Monday, August 17, 2009

thoughts on DIY mod to house wheel dynamo hub in a bottom bracket

D: I would like a dynamo in the bottom bracket.
However, Shimano controls the patent and shows no signs of making this product.
They do make wheel hubs though.
Well... I *could* make a custom bottom bracket.
It could be big enough to accomodate a wheel hub.
I suspect there will be issues with diameter difference between a pedal crank axle and a wheel axle.
This is not insurmountable, though I may require expensive high-end metal.

As an aside, one could also place gears here in lieu of a wheel gear hub.
The benefit would be
1) harder to steal
2) less in way for tire changes
3) no mass to accelerate on the wheel, which deals with centrifugal force too.

D: OK it's called a spindle and not axle.

I had endless grief with terminology building the Cruzbike.
The instruction used on set of terms.
The bike shop didn't even know what they were talking about.
I.e. Threadless or not front steering tube.

There are so many bottom bracket arrangements!

"Ashtabula (One-Piece)

With an Ashtabula crank and bottom bracket, the spindle and crank arms are a single piece. The bottom bracket shell is large..."
D: maybe I don't need to go custom.
D: here's a pic.
Nice overview of brackets, various pics.

D: I guess a dynamo is not a true electrical generator somehow.
My bud Ryan is intriged by the idea of regenerative braking on a bicycle.
I suspect the weight penalty is prohibitive.
I think the lightest I found would be electromagnetic, which would involve elaborate and demand power control.
D: I suppose yer suspension could power a battery or capacitor too.
Why waste all that energy?
The bumpier the road, the better the energy harvest.

Any talented electrical engies out there?
What is the weight a bicycle -ready electromagnetic generator?
It is estimated that regenerative braking systems currently see 31.3% efficiency;

D: a strong enough setup would remove the need for a mechanical brake.
This implies the front wheel because
1) it works better for regenerative braking and
2) not locking up the front brake is actually desirable to avoid losing control.
Energy efficiency potential for single vehicle: 5 - 10% ...
Sweet! Why waste all that energy with a stationary bike rig?
Even charging USB devices and cell phones is pretty brilliant.

I refer again back to Tetz's awesome setup.
D: I suppose it could be mod'd to double as a generator.
You could listen to tunes or chat on a (hand free) cell phone without draining batteries.
I'd recommend helmet-mounted speakers to allow listening for traffic.

D: the FWD Cruzbike layour encourages:
1) extra weight at the front end - like a battery and
2) dual drive wheels, with a power assist on the rear wheel, to deal with steep hills.

A commuter bike can use lotsa torque at slow speeds for red lights and hills.
But a touring bike could use much less torque but at medium speeds.
You can have two wheels with motors mounted, or you could swap out motors on the bike frame.

Again, I'm intrigued by the idea of a partial fairing with solar panels.
It could assist you all day and/or charge yer electronics.
But given the measly power offered by the sun, maybe charging commuter batteries during the day for the return trip home is desirable.
This would allows 2x the power to be used as assist, since half does not need to be saved for the return trip home.
A simple wall-plug arrangement could also work.

While we're at it, the motor assist could also be housed in the bottom bracket.

A poor man's Greenmachine could involve a Nuvinci or IM9 hub drive mounted in the frame at the pivot point for the suspension.
Then or later, one could add a Schlumpf bottom bracket drive.
The price still comes in wayyy below a Rohloff.
Though if they ever release the 580% range version, I might not care.

I do think my Mark I, with its single enclosed in-the-tube-frame chain is elegant.
Such an arrangment DOES mean a gear hub must occupy the rear wheel.
I don't like this from the point of view of theft risk.
The dual parallel bike frame is very easy to secure with a bike lock.

I'm tempted to try an industrial drive belt in lieu of a chain, with potentially pounds of savings, plus less noise.
I imagine torque would cause it to slip.
You'd need very good granny gearing for hills.
A Schlumpf drive would address that.

The many benefits of a belt – nearly impossible to break or cut, long life, no grease, easier on pants legs, no rust, no stretching, low maintenance – are offset to a great extent by the current lack of a derailleur design that can handle a belt

D: a belted design pretty much demands a gear hub.

D: maybe I'll try to modify some industrial belt for the Mark I GM-homage bike.
It would be one of the few mods that would improve the already terrific Flevobike!

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