I recently came into a 1924 singer Treadle sewing machine.
I wanted to see if I could improve the speed/efficiency of the treadle, and address an annoying design flaw.
Design flaw- because it’s a treadle>pitman arm>crank shaft setup, the machine can begin motion in either direction. But only one direction is useful, counter-clockwise breaks needles and ties knots in the gears.
Improvements already made
I’ve moved from a 1/4" round leather belt which has a tendency to stretch and slip to a 1/4" rough textured polyurethane belt. It has helped power transmission and eliminated slipping.
Improvements I am considering:
My back-of-the envelope math says that the rotational inertia (hub/spokes/rim calculated individually and added together)
Says that a 4lb, 12.5" iron wheel has similar rotational inertia to a 2.5lb 26" bicycle wheel (which is actually a 22" dia metal rim).
Challenges in doing that are getting a new base/treadle system fabricated, because I’m not chopping up an antique.
Ideas I’ve discarded: I considered removing the weight from the upper handwheel and replacing the belt with a chain, but I believe the belt being a slip point might be good for the machine. Nowhere else is there an engineered slip/break point if the needle hits something too hard. I think upgrading to a chain might endanger the machine.