Dynamo Belt Drive

[groily]

Looks just the job Mike. Nice one. Having had a now-much-amended SRM kit these past couple of years I guess I'll stick with it for now, but the extra-high gearing sounds great for 12-volters. Good luck! Does the drive pulley self-extract? Looks as if the small dynamo pulley passes through the case, so getting rid of one more minor hassle in re doing it up nice and firm.

[bsa-bill]

Looks very similar to my SRM belt drive, not sure how they get 20% extra , SRM claim 10% - must be a smaller dynamo pulley as the large pulley takes up all available room.

Hi Groily - not sure if I'm misreading your mail but the SRM small pulley passes through the case no problem, the big pulley I've found to come off with a sharp tap on the idler gear shaft ( with a brass drift of course)

sounds like I'm bigging up ( modern vernacular ) SRM , not really I think SRM have their belt kits made for them so possibly it's the same kit

[Dynamo Regulators Mike]

I reckon the majority of those screw bosses have seen more or less contact with the chain, Muskrat.
The small pulley does fit through the case attached to the dynamo with a bit of a fiddle.
The 20% ratio, 10 % over SRM is achieved by one less tooth on the driven, and one more on the drive pulley. Drive ratio is a shade under 3:1.
The 50% extra strength of the belt will provide low stretch and a very long belt life, even with oil contamination. By the way the belt slips onto the large pulley without removing it.
Adding two threaded holes to aid extraction as on the Hawker kit has already been fed back to the supplier. The small pulley has an internal thread so a magneto pinion extractor can be used there.

[lawnmowerman]

I have this belt drive kit on my SR which came with the bike. The belt seems quite small and is wearing already and I have only done 2 or 300 miles. Anyone know what type this is. The Dynamo Regulators kit has a much beefier belt and it is toothed whereas mine is a V.
I am interested in a higher output as I am running 12v and have upgraded the headlamp bulb and like to drive with the headlamp on all the time. I also plan to fit indicators at some stage.

Jim

[groily]

Must be going senile Bill, as I thought I remembered mine wouldn't pass! But it was a couple of years + ago, is my excuse - and p'raps I didn't try hard enough. Not having had to look at the charging electrics for that long tells me something good though. Famous last words, I hope not!
Don't know what yours is though Jim.

[MG]

hmm, I have fitteded the SRM belt drives on the A10 not too long ago, and it wouldn't pass through the cases. The pulley flange was just slightly larger in diameter than the original pinion, I think it was 1, maybe 1.5mm, and that was enough not to let it pass through.
Probably not all case openings are exactly the same size.

[Dynamo Regulators Mike]

With the new kit I rechecked and found that I cannot withdraw the dynamo with the small pulley in place after all. Don't know if the SRM flanges are the same size though. My mind playing tricks and I was only playing with the set-up yesterday.

Lawnmowerman, I reckon that your drive kit is from a chap who makes them up by word of mouth for BSAOC members, and probably others too if they ask nicely. Designed for standard drive ratio, i.e. 49:20, 2.45:1. his name escapes me but Brian at Lightning Spares told me about it. Maybe Bill will know who I mean.

[bsa-bill]

I had a belt drive similar to Lawnmowermans, I gave it to a mate who made a rear carrier for me, I think it was made by a bloke about Durham somewhere, trades as Sappy on Ebay IIRC, anyway my mate seems to think it works ok although he had o cut the cork washer in half to get the big pully to stay on.

Now you guys got me wondering about that small pulley, I can remember fitting it on the dynamo on the bench, can't remember taking it off again to fit the dynamo.
I have a spare inner case and a spare pulley so I'll compare tommorow.

[muskrat]

G'day Blokes,
                  just had mine (SRM) off. Had to remove inner cover to get it (dynamo) out with the pulley attached and reversed to assemble.
Cheers

[MG]

Ahh, so that's the trick!

[bsa-bill]

well done Muskrat, saved my sanity, I'm not away with the fairies after all (well not totally)

[alanp]

I have this belt drive kit on my SR which came with the bike. The belt seems quite small and is wearing already and I have only done 2 or 300 miles. Anyone know what type this is. The Dynamo Regulators kit has a much beefier belt and it is toothed whereas mine is a V.

Jim, you're correct to think in terms of changing that one for a toothed belt drive, vee belt drives typically need more tension to ensure that the Vee grips sufficiently which will put extra load on the dynamo bearing.
I use the SRM one which works fine, but I have added two tapped holes for extraction of the drive pulley from the taper (as mentioned in a post above) or you'll end up wedging behind the drive pulley and knocking the shaft end to break its grip on the taper when you want to dismantle that area, don't go there!
Regarding the seal between the drive pulley and the casing, which will apply to any type you buy, you need to measure the gap it has to fit into before cramming a too thick cork ring in there or it will disintegrate as I and others have found. I altered the thickness of the cork ring to fit the gap. I haven't tried a felt ring.
Alan

[chaterlea25]

Hi All,
Like AlanP I drilled and tapped  the large pulley
I have not removed the dynamo with the drive pulley attached, my SRM dynamo pulley has an internal thread for a puller
so I made up a puller before I fitted the conversion
I sounds like a lot of bother removing the inside casing

HTH
John O R

[bsa-bill]

I sounds like a lot of bother removing the inside casing sad2 sad2

My engine was stripped down to start with John so that's how I managed it

[muskrat]

4 screws and it's off. Just another gasket to make.
Cheers