A10 rear sprocket

[Shedman33#]

Hello Everybody, newbie here. My name is Bill and I live in Kent (the SE bit of the UK). I confess that I don’t currently own a BSA, but in the past an A7SS and several A10s passed through my hands. My favourite was the A7.

I have a conundrum concerning a rear sprocket which I know someone can solve for me (please).

I have always assumed that, with 47 teeth, it was one of the mythical A10 sidecar sprockets that I have read about in various forums. I also assumed that it came off a bike with the full width aluminium (Ariel) hub.

BUT, it has a small offset. The distance between the mounting face and the centre line of the teeth measures 7.15mm (0.28”).

The PCD of the mounting holes is 95.08mm (3.74”). (The distance between centres of 2 opposite mounting holes).

So, I have several questions;

1. Is this actually a sprocket for an Ariel?

2. What is the PCD of the studs on an A10 full width aluminium hub?

3. What is the offset of an A10 sprocket (mounting face to centreline of teeth)?

Pictures below.

Thanks for your time,
Bill

[limeyrob]

It looks too flat to fit a BSA. There's a noticeable step in the sprocket for the A10 Aerial hub.

[CheeserBeezer]

That is definitely not from an A7 or A10. Granted, the Ariel hub sprockets are a bit different, but it isn't one of those either.

[muskrat]

G'day S/man.
Yes the Ariel hub has different sprocket & nuts. DAMHIK. Best off searching foe Ariel Huntmaster bits.
Cheers

[Shedman33#]

Thanks Chaps, all good info.

But what would be really useful is if someone could tell me the PCD of the holes on a full width ali hub (aka the Ariel hub) and the sprocket offset (mounting face to centre line of teeth on an A10.
I can’t find this info on t’internet.

The other thing I’m wrestling with is that I’m sure this sprocket came off an A10. Well, 95% sure. (I’ve never owned an Ariel twin).
I remember buying the bike in about 1972 (you could get them for £100 then) and being disappointed in the performance because it had sidecar gearing. Hence I replaced the sprocket.
I still have the sprocket and in it is an A10 stub axle.
So although it was 52 years ago, I think that bit of my memory is still functional.

Ignore my chalkmarks in the picture, by the way.

I reckon that someone may have bodged it on to the bike. But in order to do that, the hole spacing must have been right. The mystery continues.

Hmm.

[limeyrob]

That spindle certainly looks A10, is it the iron full width QD hub?
Does it look like 42-6331?  That is the 42T version.

[Shedman33#]

Thanks limeyrob, but I don’t have the rest of the bike. If I could get the fixing stud positions on a full width hub from some kind bod with a ruler, I’d be able to tell if it would fit. That’s my dilemma at present.

It does look like 42-6331 except that my sprocket has much less offset. I’ve measured 7.15mm from the mounting face to the centre line of the teeth. But I can’t find what the standard offset on a BSA sprocket is.
And my sprocket has 47t, not the regulation 42.

Cheers