This is an interesting machine....Purchased from a chap who used to work in the BSA development shop and who apparently managed to 'spirit it away' when official interest in the project faded.

Reportedly built in the early '50s for potential trials/scrambles use...Note the monoshock rear suspension(cantilever to use the correct period term)..

To me it has the look of a trials machine more than a scrambler...Ian

email (option): ian@wright52.plus.com

I'd say trials, it looks like a Montessa Cota prototype the way the tank and side panels merge into one.
Interesting though, any more pics?
Alwyn

What engine is this ?
Not B31

It's either a ZB32A, the 'A' denoting the aluminium top end, or a ZB32 Gold Star (if it's a 350) or a '34' if it's a 500.

The difference between the two engine types is basically the state of tune, with the Goldie producing more power...Ian

email (option): ian@wright52.plus.com

That is no doubt an interesting mounting of the gearbox! Kinda confused what oil level would be appropriate ;D

/s

Quite, I think the tilting of the gearbox was probably done to allow a shortening of the wheelbase (indicating a more likely trials use).

The oil pick up from the crank case would need to be relocated as well I would think, along with the oil drain from the cylinder head...Unfortunately I don't have any more details of the machine...It appears on display periodically at the 'bonanza' scramble and similar events...I'll be keeping a look out for it...Ian

email (option): ian@wright52.plus.com

With the mainshaft at the bottom, oil leakage through the sleeve gear is likely to be a problem - but at least it will continue to throw oil round the cluster if there is any in there at all...unlike the oddly positioned M20 box.

Hi Ian
I would have thought scrambler myself.
Front mudguard mounted high, exhaust low (trials would bash the pipe)
And don't forget that scrambling was not the motor cross we see today.

Up here in Wigan it's all motocross and I have done my fair share, but am now getting into trials ( c15 trials on the bench now ) and a scrambler like this in the fifties would have been something new.
Very interesting bike that
Darren

Valid observations Darren...You may well be right...

I always find it interesting to look at these 'factory' type bikes, they frequently show that thinking on the shop floor was ahead of that in the boardroom and it's surprising how advanced some of the features look for the time..

I always think of Bert Hopwoods 'modular' range..Some of those designs had a single sided swinging arm in 1971/2...When were they finally introduced to the motorcycling world on a bike you could buy?...Maybe 15-20 years later?

In that vein I recently got a look at the only prototype engine actually built as a result of the 'modular' concept, the 250cc single built to test some of the 'modular' parts...This was the last time a British motorcycle designer came up with a modern 'whole range' concept that would have been a production engineers dream, and all at a time when BSA could still afford to do it. Sadly though, it was not to be....Ian

email (option): ian@wright52.plus.com

Yes, interesting! regarding position of the gearbox: Think it will work very well in this position as I believe the M-type gearbox is basically a lay-down version of the vertical placed Sloper ones.

The Slopers and several other models had this same vertical position of the gearbox with the mainshaft above the layshaft and the selectorshaft at the rear. With its layshaft and bronze bushes fully in oil and the large bearing for the sleeve gear way above the oil-level. No leakage through the large bearing at standstill in this position!

email (option): m.wijbenga@hotmail.com