MASCOT September-October 1995

Roadster Registrars Chat - Roadster Fan Belts and Adjustment

Bill Haverly

Over the past few years I've become very disappointed with old stock fanbelts, having fitted two in consecutive seasons to my 9 Roadster 4AB. Both developed large cracks without any great mileage being covered and had to be replaced. But nothing last forever and I suppose it is unreasonable to expect fan belts to be exempt from shelf life. Some of them must have been stored for well over 30 years in varying conditions, whilst other exposed to all weathers at autojumbles will surely have limited life as their rayon card and rubber structure starts to deteriorate. Not wanting to chance a "third time lucky" replacement I managed to track down a suitable modern belt, but being slightly shorter that the original Ferodo V392 (37 5/32" OD) it refused to fit over all three pulleys. No real surprise, of course, for even the standard belt is very difficult to get on with fan racket adjustment totally slackened off. But once on it is soon stretching perversely, and with limited adjustment available is out to maximum setting after several years use, assuming it has not developed defects along the way.

THE MOD

To get my new fan belt over the pulleys and increase the range of adjustment, the slots in the fan bracket were extended by filing out the centre "bridge" section between them and removing metal from the upper end of the top adjustment slot. This treatment extends the slack off position and makes fitting a lot easier. The hatched areas in the diagram show where metal has been removed and it is possible to extend the top slot by at least 3/16" without weakening the fan bracket in any way. And the other good point about this minor mod to a neat adjustment system is that when everything is tightened up, nothing externally appears to have changed.

Front view of fan bracket and pulley which pivots on stud A to adjust fanbelt (swiveling upwards to set tension) A, B, and C are locknut positions. Hashed lines indicate area of metal to be removed.

4AD BLUES.

The 4AD Roadster with SM1500 engine suffers too from fan belt fitting problems due to limited slack of adjustment. The system used here is the more common one with dynamo as pivoting age combined with a slotted adjustment arm. But with dynamo butting the block in maximum slack position and no further adjustment possible, the standard V170 fan belt or equivalent will still not slip over the three pulleys. And on a hot day, with very limited working access available, the temperature in the garage can rise considerably ! You can lever away with some risk of rupturing the new belt, but this is a lesser hazard in the long term than damaging worn alloy dynamo and fan pulleys frequently used on this engine.

THE METHOD.

The fitting method I use is to remove the dynamo pulley. With careful use of a wood wedge to lock the pulley blades against the dynamo front fixing stand, remove the lock nut and ease the pulley off the keyway with levers. Refitting is a bit more tricky with belt on pulley and a woodruff key which needs exact alignment, but on the whole it's a far less stressful way of getting a new belt into belt.

The question of how to extend adjustment range w here there is limited clearance is an interesting challenge, but if any owners have come up with a mod to extend belt life it would be well worth spreading the news.