Has anyone ever manufactured a motorbike with derailleur gears?
They'd be cheaper to manufacture than a conventional gear box and you wouldn't need a clutch.
You could also have a freely rotating sprocket for a neutral gear.
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Used to be m/cycles with Sturmey Archers.
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I'm sure I've seen these gears on those mopeds in France - long-ish time ago though. They definitely had the characterisitc hanger below the rear hub.
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Two main problems. The rear sprocket width and the major fact that you would have to have a free wheel or when you backed off the throttle the chain return would tension and snap the derailleur and wrap the chain around the rear sprocket and frame. I can see the rider flying through the air as I type.
I hope that thought of yours did not keep you awake last night. !!
Regards Peter
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Further quick thoughts, negative I regret! There would be a major problem with transmitting any large amount of power through a derailleur and there would be a problem with the variation in the chain alignment. A chain capable of transmitting high power would not be happy if the drive and driven sprockets were out of alignment.
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Yes, can't see it working with motorbik levels of power.
On the other hand a planetary gearbox like a sturmey archer should be fine; you'd lose a bit of power due to frictional losses, but most motorbikes have so much power they don't know what to do with it anyway.
No problem putting high power throguh planetray boxes, that's why they are used in buses.
They have the great advantage that you don't need a clutch, because all the gear changes are done using band brakes on the different gear cages.
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Quote: "No problem putting high power throguh planetray boxes, that's why they are used in buses."
But not so much in heavy lorries, which tend to be more powerful than buses. Automaitic gearboxes are mostly planetary and buses tend to have auto boxes to make driving easier in city traffic and because engines are usually at the back these days and a mechanical gear linkage would be difficult although not impossible (Some rear-engined coaches have manual gearboxes)
However, deraileur gears give enough trouble on pushbikes so imagine the problems on a motorbike!
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If gyou had petrol-electric drive on a motorbike (engine drives generator, wheels powered by electric motor) it would be easier to argange for a 2-wheel drive bike. It would probably be less efficient than manual but could be mildly hybidised with a small battery pack - oops - I think I'm talking about something that will end up heavier than a Harley-Davisdon!!!
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How does it scale? Human on pushbike ?? be generous quarter of a horsepower? Bike at 150HP. So, whats that, 600 times the power?.
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'I'm sure I've seen these gears on those mopeds in France - long-ish time ago though. They definitely had the characterisitc hanger below the rear hub.'
I think you'll find that was just the tensioner. I recall old Raleigh mopeds had the same but on just the pedal-powered chain side. The other side had a larger chain transmitting the engine power.
'Human on pushbike ?? be generous quarter of a horsepower?'
I think you'll find a fit athlete can generate approaching one HP in short bursts, and maintain three quarters of that for considerable time.
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Maybe what you saw in France was an ordinary 'push-bike' which had one of these 'bolt-on' 49cc two-stroke powe-packs, with a friction drive on the tyre?
Usually mounted on the rear carrier... they had a brief period of popularity ...late 50s, maybe? (Especially in France, I think!)
They were followed, IIRC, by the Velo-Solex, one of the first 'mopeds'.
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Maybe what you saw in France was an ordinary 'push-bike' which had one of these 'bolt-on' 49cc two-stroke powe-packs,
Yes, could well have been - mind you my memory could have been moderated by, IIRC, M.Pinot et M. Grigiot.
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