Dynamo chain

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nortom
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Dynamo chain

Post by nortom »

Hello!
I'm new here!
I have a question: is a chain 3/8"x.225" = 3/8"x7/32"? :?

Greetings Thomas
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clive
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Re: Dynamo chain

Post by clive »

7/32 is 0.21875 according to my calculator so probably not equal. According to the parts lists the width of the Chain is 0.225 inch which does not seem to equate to a fraction, closest I can get is 29/128 which is 0.22656
clive
if it ain't broke don't fix
nortom
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Re: Dynamo chain

Post by nortom »

My calculator said the same thing...
Thanks!

Greetings Thomas
nortom
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Re: Dynamo chain

Post by nortom »

Hello! I was looking for something again. The data I found says 3/8"=9.525mm/Roller 6.35mm/inner width .225"=5.74mm in my opinion. That's 3/8"x7/32". I'm thinking about increasing the distance between the two chains by one millimeter on the Engine Sprocket. I'm looking for the right gear for this. But I can only find gears for 3/8"x 7/32". Hence my question...

Greetings Thomas
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ajscomboman
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Re: Dynamo chain

Post by ajscomboman »

There has to be something missing in this as I'm struggling to fully understand what you are trying to achieve. Sprockets and chains are only available it dimensions as per factory specifications. I cannot get to grips with what the 1mm added space means. It can't be for adjustment as the dynamo is eccentrically adjustable between sprockets to set the chain deflection to around 1/4".
nortom
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Re: Dynamo chain

Post by nortom »

It's like this: I got the bike and noticed that the chains must have touched on the outside, even though they were tensioned and aligned. Since the tooth tips of the dynamo sprocket on the engine sprocket have broken off a bit, I have to replace it. I want to machine it on the lathe and put a new gear there with a little higher clearance.
SPRIDDLER
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Re: Dynamo chain

Post by SPRIDDLER »

Welcome to the club and forums, Thomas.
In brief, when correctly tensioned the chains won't clash although they do run very close to each other. Careful lateral positioning and security of the dynamo is essential. I would replace the dual sprocket with a new one from club spares. Here:
https://www.amoc-parts.com//store/comer ... duct=22838
The correct dynamo chain is endless, i.e. it doesn't have a joining link.

I don't know of any supplier of a dual sprocket that would suit your needs. As ajscomboman said, they are made to the factory specifications.

I assume that by positioning the engine drive sprocket 1mm further 'outward' it will inevitably be out of alignment with the clutch basket sprocket unless you reduce the thickness of the spacer on the drive axle, but that would bring the dynamo sprocket closer to the inner part of the chaincase. If you don't reduce the width of the spacer the pre-load on the shock absorber spring will also increase.
You haven't said the year of your model 18S in your post or on your Profile but the spacer is probably part number: 010629

https://www.amoc-parts.com//store/comer ... duct=20916

Drive assembly. Dynamo..JPG
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nortom
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Re: Dynamo chain

Post by nortom »

Hello!

Oh yes... it's a '52 18S with G80S engine, Burman GB gearbox and early CP clutch. I ordered parts from the (excellent!) club shop yesterday. Also a new engine sprocket. I'm going to use the old engine sprocket to experiment and get a new 3/8"x7/32" dynamo sprocket. And then, of course, everything has to be distanced again. I know it's very tight in the primary chaincase, but I want to try it.

Greetings Thomas
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clive
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Re: Dynamo chain

Post by clive »

Welcome Thomas it is much more likely that the chains clashed because the dynamo was not correctly set across. Originally the dynamo body had a spacing bar attached to it. This ensured the correct spacing ( once set up correctly) but made it difficult to ease the dynamo out without removing the whole primary side. As a consequence many have been removed. If yours does not have the spacer i would concentrate on making that. It will be a lot less trouble and should sort the issue of chains clashing. Basically provided they have the correct clearance and tension the chains will tend to flex up and down not side to side. The spacer is part number 010962 and is illustrated by photo in club spares.
The other possible cause of clashing is too much slack in the primary or dynamo chain. When adjusting the dynamo chain the action of tightening the clamp changes the tension and it is important to check it afterwards. I usually have to have a couple or more goes to get it right.
clive
if it ain't broke don't fix
nortom
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Re: Dynamo chain

Post by nortom »

OK. I'll take a closer look at that. Thanks for all the tips, guys!

Greetings Thomas
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