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Gallery, Projects and General => The Design Shop => Topic started by: Jim Dobson on September 28, 2025, 11:11:35 PM

Title: Advice on building s simple ‘clutch’ to stop a driven accessory
Post by: Jim Dobson on September 28, 2025, 11:11:35 PM

I’m after some advice to build a simple ‘clutch’ that can be activated by a lever to disengage a running accessory that is being run by a belt off an engine.

If in the photo below where I have drawn the red line (and that belt was longer) what type of simple ‘clutch’ could be built to be able to work to disengage the belt with a lever moved one way and then re-engage the belt with the lever moved back? This would be an extremely handy thing for me to have when running accessories of steam engines and H&M engines etc

I’ve wracked my brain and everything I have come up with would be a dud……any ideas?
Hope I’ve made some sort of sense with the above!

Title: Re: Advice on building s simple ‘clutch’ to stop a driven accessory
Post by: awemawson on September 29, 2025, 03:29:24 AM

A tensioning pulley in the drive train mounted on an “over centre” crank that can either tighten or slacken the belt much like a flat belt overhead drive shaft would be in an Edwardian workshop.

Title: Re: Advice on building s simple ‘clutch’ to stop a driven accessory
Post by: BillTodd on September 29, 2025, 04:08:10 AM

Or maybe roll the belt onto a free-wheeling pulley?

If you wanted a  stand-alone clutch unit then  a floating pulley that could be forced into contact with a moving one or a stationary block could give you both clutch and brake.

Title: Re: Advice on building s simple ‘clutch’ to stop a driven accessory
Post by: timby on September 29, 2025, 05:01:06 AM

I am old enough to have worked in a steam sawmill, a "fast and loose " pulley  as described by  BillTodd was usually the choice to stop a drive but I like  awemawson's idea better,  a jockey pulley on an arm might look better.

Title: Re: Advice on building s simple ‘clutch’ to stop a driven accessory
Post by: Jim Dobson on September 29, 2025, 06:54:33 PM

A big thanks for all the replies, much appreciated. If I can fabricate one up, this would immensely increase the pleasure I get from running small accessories of my variety of engines…..again thanks all.

Someone went to the trouble of cobbling this together to show me a way - Super appreciated!!!  :beer: :bow: :bow:

Title: Re: Advice on building s simple ‘clutch’ to stop a driven accessory
Post by: vtsteam on September 30, 2025, 12:25:28 PM

A really great reference to fast and loose pulleys, exactly as used in the day, is David Richards Steam Powered Machine Shop videos, like this one which illustrates how they worked and were set up. Dave has around 80 videos. This is only #2.

Title: Re: Advice on building s simple ‘clutch’ to stop a driven accessory
Post by: Jim Dobson on September 30, 2025, 07:32:08 PM

Thanks Steve, its been a while since I've watched any of his awesome vids of his workshop.