Hi, can anyone tell me where to look (maybe in the members area?) for a factory drawing of the B31 rigid frame? Preferably up to 1948 XB31 or YB31.
I'd like to check the subframe I have for straightness so mainly need to know the offset from the centreline on either side to the rear wheel mounting plates.
Thanks in anticipation,
Rupert.
I've never come across a document showing the dimensions for an XB31 frame. The VMCC Library may be able to help.
Found this on a NewZealand site...
I have a B31 rigid too so its interesting to see. I hope it helps
Pete
There is a service sheet (710X) with various frame dimensions .... in the members area ... https://www.bsaownersclub.co.uk/member/get-serv/710X (once you've logged in!)
I think the B range rigid frames were all the same, the 1946-48 years having different engine plates to accommodate the narower gearbox lugs. As mentioned, service sheet 710X
Thanks to you all for the replies, much appreciated.
The diagram in service sheet 710x looks the same as the diagram in Pete Gill's reply. Due to the detail in the gearbox area I'm thinking they both show a ZB31 rigid frame rather than XB or YB?
I'm guessing as Pete C says that the rear wheel set up would be the same for all rigid B31's, in which case the dimensions given in these diagrams will do fine for me to check my subframe.
As such, mission accomplished and thanks again for the replies.
Rupert.
Quote from: Pete C on 24 Dec, 2022, 17:31
I think the B range rigid frames were all the same, the 1946-48 years having different engine plates to accommodate the narower gearbox lugs. As mentioned, service sheet 710X
As well as the engine plates, the rear stays are also different from the 1949 models as the rear wheel fitments differ and the later hub won't fit the previous years.
Hi Derek, so as usual, things BSA are not as simple as they first seem!
In view of the subframe differences you mention between pre and post '48 versions, any idea if the offset from the centre line to the wheel mounting plates is different? That's the critical info I'm after to check if my entire subframe and back wheel has been nudged over one way or another.
Quote from: Rupert on 27 Dec, 2022, 11:44
Hi Derek, so as usual, things BSA are not as simple as they first seem!
In view of the subframe differences you mention between pre and post '48 versions, any idea if the offset from the centre line to the wheel mounting plates is different? That's the critical info I'm after to check if my entire subframe and back wheel has been nudged over one way or another.
I'm afraid not. I have a 1948 B32 Competition with the early, gearbox, rear subframe, engine plates and rear wheel. To measure any offset I'd need to take the rear wheel out, not a great job at the best of times but right now it's around freezing out in the garage. If I can come up with any useful measurements I'll let you know.
Rupert, a quick measurement with the wheel in the bike is all I can manage at the moment. Distance between the wheel mounting plates is approx. 165mm (6/12") and the distance from the LH wheel plate to the centre line of the chain is approx. 25mm (1"). These are only approximate and could be a few mm either way.
Hi Derek, thanks for taking the trouble to do some measuring.
Time for me to go have a look at what I've got, see if it corresponds with the frame diagram or your measurements.