As Will says, the twin wheel version is in the national motorcycle museum with the engine in line with the bike

The twin rear wheel arrangement was used by GB so that he could use the standard Austin 7 gearbox & diff, which came out on the gearbox centerline. The twin wheel arrangement did away with the need to offset the gearbox output shaft (the diff is between the rear wheels) and, as the bike was intended to be used for sidecar work, was obviously not deemed to be a disadvantage.

A pretty amazing survival rate for those particular Broughs - of the 10 built, there are 9 still in existance (Wikipedia is my friend here !).

Nigel B.