use of USA appliances on UK 220 volt power. You might even be able to borrow such a transformer for the experiment.

 

Hello everybody!

First of all thank you very much for your fast answer and forgive me for answering so late, I have been very busy. As most of you suggested I will try to fix my problem with a dimmer. I have found this one in Amazon which seems it could fix my problem. Any thoughts about it?

Also, I have been thinking where I should install the dimmer and I have some doubts. I would like to control the velocity with the pedal having the maximum limited by the dimmer; should I then install the dimmer before or after the pedal? Or it doesn't really matter? My intuition tells me it doesn't, but you never know!

Thank you all again for your time, I really appreciate it.

Manex

P.S.: For all of you that suggested the pulley solution, I don't have neither the room to attach it to the motor, nor to get a bigger one on the sewing machine; but thank you for your time

 

Are we still missing, what type of control pedal is involved?

 

The full RPM of any sewing machine motor makes no difference in the real world. As some one who sews from time to time, I/you almost never use full speed. Since your motor seems to have come with a speed pedal, it is made to fit your motor, I personally would just install it and not worry about it.