Magneto-hydraulic Torque Converter Wheel

[paultrafalgar]

Magneto-hydraulic Torque Converter Wheel

Imagine a cycle inner tube filled with a fluid (silicone?). This inner tube is installed in a cycle tyre in the normal way. Installed inside the inner tube are a number (20-30?) high performance neodymium magnets. The magnets may (or may not) be connected to each other by cords (nylon?). A pipe connects the inner tube via a valve to a radial tube connected to the hollow hub containing a reservoir of the fluid which is in the inner tube. The pressure of this fluid can be varied from a control on the handlebar. Increasing the pressure in the inner tube slightly expands it thus varying the grip of the inner tube wall on the magnets (effectively a clutch mechanism). At the cycle fork there is a 270 degree arc of magnetic coils that sits close to the tyre for some length around the circumference of the wheel. By digital control, these coils are energised such that they appropriately attract and repel the magnets in the inner tube causing the wheel to rotate.
This sketchy idea is in response to the overall dilemma exercised here concerning how to run electric motors at their optimun speed (for maximum efficiency) while running the wheel at the desired speed which will vary between stationary and say 300 rpm. To execute this design efficiently would be quite a challenge, I imagine.
What do you think?

 

[TylerDurden]

Sounds like a great way to collect hardware out of the roadway.

 

[paultrafalgar]

Ok, TD, I knew someone would say that.. so Mk 2:
Inner tube is no longer in the road outer case, but slightly smaller diameter (eg 24" in 26" wheel) and that is fixed to the spokes. The magnetic debris has farther to jump then!
Edit:
Also easier to fix punctures!

 

[TylerDurden]

Mk2 is getting closer to the F&P washing machine or Magic Pie.

Generally, we're discussing a large diameter direct-drive with external stator; yes?

It seems to involve more weight, size, complexity, exposure to environmental elements. Clutching seems un-needed for a high torque, low rpm motor.

The opposite general direction is the current trend with RC motors: low weight, small size, high RPM; the only major issue being reduction.

 

[paultrafalgar]

Mk2 is getting closer to the F&P washing machine or Magic Pie.

Generally, we're discussing a large diameter direct-drive with external stator; yes?

D'accord.

It seems to involve more weight, size, complexity, exposure to environmental elements.

I'm not sure that those factors are proven yet.

Clutching seems un-needed for a high torque, low rpm motor.
The opposite general direction is the current trend with RC motors: low weight, small size, high RPM; the only major issue being reduction.

My point is that a high torque, low rpm motor solves the mismatch that requires the reduction.
How much of the inefficiency of hill-climbing with high RPM motors is due to transmission losses? The use of high-power motors that demand high currents when nearly stalled when starting and hill-climbing may be less efficient than using slower speed motors that are designed to produce high torque without high stall currents. I have no idea whether my proposed design would be such a motor - however, I reject the idea that such a design could not better an RC motor with a large reduction. Isn't it possible that a torque converter would help to reduce the high stall currents involved?

 

[gogo]

I talked to a bicycle riding engineer at a hydraulic transmission factory and he said a 750W motor/transmission could be reasonably efficient if sized appropriately. The garden tractor transmission they made was too big and he wasn't aware of any off the shelf components that would fit the bill.

 

[paultrafalgar]

GoGO,
Yea! You'd have to fabricate all that yourself. I'm just fishing for someone who might think it would be amusing to try to do that or who had some feedback, like TD, on the concept. Thanks.

 

[Drunkskunk]

the hydrolic fluid would be heavy. Could you use air instead?

 

[mwkeefer]

I talked to a bicycle riding engineer at a hydraulic transmission factory and he said a 750W motor/transmission could be reasonably efficient if sized appropriately. The garden tractor transmission they made was too big and he wasn't aware of any off the shelf components that would fit the bill.

gogo,

I mean no offense but you found a ride engineer working at a hydraulic transmission factory? Sounds like my LBS mechanic at Perf. Bike who is a FT engineer / machinist, just not the norm.

-Mike

 

[gogo]

gogo,

I mean no offense but you found a ride engineer working at a hydraulic transmission factory? Sounds like my LBS mechanic at Perf. Bike who is a FT engineer / machinist, just not the norm.

-Mike

Actually, there were 2 of them. One was a young ex-Marine who worked next to me in production while he went to school and then moved to the engineering department when he graduated. He was also into electric R/C helicopters and thought a hydraulic drive would be great for variable load ebikes. He likes to check out my ebikes but the Marine in him keeps him from wanting one.

 

[TylerDurden]

The precise nature of the stator/rotor airgap seems a non-starter too.

 

[spinningmagnets]

For the same amount of time, effort, and cost, I think there's a lot of untapped potential in a DIY longtail, with a home-made Stoke-Monkey

 

[paultrafalgar]

the hydrolic fluid would be heavy. Could you use air instead?

I assumed that to ease movement of the magnets you would need a fluid medium to work the "torque converter" slow-takeup thing, but that may not be necessary and an air medium might work, DS.

 

[paultrafalgar]

The precise nature of the stator/rotor airgap seems a non-starter too.

Had the precise nature of the stator/rotor airgap been specified, it might be a non-starter, but since it hasn't I can't see how it could.

 

[TylerDurden]

"The development of electric motors of acceptable efficiency was delayed for several decades by failure to recognize the extreme importance of a relatively-small air gap between rotor and stator. Early motors, for some rotor positions, had comparatively huge air gaps which constituted a very high reluctance magnetic circuit. They produced far-lower torque than an equivalent amount of power would produce with efficient designs. The cause of the lack of understanding seems to be that early designs were based on familiarity of distant attraction between a magnet and a piece of ferromagnetic material, or between two electromagnets. Efficient designs, as this article describes, are based on a rotor with a comparatively small air gap, and flux patterns that create torque."
http://en.wikipedia.org/wiki/Electric_motor

Let's imagine a 16" dia. hubmotor for a moment: Would allowing the magnets to slip/clutch be any benefit? You throw away energy as heat regardless, with more parts and complexity in clutches or viscous fluids.