Chain rings and crank drives

[EddiePJ]

Something struck me yesterday whilst out riding off road. In the 5 months or so of owning the Xtrem, yesterday was the first time that I have used the granny ring. This in turn made me think about crank drive motors, and the fact that in the case of something like the Haibike below, the chainring/cog is very small.
When using power assist on the Xtrem I'm generally on the middle ring of the three chain rings, and then when in non assist mode I'm more often than not on the outer largest ring and smallest cog on the cassette.

Would I be correct in assuming that when using a pedal only non assist mode on a crank drive bike, the pedalling and gearing would be as useless on road as the granny ring would be on my current triple set up?

Example only..

 

[Artstu]

No the drive isn't direct on the newer Bosch, the drive is geared up before being transmitted to that granny ring looking front sprocket.

 

[EddiePJ]

So there is an internal unit gearbox similar to that of a motorcycle, with the gear change located on the handle bar?

If so, does this not add/create drag* to the system?

I'm just concerned that if I do eventually decide to change to a crank drive motor, that my on road enjoyment will in some way be spoilt.


*If that was the right word.

 

[Artstu]

There is a gearbox yes, but they're only one speed, so just like a bike with one chain ring on the front.

There has to be some loss involved as you say.

 

[Martin@e-bikeshop]

Hi Eddie,

The motor is geared internally on the new Bosch. The outside ring turns roughly 2.5 times to each pedal crank. So on this model it's the equivalent to roughly a 39t sprocket. It also have the new SRAM 11speed gear system with the massive 10-42t range!

I actually had the bike you pictured above in my workshop this week and I can say that I felt no drag on the cranks when the motor was turned off.

Why not read all about how the Bosch works on my blog here? - http://www.e-bikeshop.co.uk/blog/

Regards
Martin

 

[EddiePJ]

Thanks Martin, your input as usual is very helpful.

I reckon that I need to find/make the time to come down to see you.

edit.. The bike shown was only an example, albeit a very stunning one. I only need approx. 150mm max of travel up front.

 

[martin@onbike]

An Sram Dual-drive derailleur/Hub mix covers every gearing need from a single front chainring-27 speed bosch is lovely...

 

[Croxden]

An Sram Dual-drive derailleur/Hub mix covers every gearing need from a single front chainring-27 speed bosch is lovely...

Not as lovely as my Delite with a Rohloff hub.

 

[EddiePJ]

I've just spotted that the Bosch motor has a walk mode! I could have done with that yesterday, and also on several other occasions over the last month.

 

[Deleted member 4366]

Are you sure that you don't have it? I know some Neos do. Try press and hold the upper button on the display.

 

[RobF]

Not as lovely as my Delite with a Rohloff hub.

Has it arrived at last?

 

[EddiePJ]

Thanks Dave, now that you mention it I seem to recall that you are right.
Why the hell didn't I remember that one. I guess it was the lack of oxygen going to my brain whilst pushing it.

 

[Croxden]

Has it arrived at last?

Yes, picked it up yesterday. Had a ride today, it is brilliant. Only done 17 miles so far, so will wait a while before a report, so far very favorable.

 

[martin@onbike]

Not as lovely as my Delite with a Rohloff hub.

That's true Croxden...A 14 speed Rohloff is a very, very nice option indeed. Deliteful even!