Ollie
Member
Hey guys, I have an idea for an ultra-lightweight 3-speed bike that will technically be a motorcycle, but here in Brazil will still be in the motorized bicycle category as it's engine will be smaller than 50cc. I wonder if you can see any major errors with my idea or if you can think of any improvements?
I've been trying to work out a way to get gears that work directly with the engine on the left-hand side of the bike to avoid using a jack-shaft or SBP shift kit (weight-saving). I discovered that Sturmey Archer has a fixed 3-speed hub (the S3X) which I reckon I could flip over so that the engine drives the hub directly and can make use of the gears. There would be no need for a freewheel pedal chain or chainrings (more weight-saving) and I intend to bolt a different sprocket to the existing one to get the gear range right. Because the gear hub is fixed, it should be able to run in reverse, although I'd put a few spot-welds on the cog and lock-ring to stop it undoing itself.
I intend to use the Hua Sheng 49cc 4-stroke engine that is sold here as it's got a pull-start and won't need to be jump-started by pedalling like my 2-stroke. I'll stick all this onto a steel frame & forks with V-brakes and the fattest tyres that will fit. What results should be a very light 3-speed motorcycle that looks like a bicycle (cops don't stop me at road checkpoints on my motorized bicycle) and has low gears to get up some of the steep hills around here.
Any thoughts, suggestions or apparent flaws?
Ollie
I've been trying to work out a way to get gears that work directly with the engine on the left-hand side of the bike to avoid using a jack-shaft or SBP shift kit (weight-saving). I discovered that Sturmey Archer has a fixed 3-speed hub (the S3X) which I reckon I could flip over so that the engine drives the hub directly and can make use of the gears. There would be no need for a freewheel pedal chain or chainrings (more weight-saving) and I intend to bolt a different sprocket to the existing one to get the gear range right. Because the gear hub is fixed, it should be able to run in reverse, although I'd put a few spot-welds on the cog and lock-ring to stop it undoing itself.
I intend to use the Hua Sheng 49cc 4-stroke engine that is sold here as it's got a pull-start and won't need to be jump-started by pedalling like my 2-stroke. I'll stick all this onto a steel frame & forks with V-brakes and the fattest tyres that will fit. What results should be a very light 3-speed motorcycle that looks like a bicycle (cops don't stop me at road checkpoints on my motorized bicycle) and has low gears to get up some of the steep hills around here.
Any thoughts, suggestions or apparent flaws?
Ollie