Hi
That is one 'beautiful' bike - anyone know the story or anything about it? When I saved the picture it defaulted to 'Goodwood' as a file name.
Cheers
Andy 
email (option): a.tizzard@btopenworld.com
The website picture is one of the 50 pre production prototypes of the WB30, developed from the 1940 B29 Silver Sports......These were extensively lightened to reach the target weight of 288 lbs....
Even the frame and fork lugs were lightened before the frame was brazed up, the brake plates and engine plates were lightened and the engine internals were also reduced in weight...
Interestingly they were the only BSA fitted with hairpin valve springs though these had reverted to standard springs by the time production batches were built...
Front and rear brakes were both 5", the mudguards were shortened and the rear one was an 'abbreviated' pressing to reduce its weight further...
The alternator lighting system was a further effort to reduce weight though this extremely early version proved to be unreliable and some of these first bikes were retro fitted with a standard magdyno electrical system at a later date..Only alternator equipped versions used the bulb horn and to date no example of the alternator appears to have survived...(or the small headlamp particular to this version)
Although quite an achievement to build a bike to such a low weight at the time it appears they may not have been robust enough as later versions were considerably strengthened...
It is pretty certain that the bike would have been seriously under braked as well...Later versions had 7" brakes front and rear...
Towards the end of the war the model was 'rejigged' again with an updated gearbox, tele forks and other changes and became the B31..
The first two photos Ron has posted are 'last contract' bikes from a batch of 100 bikes built for the Royal Navy, The last picture is the earlier type...
Only around 200 bikes were built in total and there are 8 known examples remaining, not all of which are complete so it is a pretty rare machine.....Ian
email (option): ian@wright52.plus.com
Hi All
Thank you very much for such a comprehensive series of replies - as I said, and rightly so, a beautiful bike!
Cheers all round!
Andy
email (option): a.tizzard@btopenworld.com
It's a prototype...and although clearly based on the B29 it is very different...
After some research I believe this may have been a B29 based prototype of a model intended to replace the M24 Gold Star or was a works trials prototype. It was then used as a basis for the WB30...
BSA produced 12 sets of head and cylinder castings in aluminium of the B29/30 type..This bike has those fitted...It also has the magnesium/electron crankcases and alloy rims as well as other mods to lighten the bike....
To me it seems highly unlikely that BSA would have considered magnesium/electron as a possible material for use in the mass manufacture of the crankcases of a military bike...This was a pretty exotic material at the time...
Likewise aluminium head and barrel castings were not in general use at the time on motorcycle engines...They were generally restricted to competition and 'top of the range' models...
This is confirmed by the fact that even the 'lightweight' WB30 pre production models had these materials replace with more 'conventional' ones considered more suitable for mass production.
The bike is very much a prototype with an odd mixture of parts and finishes..
Post war BSA used the engine (with the alloy top end) to develop the ZB32 Gold Star which was introduced in 1949...
Photographs exist prior to 49 showing one of the 'works' bikes at a trial with Bert Perrigo aboard (in the book BSA Competition Motorcycles) and another prototype was entered in the 1947 Manx TT with Bill Nicholson riding it (below)...I have a copy of that photo...
Note the works front hub and 'McCandless' type swinging arm conversion on this bike as well as the other special features.
One remaining set of castings is known of for the engine, currently owned by an Ex Pat in New Zealand..Ian
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email (option): ian@wright52.plus.com