Current Vado/Tero motors

[mschwett]

@BlackHand: The industry standard between major mid-drive motor manufacturers is Power = Torque * 6.28 rad/s (60 rpm). Yamaha and Brose 85 Nm motors have the rated peak power of 520 W (meaning the actual torque is 82.8 Nm). The actual 90 Nm motor (Specialized 2.2) has the peak power of 565 W. If anyone says the Bosch motor has bigger mechanical peak power then the torque should be a way higher.

you have mentioned this "standard" multiple times - please point us to the actual standard/document. there is no rule or reason i'm aware of to only refer to power at 60rpm, when a mid-drive may in fact operate at a wide range, say 50 to 100 rpm, and the controller could easily be designed to provide different amounts of power at different rotational speeds!

 

[Stefan Mikes]

you have mentioned this "standard" multiple times - please point us to the actual standard/document. there is no rule or reason i'm aware of to only refer to power at 60rpm, when a mid-drive may in fact operate at a wide range, say 50 to 100 rpm, and the controller could easily be designed to provide different amounts of power at different rotational speeds!

How would you explain the fact Bosch E-Bike quotes the torque of its reportedly 600 W mechanical power motor as only 85 Nm if they could easily say it is 95 Nm to stand out among the competors?

Or, why would they use the strange value of 7 rad/s (67 rpm) for reference? That would make the impression of Bosch motors as having less torque than the competing ones.

 

[mschwett]

How would you explain the fact Bosch E-Bike quotes the torque of its reportedly 600 W mechanical power motor as only 85 Nm if they could easily say it is 95 Nm to stand out among the competors?

Or, why would they use the strange value of 7 rad/s (67 rpm) for reference? That would make the impression of Bosch motors as having less torque than the competing ones.

i would explain it that it doesn’t produce 95Nm? it produces 85Nm, at 67 RPM - and presumably at lower speeds as well. as you note, if it produced that amount of torque at speeds higher than 67 RPM it would be more than 600w.

torque varies with current. you could reprogram the controller for more current, assuming the battery was capable, and more torque and power would result. of course, it might not last very long. while not totally arbitrary, the torque and power output of an electric motor within a reasonable range is really up to the programming of the controller. so, again, i ask: where is the “standard” you claim which requires electric motor manufacturers to reference torque and power at 60 rpm?

 

[Stefan Mikes]

so, again, i ask: where is the “standard” you claim which requires electric motor manufacturers to reference torque and power at 60 rpm?

I base that reasoning on the published data:

• Specialized 2.2, 90 Nm at 565 W
• Specialized 1.2s, 85 Nm at 520 W
• Yamaha PW-X2, 85 Nm at 520 W.

The value of torque without specified rotational speed is useless. (It is like giving a value of enthalpy without the reference state).

 

[coffmandave]

Wait, Stefan, are you saying bike motors are at peak efficiency at 60rpm, that they are crippling their own "up to xxx power/torque" numbers by not using peak rpm values, or that peak power/torque has no relationship to peak efficiency?

Is there a fourth option? Because all three of those arguments seem ridiculous to me.

 

[Stefan Mikes]

Wait, Stefan, are you saying bike motors are at peak efficiency at 60rpm, that they are crippling their own "up to xxx power/torque" numbers by not using peak rpm values, or that peak power/torque has no relationship to peak efficiency?

Is there a fourth option? Because all three of those arguments seem ridiculous to me.

Not. The reference rotational speed to calculate the motor torque from the peak mechanical motor power is 60 rpm.

 

[coffmandave]

How is that different from my second argument: Using non-peak rpm values to generate "peak" torque?

 

[mschwett]

How is that different from my second argument: Using non-peak rpm values to generate "peak" torque?

without more information from the manufacturer (of the entire controller/motor/battery system) we really have no idea at what RPM peak torque OR power are achieved. several manufacturers reference those two values at 60RPM, and many others do not. if, for example, the bosch gen4 is 680 peak mechanical watts and 85 nM peak torque, we can conclude those two values could not be reached together at 60RPM. the math says 75 RPM. which is a perfectly reasonable rotational speed for a mid-drive bike motor.

it is simply not correct to say the peak torque is something other than the manufacturer claims without some testing, more information, or qualifications, like “at 60 RPM the torque is…”

remember also that much of this is software. bosch “upgraded” their motors from 75 to 85 nM with software. more current, more torque!

 

[coffmandave]

Sure, I can't argue that there are zero bike motors that have a peak rpm of 60, but I STRONGLY doubt that's the norm since the typical cycling cadence is quite a bit higher. I would guess if it applies to any ebike motors, it'd be cargo bikes and/or the very low end.

Specialized, for instance, has said their peak cadence is between 70 and 90rpm, and the display on my Tero will monitor your cadence and give you a color-coded nudge that maybe you should change your gearing if you fall too far outside of that range. (I think the "green" area is 70-100, but I might be off on that).

Anyway, my main point is that it's silly to suggest a bike company would use "up to ____ power/torque" numbers at anything other than peak rpm, so they can make themselves look as impressive as possible.

 

[Stefan Mikes]

Guys, just tell me: so Bosch has a motor that can pump as much as 680 mechanical watts and only get 85 Nm? What's wrong? If Specialized can get 90 Nm at 565 W and Yamaha gets 85 Nm at 520 W, what's wrong with Bosch?! What a waste of the battery charge...

 

[Stefan Mikes]

@mschwett: Did you know Austria e-bike law limited the maximum e-bike motor power to 600 W mechanical? No wonder Bosch is so tight-lipped about the peak power of its motors and perhaps that's the reason they use as low torque figure in their marketing?

 

[coffmandave]

Funny enough, I've got a friend who just bought a Trek 9.8 GX with a Bosch Performance Line CX motor that has a specified 85nm torque.

I'm objectively a stronger rider, riding a more powerful motor (90nm torque), but climbing a steep hill, she's faster than me on my Tero 5.0 when we were both in turbo.

Obviously there's a lot of other factors at play...for instance, I weigh significantly more than she does. But anecdotally, I still gotta say, the struggle of keeping up with her was enough to make me suspect that, paper stats be damned, her motor might be more powerful than mine.

 

[mschwett]

@mschwett: Did you know Austria e-bike law limited the maximum e-bike motor power to 600 W mechanical? No wonder Bosch is so tight-lipped about the peak power of its motors and perhaps that's the reason they use as low torque figure in their marketing?

or they could just program the controller to provide slightly reduced current at higher RPM, making both the peak power and the peak torque figures true. with the exception of very small motors (like the SL or X20) which are running close to thermal limits, these numbers are driven by software more than anything, and the software delivers different amounts of current under different conditions, making any notion of a fixed relationship really silly.

it makes a lot of sense for torque to peak lower, where it aids acceleration rather than top speed and thus peak power.

 

[Stefan Mikes]

Obviously there's a lot of other factors at play...for instance, I weigh significantly more than she does. But anecdotally, I still gotta say, the struggle of keeping up with her was enough to make me suspect that, paper stats be damned, her motor might be more powerful than mine.

It is definitely too many factors, Dave.

The motor that I perceive as the strongest I ever owned was Yamaha PW-X2 in a Giant Trance E+ 2 Pro (85 Nm @520 W). Bear in mind, the e-MTB has a very low available gearing, is made for climbing, could be tuned for very low speed/extreme climbing, and probably had the max motor power unlimited (!!!). Fancy me climbing a steep river embankment in the straight line up! Or, climbing a very steep concrete bridge base (it looked 45 degrees, perhaps 30%?), which I climbed in the granny gear and Turbo in front of my shocked brother! I would have never done it with my 85 Nm 520 W Specialized 1.2 s on Vado 6.0.

Too many factors.

 

[BlackHand]

I mean, we all know that marketing are the ones who set the specs, probably after running it by legal. I bet the engineers didn't even get to see the official specs until the launch press release came out.

It is a minor miracle that so many motors from different manufacturers happen to have all arrived at 85Nm. I guess Brose didn't get the memo when they set their motor at 90Nm.

 

[Stefan Mikes]

I mean, we all know that marketing are the ones who set the specs, probably after running it by legal. I bet the engineers didn't even get to see the official specs until the launch press release came out.

It is a minor miracle that so many motors from different manufacturers happen to have all arrived at 85Nm. I guess Brose didn't get the memo when they set their motor at 90Nm.

I vaguely recall some paper talking about the European rule: Never amplify human legs above 4x. That rule was respected for a few years. Now, we can see individual motors with 410% boost.

 

[coffmandave]

I agree, many variables, but still:

In a "Drag Race", the Bosch CX was about 40 seconds faster than the Specialized 2.2. This still isn't necessarily a "scientific experiment", but....yea, I really do think the CX is more powerful. That said, it's also very "un-natural". If you touch the pedal, it lurches ahead in a way the Specialized doesn't. I still prefer the Specialized, even if I can't keep up with her in a drag race up a steep hill.

 

[Stefan Mikes]

That said, it's also very "un-natural". If you touch the pedal, it lurches ahead in a way the Specialized doesn't. I still prefer the Specialized, even if I can't keep up with her in a drag race up a steep hill.

It is either MTB motor tuning or lack of max motor power capping (the second parameter in Specialized) or her low weight or...

Set your assistance to xx/100% and she can hold your beer