Option 😄 Clutch Motor

See the parent article: Choosing a Motor

Online mostly you will see clutch motors disparaged as a thing of the past, going too fast, with little control. Yet there are ways to tame them by slowing them down and getting better at feathering the clutch.

1. What is a clutch

Just like in an old school automobile with a manual transmission and a clutch, a clutch in a sewing machine motor allows the motor and the sewing machine to move at different speeds. The pedal motion is opposite that of an automobile though— on a sewing machine you press harder to achieve full engagement, and let off to stop.

1a. What is the clutch made of

The clutch typically has a cork surface pressing against a steel pressure plate.

1b. Why do they go so fast

Not all clutch motors go the same speed. A clutch motor is typically run by an AC induction motor. The no-load speed of the motor is determined by the input frequency (typically 50Hz or 60Hz) and the number of electromagnetic poles (how the motor is wound).

The clutch motors I’ve seen are either 2-pole (about 2800rpm @ 60Hz) or 4-pole (about 1400rpm @ 60Hz). Notice one is twice as fast as the other. You want the slower one.

1c. How to reduce the maximum speed

Here are some ways you can reduce the maximum speed of the machine when using a clutch motor:

1. Get a 4-pole motor instead of a 2-pole motor.
2. Buy a 45mm motor pulley (the pulley that goes on the end of the motor) for about ten dollars.
3. Add a gear reducer (about $110 for 3:1 belt gear reducer)
4. If it’s a 3-phase motor, reduce the input frequency using a VFD

1d. How to get better at driving it

1. If your clutch motor is hard to control, first slow it down so that its maximum speed is actually of use to you. That is, so that on your long straightaway runs you can comfortably be full on the gas.
2. Then take the clutch apart and clean and sand lightly the cork clutch and the pressure plate.
3. Figure out where the oil hole is for the actuating lever so you can oil it so it releases smoothly.
4. Experiment with varying levels of spring tension on the actuating lever.
5. Experiment with how much leverage the treadle has against the actuating lever, and find what works best for you.
6. Practice with short stitch lengths, since this will be more controllable at first.
7. Wiz recommends greasing the clutch surface, but I have not tried that yet so I don’t have any data.

2. Is a Clutch Motor the Right Motor for Me?

Choose a clutch motor if:

• You already have a 4-pole (1400rpm) clutch motor
• You like driving manual automobile transmissions
• You appreciate the extra challenge
• You are good at adjusting things
• You don’t want to use a needle position sensor
• You are going to gear it down anyway
• You have a 3-phase clutch motor (allows using VFD to slow it down)