1947 A7 belt driven dynamo Home brew

[jhg1958]

The Alton alternator is driven by a plane belt on a v pulley. It is hard to check the tension so I just turn the alternator as far as I can.  I forgot last year and the belt came slack and burnt out. I carry a spare belt on log trips now.

John

[shabashow]

I've used several different belt drive systems over the years and have had various problems with belts stripping teeth, pulleys coming apart and other niggles which reduced my confidence in holding a good charge in the battery (I like to drive with my headlight on). I've replaced all my bulbs with LEDs, and they draw very little current, so I went back to the standard chain drive. I have no worries now about battery charge now and the charging system can easily meet the low demands put on it.

[chaterlea25]

Hi All,
The old type SRM 10mm(?) belt drive on my SR has been on there now for 20+ years, still on the original belt. Some years later on SRM's recommendation I added grease to the compartment , They said it reduces the belt temperature ???

John

[Rex]

It does, as it reduces friction.
There's an industrial aerosol spray for this very issue, which is also used to reduce/eliminate cyclical squeal which can be irritating in some production environments.

[jjbsa]

Many interesting points made.  It's handy to know the tapers on the dynamo and timing gear.
My RGS has a 14mm toothed belt conversion which has not yet given trouble after about 10 years, although I do think that the impulsive loads on the belt teeth when one changes gear at high rpm are just asking for trouble, though I still do it sometimes .  A belt with teeth missing is a smaller mishap than a snapped dynamo chain.  I have wondered about making my own flat belt conversion, or even running the toothed belt with the belt turned inside out, thinking that the dynamo could just slip briefly when doing high rpm gear changes.  Has anyone tried that?  Velocettes run well with flat belts.  I have wondered about making my own V belt conversion, and did find a web page which showed how to do the calculations.  I dimly remember seeing a posting long ago from someone in New Zealand or Australia (this site?) about a V belt kit one could buy.  I also tried doing engineering drawings putting a small friction clutch inside the larger pulley that drives the dynamo belt, like on the dyanmo clutch drive inside a Lucas Magdyno, but I could not convince myself that the component parts would not wear after high mileages.