Most powerful eBike for long uphill journeys?

[Zlatan]

Just seen graphs...they would also infer a flat torque curve , with power simply rising as a function of higher rpm, until approx cadence of 90 or so is reached.

Graph is contradictory to earlier link showing power meter on Yamaha. That showed max power of around 700, the graph under 500 ???

 

[Woosh]

Correct me by all means DV but isn't motor torque with respect to rpm just,about a flat line until max rpm ?

straightline until about 65-70 RPM then the ratio power./rpm drops rapidly toward the noload RPM (110-120rpm).

 

[Deleted member 4366]

The Bosch CX becomes current limited by the back emf at about 70 RPM. The PL seems to go on to about 82 rpm, so must be a faster winding. You'd therefore expect the PL to have lower efficiency than the CX at lower RPMs.

They don't say whether those graphs are input power or output power. I would say input power.

There's something fishy about them anyway. Brose 320w, Bosch CX 580w, nearly twice as much. I don't think so.

 

[soundwave]

 

[Woosh]

They don't say whether those graphs are input power or output power. I would say input power.

I think they are output (mechanical) power. The CX plot peaks at 580W, at 80%-85% efficiency, 683W-725W input, comparable to a 36V 20A controller.

 

[Deleted member 4366]

The more I look at those graphs, the more they don't look right to me. There's no way that the output power can be a straight line from 20 to 70 rpm or whatever because efficiency falls off increasingly as the rpm goes down. every other electric motor power curve I've seen, the power curves down as the revs go down. Also, once the motor starts to limit the current, the power rapidly ramps down in a straight line to zero as the rpm rises. neither of those features are shown in those graphs.

Either, we've misunderstood what they're supposed to be or the information, as presented, is wrong.

How do they get those motors to provide their power to make those graphs? There's no throttle.

Also those graphs show the Bosch motors giving power way beyond 120 rpm. I never heard of that before!

 

[Woosh]

let's take a closer look at the CX plot:

The formula is
P = Torque * rotational speed

at 20 rpm, rotational speed = 20*2*3.14/60 =2.1 rad/s, P = 150W
Torque = 150W / 2.1rad/s = 72NM

at 50rpm, rotational speed = 5.25rad/s, P = 380W
Torque = 380W/5.25rad/s = 73NM

at 70rpm, rotational speed = 7.35rad/s, P=530W
Torque = 530W/7.35rad/s = 73NM

So they simply run the motor at 73NM.

 

[Deleted member 4366]

That would be nice if you could, but physics doesn't allow that. I'm wondering if those graphs are calculated from an arbitrary incorrect formula rather than actually measured, or extrapolated from some other data using an incorrect algorithm, but how do they get the Brose one to go all over the place then? Something is definitely not right. I'd take those graphs with a pinch of salt.

Can someone confirm whether their Bosch CX still makes 400W at 120 RPM?

 

[Woosh]

I think what they do is to get to a set RPM (20,30,40,50,60,70 etc) then push hard on the pedals to milk the motor.
As the motor can't go over 80NM, the torque at those RPMs is a little under 80NM, so 73NM is credible until the back EMF begins to bite back beyond 70rpm.

For example at 110RPM, the rotational speed is 11.55rad/s, P = 480W
Torque = 41.5NM

 

[Deleted member 4366]

I think what they do is to get to a set RPM (20,30,40,50,60,70 etc) then push hard on the pedals to milk the motor.
As the motor can't go over 80NM, the torque at those RPMs is a little under 80NM, so 73NM is credible until the back EMF begins to bite back beyond 70rpm.

For example at 110RPM, the rotational speed is 11.55rad/s, P = 480W
Torque = 41.5NM

How do you account for the 400W at 120 rpm, when Bosch themselves say no power after 120 rpm?

https://www.bosch-ebike.com/en/components/drive-unit/

 

[anotherkiwi]

To my inexperienced eye that looks very much like a Bosch marketing graph. I bet they got Dieter from the graphics department to build by ear it in Adobe Illustrator...

 

[Woosh]

I reckon my Rio FB could have a decent mountain climbing race against the CX.
I may have to replace the 17A controller with a 20A or 25A one.

EddiePJ?

 

[soundwave]

https://www.bosch-ebike.com/de/service/reichweiten-assistent/

 

[soundwave]

according to that i get 19.9km with 110rpm sclass motor and 500w batt.

i get more than double that lol.

 

[EddiePJ]

I reckon my Rio FB could have a decent mountain climbing race against the CX.
I may have to replace the 17A controller with a 20A or 25A one.

EddiePJ?

Not sure why I am being dragged into this?

That is now two comments within the same thread that mentioned my name in relation to racing.

In respect of the CX motor, it wouldn't be and isn't my preferred choice in respect of the mountain/hill climbing that I enjoy tackling so much. I'd sooner use a combination of a Performance Line DU and 36V 500wh 13.4ah battery pack.

Having ridden many of my climbs using both the Performance and CX DU, I can't say that I require the extra claimed torque that the CX has to offer, and see it as a disadvantage in respect of battery drain.

As I see it, there are only three possible limiting factors to what I can or can't get up. The first being the terrain in respect of ruggedness, the second being the rider, and third being the final drive gearing.

What I do find amusing, is that within the two comments referring to racing, both have elements of cheating. It doesn't say very much if modification outside of OE spec is required.

I also haven't been giving second thought to this thread as the OP was asking what is the most powerful bike for long hill climbs, and that isn't a priority on my list of requirements or wants.

Rupert1 has already shown that his Woosh can climb, and all credit to him for that. Just a shame that so few people seem to tackle what could be considered as a proper climb.

As a point of note to this willy waving thread, people brag and state that their bikes can climb this, climb that, yet no one other than myself actually presents proof of this. In the scheme of climbing, to my mind any climb less than five miles long is just a bump in the landscape. I can't answer for other parts of the UK, but the average elevation over one mile in the South East of England is 120ft. Again just a bump in the landscape. To represent any kind of sensible of climb, you are looking at an elevation gain of approx 500ft per mile.

 

[soundwave]

Not sure why I am being dragged into this?

That is now two comments within the same thread that mentioned my name in relation to racing.

In respect of the CX motor, it wouldn't be and isn't my preferred choice in respect of mountain climbing. I'd sooner use a combination of a Performance Line DU and 36V 500wh 13.4ah battery pack.
Having ridden many of my climbs using both the Performance and CX DU, I can't say that I require the extra claimed torque that the CX has to offer, and see it as a disadvantage in respect of battery drain.

jimmy at insat can get 14ah worth of cells in a bosch pack when the time comes

 

[chris_n]

I reckon my Rio FB could have a decent mountain climbing race against the CX.
I may have to replace the 17A controller with a 20A or 25A one.

EddiePJ?

Oi I've already told you I'll test this in the Alps for you. I'm here all summer and would be very open to carrying out some back to back testing whether it be in private or public màkes no difference to me. I'm really interested in whether a hub motor can cut it compared with my Yamaha when it comes to extended uphill rides.

 

[mountainsport]

I reckon my Rio FB could have a decent mountain climbing race against the CX.
I may have to replace the 17A controller with a 20A or 25A one.

EddiePJ?

Be careful now, because the next stage you will be asked to produce a Woosh graph showing how your prices have suddenly and significantly shot up. We don't need to start tampering with your already good figures or do we?

MS.

 

[Trevormonty]

The Bosch CX becomes current limited by the back emf at about 70 RPM. The PL seems to go on to about 82 rpm, so must be a faster winding. You'd therefore expect the PL to have lower efficiency than the CX at lower RPMs.

They don't say whether those graphs are input power or output power. I would say input power.

There's something fishy about them anyway. Brose 320w, Bosch CX 580w, nearly twice as much. I don't think so.

Group tests of eMTB drives show considerable faster climb speed for CX compared to Brose. Power differences on graph would explain this.

After owning a CX drive I find I rarely use Turbo. Never on single track more on fire roads if battery range isn't issue. With 14t chainring and 11-46t cassette, eco or tour would climb any hill.

 

[brightonebikes]

Group tests of eMTB drives show considerable faster climb speed for CX compared to Brose. Power differences on graph would explain this.

After owning a CX drive I find I rarely use Turbo. Never on single track more on fire roads if battery range isn't issue. With 14t chainring and 11-46t cassette, eco or tour would climb any hill.

And in real life the Bafang BBS02B 36V 250W trumps the lot hands down
Just saying.

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