smaller dynamo sprocket query

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asterysk_usa
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smaller dynamo sprocket query

Post by asterysk_usa »

I read somewhere that it is possible to get a smaller dynamo sprocket to allow dynamo to spin faster. Is there a name for this smaller sprocket ?

The only dynamo sprocket listed is 000725 which is the standard
1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).
Stan Palmer
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Re: smaller dynamo sprocket query

Post by Stan Palmer »

I believe the smaller sprocket is part of the engine primary drive sprocket. So you have to get one with the correct number of teeth for your primary drive. From memory the choice of dynamo drive is 17 teeth or 21 teeth. Going down to the shed to se what I have.
Stan
Stan Palmer
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Re: smaller dynamo sprocket query

Post by Stan Palmer »

I have sprockets of 18, 19 and 21 with the small 17 tooth dynamo sprocket. These are all of the plain bored shock absorber type. Don't think they made the splined one at 17 tooth. They have little value as everybody wants to drive the dynamo faster. You can have one but I just noticed you are in the USA.
Stan
asterysk_usa
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Re: smaller dynamo sprocket query

Post by asterysk_usa »

Stan Palmer wrote:I have sprockets of 18, 19 and 21 with the small 17 tooth dynamo sprocket. These are all of the plain bored shock absorber type. Don't think they made the splined one at 17 tooth. They have little value as everybody wants to drive the dynamo faster. You can have one but I just noticed you are in the USA.
Stan
Thank-you for your kind offer. I will have a look at mine and see how many teeth it has. At the moment it's at the soda-blaster and I should have everything back next week,
1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).
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clive
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Re: smaller dynamo sprocket query

Post by clive »

Stan I think Steve is talking about getting a smaller sprocket which fits on the dynamo shaft. Personally I have only ever seen one size the standard type. As you say there are primary drive sockets from the early bikes which had 17(?) teeth on the smaller dynamo drive side. Later they introduced 21 tooth for the dynamo side of the primary drive sprocket. So Steve if you have a primary drive sprocket which has 21/21 teeth there is not much option for you, if yours is 21/17 you could speed up the dynamo by getting the correct 21/21 type. If you already have the 21/21 you could instead speed up the engine by looking for 19or20/21 but in my experience they are hard to track down. Your 500 would be under geared if you went for the 350 sprocket of 18/21(which are more readily available) but you would get extra engine revs for your dynamo and better acceleration at the cost of higher engine revs than necessary so lower top speed and less good mpg.
clive
if it ain't broke don't fix
Stan Palmer
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Re: smaller dynamo sprocket query

Post by Stan Palmer »

You are right Clive. I identified that Asterisk was querying the wrong sprocket but missed that he wants the dynamo to spin faster. As you say if he already has the 21 sprocket there is little that can be done. It might be possible to buy sprocket blanks that can be machined for the dynamo end. A lot of work !
Stan
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Re: smaller dynamo sprocket query

Post by SPRIDDLER »

If you converted your 6v system to 12v using your existing dynamo it's even more necessary for the dynamo to spin faster than with the standard system at 6v.
The so-called 'short' E3N Lucas dynamo which is the one you probably have will produce around 40watts in prime condition at about 40mph in top gear. The standard headlamp with 36w filament bulb will soak up most of those.
I would expect your existing set-up (at 6v and with the original mechanical regulator ?) would be fine if you fit LED lamps since they draw almost negligible current.
There are modern solid state regulators available which are configurable for 6 or 12v, Pos or Neg Earth. Here's one of the most popular:
http://dynamoregulators.com/dvr2.php
'There is a tide in the affairs of men
Which taken at the flood............'
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