Freewheeling crank drive (was: Stepper motor as ebike drive)

[knoxie]

Hello Malc

Yes really nice build for sure, I would love to see it in action, I havent built or done much for a while now, new job and new lady being my excuses also the fact that the Puma once fitted and working doesnt need much fettling to make it any better! and I have some good life left in all my lipo packs to last me a while which is good news. I wont ask about the price then! ha ha I know it hurts ha ha you should get some good life out of it though.

I was in west wales the other day near Tenby in this place called Amroth and I noticed this chap whizzing up and down the promenade on a bike and wasnt peddling at all, I popped along with my camera but he had gone? I then missed him coming back! as he was silently nipping back, it looked a little like one of those 50 cycles bikes but it had a black and silver rear hub motor, what was most impressive though was how well it climbed this steep hill out of the village, if it was a legal stock machine then it was doing very well! its great to see more e-bikes esp in holiday resorts as a lot of people were looking at him as he wasnt peddling.

Your little bike should crack along, let us know if the new chain and cassette fixes the problem, geared hubs can be heavy, the Nuvinci is 10lbs! see how you get on.

Thanks again

Knoxie

 

[Mathurin]

Nice indeed, can we have some pron of the bb area, how the motor holder and parts all fit together on the bike and stuff like that?

 

[Malcolm]

Here's a couple of photos without the cranks and chainrings.
I cut an old BMX bottom bracket shell in half lengthways and welded a circular plate on one end with a hole in it that's just big enough to insert the bottom bracket. I found another piece of tube in my scrap pile that was slightly bigger than the downtube and cut that in half lengthways too. Then you just join them together, make a giant jubilee clip from a piece of perforated strip, add a piece of scrap oval tube to reinforce the whole thing and Bob's your uncle. The mount is just held in place by the bottom bracket cup and the little jubilee clip.

 

[Malcolm]

Here's one that shows the motor mount more clearly. Should have spent a bit more time cleaning up with the grinder...

 

[John Grant]

Malcolm, that is very slick! With your ingenious motor mount and the eccentric lay out of the transmission “Bob truly is your Uncle”. Way to go. -grant

 

[Malcolm]

Thanks John I was much happier with this than my first attempt, which had the structural integrity of a piece of al dente linguini.
I reckon the mount could be simplified a lot to make it easier to fabricate, maybe using a short length of deep U-channel that's just wide enough to fit either side of the downtube. The circular section that grips the motor could be made from a slice of thin-walled pipe of roughly the motor diameter.

 

[vanilla ice]

Sweeet.

 

[Drunkskunk]

Damn.
Nice.
Market it and sell it.

 

[Mathurin]

And so, the emperor's enemies were overwhelmed by the aura of awesome, in accordance with the prophecy.

 

[Malcolm]

Deeply honoured am I. though without wishing to presume I would have preferred one of your feline friends Mathurin

 

[paultrafalgar]

...
I cut an old BMX bottom bracket shell in half lengthways and welded a circular plate on one end with a hole in it that's just big enough to insert the bottom bracket. I found another piece of tube in my scrap pile that was slightly bigger than the downtube and cut that in half lengthways too. Then you just join them together, make a giant jubilee clip from a piece of perforated strip, add a piece of scrap oval tube to reinforce the whole thing and Bob's your uncle. The mount is just held in place by the bottom bracket cup and the little jubilee clip.

What's so brilliant about this is that it's generic (like the Electrodrive) - it will fit on so many bikes! How many motors are there of that diameter? How many bottom brackets could it encompass? And down tubes? Maybe, someone could manufacture them. Maybe you could make the perforated motor strap longer and adjustable to adapt to different diameter motors? Well, done Malcolm!

 

[Malcolm]

Thanks Paul! I did have other motors in mind when I made this, as I'd like to try out a Kollmorgen with a planetary drive sometime. That would probably mean going to a smaller chain pitch though to get the pedal cadence down around 80.

The material I used for the strap isn't ideal; it needs to be more flexible. Perhaps a thinner strap like the stuff they use on packing cases would work better. Another idea would be to create a rigid semicircle that cups the motor, and use a pair of large hose clips to secure the motor to it. The Unite motor has a diameter of just over 110 mm and the Kollmorgen is 128 mm. Does anyone know what the diameter of the 500W Cyclone motor is?

 

[RLT]

Very ingenious! The ideas you guys come up with are such an inspiration.

 

[fitek]

Hey, I tried skimming and searching through the thread, but what controller is that MY1018 mated with? I've never used mine for driving and, well, maybe I should.

 

[Malcolm]

Hi fitek
It's a 4QD Porter controller: http://www.4qd.co.uk/
It's a fairly basic controller in terms of features, but very well made. It works well for me as it has a built-in throttle ramp up and ramp down of about 1 second, which means you can crack open the throttle without mangling the chain and sprockets. It also has automatic reverse polarity protection, which I've tested thoroughly