Indirect (via sprockets/chain) drive using hub motor?

[pullin-gs]

Has anybody here ever taken a hub-motor and delivered power to wheel via sprockets/chain?
Details please?
The non-powered coasting human-power-suck of hub motors make them un-usable for my application. An indirect hub motor which is chain-driven.....to a wheel-mounted freewheel sprocket, or a crank-mounted freewheel sprocket makes a lot of sense. Gearing also makes for better matching of KV to specific requirement (hills, input voltage, wheel diameter) which a simple across-the-board hub motor simply can not deliver.
PS: Show me a good solution and I'll give you a GREAT deal on a NEW (not even delivered to my home yet!) HXT63/74.
PSS: Hacker brushless RC inrunner motors dont cog. Smooth as silk are they. Does that mean they dont exhibit parasitic resistance to non-powered movement which cogging outrunners have?

Cheers!

Pullin'

 

[TylerDurden]

http://cleverchimp.com/products/stokemonkey/

 

[MitchJi]

Hi,

Geared Hub Motor to a geared rear hub (Nexus 8 standard, Rohloff optional):
http://www.pimobility.com/

 

[boostjuice]

There is a thread buried somewhere on the forums about this build. I cant seem to find it, but i did have these photo's saved on my hard disk of the guys work. Replicating a similar design of mount for use with a Chinese hub-motor kit would be a cheaper option over the purpose built stoke monkey/pimo, but only if you've got some decent metal fabrication skills. It would also be the most compatable with a regular mountain bike without being forced to convert to an Xtracycle extension to make it fit (eg. stokemonkey) or buy an expensive/ugly entire bike resembling half a McDonalds sign with the kit attached(Pimo). If your bicycle had a regular/large enough triangle frame, im sure it could be made fit inside the triangle instead of as the example above.

IMHO this is a very clever design (gearing advantage keeping the motor in its efficiency sweetspot) AND it removes the large unsprung weight from the wheel. I dont know why more people with modest fabrication skills dont attempt it more often.

 

[pullin-gs]

Thanks!
Everyone's replies are exactly along the lines of my thoughts.
Filling in the gaps of what is needed to pull this off:
1) A freewheel crank assembly. Two sprockets. One directly connected to crank for people-power. The second sprocket freewheel-connected to crank assembly for motor drive.
2) A freewheel counter-sprocket assembly attached to hub motor (GP 1000w?). Perhaps fasten counter-sprocket to plate the diameter of motor and screw plate to motor?

Budget: Cheap enough so the wife does'nt notice (I love paypal!....sell the old toys to fund the new toys!).
I think I have battery/controller figured out. Lots of options here.

Cheers!

Pullin'

 

[MitchJi]

Hi,

Filling in the gaps of what is needed to pull this off:
...
2) A freewheel counter-sprocket assembly attached to hub motor (GP 1000w?). Perhaps fasten counter-sprocket to plate the diameter of motor and screw plate to motor?

I think most (all?) geared hub motors have a built-in FW.

I believe that geared hubs are designed to operate most efficiently at an RPM that is closer to pedal cadence than most DD hubs.

A major advantage of driving through the cranks with a hub motor is the advantage of gears. I think the Pi bike has a (legal in the U.S.) 750w motor. Without the Nexus Hub there is no way a legal ebike could climb a 25% grade and have a 20mph top speed.

 

[gogo]

Check out this new BB drive:
BIMOTO MODIFIED Free Wheeling CRANK MECHANISM

 

[ron van sommeren]

... Hacker brushless RC inrunner motors dont cog. Smooth as silk are they. Does that mean they dont exhibit parasitic resistance to non-powered movement which cogging outrunners have? ...

Cogging is energy neutral.
Slotless/coreless motors don't cog. Lack of ironlosses makes them more efficient, this has nothing to do with the lack of cogging.
Note that cogging, or the lack of it, is not a good indicator for power, torque, efficiency, quality etc. Too many paramaters affect cogging: magnet strength and placement, iron magnetic quality and thickness, number of statorpoles and magnetpoles, statortooth and magnet geometry, distance between magnets. Cogging does not depend on winding diagram, number of turns/winds, termination (star versus delta) and inrunner or outrunner.

Vriendelijke groeten Ron
• brushless motor building tips & tricks • diy brushless motor discussion group
• Drive Calculator download & discussion group • int. electric fly-in, Nijmegen, the Netherlands

 

[swbluto]

... Hacker brushless RC inrunner motors dont cog. Smooth as silk are they. Does that mean they dont exhibit parasitic resistance to non-powered movement which cogging outrunners have? ...

Cogging is energy neutral.

Is it really? What is it then that requires the most energy to rotate the motor by hand? Some energy is definitely expended doing that.

On one hand, it would seem like the jerkiness of the "cogging" yin would have a yang, a yanking from the nearest magnet corresponding to a pulling on the next, so it would seem like the "cogging" in the context would cancel out. So what is it that seems to expend noticeable amounts of energy needed to rotate the motor? I really hope the mechanical friction on my HXT isn't that much.

Could it really be eddy currents? But I seem to rotate it so slowly by hand.

 

[TylerDurden]

What is it then that requires the most energy to rotate the motor by hand?... a yanking from the nearest magnet corresponding to a pulling on the next, so it would seem like the "cogging" in the context would cancel out. So what is it that seems to expend noticeable amounts of energy needed to rotate the motor?

Same as going up a hill and down, except your hand can't recover the return of energy, but a rotating wheel can.