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

[Blue HeelerParticipant @blueheeler]

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!

[JasonBModerator @jasonb]

If you could move it to the input side of your gearbox then a simple “fast & loose” pulley arrangement would be easy to do and in keeping.

Basically have a longer shaft and a second matching input pulley. However this new pully is free to rotate on the shaft so mount it inboard of the fixed driver puley which will retain it on the shaft. You then have a simple lever that pushes the side of the belt off the driver pully and onto the loose which stops the drive.

Often found on overhead line shafting or on the actual item being driven such as this pump

[Blue HeelerParticipant @blueheeler]

I think I follow what you mean Jason. Do you mean mount another pulley wheel onto the base of my transmission and have it on a lever system and then another pulley off that and a loose belt/tight belt depending on where the lever is?
That would ease the engine into engaging and running the accessory and also ease the disengaging so as there is no big ‘clunk’ which could abruptly stop a lower powered toy engine.

I’m horrible at drawing stuff, I wouldn’t even classify this as a thumbnail dipped in ink.

 

[JasonB]

On JasonB Said:

Appreciated Jason.

 

[Robert Atkinson 2Participant @robertatkinson2]

Two free turning pulleys on a shaft with a felt washer between them with one pulley able to move axially. Then a spring loaded mechanism to hold then together when drive required. For example if the pulleys have ball bearings, a tube over the shaft pressing on the inner race of one bearing. So from end of shaft: pulley, friction washer. pulley, tube, spring, lever.
If more power transmission required harder friction material and stronger spring.

Robert.

[DC31kParticipant @dc31k]

With a traditional flat (leather) belt driven setup, the ‘springiness’ in engagement or disengagement is very much a function of belt slip.

There is nothing in the mechanical operation of the fast/loose setup which inherently ‘eases’ the clutch in or out of engagement. It is similar in that respect to a standard friction clutch in your car, where you feather the clutch for a smooth get away. The contrast would be a dog clutch, which is either ‘in’ or ‘out’.

The reason I mention this is with the belt you use, the operating characteristics may differ to a flat belt (it is very narrow so effectively is on one pulley or the other, barely in any intermediate state).

[JasonBModerator @jasonb]

Baker’s did make clutches for their ball hopper and horizontal engines. They fixed to one of the flywheels using the same lugs that mount the fixe dpulley that you have.

Basically a tube with a flange on it. Th eflange carroed the clutch friction material and the pully was monted to a hub that ran on the tube. On te hend of teh tube was a thread and handwheel, by tightening the handwheel the pulley carrier was pushed against the friction material and that then drove the pulley, loosen th ehandwheel again and the pully will freewheel.

If you are on facebook, this shows such a pulley lugs spaced for the correct 5 spoke flywheels that teh model should have https://www.facebook.com/groups/389755754714535/permalink/2080467638976663/

Similar arrangement is used on many hit ang miss engines, this is a Galloway one.

Friction material on the flange at an angle

mating conical cup in the foreground that fixed to the pulley of your chosen diameter

Pully on it’s hub and side view of the handwheel

Setup on a crosscut saw rig, two handwheels act like a pair of locknuts

Flat flanges and a ring of friction material would do for a simple model

[Nigel Graham 2Participant @nigelgraham2]

I have used a lathe with a “fast and loose” pulley drive! I first met it, an IXL-badged Erhlich 6″ machine, in my own model-engineering club’s workshop. It came to when that facility closed, and last I knew is that the Lynton & Barnstaple Railway workshop has it.

 

This sketch below, though sparse and rough, shows the principle.  I could not draw the two belts, and trying to add the bearings, motor, operating-lever and support frame, would take me all day!

 

The pulley bottom left, longer than the combined width of the two pulleys above it, is on the motor. A flat belt joins it to those pulleys.

I have shown the countershaft above the motor and machine, the normal arrangement, but it can be away to one side. It runs in bearings fitted to suitable supporting framework.

The left-hand pulley is the “loose” one, with an internal bearing so it runs freely on that shaft. A collar on its far side, so would be hidden here, keeps it close to its neighbour.

The middle pulley is the “fast” one, in the sense of made fast. It is keyed to the countershaft – indicated by its keyway. (Shaft keyway and key omitted.)

The right hand pulley, on its own, is also secured to the countershaft and drives the machine via a second belt.

Those three pulleys are all crowned to keep the belt centred. The long pulley on the motor is fully cylindrical.

I say “keyed”, but it was common to use big set-screws or grub-screws acting on the plain shaft, our IXL lathe’s assorted pulleys were so fitted.

 

In front, and between the motor and countershaft, is the “striker” bar with two prongs. That uses guides on the framing so it can slide parallel to the countershaft, but not rotate. The belt runs between the prongs, so when the striker bar is slid one way or the other the fork pushes the belt accordingly.

It is operated by a lever (not drawn) using the pivot hole in its far end. As the belt is pushed from one countershaft pulley to the other, it moves along the cylindrical motor pulley all by itself.

The striker is a small but appreciable distance along the belt from the countershaft. I think on our club’s lathe, it was about a pulley diameter below the fast & loose pair. It may need some experimenting to find the best position.

…..

This system was developed early in the Industrial Revolution for driving entire factories of machines from a single waterwheel or steam-engine. The countershaft as here, was replaced by “line-shafts” along the ceilings, with a fast & loos pair and fast final-drive pulley for each machine. Any speed-change pulleys were on the machine itself, rather as on a Myford lathe.

..

For grooved pulleys a different arrangement would apply. A proper friction-clutch, perhaps combined with a single pulley to put that in fast or loose state, is preferable. Some garden machines use a Vee-belt whose tensioner is on an arm swung in and out of drive. This of course means the belt is in constant rubbing contact with the pulleys when out of drive, so is low-cost but not perhaps the best engineering!

[SillyOldDufferModerator @sillyoldduffer]

Fast and loose would be my choice.  Easier to make than a dog, magnetic, or friction clutch and very common in full-size belt systems.

It consists of a drive-shaft with two identical pulleys mounted close together in parallel.  :

• One is made fast to the shaft.  When the pulley is turned so is the shaft.
• The other is loose on the shaft, free to rotate on a bearing.  When this pulley is turned, the shaft doesn’t.

The operator engages and disengages drive by sliding the belt from one pulley to the other.  In the good old days, the belt was shifted with a wooden pole.   Belts were fairly slack, making it possible to lift and shift a moving belt between pulleys.   No levers necessary!

Later, more elaborate mechanisms appeared:

The cluster is hung from the ceiling.  The fast and loose pulleys are on the right.  Pulling on the dangling chains (bottom left) turns a wheel and moves a crank, to which is attached a slider with two vertical fingers.   The belt runs between the fingers, so they shift the belt.

It’s similar to the pulley cluster marked “Bear” in Blue Healer’s photo.   A man with a lathe could modify it!  The main complication is that the model uses a tight round belt, whereas fast and loose pulleys work with flat belts.

Here’s a youtube video showing a dog-clutch made of Meccano.

Dave

 

[JasonBModerator @jasonb]

The main complication is that the model uses a tight round belt, whereas fast and loose pulleys work with flat belts.

Should be OK with round belting, might be worth adding a slight dish (not crown) to the surface of the pullies.

Quick practical proof of concept. two ball races and a vee block to hole them in a vice, piece of 10mm HSS ground rod, two bits of slippery Polyprop. The lower free to rotate on the shaft the other a firm push fit. Old o ring and away you go. Gravity was pulling the ring down but a bit of tracking adjustment or above mentioned dishing would do it as would a fixed guide/changer.

[Nigel Graham 2Participant @nigelgraham2]

Neat experiment!

I would suggest minimum clearance between the pulley rims so the belt does not try to dig into the gap, and perhaps a small flat land on the rim of both pulleys to aid the transfer.

[Blue HeelerParticipant @blueheeler]

Thank you Jason for cobbling that together and making this video. As the old saying goes a picture tells a 1000 words…..the above video tells a tome. Super appreciated

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.

[JasonBModerator @jasonb]

Jim, I missed yoy sketch at 7.33 yesterday. Hopefully subsequent posts have shown you what I mean if not.

Take the input pully off your transmission, make two circular discs that fit on the shaft. The inner one free to rotate the outer fixed with a grubscrew or similar. You can make up a lever of some sort using teh space on the base where you dre wthe other pully.

If your existing shaft is too short then you can have the loose pully running on a boss that is part of the fixed pully, it is not a sthough you ar edriving heavy machinary so a bit of overhang on the shaft wont hurt. Infact you could cobble something together yourself just by turning that pully the other way round and making a disc with a hole large enough to run on the the small existing boss.

[David AmbroseParticipant @davidambrose86182]

The clutch on my dad’s Webb lawnmower just moved the belt tensioner to tighten or slacken the belt.

[noel shelleyParticipant @noelshelley55608]

Find(buy ) a leather belt (trousers for the holding up of ) and cut as needed to make the very simple fast and loose system as shown here (above ).  It will be true to the era of the engine and can be scaled to suit. Good luck. Noel

[JasonB]

On JasonB Said:

Jim, I missed yoy sketch at 7.33 yesterday. Hopefully subsequent posts have shown you what I mean if not.

Take the input pully off your transmission, make two circular discs that fit on the shaft. The inner one free to rotate the outer fixed with a grubscrew or similar. You can make up a lever of some sort using teh space on the base where you dre wthe other pully.

If your existing shaft is too short then you can have the loose pully running on a boss that is part of the fixed pully, it is not a sthough you ar edriving heavy machinary so a bit of overhang on the shaft wont hurt. Infact you could cobble something together yourself just by turning that pully the other way round and making a disc with a hole large enough to run on the the small existing boss.

Thank you Jason, very much appreciated 🙂

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