Dual freewheeling bottom bracket design

[Miles]

I thought I'd throw this one out, in case anyone is interested.

It has the advantage that the torque passes through the motor freewheel in its locked mode (no extra support bearing needed). Also, the motor drive is completely isolated when pedalling.

I've illustrated it with outboard bearings. Using roller bearings pressed into the BB shell would make it more compact.

More room to implement it if you had a BB30 shell, of course....

It's work in progress, not a final model.

 

[liveforphysics]

That is some very clever work my friend! I like it a lot!

The capturing of motor drive torque through the freewheel removal spline is particularly clever.

Of those parts, do you have drawings for the ones that are not off-the-shelf? I bought a very nice CNC lathe, and I've got a nice mill at work.

 

[Miles]

Hi Luke,

Sure, I can generate drawings of any of the parts. No problemo. :wink:

I'm not happy with the coupling at the other end of the motor axle, at the moment. It's not very elegant........

 

[Idontwanttopedal]

Lol like was trying to say to on phone

 

[farmkid4]

Very nice!

what program do you use?

 

[Miles]

Thanks.

what program do you use?

Alibre: http://www.alibre.com/products/mainpage.asp

 

[amberwolf]

this would be interesting to try on my nishiki/tongxin build. i wonder if i could turn an isis crank into the necessary pieces? i have one somewhere, dunno if it iss complete. i think it's just the crank arms and shaft. i will have to study the way your design works and the parts i have to see if they cn be made to do this.

 

[Miles]

Let me know if I can help, amber.

Another advantage of this set-up is the possibility to have 3 chainrings on the output.

 

[GITech]

Cool! I admire all your work miles!

Skin that cat!

Jay

 

[Miles]

Cross ref.: http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=37224

 

[Miles]

Decided to have another go at this.

Neat as the previous connection with the motor side ENO was, it precluded using other freewheels, so...

 

[Miles]

...

 

[Miles]

Need to find the best way to constrain things axially, now we're using roller bearings....

 

[MotoMel]

Here's one that works, and it's shortly to production: http://www.youtube.com/user/BikeMotive?feature=mhee.

 

[Miles]

Here's one that works, and it's shortly to production: http://www.youtube.com/user/BikeMotive?feature=mhee.

Well done, Mel!

I'm working in a different direction. That's why I haven't pursued this.

 

[ITgreybeard]

Hi Miles. Your bike looks like such a sweet setup! I love it. How well are you able to minimize weight to maximize its portability?

 

[Miles]

I have the batteries in a backpack. The bike is easily lifted with one hand.

It's not actually a folding bike, though....
http://www.moultonbicycles.co.uk/models/TSR27.html

 

[crossbreak]

do you have any supplier for the 30mm outer dia needle bearings miles? 30mm is fairly uncommon in the industrial area.
btw. the axial constraints could be achieved simply by Polyamide bushings. I use one as support bearing on my BB shaft, they produce hardly any drag.

 

[Miles]

do you have any supplier for the 30mm outer dia needle bearings miles? 30mm is fairly uncommon in the industrial area.

Yes. I did come across them, though. I'll look it up.

 

[Miles]

Sorry, they're 24mm ID, 31mm OD.

http://simplybearings.co.uk/shop/p9727/IKO+TA2420Z+Needle+Roller+Bearing+Open+End+Type+24x31x20mm/product_info.html

 

[crossbreak]

do you think the cups won't get too thin with these? I've never had such a cup on my lathe.

 

[spinningmagnets]

I like this a lot. Since the left-side motor drive is isolated, a despoked hub (cell_man geared?) can use its disc brake flange as a mounting point for a small sprocket. Opens up a lot of options. Looks like a Stokemonkey, but it freewheels under power.

 

[crossbreak]

I just measured the thickness of the material of such a cup. It is only 1.10mm thick. If we take away 0.5mm it gets really thin :?

Nice design btw

 

[Miles]

Not sure what you mean? Standard cups are 31mm ID... No?

 

[crossbreak]

no it's 30mm, i've got 2 on my desktop atm, a stock one from a 2002 giant and one from a cyclone 153mm BB

Edit: there are 30x22x20mm bearings at this shop. I hope 22mm is enough. The dia of the BB shaft is 16mm, so there are only 3mm space for the hollow shaft