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Belt drive

Rocket3

Well Known and Active Forum Website User
VOC Member
As i am having problems with my V3 clutch and also the shock absorber i am thinking of converting to a 40mm belt drive possibly a Bob Newby set up, has any one fitted this conversion or similar and will it all fit under the chain case cover as i want to keep it looking original.
 

john998

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VOC Member
Hello, the belt used is double sided, ie has teeth both sides.
It looks like a beautiful job . See bob Newby's web site.
John.
 

timetraveller

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VOC Member
A few years ago at the French Rally when it was just south of Dieppe I spoke to one of our French members who had solved this problem a different way. He had used a small section belt, being driven from behind a multi plate clutch to drive a small alternator in the same place as a normal dynamo. The cover for the primary drive was a one-piece moulding which covered the clutch as well as the belt drive. This was to keep dirt out rather than oil in as there was no oil to be kept in. One bolt released the whole thing. I have no idea of the output from the small alternator but it is possible that a larger section belt could be incorporated to drive a more powerful generator.

I use double sided belts to drive domes to cover telescopes, up to 6.4 m (21 feet) diameter, and to drive telescopes where arc second accuracy is required. From my experience I do not think that a double sided belt would be happy if only one tooth at a time was used to drive a generator, in the manner of the original Vincent drive system. The trick would be to use a small idler pulley, or two, so that a short belt covering several teeth drove the generator but fitting that into the available space would take some design time and might even be impossible.

As this Forum is in English that might deter the Francophones among us from contributing to this but if the gentleman in question is prepared to try out his written English on us then there is information out there to solve your problem.
 

timetraveller

Well Known and Active Forum Website User
VOC Member
OK! Very neat. Do we have any idea of longevity? I know that the belt drive is well proven in various racing bikes but I have not seen this system before.
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Belt drives

I've had a belt drive on my Manx since 1994. (They're encouraged in European classic racing since unlike chains there's no source of oil leaks.)
I've broken one belt (stone damage) and replaced one. The current one is about five years old. Since there is no sign of fraying, I've left it alone. A spare belt takes no space anyway, coils down by "a deft double flick of the wrist" - familiar to cyclists coiling down tubular tyres - to a 4" toroid.
I run mine slacker than recommended, about 1" total up and down play. I haven't touched the adjuster in five years. Some guys dispense with adjusters (saving the odd ounce) and drill a single hole in the engine plates for the top bolt.
It evidently has a certain amount of shock absorption, since what eventually happens, with an ally engine pulley on straight splines in a transmission with no other shock absorption, is that the pulley grows slack on the mainshaft splines. I've only replaced one pulley.
Mine is run open (stones come in - stones go out again...) but they are also used fully enclosed on Commandos - stones don't come in.
For the record, last time on the dyno the Norton was putting out 52 bhp at the back wheel, with a virtually flat torque curve, 42 lb.ft, from 5000 to 7200.
Whether they would perform as well on a Vin twin, at much lower rpm, is moot. But the Vin also has an ESA, so maybe everything would balance out. What is certain is that if the belt drive on your Vin let go, it wouldn't wreck the castings, and a spare could easily be carried in the pocket of a Barbour jacket.
 

vibrac

Well Known and Active Forum Website User
VOC Member
converted both my twin and single racers to belt drive both done a season bought two new belts for backup £60 the lot never used them.And there is another reason for a belt when I came to build the twin racer all the parts (except the clutch) for a primary drive came to £900 the Newby was £450 including a clutch oh and some alloy for a cover.
I think I shall be fitting a double tooth belt when I put my alphabet twin back on the road it may stop some of the ragged sprocket forces I note on rotating my Alton as the magnets cut in and out.
 

dagriise@online.no

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VOC Member
Newby belts

I just read MPH the other day and was made aware of the double belt solution. As i am in need of a primary transmission solution, and have had great service from a Newby belt drive from the early nineties, i probably will go for that solution. I have had it on a tuned A10, whith no engine shock absorbing, whith no ill effects. -Have changed plates twice, and treated myself to a new belt, and balls in the "trust bearing" for this season. What i like about this is that i can run the primary dry, and dont have to think about primary chain tensioning, and of course -it runs silent..

Regards Dag
Norway
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Belt drives and Altons

I have a Velo friend who has an Alton, and who queried the fact that it appeared "notchy" when turned over by hand. This is apparently because it has permanent magnets, and what he was feeling was the magnets passing "the flux point". Allegedly, at engine speeds, it isn't a problem. I find this intrinsically plausible, because my experience is that a magneto that is "notchy" is a good 'un, because it means the magnets are working.
converted both my twin and single racers to belt drive both done a season bought two new belts for backup £60 the lot never used them.And there is another reason for a belt when I came to build the twin racer all the parts (except the clutch) for a primary drive came to £900 the Newby was £450 including a clutch oh and some alloy for a cover.
I think I shall be fitting a double tooth belt when I put my alphabet twin back on the road it may stop some of the ragged sprocket forces I note on rotating my Alton as the magnets cut in and out.
 
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