Fan Belt Size - Again

[Ian Vincent]

I know this topic has come up lots of times before - I have just spent an hour reading various posts on the forum and completely confused myself.

 

I have fitted a Moss narrow belt kit (with damper) to my TR3a along with an alternator. The belt supplied with the Moss kit is marked Quinton Hazell QBA975 and it is too long, I don't have enough adjustment to tension it properly.

 

I have measured the Moss belt and it appears to have an OD of 38 1/4" which as near as dammit is 975mm which is where I guess that bit of the name came from. I estimate that I want a belt that is about 1 1/2" shorter.

 

I have looked on various belt supplier websites and they say that standard notched V belts are 13mm x 8mm whereas my Moss item is 10mm x 8mm. They also seem to measure (and identify by) the ID rather than the OD that I have measured.

 

So my question is, does anyone know the standard belt to order for a narrow belt conversion with alternator?

 

Rgds Ian

[david ferry]

Ian,

 

I think that there are variations from car to car.

 

Personally, as your current belt is too long, I woul dtry a QBA950 belt and see if that's short enough.

 

I think you may find that it is.

 

Good luck.

 

David

[littlejim]

Ian,

 

when I was having a similar problem, VivDU suggested, if I was prepared to sacrifice the old belt, that I cut the ends then measure the correct length with the adjuster in the middle or near the 'not stretched' end. (You still have to be able to get it over the pulleys.) In my case I was after a short one, because I left the water pump pulley out of the equation; I got the belt I required at an engineering supply shop not an auto supply shop.

Edited April 14, 2010 by littlejim

[JJC]

Ian - I had exactly this problem recently. The Moss kit had a pulley suitable for an alternator conversion. I retained my dynamo so needed a different pulley. After that everything worked fine. I can probably find the diameters somewhere but ring up Mick Pratt at Moss, he'll help you. Best regards JJC

[ianc]

I have a revington conversion, for which there are new, narrow, pulleys on crankshaft, water pump and alternator. I am using a Unipart GCB10963 (11269-K8) narrow, notched, belt. It is exactly the correct length.

Ian Cornish

[Ian Vincent]

Many thanks for all the replies, I have found a blet that fits - just!.

 

I went to my local motor factors with the intention of taking David's advice and buying a QBA950 but when I compared it (manufactured by Wyko) with the QBA975 that came with the Moss kit it was only marginally shorter so I opted for the next size down QBA937 which happened to be made by QH.

 

When I got the QBA937 home it was too short to fit so today it was back to pick up the QBA950 and it fits but only just - the adjuster is only half an inch away from the end of its travel. I suspect that there are marginal differences between the profile size between the two manufacturers that are enough to make choosing the right size belt a bit of a trial and error job.

 

Anyway for anyone searching in the future a Moss narrow belt kit with a damper and running an alternator with its smaller pulley needs either a 'small' QBA950 or a 'large' QBA937. And don't ask me what the Unipart number is - I quoted the QH number to the guy in the motor factors and that was all he needed.

 

Rgds Ian

[vivdownunder]

Fan belts are a can of worms as some countries measure the inside circumference and some measure half way down the taper.

 

Industrial belts can have different taper angles to auto belts.

 

When a belt is found that fits, whether wide or narrow, immediately get another the same as a spare.

 

It's a small investment to save all the hassle of scratching around for a replacement after one breaks out on the road and is lost, and you have no idea of a size or supplier.

 

Regards,

 

Viv.