WarpedOne
01-25-2009, 09:52 AM
Chain drive is already quite old and usually very effective, efficient and elegant method of torque transfer especially in lower power applications like ordinary bikes.
http://weightweenies.starbike.com/images/lightbike/bike.jpg
In bikes such as this one chain is around one meter long and doesn't need intermediate fasteners or special guidance to stop it from vibrating or falling off.
There are some other types of bikes where chain drives starts to become a problem or at least very awkward. Now look at this marvel. Its a very nice thing but that chain has to be at least 4 meters long. Imagine the vibrations, noise, filth and inefficiencies because it has to "go around the corner". These are the biggest downsides of chain-drives.
http://img.photobucket.com/albums/v207/evanbelkom/4a478622.jpg
Could we design a system of torque transfer that would use some principle other than rotation?
I thought about it and came out with this:
http://www.shrani.si/f/3k/8y/2meSZwQH/hydro.png
The system consists of two identical triangular modules. One on the torque input side, the other on the output side.
On the input side blue rotating shaft inputs the torque. The shaft pushes against green cylinders which are connected to cylinders on the output module with hydraulic lines filled with incompressible fluid (like one in hydraulic brakes). The cylinders on the output side push against the blue output shaft and induce circular motion. Both shafts would end turning with same speed.
Between these two modules there are only three quite flexible hydraulic lines than can be easily routed almost along any path, take very little space, can easily pass any joint in the frame (like with suspended frames), don't suffer much vibration and cannot fall off etc.
I am not a mechanical engineer so I am not sure what mechanical problems could arise in such a system. I fear the forces could be quite high. If usual front pedal is around 0,2m long and that eccentric shaft has 2cm long "arm" (if it is much longer the whole module could become to big to fit a bike) then the force with which the cylinder would push against that arm (and vice versa) would be 10x times the force with which you'd push against the pedal. Up to 1 tonne or even more.
Creating such a hydraulic module in your own garage would be a demanding job even with some advanced tools. For starters or concept prototype I adapted the design to use ordinary steel cables like in bike brakes. There are no hydraulic cylinders anymore so that eccentric arm can be quite longer with same module dimensions - up to three times as long meaning the forces would be three times smaller.
http://www.shrani.si/f/1f/Ri/1u7oJd1M/cables.png
The basic difference between both designs is that cabels would pull the arm and cylinders would push against it.
With both designs there is one cylinder or cable working at arm for half a rotation. For the other half of it there are two of them pushing/pulling it but at smaller or bigger angle.
Coupling these modules with pedals and rear wheel could be done like this:
http://www.shrani.si/f/3p/sT/3n6e8cq8/pedals.png
With such a system you could even go build an AWD bike!
I'm not sure how beneficial would it be but it might have some use where traction on the rear wheel is not very certain like with mountain biking through woods. When you are pushing hard against the hill and suddenly rear wheel looses traction and starts to turn freely you are bound to fall or at least stop.
In such moments this system on the front wheel would automatically start to pull you forward. Why? Front bicycle wheel always has to travel longer path than the rear one - so it turns faster than the rear. Bicycles don't have reverse gears so they can always go faster than you are pedaling without stealing the pedals from your feet. So the front wheel would normally just turn faster than you are pedaling - except when the rear wheel would try to spin faster then the front one because it lost traction. In those moments the front would jump in and help. Magic :)
You could also put gearing into the front wheel but I don't see the point to that. It could always just be in the lowest gear and only work when really needed.
Thoughts?
http://weightweenies.starbike.com/images/lightbike/bike.jpg
In bikes such as this one chain is around one meter long and doesn't need intermediate fasteners or special guidance to stop it from vibrating or falling off.
There are some other types of bikes where chain drives starts to become a problem or at least very awkward. Now look at this marvel. Its a very nice thing but that chain has to be at least 4 meters long. Imagine the vibrations, noise, filth and inefficiencies because it has to "go around the corner". These are the biggest downsides of chain-drives.
http://img.photobucket.com/albums/v207/evanbelkom/4a478622.jpg
Could we design a system of torque transfer that would use some principle other than rotation?
I thought about it and came out with this:
http://www.shrani.si/f/3k/8y/2meSZwQH/hydro.png
The system consists of two identical triangular modules. One on the torque input side, the other on the output side.
On the input side blue rotating shaft inputs the torque. The shaft pushes against green cylinders which are connected to cylinders on the output module with hydraulic lines filled with incompressible fluid (like one in hydraulic brakes). The cylinders on the output side push against the blue output shaft and induce circular motion. Both shafts would end turning with same speed.
Between these two modules there are only three quite flexible hydraulic lines than can be easily routed almost along any path, take very little space, can easily pass any joint in the frame (like with suspended frames), don't suffer much vibration and cannot fall off etc.
I am not a mechanical engineer so I am not sure what mechanical problems could arise in such a system. I fear the forces could be quite high. If usual front pedal is around 0,2m long and that eccentric shaft has 2cm long "arm" (if it is much longer the whole module could become to big to fit a bike) then the force with which the cylinder would push against that arm (and vice versa) would be 10x times the force with which you'd push against the pedal. Up to 1 tonne or even more.
Creating such a hydraulic module in your own garage would be a demanding job even with some advanced tools. For starters or concept prototype I adapted the design to use ordinary steel cables like in bike brakes. There are no hydraulic cylinders anymore so that eccentric arm can be quite longer with same module dimensions - up to three times as long meaning the forces would be three times smaller.
http://www.shrani.si/f/1f/Ri/1u7oJd1M/cables.png
The basic difference between both designs is that cabels would pull the arm and cylinders would push against it.
With both designs there is one cylinder or cable working at arm for half a rotation. For the other half of it there are two of them pushing/pulling it but at smaller or bigger angle.
Coupling these modules with pedals and rear wheel could be done like this:
http://www.shrani.si/f/3p/sT/3n6e8cq8/pedals.png
With such a system you could even go build an AWD bike!
I'm not sure how beneficial would it be but it might have some use where traction on the rear wheel is not very certain like with mountain biking through woods. When you are pushing hard against the hill and suddenly rear wheel looses traction and starts to turn freely you are bound to fall or at least stop.
In such moments this system on the front wheel would automatically start to pull you forward. Why? Front bicycle wheel always has to travel longer path than the rear one - so it turns faster than the rear. Bicycles don't have reverse gears so they can always go faster than you are pedaling without stealing the pedals from your feet. So the front wheel would normally just turn faster than you are pedaling - except when the rear wheel would try to spin faster then the front one because it lost traction. In those moments the front would jump in and help. Magic :)
You could also put gearing into the front wheel but I don't see the point to that. It could always just be in the lowest gear and only work when really needed.
Thoughts?