Domestic Motors

[friquant]

@Darren Brosowski once told me you could put a domestic sewing machine motor on an industrial sewing machine, as long as it was not a walking foot. Here is my riff on that.

Singer 31-15

245mm plywood machine pulley

1-amp, 7000rpm universal motor

PU belt

Several wood screws were used to hold the plywood to the hand wheel. My inner diameter was cut a little too big, so the position and concentricity of the plywood is determined by which wood screws are screwed in more---the ones on this side vs the other. A round-tipped grinding tool was used to put a groove in the pulley for the belt to rest in. The groove is 0.5mm at its shallowest, 1.3mm at its deepest. (Crude tools, crude tolerances 🤷‍♀️) But it's enough to keep the belt in place.

You'll notice a graphite circle etched onto the left side...that was made after the first assembly by spinning the machine with the motor and holding a pencil steady against the wood. From that I was able to determine which direction to shift the plywood to get it better centered. It's easier to drive at low speeds once it's well-centered.

I'm using this 7000 rpm, 1-amp universal motor: https://www.amazon.com/dp/B0DYSNR32D

The motor came with a pedal but I didn't like the pedal so I bought this one instead: https://www.amazon.com/dp/B08D8WPWTY

The stock handwheel measures 66mm diameter, and top speed was measured at 980 stitches per minute in that configuration. After adding the 245mm plywood pulley, the top speed now clocks at 620 stitches per minute. I expected more speed reduction. My running hypothesis is that with the stock gearing it was too much load for the 1-amp motor to spin at its full speed.

And here's a video.

 

[AlZilla]

I've reported you to the Society for the Prevention of Cruelty to Sewing Motors.  

[dikman]

 (This is for Al, not you friquant).

In my early experiments I made a pulley out of wood - but it was a lot smaller! If you paint it black it might blend in better. Anyhow, as long as it works is the main thing. I wonder how it would go on a 441? 

[friquant]

22 hours ago, AlZilla said:

I've reported you to the Society for the Prevention of Cruelty to Sewing Motors.  

My girlfriend says I can get a reduced sentence if I paint the pulley 😀

[jrdunn]

This may be a foolish question, but why???

[friquant]

17 hours ago, jrdunn said:

This may be a foolish question, but why???

Hi jrdunn

I suspect you are asking "Why power an industrial machine with a domestic motor?"

I would say the benefits are:

1. Portability. The motor attaches to the wooden skirt. Now you can pick up the whole machine, skirt, and motor and move it to another place in the house. I could even give the whole thing away as a gift (machine + skirt + motor) and someone could haul it home in the passenger seat of their car.
2. Cost. I paid $20 for the motor and $20 for the pedal. I got the wood for free. I had some PU belt left over from a previous project.
3. Driveability. My girlfriend doesn't stress when driving this machine.
4. Unconventional.

Or you might be asking, "Why gear down an industrial machine?" but the answer to that has been gone over LOTS of times so I'll bet you're not asking that. I think it is an obvious boon. 😉

Or you might be asking "Why use plywood and a PU belt as your means of gear reduction"? To that I would say both can be cut to the size you need. Meaning "choose your own gear reduction" and if you don't like it, choose again! (Compare this with the limited choices that you can find pre-built.) Also note that this gear reduction uses a single belt instead of two.

Or maybe you're curious how it feels to tug on a plywhood hand wheel? It's actually quite nice. The stock handwheel is spoked and I used to have a reminder taped on the machine "Keep your fingers OUT of the handwheel" for safety. That is no longer an issue.