Posting for someone else.

Mechanically variable pulley on an electric motor. 5/8" motor shaft around 4.25" at outer diameter. This picture is only half of the pulley. Cast iron and got broke when trying to get off the burned up motor shaft. Pulley is threaded and you can adust the diameter and then lock in place with set screws.

This setup allows very fine speed control for timing a process to a moving conveyor belt.

Single phase 110 motor 1hp that is triggered by a switch thousands of times per day on and off. The conveyor belt speed is fixed so this motor needs to be perfectly timed for speed to make everything work as smooth as possible.

I found this at Grainger and it looks like it may work.

https://www.grainger.com/product/ESSICK-AIR-PRODUCTS-Variable-Pitch-V-Belt-Pulley-6FFH8

Also is it possible to control a motor with a dial rheostat type device.I know it has been discussed using a variable frequency drive with 3 phase power but is it possible with single phase 110 ?  Would need to stand up to thousands of cycles per day without overheating and tolerate the constant on and off cycles too.

This actually times a sewing machines stitch speed to a bagging line.

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20210824_120140 (full).jpg (78KB - 215 downloads)