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Rev counter take off
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Sat Nov 18, 2017 4:04 pm    Post subject: Rev counter take off Reply with quote

Hi all,

I'm sure that I have posted this question before so forgive me if I have.

I am almost finished with my Aero Minx Streamlined restoration and almost forget that I never did solve the rev counter take off problem.

I have a C39 or equivalent dynamo with a threaded rev counter take off at the rear end, I also have a 2-1 Smiths rev counter R-R 8 423.



If my crankshaft and dynamo pulleys are the same diameter I can assume that the ratio is to that point 1:1. As the rev counter is marked 2-1 can I therefore assume that I need a reduction gear at the dynamo ?

Really not sure about this

Many thanks,

Tim
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Penman



Joined: 23 Nov 2007
Posts: 4750
Location: Swindon, Wilts.

PostPosted: Sat Nov 18, 2017 4:56 pm    Post subject: Reply with quote

Hi
Is the picture the back of the Dynamo?
I ask because the take off does not appear to be in-line with the spindle, in which case you need to know if there is a gearing difference in there.
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Sun Nov 19, 2017 1:04 am    Post subject: Reply with quote

Hi,

No it is the back of the rev counter, the square pin will centre when the correct cable fitting is screwed on
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alastairq



Joined: 14 Oct 2016
Posts: 1950
Location: East Yorkshire

PostPosted: Sun Nov 19, 2017 12:58 pm    Post subject: Reply with quote

I think what penman meant is, the whole take-off drive is not in line with the dynamo shaft? Rather, it is offset, indicating there may be gearing inside?
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Sun Nov 19, 2017 6:36 pm    Post subject: Reply with quote

Yes, of course, I misunderstood
As I said though the gauge is marked 2-1
What I would like to know is, am I correct in thinking that if the output from the dynamo is 1-1 due to the crank and dynamo pulleys being the same diameter, then I simply need a direct drive cable between dynamo and gauge ?
I can of course simply experiment but would rather not have to buy more than one cable.
Many thanks
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Sun Nov 19, 2017 11:20 pm    Post subject: Reply with quote

Take advice from http://www.speedograph-richfield.com/html/minature_gearbox.html

Peter
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Mon Nov 20, 2017 8:17 pm    Post subject: Reply with quote

Thanks Peter, I have dropped them a line for advice and await a response.
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MVPeters



Joined: 28 Aug 2008
Posts: 822
Location: Northern MA, USA

PostPosted: Mon Nov 20, 2017 11:25 pm    Post subject: Reply with quote

Could you stick a plastic straw, maybe bent to a right-angle to give you a pointer, into the gearbox end?
Then turn the dynamo - you could probably tell if it's 1:1 or 1:2 or something else.
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