Definately a conversation piece. But it appears to rely on an external power supply, stretching the definition of 'motorcycle' a bit for my book . . .
Along with chain- shaft- and belt drive I can add rod drive as a new variation to the list though. Probably not a fast ride, but torque is tunable with a twist of the pressure valve, and should increase linearly until the cylinders blow!
It appears the 'boiler' has never been fired, or fitted with a shell. Just as clearly, the front downtubes were routed forward and down to clear the boiler assembly. I'm guessing a modest water tank would fit behind the seat, between the cylinders. Or maybe that would be the fuel tank, and a water tank would fit where a normal motorcycle fuel tank goes.
The bike is resting on blocks where a centerstand would be, and the rear wheel is slightly off the ground for what is clearly an engine test with an external steam supply. I think I see 'motion blur' on the rear wheel spokes and a little exhaust steam behind the rear wheel, suggesting that the first two pictures (duplicates?) were taken with the engine running.
Solid forensic engineering there Mike. I foolishly hadn't considered the snapshot was from development work. Wonder if she ever flew, and what was the intended on-board fuel source?
On a (distantly) related note, I spotted a beutiful tin-lizzie coming up behind me on the road one Sunday last year, obviously on the way to one of the many local drive-in car shows popular around here. Problem was he was throwing so much white 'smoke' I expected he wouldn't make his destination. He pulled up behind me at the light and all was made clear when I decifered "yelnatS" on his radiatorless bonnet in my rear-view mirror. Tickled me to find the old puffers are still roadable!
A steam powered bike was designed and built in 2005/6 as a the result of a challenge in UK. It was ridden round a fairground "wall of death" at a steam rally in Cornwall in 2006. It did a dozen or so laps of the wall. One design requirement was that it dropped no oil/water whilst on the wall, for safety reasons. I believe £1000 was won as a result!