The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Superflash on 23.01. 2021 04:57

Title: Dynamo chain
Post by: Superflash on 23.01. 2021 04:57

So....went to put the dynamo chain on and it looks to be an inch or 2 too short. Question is.. are there different chain lengths or have I missed a trick somewhere? Cheers

Title: Re: Dynamo chain
Post by: Slymo on 23.01. 2021 05:44

Looks like a big sprocket on the generator side maybe?

Title: Re: Dynamo chain
Post by: RichardL on 23.01. 2021 05:47

Appently, you have the chain for the 11 tooth dynamo sproket , while yours is 13.

Richard L.

Title: Re: Dynamo chain
Post by: Superflash on 23.01. 2021 06:13

Thanks for the info. I see Mike's classics has a 52 link chain. Mine is 48 and with the 13 tooth dyno sprocket me thinks that be the problem.  Is there any reason why I can't use the 13 tooth sprocket? Cheers

Title: Re: Dynamo chain
Post by: RoyC on 23.01. 2021 08:26

Quote from: Superflash on 23.01. 2021 06:13

  Is there any reason why I can't use the 13 tooth sprocket? Cheers

Just means that your dynamo will run a little slower.

Title: Re: Dynamo chain
Post by: Swarfcut on 23.01. 2021 09:03

 Other possible is that the chain is the shorter A7 Longstroke type, in combination with the wrong dynamo sprocket.

 Swarfy.

Title: Re: Dynamo chain
Post by: Rookie_V#60 on 23.01. 2021 09:38

Quote from: RoyC on 23.01. 2021 08:26

Quote from: Superflash on 23.01. 2021 06:13

  Is there any reason why I can't use the 13 tooth sprocket? Cheers

Just means that your dynamo will run a little slower.

Ok will be 18 % slower, I don't think you can neglect that.

Title: Re: Dynamo chain
Post by: Superflash on 23.01. 2021 10:01

Thanks guys. Pretty much just as I thought. So have tracked down an 11 tooth sprocket and a 52 link chain. Hey I see Mike from Mike's classics has got the business up for sale.....  *eek*

Title: Re: Dynamo chain
Post by: trevinoz on 23.01. 2021 21:07

Have you got a long generator or a short?

Title: Re: Dynamo chain
Post by: Superflash on 24.01. 2021 03:16

It's 190mm. Imagine my surprise to find out there are long ones and short ones.  Then again why not..... *problem* nothing else is standard or simple with these bloody things.

Title: Re: Dynamo chain
Post by: trevinoz on 24.01. 2021 20:22

Different type for different years.
The short 45W generator was used until 1948 or 49 and superseded by the long 60W generator.
Short has one pole screw and long two.
Short uses 13 tooth sprocket and long uses 11 with obviously different chains.

Title: Re: Dynamo chain
Post by: tore on 17.10. 2021 15:46

Information about type of BSA A7 dynamo chain:

You can find it with Renold number 110500 or ISO number 05B-1 (Pitch 8mm,  Inside Width 3mm).

There is also spring link (26) available for the chain. I have obtained spring link (110500/26 or 05B-1/26) and used it when installing the dynamo chain. It make dynamo installation much easier.

It also make possible to obtain 52 link dynamo chain and shorten it to long stroke (48 link) use.