Let's Build a Hybrid Cycle

[GAHD]

so I will shortly have access to an autoclave and machine shop to do a bit of fun, and I've decided on a personal project of a FWD electric assist/brake mechanism for a standard bicycle.

I'm considering my options on how to accomplish this, so far I've considered; embedded and brushed solenoids in the hub interacting with perma mags on the forks, and a sectored variety of a unipolar motor where a heavily spoked wheel with properly sectioned and isolated rim-sections acts with forked perma mags.

I'm curious as to hypography's imput on the matter? Any funginerrs wanna help me out?

[Roadam]

It may be quite a good idea to put permanent magnets between the spokes so that velocity and torque is greater. As far as I see it you need some kind of a linear motor, or usual one unrolled, and most probably AC.

[CraigD]

Just throwing out some first thoughts, here’s what I’d try:
With whatever rim (true them – make sure they’re very close to round - first) and forks you have handy, some magnet wire, a couple of strong permanent magnets (the cubical shaped rare earth kind) and a small (ie: pocket size) multimeter, and whatever clamps and locking pliers you have
wrap a bit of the rim with a single layer of wire
tape the multimeter as close to the hub as you can
connect the wire ends to the multimeter
clam the magnets to the forks with a mm or so clearance for the rim
give it a spin and see what voltage the multimeter displays.

This, and max charging voltage and current data for whatever batteries you plan to use, should give you the data you need to scale it up to the needed power.

Ultimately, I imagine you’ll want to epoxy and autoclave cure wires into/onto something like a 4-spoke carbon fiber wheel/rim, and use some sort of brush commutator near the hub to get the current to the battery. It would be really nifty if you could manage some way of doing it brushlessly, via inductance (the wheel will, after all, be moving most of the time), but that seems a lot more complicated to me.

Remember, you still want the bicycle to have good performance as a bicycle, so keeping wheel mass to a minimum, especially near the rim, is as important as ever, which to my thinking rules out permanent magnets on the wheel schemes.

Good luck and post pictures!

[GAHD]

Originally Posted by CraigD

Remember, you still want the bicycle to have good performance as a bicycle, so keeping wheel mass to a minimum, especially near the rim, is as important as ever, which to my thinking rules out permanent magnets on the wheel schemes.

Exactly my thoughts. Curses and praises to rare earths being so damn heavy.

Originally Posted by CraigD

Ultimately, I imagine you’ll want to epoxy and autoclave cure wires into/onto something like a 4-spoke carbon fiber wheel/rim, and use some sort of brush commutator near the hub to get the current to the battery.

Fairly accurate, though I was considering 2 seperate brushes one near hub one near rim, and Using a high-current low voltage idea akin to a faraday wheel. Being an ASS, I 'sume that if the wheel were sectored the counterflows of current would be almost negated, the mass of wheel not exposed to brush & magnets mounted to the forks not receiving a charge. Again being an ass and suming I understand the basics of lorence I was thinking having a mass of parralel wires running radially, ignoring the customary coiling structure of motors as this would essentially become a brushed linear motor.

First design:
The rim would be "spokeless" in that I expect it to have a smooth and unbroken outer surface, the sectored brush conacts being inlayed radially close to the rim and bearing hub. The wireing itself would be affixed below a .004-.016" Boeing prepreg carbonfiber/epoxy skin, and on top of another skinreinforcing an as-yet unspecified grade/type Boeing 'honeycomb' core. (the shop is supplied by Boeing stock).

I expect to have to make the final magnets for the forks myself, first blocking two Halbach arrays and then chopping out a grouve for fork mounting in the final model, though I'd love to hear some other ideas there.

any theory math you could throw at this? The devil's in the details but I'd like to see what others think the math should look like.

Originally Posted by CraigD

It would be really nifty if you could manage some way of doing it brushlessly, via inductance (the wheel will, after all, be moving most of the time), but that seems a lot more complicated to me.

Indeed! Another drawback to this inductance scheme is an inability for regenerative braking which would limit usefulness and range. The whole point of this wheel is to mitigate the stop-start of in-city movement.

[Roadam]

Well I think it is possible to build it like a linear motor.
Linear motor - Wikipedia, the free encyclopedia

In the attachment I sketched what I am thinking of. Basically it is a permanent magnet AC motor with only a small portion of a stator. In fact I just inverted the one shown on wikipedia.

Thing is that you would need AC inverter and a controller for this. I am also unsure how to wire it all. But with this you could brake regeneratively and also the wheel wouldn't get that much heavier. With a battery the bike is heavy anyway.

Also, while heavy wheel might slow the acceleration, make a ride a bit bumpier and stabilize the bike(gyro effect).

[GAHD]

problem I see with purely rim-mounted driving force is how low a gear ratio that's creating, seems I'd need to really pump those motors to get any decent speed(heavyer rims WOULD help kill any "squaking" but I don't think that'd be an issue). My logic train goes that by having a larger portion of the rim as an effective motive area, I can probably get the best of all the drive ranges...least I hope so!

as to power concerns ,I was thinking I'd tap a capacitor array for that; good cycles on caps, and they just might stand up to the -40 weather we experience here in winterpeg better than batteries
.

[DFINITLYDISTRUBD]

They make hub motors (integrated into the hub of the rim) for bicycles already...not as cool as embedding the drive coils or magnets into the rim and forks though.

Re. Winterpeg...Lol here on the southern shore of lake Erie we're in the middle of gettin dumped on...Got about a 8" (about 20cm. I think) of the white stuff in 3 hours so far.

You going to put some studded snows on it when you're done?

2,134 km – about 21 hours 0 mins...Hmmmmmwere practicaly neighbors

[Roadam]

Well if you mount the motor closer to the hub you get less torque. And it will probably be harder to build as it would have to be smaller.

Chinese are quite far as far as electric bikes go. I am not sure if technology comes from there, but at least they are producing them on large scale.

Motors on the rim may have low gear but at least they have better torque. And typical electrical motors operate at high rpm so the motor mounted at the rim has at least comparable rotor/stator speed.

[GAHD]

Originally Posted by Roadam

Well if you mount the motor closer to the hub you get less torque. And it will probably be harder to build as it would have to be smaller.

Originally Posted by GAHD

problem I see with purely rim-mounted driving force is how low a gear ratio that's creating...larger portion as an effective motive area...

Originally Posted by DFINITLYDISTRUBD

They make hub motors (integrated into the hub of the rim) for bicycles already...not as cool as embedding the drive coils or magnets into the rim and forks though.

yup

Originally Posted by DFINITLYDISTRUBD

You going to put some studded snows on it when you're done?

If it gets that far, supertweel of my own redesign.

[Roadam]

Not exactly sure what were you aiming at.

Anyway, as you pointed out and which I also understand:
->closer to the rim, bigger efective area, bigger torque, longer the rotor(more magnets on the rim), more rotating weight

->closer to the hub, less torque, shorter rotor, less rotating weight

But I wonder, do motors do better when magnets and coils are moving faster relative to each other. I do know that generators with more magnets&coils generate more voltage per rpm.