Woodruff key – sideways location

[Sub MandrelParticipant @submandrel]

I found a nice cast iron pulley of wheel that made an excellent pulley for my ex-recycling centre Suffolk engine. I had to sleeve the bore, but there is plenty of meat in the boss.

I made a woodruff key from a slice of alloy steel, which makes the pulley a nice firm push fit, but after 20 minutes running it crept approaching 1/8" (that's 3mm, youngsters) along the shaft.

Obviously if left unwatched for a lengthy period it could creep off the end with unfortuante consequences. So… what is the normal way of securing a pulley to an overhung shaft when a woodruff (or other key) provide positive location.

Neil

[Sub MandrelParticipant @submandrel]

[Steve GarnettParticipant @stevegarnett62550]

Dunno about 'normal', but last time something similar happened to me, I loctited the key to the shaft. It's still there…

[JasonBModerator @jasonb]

The key provides no hold along teh shaft, it onlt stops the pully rotating on the shaft.

 

Drill & tap the end of the shaft and fit a turned washer retained with a screw or cross drill the shaft for a pin

Edited By JasonB on 03/07/2012 20:47:42

[Sub MandrelParticipant @submandrel]

> Drill & tap the end of the shaft and fit a turned washer retained with a screw

Not enough room for a pin, but that's an ideal solution.

Sound advice Jason, thanks.

Neil

[RICHARD GREEN 2Participant @richardgreen2]

Neil,

As Jason says, a woodruff key provides no retaining of the pulley, it only provides a "drive" between the shaft and the pulley.

You're going to need some other method of fixing the pulley in place, that all depends on the set up that you've got.

I've got a Suffolk engine,probably 1960's, we used to rebuild them years ago, they made a 75cc and a 98cc, same block bored out bigger,

Richard

[Gordon WParticipant @gordonw]

Woodruff keys should be for location only, as in timing gears, not for driving. But it is an imperfect world. Just had a look at my old motors, those that aren't held by rust seem to have a grub screw fixing.

[KWILParticipant @kwil]

How about a grub screw that is threaded in boss of pulley and bears upon the key, pushing it into its seat..

Strictly speaking a Woodruff Key is semi circular and sits in a matching recess, a parallel key is the one that can slide out.

[Sub MandrelParticipant @submandrel]

Richard – as far as I can tell it's a 75cc with a cast iron head, as I understand the 98 was an alloy head bored out for a CI liner. I haven't fully dimantled it, I just fixed a broken flywheel and various bits, cleaned the outside and did a major restoration of a paint-encrusted carb.

Gordon – it's an ex-lawnmower engine, so it must have been able to transmit all the power of the engine in the original application.

Kwil – It is a woodruff key, so the key isn't going anywhere, it's the pulley with its parallel grove that's moving.

Neil

[Steve GarnettParticipant @stevegarnett62550]

Posted by Stub Mandrel on 04/07/2012 21:12:26:

It is a woodruff key, so the key isn't going anywhere, it's the pulley with its parallel grove that's moving.

Ah, I see now where I was thinking about this wrongly. How about two screws threaded through the boss either side of the key? That would stop it sliding in either direction.

[Ian S CParticipant @iansc]

Neil, Steves got the idea, but I would fit the grub screws so that looking at the end of the shaft, the key is top, and screws at 120* either side, pushing the key up into the keyway. Tighten the screws, to mark the shaft, them loosen, andtake the pully off and drill dimples for the screw tips, they will be more positive, and the shaft won't get burred. Ian S C

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