Gearbox ID

[Peter in Aus]

Hi, can anyone ID this gearbox?  It has an “R” stamped on it where the “STD” is usually stamped; it is a bolt on box so must be off an A Ser. Plunger.
The bit that is puzzling me is it had swinging arm main shaft with the tapper and key way for the clutch spigot. At least I think these were fitted only to the swinging arm models?
There is some other markings on the large mounting bracket, bit hard to read but it looks like “2/OB”
I obtained this box along with another box and some other bits so don’t know what they are off or history.
Peter

[Peter in Aus]

Looks like I"v asked a bum question?

[duTch]

 Dunno Pete- I'm not sure that Plunger cases were stamped in general- if I remember tomorrow, I'll have a look at the ones I have....I think an 'R' usually refers to needle rollers in either the layshaft or the sleeve gear or both, but they are (generally) only in Swing Arm models...sooo um

[Peter in Aus]

Thanks Dutch for the reply, I'm beginning to think it has had a very checked past.

[muskrat]

G'day Peter.
Both my gearboxes (plunger & s/s) are stamped std. The mainshafts are interchangeable so they may have fitted a 4 spring clutch to a plunger 
I think R meant needle rollers on the layshaft and RRT2 was needle rollers on both shafts. I may be wrong (I'm sure someone will delight in putting me right).
Cheers

[Greybeard]

I just had a look at my box. I cannot see anything on the clutch lever area, (your second picture). On the front of the top mounting, there is a B with 20 under that.

[morris]

The mainshafts are interchangeable so they may have fitted a 4 spring clutch to a plunger 

The 4 spring clutch sprocket is to big for the plunger case.

[chaterlea25]

Hi All,
R, RR, SC. TRI, ASC and so on indicate the gear ratios fitted

T (for Torrington) indicates needle roler bearing layshaft. T2 indicates that a needle roller bearing is also fitted to the mainshaft high speed gear

Peter,
Probably someone wanted the splined shaft  so they could fit a Norton clutch to a swing arm gearbox
Then fitted the S/A shaft in the plunger box and flogged it on
(I have seen this happen )

John

[duTch]

 

Probably someone wanted the splined shaft  so they could fit a Norton clutch to a swing arm gearbox
Then fitted the S/A shaft in the plunger box and flogged it on
(I have seen this happen )

 I nearly did that,  but it was going tho be more than I could cope with at the time so standard insanity prevailed...

 I had a look at the four unused cases I have and three have what looks like variations of 'B 2 0' on the to rear lug, and the fourth has '55' on the inner (biscuit) case and a stamp (V98)? on the outer,  keeping in mind they are all mix-ups of early flat spring outers and
composites of other bits and pieces-except for one (kinda)

[a]

No Doubt you and everyone else already knows of this chart outlining the normal stamping and gears etc.
https://mikesclassiccyclespares.com/bsagearchart/ But that is for the Swing Arm style box
The plunger/Rigid did not use these markings, as discussed in this earlier post
https://www.a7a10.net/forum/index.php?topic=6018.0
we have 5 plungers/rigids here all with a different markings on the "Sandwich" plate....

[BSA_54A10]

No Doubt you and everyone else already knows of this chart outlining the normal stamping and gears etc.
https://mikesclassiccyclespares.com/bsagearchart/ But that is for the Swing Arm style box
The plunger/Rigid did not use these markings, as discussed in this earlier post
https://www.a7a10.net/forum/index.php?topic=6018.0
we have 5 plungers/rigids here all with a different markings on the "Sandwich" plate....

So whiles dad is away you get to scythe off and play on the computer eh.

And nice job on the new web page.

[Peter in Aus]

Thanks all for your input. It is quite apparent that the box in question is not as it came out of the factory, by a long shot.
It has the standard gears B 17 tooth D 23 tooth F 19 tooth and H 27 tooth. The gears are in good condition so will change the main shaft to a spline one and build it up for a spare box for the A7/10 plungers.
And thanks Mike for those links very helpful.
Peter