04-01-2020, 05:38 PM
I understand that pulleys for flat belts have a slightly domed section rather than being completely flat, or perhaps I should say cylindrical. If correctly set up the belt will run straight without the need of the flanges at the sides of the pulleys. With use the pulleys wear and become flat or indented, and particularly if one is more worn than the other, the blt is unlikely to run straight. With a new bottom pulley, as suggested check if it runs true, but also check if it runs in line with the top pulley by putting a straight edge across the face of the bottom pulley. It may well be possible to improve the alignment by a small movement of the top spindle. You refer to a new belt bought 30 years ago, in which case it is no longer new and may have reduced flexibility which will not help the situation. Not also that the belt should be just tight enough to turn the fan without slipping. Over the years I have encountered many tight belts, and when questioned the owner has said 'the fan belt has to be tight doesn't it?' having previously had a car where the belt drives the dynamo as well as the fan. For the Austin Seven a flat belt with minimal tension is perfectly satisfactory.
Robert Leigh
Robert Leigh