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Hi,

I own a 1891/92 Class M.

I was curious how stable it runs in terms of speed because when I play a recording there is some noticeable variation.

I used a tachometer and recorded with the feed screw involved. The belt is in good shape and evrything is lubricated well.

Here is the result around 147 RPM ( different speeds give similar results). Speed stability is a bit better with feed screw not involved.

https://youtu.be/hyXVxTnPApA

I actually think it is not bad for a machine of this vintage.

What do you guys think?

Is it unreasonable for a machine of this technology and vintage to expect better?

Is there anything I can do to improve speed stability?

Thanks in advance,

Erwin

Hey Erwin,

Your video is private, so not available for people on the forum to see.

I am sure that you know this, but for the benefit of others, an understanding of how a Class M governor operates may help.

The Class M governor governs the speed of the motor by constantly making, then breaking electrical contact.

As the governor spins, the weights on the governor springs splay out, pulling up the bottom plate (A in the picture). At some point, the governor spins fast enough to separate the bottom plate from an electrical contact (C in the picture). This breaks the current previously flowing through the two electrical contacts (B and C in the picture) through the bottom plate (A in the picture). Without current, the motor, and governor slow down. Slowing down the governor brings the bottom plate back down to the electrical contact (C in the picture) reenergizing the motor. The cycle of making then breaking contact happens very fast. However, if everything (Mostly the governor, but also motor, mandrel, pulleys, etc.) isn't cleaned and well lubricated, and the electrical contact brushes don't have every strand of copper aligned together and flat for a crisp contact, it can lengthen the delay between cycles (breaking and then making contact) to the point where it becomes noticeable.

Hope that helps.

Thanks for your reply!

Sorry about the inaccessible video. It is public now!

EKzono wrote: Sat Mar 07, 2026 10:13 am Thanks for your reply!

Sorry about the inaccessible video. It is public now!

Still says private. Maybe update the link?

sorry hope this works !

new link

https://youtube.com/shorts/hyXVxTnPApA? ... VTxVNhaQ9-