Dynamo drive sprocket

[ianselva]

Hi, I have just found that the rivets securing the sprocket to the centre on my dynamo drive have failed. Is there any reason I can't just weld the two parts together with MIG ? Or do the rivets form a fail safe function ?

Ian

[wardleybob]

I can't see why you can/t weld them together as long as they are true

[warmshed]

Or use the money you would pay for the repair to get a belt drive.

[bsa-bill]

Or use the money you would pay for the repair to get a belt drive

I'll second that

[ianselva]

If I could get a belt drive for the cost ,I would but the welding will be FOC.
Thanks for your thoughts

Ian

[bsa-bill]

well FOC is a big consideration right enough

[ianselva]

Actually I have been giving this some thought and I believe the aluminium rivets are there as a safety factor ,if/when the dynamo chain breaks it would fly around and settle in the bottom of the compartment where it would be caught up again by the whirling sprocket and maybe burst the timing case , but the aluminium rivets would shear and prevent this.
So I am going to have to look for another sprocket and just use the welded one for the time being.

Ian

[chicago]

Hi there fella, I could be compltely wrong but i was told that the reason for the soft rivets is to let the sprocket centre itself over time, I was also told that even from new the dynamo drive sprockets were never 100% centered and when fitted you ended up with a tight chain with the sprocket half way round a revolution and a slack chain on another half a revolution. I found exactly that problem when I bought a new dynamo chain and sprockets so i give up in the end and bought a longstroke dynamo belt conversion kit from srm. Did make a massive difference in the noise department, a lot less rattlely. All the best, Chicago

[bsa-bill]

good point well made chicago, explains why some of us (me) could not keep my A10 in dynamo chains in the sixties while others had not trouble at all

[chicago]

good point well made chicago, explains why some of us (me) could not keep my A10 in dynamo chains in the sixties while others had not trouble at all

Cheers bill, I was shocked how badly off centre the new sprockets that I bought were, apparently the problem is worst with the newer none original sprockets, all the best bill, Chicago

[ianselva]

I find that hard to believe , when BSA were a machine tool manufacturer and managed to make every other gear and sprocket within tolerances. I can believe it of non-original reproduction bits unfortunately.
If the rivets were loose enough to allow a certain amount of self-alignment they would soon fret and shear.

Ian

[Topdad]

ian, if it would be of help I've got about 4 of the beggas count the teeth and let me know and hopefully I'll have a match or something which will do pm  me to sort best wishes BobH

[bsa-bill]

and managed to make every other gear and sprocket within tolerances

They didn't make everything though many well known suppliers Lucas, Dunlop, Campbells and many others who's names are not household known, so quite possible someone stamped out sprockets for them.

About ten years or so ago I asked C&D Autos for a set of S/A bushes they were out of stock but had an order with the original makers from original drawings, a bit more expensive but slid into the S/A a treat - spot on
BSA certainly were not just assemblers but made what they made well and I think would have outsourced were necessary