Dynamo screws

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Dynamo screws

Postby matchbart » Tue Jun 12, 2018 11:09 am

Could anyone tell me what size the screws are that fit the end of a Lucas dynamo, they hold on a triangular shaped plate (with rounded corners) on the end of the dynamo between it and the inner primary, there are three and countersunk, they look as if they may be 1 or 2 ba ? thanks

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Re: Dynamo screws

Postby Mick D » Tue Jun 12, 2018 12:43 pm

Hi

Thread dimensions here if you have the means to measure the thread:

https://britishfasteners.com/threads/

1BA is rather an uncommon size whereas 2BA is very common.

This chap is very helpful if you need replacements:

http://www.ba-bolts.co.uk/index.html

Regards Mick

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Re: Dynamo screws

Postby Groily » Tue Jun 12, 2018 3:26 pm

They are 5BA for the bearing retainer plate, or should be if original Matchbart.

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Re: Dynamo screws

Postby matchbart » Tue Jun 12, 2018 3:58 pm

Thanks everyone, 5ba ? that`s tiny isnt`t it ?

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Re: Dynamo screws

Postby Mick D » Tue Jun 12, 2018 4:03 pm

Hi

5BA has a thread diameter of about 1/8"

Regards Mick

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Re: Dynamo screws

Postby matchbart » Tue Jun 12, 2018 7:01 pm

apparently i don`t have a matchless dynamo fitted, so until i get it off and inspect properly i can`t really check the size, many thanks for your help anyway..

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Re: Dynamo screws

Postby Groily » Tue Jun 12, 2018 9:10 pm

Pretty small yup.
There are those with a 2BA (much fatter) draw stud also in the same area (dynamos for our twins, or dynamos fitted to magdynamos for example) but the screws that hold the retainer plate for the drive end bearing on Lucas 3" dynamos should be 5BA as standard.
Unlikely for there to be other than a Lucas dynamo on there I'd have thought. Might not be the exact model as per catalogue, but the variants that will go on a Matchie single are all much the same at the drive end.
An idle query - but do you know you're missing some screws Matchbart? Or do you just want to have everything to hand in case you find you are when you get things apart? (These screws are usually present, although the threads in the alloy end of the dynamo are sometimes a bit knackered. More typically absent are the very specific fixings to ensure the sprocket stays on and can't fall off in the primary chaincase . . .)

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Re: Dynamo screws

Postby matchbart » Wed Jun 13, 2018 7:46 am

there is only one screw left in and its doing its best to escape, i am doing the Beamish Reliability run on sunday and don`t have time to strip and repair before then, so for now it`s bodged and wedged to hold in place,,, it might last it might not, i did 160 miles at the weekend and it was loose for the last 100, fingers crossed, also, i think your right about the alloy /threads being knackered, they may need re tapping , ta

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Re: Dynamo screws

Postby Groily » Wed Jun 13, 2018 9:05 am

Aah! It can happen ... esp if the female threads are mullered. 5BA insert kits are hard to get I think - but you could go out to 4BA (or a close equiv in metric might be easier) and solve it that way, there's enough monkey metal there.

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Re: Dynamo screws

Postby 56G80S » Wed Jun 13, 2018 2:46 pm

Where are you in the North East I have BA taps and dies, can't recall the sizes but will take a look.

I did the Beamish a couple of times years ago and it was a load of fun. Does it still stop at Allenheads?

Johnny B

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