The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: WozzA on 21.03. 2021 04:04

Title: Plunger gearbox Letters & Numbers
Post by: WozzA on 21.03. 2021 04:04
Today I called in to see old mate that sold me his dads '51 GF plunger,... for a coffee & a chat ...
Came away with a plunger gearbox & outer cover, a rocker cover & a stuffed inner timing cover.. for FREE  *smile*
The gearbox has a small capital letter L & numbers 20B stamped into it...     any ideas what the L stands for?
Title: Re: Plunger gearbox Letters & Numbers
Post by: Superflash on 21.03. 2021 05:22
So the 51 plunger GF cost you a coffee and a chat??? SCORE.. all the new bits double SCORE..   *clap* . Suffice to say I have no idea what the markings are.  *conf*
Title: Re: Plunger gearbox Letters & Numbers
Post by: WozzA on 21.03. 2021 06:49
Guess I didn't word that too well did I..   Dohhh *eek*
Bike cost $1K   ... parts Free...  coffee & chat free... 
Title: Re: Plunger gearbox Letters & Numbers
Post by: Greybeard on 21.03. 2021 09:12
So the 51 plunger GF cost you a coffee and a chat??? SCORE.. all the new bits double SCORE..
Damn, I was going to make the same comment 😜
Title: Re: Plunger gearbox Letters & Numbers
Post by: BSA_54A10 on 22.03. 2021 02:21
They are production identification stamps.
If you ever decide to polish a set of cases you will find lots of them.
Parts were inspected using go / no go gauges and the gauge size got stamped into the part
Then there were batch numbers because BSA did not use modern "just in time" production planning.
Thus a gearbox casting could have been made anything up to 3 years before it was finally fitted to a bike.
So if for instance the 20 B was a gauge number , all of the 20 B's would go into a stillage till there was enough of them to warrant final assembly using the "B" set of shims on the "B" shafts .
Parts were mostly machined on production machinery using production workers.
The machines were phnumatically controlled so worked between stops.
The operator would take samples if it was a high volume production or check every one against a set of gauges.
They would either be tosses into stilages according to the finished size or when they got to a certain gauge the operator stopped the machine and pressed a bell alerting the tool setters to come & readjust the machine, change tools etc etc
There were no tradespeople fastidiously measuring then machining then measuring & machining as you or I would do today except in the competition shop , experimental shop rectification shop & other such departments .
BSA pioneered this method of production of motorcycles and cars starting back in 1926 with the round tank that was the first model designed to be built with fully unskilled ( well not trade qualified ) labour .
Th tradespeople made the tools and the gauges that the production workers used, not the actual motorcycles with the exception of the preproduction bikes including the trade bikes & some of the competition bikes .
Title: Re: Plunger gearbox Letters & Numbers
Post by: Greybeard on 22.03. 2021 09:37
BSA_54A10
That was very interesting. My Grandpop, (my mother's father) was a capstan lathe operator in Chatham, (Royal Navy) dockyard. He was a farm boy before this. I imagine his job must have been along the same lines that you describe.
Title: Re: Plunger gearbox Letters & Numbers
Post by: BritTwit on 23.03. 2021 23:57
Weather by design or chance, my three Super Flash gearboxes were stamped XX.
Title: Re: Plunger gearbox Letters & Numbers
Post by: BSA_54A10 on 24.03. 2021 07:34
But where was the xx stamp ?