A scan of the brochure for the Villiers two speed gear. Not a derailleur system as it is essentially a chain gearbox. An interesting dead-end in bicycle gear design. Puzzlingly complicated to fathom and rather heavy the Villiers two speed was a product of the thirties, though when production was started and ceased exactly I am not sure.
So... There are four gears, two upper (firmly attached) and two lower (free to rotate independently of one another). The inner gears carry the main chain. The outer gears carry the short secondary chain. In low gear, the upper inner gear drives the wheel. This of course turns its attached upper outer twin and thus the short chain, but these aren't connected to the inner lower gear riding on the main chain, so they play no roll. The key is that pulling the control cable pushes plungers into the lower gears, locking them together. The inner lower gear, turning with the main chain, is now firmly connected to the outer lower gear, which now powers the short chain. The short chain carries this power to the outer upper gear, which now overpowers its inner twin and drives the wheel. Why doesn't this jam as, in effect, two sprockets of different sizes, both carrying chain, are trying to drive the same wheel? Because the secondary chain and outer gears are producing a taller gearing. The original gearing being activated by the inner upper sprocket alone now just freewheels as it would on an ordinary bike that is rolling downhill faster than the rider can pump.
ReplyDeleteIt is baffling isn't it! Apparently the model of simplicity but also devilishly complicated at the same time. I would love to find a cycle with this gearset fitted and purchase it just so I could get to fathom how the damned thing works!
DeleteI found one, just the three parts. Then built a wheel for it to fit in. Never got round to putting in a bike. Works in a static frame.
DeleteI've got a new old stock set but never got round to fitting it. Is the freewheel like a standard one but with two sprockets or do the sprockets rotate independently of each other?
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