750 W Chain Puller; Fits Most Bikes (+Video)

Ron Z

10 mW
Joined
Feb 18, 2011
Messages
26
http://www.youtube.com/watch?v=ytYuosP2Blg



Since I started developing drive systems 3 or 4 years ago, I have had as a goal, a chain puller that would fit nearly any bike. Finally! Shown below is a 750 Watt Drive Kit that mounts on a standard, slightly modified, bottom bracket. The only other connection to the bike frame is thru a pressure pad that contacts the bike down tube. The system pushes (rotates) into the frame under power, and is prevented from rotating away from the frame by a single large tie wrap. The entire system fits betwen the arc of the pedals.

Img2011-03-23_0005.jpg


The system mounts on two arms with ball bearings that rotate on the bottom bracket spindle. To my surprise, this mounting method results in a very quiet system. RC motors have significant torque ripple, as high as 18 percent. When that torque ripple couples into the bike frame (especially aluminum frames) it set off multiple resonances that create noise. In this system, the ball bearings isolate the frame from the torque ripple. The decoupling along with the precision gearbox result in a whisper quiet system.

Img2011-03-31_0002.jpg

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The motor is an Astro Flight 3205 8 turn Kv 375 rpm/volt, Rm 0.055 ohm, Io 0.8 Amp, length 1.5 inches. The gearbox is a Neugart PLE 60, 32-1, precision 2 stage planetary. On the gearbox output shaft is an Odessey 13 tooth BMX free wheel (metric). Primary drive is thru half link chain, for the small free wheel, and quietness. Vision IPS freewheeling cranks are used (EVDeals). The kit allows mounting up to 50 tooth chain wheel in either inner or outer position. The bottom bracket is a standard Shimano UN-54, 127mm. A 0.035 inch bevel is ground off the left side of the bottom bracket. This removal does not affect the ability to tighten and untighten the bottom bracket whatsoever.

Img2011-03-31_0007.jpg

Img2011-03-31_0009.jpg


The primary chain tension is adjusted with 8 bolts connecting the motor/gearbox mounting plate with the bike mounting plate.
4 screws set the spacing (chain tension), and four screws clamp the two plates together. There is 1/4 inch of adjustment. After that, links can be added or removed.

Img2011-03-31_0010.jpg


I use 25 volt LiFePO4 battery system rated at 42 amps max (Battery Space). The Speed control is a Castle Creations HV 80.

MountainE-bike007.jpg


The last picture shows a prototype system mounted on a full suspension mountain bike, which I consider the worst case. I am presently riding a Electra Townie with the final system shown in the pictures. The rear hub is an Nexus 8 speed internal. So far I'm pleased. The bike is powerful, but not drive system destroying powerful. I'm presently sorting out gearing. Pictures later.
 
Very nice work! I would love to see some video of this in action! So does the bottom bracket mount just float there, or is it rigidly mounted in some way?
 
Looks very nice. :)

Gotta love the ability to get a 32:1 gearing reduction in such a tiny form factor. Multi-stage planets rock.
 
StudEbiker said:
Drool..... I'm not understanding why it looks like there are two sprockets on the planetary tough.

I was thinking that maybe so one could have a chain to the rear wheel? ;)
 
amberwolf said:
StudEbiker said:
Drool..... I'm not understanding why it looks like there are two sprockets on the planetary tough.

I was thinking that maybe so one could have a chain to the rear wheel? ;)

Good eye. +1 8)
 
Unless I'm missing something, I think the chain to the rear wheel would go from the second sprocket on the crank. That still doesn't explain why there is two sprockets on the drive unit. This is the picture I'm looking at.

Img2011-03-31_0009.jpg

There are two sprockets on the freewheeling crank, but there are also two on the drive. One with a chain to the crank...the other for???
 
Nice workmanship Ron, The 32:1 is quite high for the second stage, sounds like a torque monster. I plan to do something similar, but more like Burtie's setup. When you mentioned how quiet your drive system is, this really caught my attention. Any video possible? I've been trying to get a Nugart planetary, no luck. I did get an 11:1 reduction recently from a different brand, but still waiting for it in the mail. Hopefully it will be strong enough for my setup.

Field reports please, once you get that baby on the road and hill climbing results as well. Again nice job!
 
Initial answers to questions.

Whiplash said:
Very nice work! I would love to see some video of this in action! So does the bottom bracket mount just float there, or is it rigidly mounted in some way?

MountainE-bike020.jpg


It floats on ball bearings. Provide a rider (I'm 66), and a videographer on the east coast, and we'll talk.

Gordo said:
amberwolf said:
StudEbiker said:
Drool..... I'm not understanding why it looks like there are two sprockets on the planetary tough.

It's an optical illusion, probably due to reflections and the wide angle lens. There is only one freewheel. There is not room for two.

I was thinking that maybe so one could have a chain to the rear wheel? ;)

Good eye. +1 8)

Simply turn the motor gearbox system around (It's symetrical, only four screws), and drive the left side of the rear wheel. The freewheel has an insert that fits on the gearbox keyed shaft. So turn around the motor/gearbox, flip the freewheel on the shaft, and swap two wires on the motor phases, and you are in business. Probably would need a different gearbox ratio, lots of ratios available. The present gearbox full throttle output rpm is 300.

recumpence said:
Lookin good Ron.

I never heard back when I asked about making more 3205s. :? I love the clean design.

Matt

More motors are coming! Sent you a pm.

Matthijs said:
Amazing! Do you wish to share the weight of a complete unit? :)

The system including the cranks and bottom bracket weighs approximately 11.5 lbs. Thats about 8 pounds added weight above a standard crank set, and bottom bracket.

boostjuice said:
Vision IPS freewheeling cranks are used (EVDeals)

Could you please provide a link? I cant find them on the EVdeals website.

Top work BTW!

I get them in quantity thru EVdeals. They are not on his website. I will call Scott at EVdeals, and will report back on this thread.
 
I don't want to turn this thread into SPAM. Pm me and I will provide information as to availability of parts and pieces.
 
Nice! So the brackets simply straddle the protruding portions of the bottom bracket pieces! Great idea!
 
Very very nice work Ron, looking forward to seeing a video of the system in action.

boostjuice said:
Vision IPS freewheeling cranks are used (EVDeals)

Could you please provide a link? I cant find them on the EVdeals website.

Top work BTW!

Boost I bought mine here http://www.hostelshoppe.com/cgi-bin/readitem.pl?Accessory=1098307215

you'll need the stoker set. They come with a Shimano FW, I've changed mine over to use a white Eno.
 
Mounting a BB drive off the BB-cartridge (instead of the downtube) is a brilliant idea. Other BB-drives had cumbersome attachments that had issues with mount-rotation on the round tubing when under load, and adaptation difficulties due to the variety of downtubes styles (some of which do not have a round cross-section).

The motor needs a splashed-mud cover, but theres a lot to really like about every part of this!

http://www.acpd.co.uk/planetary-gearbox-sectional-drawing.html#e1023387
126.jpg
 
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