Amberwolf's other "Bottom Bracket"-type Drivetrain Idea

[bandaro]

So, just chucking the idea out there, but if one was to run a lower voltage/lower kv motor than i have seen, then they could fit the motor above the kickstand mount right in tight to the bb, and have a gear made with say 5 teeth or so that would fit directly onto the regular chain sprockets. so the gear will need to be made to be a chain basically, but a chain fixed in a ring and bearing on the teeth etc to reduce friction on the gear. that way you can leave the bike unmodified (assuming the motor fits in front of the rear wheel there) and have the full range of gears you normally would. then it would be simply add a freewheeling set of cranks and your set. the drive would essentially run the unused half of the gears not interfering with the chain in any way.

so what do you guys think, would it be a viable option for decent powered systems? or would it be too hard/expensive to make a pinion that would fit as a chain would but only contacting 2 teeth at a time? i can make up a cad of this if anyone is still unsure of this idea, its just off my head atm.

 

[[Team1] Gabriel]

Wow, another new idea of a variation! And also sounds very reasonable - at least for me. Never thought that there were so many possibilities.
@bandaro: Sorry, I cant comment to the viability of your idea, because I have no experience whatsoever yet...

I just wanted to say:

Isn't it great how many variations and additional ideas came into being just out of this one idea? - man, you all are awesome

 

[Miles]

So, just chucking the idea out there, but if one was to run a lower voltage/lower kv motor than i have seen, then they could fit the motor above the kickstand mount right in tight to the bb, and have a gear made with say 5 teeth or so that would fit directly onto the regular chain sprockets. so the gear will need to be made to be a chain basically, but a chain fixed in a ring and bearing on the teeth etc to reduce friction on the gear. that way you can leave the bike unmodified (assuming the motor fits in front of the rear wheel there) and have the full range of gears you normally would. then it would be simply add a freewheeling set of cranks and your set. the drive would essentially run the unused half of the gears not interfering with the chain in any way.

so what do you guys think, would it be a viable option for decent powered systems? or would it be too hard/expensive to make a pinion that would fit as a chain would but only contacting 2 teeth at a time? i can make up a cad of this if anyone is still unsure of this idea, its just off my head atm.

The "Anytime" folding bike, which won second prize in the 2009 IBDC, used this system:

Ref: http://bicycledesign.net/2009/03/international-bicycle-design-competiton/
More details here: http://www.t-onedesign.com/anytime-photo.html
See also: http://endless-sphere.com/forums/viewtopic.php?f=28&t=17399&start=0

 

[JohnH]

I'm usually quiet here, because while I'm comfy building up a bike from components, I've yet to build anything at all e-bike-like. However, I've done a lot of reading and absorbing, here and elsewhere on these topics, and picked up on a few things. So all this is my interpretation of other folks' ideas, nothing original at all. Disclaimer away , here goes:

Team1 has a very elegant concept, but it has a significant failing IMHO. When I'm pedaling, especially when I'm providing all the power (AW's "limp home" scenario), I want to maximize my pedaling efficiency. AW's idea, and the cyclone it sort of resembles, interrupt the return side of the chain with a pair of cogs - the drive cog and the idler to wrap the chain around said cog. This introduces some drag, but this side of the chain would be slack anyway - the upper run of chain, the drive side, is the one under tension. So the loss of efficiency is minimized. Interrupting the drive-side of the chain maximizes this loss in efficiency, and I'm stuck with it.

A second, related, issue: a motor in the return side of the chain pulls my feet around if there's no freewheel on the crank. I can live with that in exchange for not putting up with a freewheel in my drive line. I'm riding a bike, and I expect to be pedaling. Not everyone's taste I know, but there you have it. A drive a la Team1's design above "pushes" the chain onto the chainrings. If I stop pedaling, or even drag a bit for *just a moment*, a variety of bad things happen starting with derailment and (likely) ending with unplanned pavement contact. Even with a freewheel in the crank, "pushing" chain is just a *bad idea* in my mind.

I'll take my drive below and behind the crank, or driving a left-side chainring a la stokemonkey, thanks.

Now, I think you could mount the motor low and run a rod up to a front derailer cage and still shift the motor and chain sideways at the same time - the cage would just be an extension of the motor mount. After all, the original front derailers weren't cable-actuated at all - they were rod-actuated, from the seat tube (shifting must have been a real adventure!).

My $.01, not quite worth $.02

 

[[Team1] Gabriel]

My $.01, not quite worth $.02

I wouldn't say that, your post was a very constructive comment.
Your answer was logic, you revealed (the not so obvious) weaknesses of the idea, explained their consequences and also made a suggestion which took the good features of both ideas into one reasonable sounding solution.

There are people here, experienced in building, some are good at electronics, some at programming and some gain experience through reading a lot.
But I've no experience at all yet - I'm just creative

- So there are people needed like you, to take the good parts of that ideas and reflect them in the right way, so that the others can see them better too.

 

[jdcburg]

Regardless of whether the chain is bottom- or top-driven, I believe strongly that a crank freewheel is necessary for rider safety. I also don't see any advantage to not having one. By being able to shift the front derailleur into a lower gear, the front cranks will be spun by the motor even faster and more powerfully. A foot slipping off in front of the crank in that situation (with no crank freewheel) puts the rider in serious danger - jd