Author Topic: B21 Speedometer  (Read 266 times)

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B21 Speedometer
« on: 21 May, 2019, 21:13:10 »
Hi, I'm very new to the forum and BSAs, having recently acquired a '39 B21.    I'm sure there will be many questions but to kick off;

It suddenly struck me after a good "look-at" that there is no speedo on the bike - I'd been hoping for a lovely Smiths Chronometric which I happen to think is an amazing instrument.   More importantly, I also noticed that there appears to be no speedo drive gearbox fitted to either wheel.

1) Is it likely that the bike did not have initially / has never had a speedo? (I don't know when it became a legal requirement to have a speedo)

2) Is there a cunning speedo drive output from the final stage of the gear box lurking somewhere?

3) If there is no provision for a speedo drive originally, is it possible to fit one and is it easy to do?

Otherwise I'll have to go down the route of crafting or purchasing an electonic replica.

Thanks in anticipation.

Alan


BEVANC

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Re: B21 Speedometer
« Reply #1 on: 21 May, 2019, 21:32:12 »
Hi Alan,
I'm no expert on B21s, but a quick Google search shows a number of 1939's with a speedo drive off the front hub.
See attached example.
Cheers,
Bevan

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Re: B21 Speedometer
« Reply #2 on: 22 May, 2019, 22:19:27 »
Thanks Bevan,

Ah, so this is looking like a likely mounting location then.     

I'll have to investigate further.

Alan

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Re: B21 Speedometer
« Reply #3 on: 27 May, 2019, 13:57:59 »
So what lies behind the mesh?  Is there a gear to drive the speedo?

Doesn't look like it.  All I can see is the bearing housing (presumably), a brake shoe and a brake shoe spring.

Any ideas as to how or where the drive is or should be?

Alan




Gustafsson

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Re: B21 Speedometer
« Reply #4 on: 28 May, 2019, 13:37:33 »
You have the wrong hub

JulianS

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Re: B21 Speedometer
« Reply #5 on: 28 May, 2019, 14:54:29 »
Not the best copies but below from the 1939 parts book.

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Re: B21 Speedometer
« Reply #6 on: 28 May, 2019, 22:28:51 »
Ah, thanks for the information chaps.  So, likely to be the wrong hub and the wrong wheel (no gear).

Now, where to find the right bits and, oh yes, a nice chronometric to go with them that doesn't cost a small fortune?

Alan