Technical Dynamo pulley hub

[Berlinette]

Has anyone experienced any of the studs on the dynamo pulley hub shearing off?

Took our 500F out for a 50 mile round trip yesterday afternoon and the pulley was only being held on by one of the studs when we got back. The drive belt had also been damaged. Making a lot of noise also obviously.

Managed to get the hub off the end of the dynamo shaft today and two of the three studs had sheared off.

I can't quite make out what has caused this.

Thanks

 

[the hobbler]

The most logical cause of this problem would be misalignment of the belt. One of the pulley halves is an 'inside' half and the other is the 'outside' half---they are different. When you rebuild/refit/replace the pulley and replace the belt, make sure that the belt and pulleys are aligned correctly. I am sure that you are aware that you adjust the belt tension by adding/subtracting (as required) the shims between the 2 pulley halves. The unused shims should be on the OUTSIDE of the outer pulley half---if they are put on the inside, the pulley will be out of correct alignment.

 

[Berlinette]

Thanks, yes the shims were on the outside but the pulley may still have been misaligned.

When fitting a new drive belt is there any guidance as to how many shims you should start off with between the two pulley halves? I know that the tension may need checking a few times as new belts stretch.