Maybe a thread for 5kw+ conversions?

[Stalkingcat]

I reckon a gearbox like the one in the BBS02 could be OEMed for about $100 from China. May be worth developing this into a kickstarter project. 5kW CD motor for £500?

Now that would be nice, would have to use some pretty tough cogs at those power levels but ts surely the way forward.

Ive never used a BBS02 but am temped to get one to test to failure, see where the weaknesses lay and then manufacture tougher internals.... hmmm

 

[trex]

The weakness of these gearboxes - used in almost all the Chinese CD kits, are the dimensional acuracy and long term stability of the gearbox shell. The other problem with a CD build is the bottom bracket weld. Is it strong enough against the awesome power of the kv120?

 

[Stalkingcat]

I'm on the case looking into this; would be great to bring back some precision English engineering rather than having to rely on China. Germany continues to make great products so I'm sure we can too?

 

[trex]

member mechaniker is based in Fuerth, where Sachs Motors are and I understand that he's connected to SFM. Mechaniker has extensive knowledge of CD gearboxes, may he be interested in joining your project making a kv powered CD kit?

 

[Stalkingcat]

Thanks for that. Its a tough one from looking into it.
The lightning volts kits look to be the most powerful at the moment, by doing exactly what was said, re-engineering an existing Chinese kit for high power.
I'm sure someone may correct me on this but some research has been done into the efficiency benefits of running through bike gearing and the results showed little or no efficiency gains compared to DD motors. apparently the motor's 'running at better efficiency' gains are taken up by the gear shifts and chain friction?

Thinking that maybe a centrally mounted, precision and cooled planetary geared dd motor, running no chain reduction to a rear beefed up internal geared hub,(or single speed) may be a possibility???

 

[trex]

There is currently very little work done in the area of high powered geared motors, may be worth looking into. I think that at over 1,200W (about twice the power of the BPM), the geared hub motors will become too brutally direct and powerful to control.

 

[Stalkingcat]

I think that at over 1,200W (about twice the power of the BPM), the geared hub motors will become too brutally direct and powerful to control.

Arr ok I see, Ive actually got a BPM on its way, in order to check out any possibilities of manufacturing more durable internals for more power. Thought that id take apart something cheap in order to suss it out, suss out the ride qualities and then maybe upscale if not too brutal as mentioned?
My personal brief is to take the weight off the back wheel so that the bike can be jumped and has better balance overall.
Has enough torque so that the throttle can be blipped.
Not too bothered about top speed but it would be nice to be able to program it for more if required or at least run 100v.
and all the other probably unrealistic requests, smooth, lightweight, stealthy, economical, good range etc. I'm thinking battery technology will make this somewhat possible fairly soon, would be great to have a drive system to compliment it

 

[trex]

it difficult to match the ride quality of a DD motor at 72V, certainty not the BPM. I reckon the BPM won't melt at 72V for 10 minutes.

 

[Stalkingcat]

OK thanks, was just about to ask if anyone had comparisons, as I've pretty much stuck with DD's
I have a very strange desire to melt motors and have been reading that BPM's or Macs can pull at 3kw the same as a 4kw DD but for how long is the question?

 

[Stalkingcat]

Been interested in this build below and wondering if it may be the way to go if refined. Lots of people saying a smaller geared DD motor would be better for it?
http://endless-sphere.com/forums/viewtopic.php?t=37489

 

[Deleted member 4366]

I ran a 250 rpm BPM at 16S (64v actual) and 30 amps, so that's just about 2KW. It didn't feel like it was under any particular stress. It just went fast. Cwah commuted with his at 72v(?) for a while, but he did eventually get a problem of some sort. The later ones (BPM2) have improved gear material (AFAIK).

 

[trex]

IIRC, cwah prefers his BBS02 48V 750W kit before he broke it.

 

[Stalkingcat]

So maybe back to refining a BB 750w style set up; proof is in the pudding so I'm going to try them both out unmodified to see which may have potential?

Its occurred to me that ive spend too much time trying to develop 'bad' ideas from the start due to diving in, getting excited, then realising half way through that if id thought about it, the approach is the wrong one

 

[trex]

I don't think you just 'dive in' - your previous bike is superbly built, the current bike will have better riding position, lighter, more power and more bike than the previous one. The bike after this one will, I am sure, be even better still.

 

[Stalkingcat]

One thing ive been things about (probably done before as most things have) is
Extending the dropouts to get the extra wheel base needed on a powerful build, far enough so that a powerful DD motor can be positioned just to the rear of the bottom bracket, getting the weight off the back but still driving the wheel with a fairly short chain and at almost full power distribution..
Smaller motorbike wheels (17/18") to help with torque at less amps/heat. Kind of like the production ebikes that have space for the battery to the rear of the bb but stick a motor in that space instead?

 

[Stalkingcat]

I don't think you just 'dive in' - your previous bike is superbly built, the current bike will have better riding position, lighter, more power and more bike than the previous one. The bike after this one will, I am sure, be even better still.

yep that's a good way of looking at it, natural progression/learning curve i suppose

 

[Rod Fuller]

Come on peeps, enough of this legal / illegal bore-fest.... AGAIN...

Can we ban those two words in this thread please, as it's getting interesting

Has anyone tried to make a pedelec an legal electric bicycle?

 

[Stalkingcat]

Sorry Rod, I didn't quite understand your post?