Fan belt sizing

[jamesheath]

I'm fettling a seven special, and have pretty much got it back on the road...
The previous fan belt was somewhat shredded and was tracking right to one side of the pulleys. It was also very tight.
I've fitted a new fan belt, which felt awfully tight and it's heading in the same direction - running rammed up against one flange and wearing...
I've got the top pulley turned so that it's pointing at the centre of the bottom pulley, and still the belt feels really tight. It feels at the sort of tension I'd put on a car where it was driving the alternator or dynamo.

I've checked my other special, for which the fan belt has always been fine - I've taken the belt off that and it too is really tight.
The "new" belt is marked SA 0044 and the one from my other special is marked SA 0045.
The special I'm working on is regd in 1927, the engine is coil ignition, with a bacon slicer starter - do they have a different sized fan belt?

Thanks

James

[Tony Betts]

any chance of a picture of the system it is tight on.

there should be 3 different sizes, the suppliers only stock 2. and one of those is two small for what it is sold for.

tony.

[Howard Wright]

Hi James

I think there may be two sizes of fan pulley.  Not sure the exact sizes but i think the later pulley is a bigger diameter.  It is possible that the later pulley has been fitted to an early engine?

Cheers

Howard

[David Stepney]

I had the same problem with my special that I owned in the ‘80’s. I used some whittle belting and had no problems.

["Slack Alice" Simon]

If you are running a standard radiator height set-up, you don't need a fan belt until the world warms up in late spring.

If you can't find the right belt/pulley combination, get a saddler to make you a leather belt the right size..

[squeak]

If the pulleys are in line and have a 'crown', but the belt still runs up against the side of one pulley, then the top spindle is not inline with the engine. Probably down due to the too tight fanbelt. They perform nicely quite loose.

[jamesheath]

Hi Tony,

Here are some pics - the wiring is NOT mine - but works so hasn't been tidied yet!
Unfortunately the area around the fan is a bit enclosed 

   

   

Cheers

James

[squeak]

Your top pulley is 'dished' due to wear. The belt will ride UP to the high point at the edge/lip hence a centre crown is desirable If there is enough meat in the pulley, you could have it remachined and thus reduce belt tension. The belt is undoubtedly short but this may be a workaround.

[Tony Betts]

Hi james.

Yep, one of things that comes up very often for me.

You have a mag engine top pulley.

The SW on the belt is seven workshop, I dont like pulling the workshop down for this. As Jamie is fantastic for the 7 world. But as I sed one of the belts supplied has never been long enough.

I loved it when one of my favourite lady customers came up to me, and seriously reprimanded me because my accurate copy pulleys didnt fit these belts. And I should alter the size of the pully to fit a miss fitting belt

It's easily rectified, fit the early coil pully and a coil belt. Your fan blade will spin faster.

You can either contact me for the accurate billet cut pulleys, OR EVERYONE ELSE who copied what I produce.

Tony.

[Dave Mann]

    Like this, you must have Hawk's eyes Tony.