Idea for Motor intergrated into Bike Cranks

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7circle
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Idea for Motor intergrated into Bike Cranks

Imagine the Left crank is removed and replaced with a "NEW" crank that allows the rider to pedal normally by maintaing the mechanical connection to the spindle. But the crank provides a slip ring for a brusless motor to rotate on with a stator structure that can clasp the bike frame (ie near the drink bottle holder).

I have considered the available space around the left crank as it rotated, and can invisage enought volume to fit a 250W- 500W brushless motor (Custom designed of course).

I have been wanting to power my giant NRS full suspension MTB with a Mid Drive system.
As the rear hubs often have mounting for brake disks this could be used for chain sprocket. The chain linking the motor would need a tesnioner. But the beauty of the left drive approach allows regenertive braking to be applied.

The intergrated motor/crank is quite complex due to slip rings and bearings.
So if the design worked effectively sales would have to quite high to make it cost effective.

I have thought of ways to include crank torque sensing so a throttle doesn't have to be used and just apply a tourque multiplier like some other ebike use.

The concept never left my mind for the last few years as I see people investing up to AUD$4000 on moutain bikes. And I know I would rather retro fit a motor to my bike than buy a new one.

The other point is I just can't accept that a hub motor of 500W on a suspension arm front or rear would allow the suspension to operate effectively.

I love the optibike concept (http://www.optibike.com/Frontpage)

But would like to have some thing similiar that can easily be fitted to most bikes.
I probably will try a motor mounted under the bottle bracket first and run a chain to the slip ring on the left crank then another chain to the rear wheel. I'm sure someone has already done this. And it it would allow regen to.

I'm interested on comments on bikes that have really good regen braking.
And regen effectiveness with different battery chemistries.

Better stop here, it's my first post.
I have found this site great reading.

P.S. I hope this post doesn't end in war of words. Peace :P

7circle
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Re: Idea for Motor intergrated into Bike Cranks

I have often reviewed this site for Mid-mount ideas.
http://www.users.bigpond.com/solarbbq/cheapdiybike.htm
I like the Epac system.

Efried
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Re: Idea for Motor intergrated into Bike Cranks

war on chain or worm gear driven bikes ;-) I rode them and I can tell you- scrap - after some time you have to replace! So buy some spare parts with it.

7circle
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Re: Idea for Motor intergrated into Bike Cranks - Chain Tension

Interesting Efried.
Well this system wouldn't need worm drive (No Go for regen)
And the chains would be standard bike pitch and the sprocket diameters would be larger than the tiny 11 or 15 tooth sprockets I've seen on many scooter (and bike) motors. If the ratio pair of sprokets are larger (ie 22:40 instead of 11:20) then the chain tension would be managable. And I accept that the torque from a 250W motor could damage a chain if the speed range of operation is not considered.

davew
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Re: Idea for Motor intergrated into Bike Cranks

I have seen similar designs for sale. There's an Australian one: elation ebike and Cyclone USA sells something similar. Is this what you had in mind?

"we must be the change we wish to see in the world"

spinningmagnets
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Re: Idea for Motor intergrated into Bike Cranks

I am "electrically challenged" (I tried to fix a computer with a sledge-hammer once...it just made it worse), but...

From what little I've learned, I think the big breakthrough for regen will be in adding a large capacitor to the controler. As to where and how, I haven't figured out that part yet. Its my understanding that chemical batteries can only absorb a small amount of amps, and most potential regen watts are lost.

Just an idea,...thoughts??

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Re: Idea for Motor intergrated into Bike Cranks

Hi Davew

The elation ebike and Cyclone USA kits have a freewheeling or one-way bearing intergrated into the right crank. But these don't allow regenerative braking.

I have seen some bikes with a motor on the pack rack above the rear wheel using a chain on the left that have regen. But this wouldn't be suitable for suspension bike.

I'll have to get a drawing together. Knowing that the elation ebike and Cyclone USA bikes have freewheeling bearings gives me a bit of confience that a pancake motor could be built into the crank.

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Re: Idea for Motor intergrated into Bike Cranks

Hi Spiningmagents

Recharing batterries. Little B**#*@rs

I'd like to tell you about me capacitor experiment but I haven't done it yet.
My xooter scooter broke (under my 100kg gutter jumps). Need to weld the cast aluminium.

I bought some 1 Farad 12VDC caps used by LOUD car amps.

2 Farad Capacitors

These are newer and smaller than mine. And not sure on max voltage they can cope with.

I was simply going to conect it the the controller battery input and with a full battery see how many laps I could get on my usual test route on the streets.

Often you don't see the pulsing currents going into motor controllers unless you have a CRO. So adding extra capacitors across the batteries close to controller will improve percieved Amp.hour as caps will release the current required before the battery.

Some of the controllers are pretty small so I can't see how they could fit caps in there. The 1 Farad cap at 12V is pretty big. I needed two for series connection to 24V but this would half the Farrads.

The internal series resitance of batteries/chemistries is a challenge as its different going in than coming out. The state of charge and age/health of the battery effect it too. So its worth investigating the effect of extra input capacitance to the mottor controllers.

The new nanotech Lithiums (A123) with eg 100x the surface area of the earlier generation sound really good.
But I haven't seen the voltage curve for charging.

I have seen that the 3.6V cells often start there discharge curves at 4.02V and quickly fall to 3.60V no load until 80% DOD. Then under load they can drop to 3.0V under heavy loads.

I agree that many battery types would loose much of the enregy during recharging or regen' braking.
The old test of does it get hot then its loosing power is how I would explain NiCads. But I haven't used lithiums much yet to compare.

I any one with new lithium like A123's can somment on how hot they get before the reach full? And on the voltage required?

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