terryp wrote:Rohan
Forgive me for being silly but why is it that the brackets break and why is the mounting for the alternator so much beefier than the dynamo, as I think I could make the dynamo bracket work with a length of threaded rod?
The engine vibrates the same but I suppose the alternator has a smaller pulley and spins faster??
Do you think my dynamo bracket would be Ok for an alternator for normal road use?
Thanks
Terry
I suspect the alternator is more vulnerable to a resonance due the inherent vibration due to its moountnig geometry and because more of its weight is concentrated up near the nose where the twink vibrates the most, its not due to the alternator spin speed itself. The heavy standard lotus bracket is not really needed for road use as it only becomes any issue with 8000 rpm plus engines in my experience. My plus 2 has a simple welded up bracket in a similar style to the standard dynamo mount for the bottom alternator mount and the standard top connection and has never had problems.
In my race engines I cracked the same simple welded lower bracket on several occassion and also cracked a block bolt hole where it mounts before swapping the mount from the plus 2. I have also cracked the front cover where the adjusting top link goes and now use a reinforcing plate that picks up the 3 bolts on that side of the cover. The top link still breaks ( hopefully not now) and the alternators have a limited life as their internals shake to bits but now it mainly stays in place
cheers
Rohan
A long rod through the standard dynamo bracket may work ok but could be subject to fatigue failure as it will see bending due to vibration