MatthewMore
New Member
um. ok. youre right.
Geared motorized bicycle... on the left side?
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FurryOnTheInside
In Memoriam
From recent threads it seems Grubee make a both side drive hub mainly I suppose for the 4-strokes.
If you have a pull start and the wide cranks that pull start requires, and you buy their opposite thread left side freewheel and sprockets then you're all set.
Just have to make a way to change gears and keep good tension then.
(I think it would be easier with the freewheeling sprocket, but I don't personally want to have to use a pull start, so I'll have to try a fixed sprocket system.)
If you have a pull start and the wide cranks that pull start requires, and you buy their opposite thread left side freewheel and sprockets then you're all set.
Just have to make a way to change gears and keep good tension then.
(I think it would be easier with the freewheeling sprocket, but I don't personally want to have to use a pull start, so I'll have to try a fixed sprocket system.)
gary55
Well-Known Member
Wouldn't all it would need is the shifter hub manufactured with a left hand free wheel? I'm using the Nuvinci and it seems that it would work if the ratchet and pawls were just reversed. Don't know if their would be enough demand to have the design change implemented, but it sure would be nice to eliminate all that extra drive train weight and resistance.
FurryOnTheInside
In Memoriam
I think IIRC someone already asked the makers of the Nuvinci to make a mirror version and was told it just isn't going to happen. It would be great though if it was to happen.
A derailleur based two (or maybe three) speed system should be easy enough if you don't mind stopping, getting off your bike, putting the kickstand down, pull starting the engine. . . .
I would certainly be very confident about the derailleur based system if it had the freewheel mounted sprockets like the Grubee HD hb apparently can have.
I'll have a go at throwing something together without it though. It's already going to be expensive (but less than the Shift Kit) even without the special hub, freewheel and sprockets imported from America.
Of course the Grubee sprockets would need to be modified a bit, made narrower and perhaps with some shift ramps and shortened teeth to mimic normal geared bike sprockets.
Frankenstein
Deceased - Frankenstein 1991 - 2018
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I'm with you on the nuvinci, the design is particularly simplified when it comes to power transfer from the sprocket to the wheel, it's a reversible design in that area. If you somehow reversed the paws it would almost definitely work, I also would think that locking the freewheel up could do it if you had a freewheel before that cog, like how the bullet train runs a one way clutch just before the drive gear, then it wouldn't need any real modification.
Other than that the options aren't great without using a jackshaft, you could probably use other internal gear hubs if the design allowed them to run in reverse but still leaves freewheel related issues to kink out.
FurryOnTheInside
In Memoriam
Not to mention reduction. You need to get the right size sprocket with the right type of mount to fit the hub.
Idk what the Nuvinci uses for sprocket mount, but I wouldn't be keen to experiment with trying to reverse the freewheel if it's built in, lol... those are expensive hubs.
Idk what the Nuvinci uses for sprocket mount, but I wouldn't be keen to experiment with trying to reverse the freewheel if it's built in, lol... those are expensive hubs.
gary55
Well-Known Member
Then once you stop to think about it not only is the reduction a really big issue but you no longer have a motor assisted bike. I mean what are the pedals doing. I'm beginning to like my j shaft more be the minute.
FurryOnTheInside
In Memoriam
Oh yeah hahaha I wasn't even thinking about that. The pedal chain would have to go to a rag joint and have its freewheel at the crank. That would really suck!
The pedal chain would have to go to a rag joint and have its freewheel at the crank. That would really suck!
Frankenstein
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If you are daring you can do the flintstones thing and run around to start it should you decide to omit the freewheel you could shift with the right hand and use a thumb throttle... Using brakes might be hard...
If other internals could handle pushing an underspeed engine without demolishing and used a thumb shift it may work better..
Reduction is subjective, use a 9t drive and a mid sized gear and don't forget a nuvinci swings 180% both directions, a 28 cog is like having everything from a whopping 50 tooth down to a 15, you can get slightly larger single cogs that fit BMX style bikes and other fixed hubs, just get one that covers what you need. 9t on a 50 is similar to a 10t drive to a 55 rear, pretty good for pulling out though you'd probably never use the highest gear ratio.
Anyway as far as cranks go you can always left hand side the sprocket and maybe freewheel the connection there but that's no better than a jackshaft, at least you can buy a ready made kit lol
gary55
Well-Known Member
With the resources and creativity it could be surely done. I'm not up to the adventure. As for the gearing the minimal approved under electric power is a 33 chaining ring with a 16 cog. With pedal power you can pair the 16 to a 30. At no point is the drive gear to be less than1.8 of the cog. It's range is not equal in both directions .5 underdrive to 1.8 overdrive.
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