Advice on building s simple ‘clutch’ to stop a driven accessory

[Jim Dobson]

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!

[awemawson]

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.

[BillTodd]

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.

[timby]

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.

[Jim Dobson]

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!!! 

[vtsteam]

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.

[Jim Dobson]

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