Discussion in 'Performance Mods' started by Proboscis, Jan 23, 2007.
1 2 3 i gots a 44 tooth and a 3 gear hub (shimano) i want to make a three speed on the left side
i've pondered that modification, wonder if anyone'll come up with something...
how about the speed, tho? how do you propose to shift without blowing the thing to shards?
I would think it would be much easier to install a jackshaft than to turn the hub over.
The process would be just like driving a (pre steering column lock) car with the clutch system out. Start in first accelerate to 10mph. push out of gear, shut off engine until rpms reach 0. Shift into second, restart engine, accelerate to 30mph. push out of gear, shut off engine until rpms reach 0, shift into third, restart engine, etc.
I did this with a 76 Datsun B210 to avoid a ruinous tow bill. If you do this in a modern car, the possibility of the steering wheel locking during the shut off makes this a dangerous practice.
Back to the bike, shifting gears during a coasting in neutral step, rather than shifting under power, would avoid catastrophe. -Edward
I have been thinking about using a two or three speed hub as a transmission. My idea is to use it as a gearbox mounted directly behind the motor. I will machine a flange and braze it to the hub shell on the left side of the hub. Add a removeable sprocket to the flange. My fabricated mounting brackets, similar to rear droupouts will be added to my frame to hold the hub. The hub will act as a multi-speed jackshaft. The primary chain is from the engine to the left hub sprocket. The secondary chain is from the pre-existing hub sprocket, on the right side of the hub, to the factory cog on the rear hub. This gets rid of the leftside add on hub sprocket. Because of the ratchet in the three speed hubs, you can't just flip the hub and use the existing gear on the left side. The freewheeling aspect of the hub also means no bump starting the engine as most of the chinese engines require. There were some fixed gear threespeed hubs made at one time, but they are rare and in the world of ebay, now very expensive. There are ways to defeat the freewheeling of regular hubs, but this requires modifing the hub internally.
My first wife's father demonstrated this technique to me using the B210,needless to say, shortly afterwards the transmission suffered a catastrophic failure from the gear grinding. Its more of an art than science best left to those driving a company vehicle.
Too bad you can't shift the engine output to the opposite side so you can use the 3 speed hub. I'm not knowledgeable enough about these hubs to crack one open and see if it can abe modified to work on opposite side.
How about using a derailer, bicycle chain, and stacking a 36 tooth, 44 tooth and a 48 tooth together, separated by washer spacers? You'd have to cut the throttle to do the shifts. I may just try it this summer when I have some time. At best it would work and at worst, it wouldn't.
hmmmm? is there such a thing as a left side derailer? I know there are left side drive (LSD) components for freestyle bikes. come on you bicycle mechanics out there.....gives us some input.
Interesting comments....... Derailer will not work as they are designed to have the chain drive in one direction only, and that is when you pedel..the slack chain is taken up by the sprung loaded tensioner..... Try and pedel to start the engine and this unit will wrap around and jam the chain as it is not designed for bi directional operation....
I've never seen or heard of a LSD DeR. Anything LSD oriented is going to go on a bike w/o multiple gears.
There has got to be a way.....but I don't think the bicycle world may provide the answer directly.
Why not fabricate some dropouts. Weld them on the bike frame. Weld spockets to both sides of a hub mount hub chain from hub to motor, motor to rear hub then you have capability of using that side
The only question is what to do about the pedals :shock:
Shimano Nexus would be rather neat with 7 speed for that eh?
Might however need to create a crank starter for the motor that you can put on the hub however to make it start. or maybe make a way to put something like this on there for kick starting. http://www.global-b2b-network.com/direct/dbimage/50236258/Kick_Start_Mechanism.jpg
Has anyone tried using an internally-geared hub like the Nexus-7 with a bikemotor? I have read max torque values for some of these hubs but am not sure if they could handle a 50-70cc two stroke engine output... Some real world tests would be more useful than specs on paper. Also the max-torque specs for geared hubs are (I assume) for very low rpm consistent with pedaling speeds, So if the geared hub is mounted like a jackshaft in the frame and not in the wheel and spun at a higher rpm(lower torque), Would it be able to handle the overall power better? Would the higher rpm wear the hub out faster? Maybe someone out there has some experiences they can share? Sure would be great to have a 7-speed tranny.
no idea I have never used a internal hub at all. It was just a random thought I had
Found a old thread that Augi posted in and found this link.
I called them thats what i am going to do for the crankset then using the jackshaft thats in the old thread.
And that should be enough really to do what I want. 3 Speed! I may get the 8 speed I do not know would 8 be overkill?
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