will KMC Kool Knight Chain fit on regular bicycle sprockets?

[Hugh-Jassman]

I am still trying to find the rpms at the wheel. I think the chain I use is going to need to be shiftabe, at least untill I know if I need only one speed or two.
If I can get by with only one then a bushing chain would be best for sure.

RPM's
If the cyclone 3000 planetary gear ratio is 6:1 and using a 32 sprocket chainring to drive the 34 sprocket on the rear hub, what is the total combined gear reduction?

9.33:1 should be more than enough for 450lbs (total combined weight) on a 9%grade. but that is not what teh ratio is.

The ratio is 6.375:1 with a 32 to the 34, because I have to multiply the 6:1 by the second ratio.
Which would give my 23” tire 25.9 mph at 400 motor output rpms?

If I were to use a 44 sprocket on the rear and 32 on the front it would still be only about 20mph.

So I definitely need a lower gear: 1.83x6=10.99:1 ratio with the 24sprocket on the front. For about 15mph.

It looks like I will have to use the 36 and 24t sprockets on the crank. With a 44t on the rear. To get the ratio close enough to the target of 1300w and 13mph on the 9%grade.

That means I need a shiftable chain (front only).....

If I were to use a 36 volt battery I would get a lower RPM,What would the rpm be at 1300watts? But what are the cons of a lower voltage? Would the battery act the same when draining 1600w out for the1300w output because it would be sucking more amps???

Too bad no one has made a performance graph for this motor.

 

[Hugh-Jassman]

I think I should try to find a 60t sprocket for the rear. The 32t being the third chainring?? Looks like some one figured this out before telling us what chainrings they would give us.

But what size is a bicyle chain? #25? or #35 or #40?


And then there is the pitch!
#25 Roller Chain Sprocket 1/4"pitch 6.35 50Tooth 55T 60T 70T 75T and 80 Tooth on ebay. And of course they don't tell what the center hole size is.

All this is the reason I wanted to mount the motor for a left side drive. But I would need a differnet oneway bearing for the motor.

 

[Chalo]

Bicycle chain has the same pitch and roller diameter as ANSI #41, but bike chain is narrower. Sprockets made for #41 are not likely to mesh with 1/8" chain let alone 3/32" chain, and they definitely won't shift right.

On the other hand, if you don't need to shift, you can use #41 chain as a very durable alternative to bicycle chain.

You can't just stuff unlimited amounts of torque through an ordinary freehub body. There are physical limits which you are sure to find if you lower the gearing enough.

I'm very heavy-- my bike is close to 450 pounds with me on it and the usual random junk in the cargo box. I'm using a normal 750W BBS02 running on 48V. My low gear is 46/34. I lived in Seattle for years, a few blocks from the steepest pavement in town which is at 25th and Roy if I remember correctly. While I am sure my bike would not drag me up that grade without a lot of help from me at the pedals, I am equally sure that even with just a BBS02, I would not need anything close to 34/60 to winch myself up that hill. And I'm rolling a 700c wheel.

 

[Chalo]

Do yourself a favor. Cyclone makes a bunch of different motors, so you need to find the one that fits your application best. Go here: http://www.cyclone-tw.com/motor.html

You're looking for the 24-72V, 2000-4000W model. It's good for 130Nm of torque according to Cyclone. It runs at a lower kV than what a lot of speed addled dingdongs prefer.

For the kind of wheel torque you're looking for, I would attach the drive sprocket to the left side disc rotor mount, not the freehub. That way you can run as big a drive sprocket as you like, while not breaking stuff as much.

 

[Hugh-Jassman]

This is great, but I did already buy the motor just because my knees wore out so completely I can no longer ride my bike, I can't put any pressure on my right knee without screaming pain. And the left is not far behind.....

The only thing keeping me from putting it all together is money for the battery, and rigging the whole thing correctly.

I was looking at 1/8th inch thick sprockets for 410 chain, that looks like really cheap single speed chain. And the sprocket would have to be bolted into an old cassette. Backyard engineering.

What I would really like to do is use a second freewheeling crankset some how turned around so I can drive the expensive velocity hub I put on my bike a year or so ago; on the left side. But I may need to find a one way bearing to replace the one on the motor... because I can't just turn it around. (it has a lip for a puller that has to face outwards)

I suspect that I can't get a crankset that can be turned around. So maybe I could just use a plain crank set installed backwards? And run the motor's power threw the BB spindle??? probably not the best solution.

Got any ideas on that? maybe I don't really need that extra gear reduction with the crank. But I was hoping to keep the power down to 1300w output.

Would there be an advantage to run the motor on 36v rather than 48v? seems like I would need to use more amps..but maybe the motor has so much copper it would not make a bit of difference?

 

[Hugh-Jassman]

Luna cycles has the motor specs as “Max Torque 100Nm” (73.75foot pounds) so what is the max torque a MTB freehub body can take?

I simulated several hub-motors at 1300w with correct gear reduction for climbing a 9% grade with 450lbs, to lower the amount of stress as much as possible. I got 46 to 51 lbs thrust. But climbing a hill not geared for would produce up over 92lbs thrust on 20% grade. So this is a good reason to have the gear reduction as close as possible to my worst-case hill climbing. 92Foot-pounds = 124Nm and 51foot pounds = about 69Nm.

I don't know how accurate the simulator is in estimating for gears. I just used a smaller wheel to find the right reduction. Not knowing how much a free-hub body can take I would not want to find out the hard way.

I can reverse everything on the crank, except the oneway bearing.
And threads for the crank arm. So I will have to bypass putting a crank on the left side and go directly to the drive wheel with as big sprocket as I can put on it. And then I am going to need to figure out how large of a battery pack I will need. Hopefully not more than 17.5Ah were as that one is $600 plus a charger...

so for now I need now is a reversed oneway bearing to hold a small sprocket on the motor.

 

[Hugh-Jassman]

info from another forum:
1000 watts is produced by:
continuous 80 Nm at 120 rpm
continuous 159 Nm at 60 rpm

this is about kinetic energy....and momentum.

"neither Nm nor foot pounds are units of force." so how should I be refering to force?

 

[Chalo]

Nm and lbs-ft are torques, meaning force tangent to a radius. Divide those numbers by the radius of your drive wheel, and you have tractive force.

 

[Hugh-Jassman]

is tractive force the thrust of a motor?


1000 watts is produced by:
continuous 80 Nm at 120 rpm
(“spinning” in low gear)
continuous 159 Nm at 60 rpm
(“pedal mashing” in high gear)

I do not understand why the hub of a larger sprocket will have more stress at a higher rpm. Seems like the whole thing would have less stress in lower gear. Even when ran at a higher RPM.
yet I can see there is more leverage with a larger sprocket.

Nm and lbs-ft are torques, meaning force tangent to a radius. Divide those numbers by the radius of your drive wheel, and you have tractive force.

 

[Chalo]

is tractive force the thrust of a motor?

Yes.

I do not understand why the hub of a larger sprocket will have more stress at a higher rpm. Seems like the whole thing would have less stress in lower gear. Even when ran at a higher RPM.
yet I can see there is more leverage with a larger sprocket.

The same motor torque feeds more torque to the wheel the lower the gear. In practical terms, drive torque is limited by tire adhesion, though there can be higher instantaneous torque peaks that react against the inertia of the wheel. These peaks matter when the question is whether a freewheel or freehub body will be broken.

Everything on the motor side of the gear reduction is under less stress when the gear is lower. The chain is under less stress the faster it's moving to produce a given amount of power (which is why big sprockets are good, independent of ratio).

 

[Hugh-Jassman]

so the secret to not braking the hub is slow acceleration?

 

[Chalo]

so the secret to not braking the hub is slow acceleration?

That couldn't hurt. If you can program a soft start into your controller, that would be the way to do it consistently. Whether your hub can tolerate the steady max torque of your motor and gear reduction is a matter of how much torque that is.