PAS Levels, torque vs speed?

[RMW]

I do not yet own an ebike, and am trying to learn more to make a smarter buying decision.
Do internally-geared rear hub motors have more torque (but lower speed) for low PAS settings? And conversely, have less torque but higher speed for high PAS settings?

 

[RMW]

You should watch this.

Interesting. I am open to learning anything, but that video did not really address the PAS level settings.
I am a (retired) engineer, and think about the power consumption as it can be applied as a combination of torque and speed. Are PAS controllers capable enough to adjust the torque vs speed?

 

[mogulskier]

I do not yet own an ebike, and am trying to learn more to make a smarter buying decision.
Do internally-geared rear hub motors have more torque (but lower speed) for low PAS settings? And conversely, have less torque but higher speed for high PAS settings?

Not observed on my Surface 604 Shred. It has a torque sensor and hub motor. At PAS L1, you don't get much torque or speed unless your really working, but by PAS L3, you really feel the lurch forward with a strong torque pull when you start to hammer the pedals, and keep it up, and you can hit some impressive speeds.

Haven't been to L4 or L5 yet, but I would image the torque and speed increases at each PAS increment.

 

[Sierratim]

Interesting. I am open to learning anything, but that video did not really address the PAS level settings.
I am a (retired) engineer, and think about the power consumption as it can be applied as a combination of torque and speed. Are PAS controllers capable enough to adjust the torque vs speed?

As to PAS vs torque for geared hub motors I'm not aware of any data that directly answers this question. My mid-drive bike, a Specialized Vado 5, has adjustable PAS levels based on motor power. The bike has torque and cadence sensors so it must convert torque to power but does not report the torque info. Torque/power speed curves are available for these motors that can help shed some light on this relationship;

I'm not aware of similar performance curves for hub motors.

 

[legsofbeer]

Do internally-geared rear hub motors have more torque (but lower speed) for low PAS settings? And conversely, have less torque but higher speed for high PAS settings?

It works a bit differently. Geared hub motors have their torque mostly available throughout their range, and lots of speed and torque at the low end of power application. From a stop they accelerate very well. But they reach a speed ceiling in the mid-high twenties (mph) where a direct drive hub motor is still willing to go faster. As you approach that ceiling you can burn silly amounts of battery power on a geared hub going 20+ if you're not working your legs. The direct drive won't get you up to that threshold speed nearly as quickly, but it will take you beyond it, with more power consumption efficiency. Note that if your intent is to carry or move a heavy load (300lb+) regardless of speed those geared hub nylon gears may eventually strip and leave you stranded.

 

[Bruce Arnold]

Reading the answers, I don't think folks are getting your question. You're not talking about internal gears in the hub motor. You're talking about a bike with an IGH, or Internal Gears Hub. If I'm wrong, then disregard the rest of my comment.

An IGH bike will have a mid-drive motor, which is centered around the crank rather than the wheel. A mid-drive motor could have either derailleur gears or an IGH. A hub drive motor can't have an IGH.

Most mid-drive motors have a higher torque rating than hub drives. There is overlap, of course, but generally speaking you will find this to be true. For instance, e-mountain bikes pretty much always have mid-drive motors -- I can't think of any exceptions off the top of my head -- because they need the grunt to get up steep inclines.

This doesn't necessarily affect their top end speed. That would depend on several factors, including how steep the high gear is, and how the software is configured.

In all cases, torque will be proportional to the PAS level, because that determines how much electrical power is being transferred to the drive train, however it's configured.

I've never owned a bike with a mid-drive, so I'm sharing what I've learned from people I trust, not direct experience.

I hope that helps.

 

[RMW]

Reading the answers, I don't think folks are getting your question. You're not talking about internal gears in the hub motor. You're talking about a bike with an IGH, or Internal Gears Hub. If I'm wrong, then disregard the rest of my comment.

An IGH bike will have a mid-drive motor, which is centered around the crank rather than the wheel. A mid-drive motor could have either derailleur gears or an IGH. A hub drive motor can't have an IGH.

Most mid-drive motors have a higher torque rating than hub drives. There is overlap, of course, but generally speaking you will find this to be true. For instance, e-mountain bikes pretty much always have mid-drive motors -- I can't think of any exceptions off the top of my head -- because they need the grunt to get up steep inclines.

This doesn't necessarily affect their top end speed. That would depend on several factors, including how steep the high gear is, and how the software is configured.

In all cases, torque will be proportional to the PAS level, because that determines how much electrical power is being transferred to the drive train, however it's configured.

I've never owned a bike with a mid-drive, so I'm sharing what I've learned from people I trust, not direct experience.

I hope that helps.

I wrote "internally-geared rear hub motor" to distinguish from direct-drive rear hub motors. I read many comments that claim direct-drive motors don't have a lot of torque at low speeds. (Decent torque is desired for accelerating from a dead stop, especially when going up hill.) So I have eliminated direct-drive from my buying options.

 

[Sierratim]

I wrote "internally-geared rear hub motor" to distinguish from direct-drive rear hub motors. I read many comments that claim direct-drive motors don't have a lot of torque at low speeds. (Decent torque is desired for accelerating from a dead stop, especially when going up hill.) So I have eliminated direct-drive from my buying options.

Grin Tech's Motor Simulator is a handy tool to compare motor performance curves. The curve set I've linked to is for Grin's GMAC motor at 48V but of course every motor/battery/controller/gearing combo has it's own set of curves. This still doesn't address your original question re PAS vs torque. As I mentioned I'm not aware that this data exists.

Good hunting.

EDIT: I neglected to set the motor as a 'hub motor' in the simulator in my original post. I've corrected this in the simulator link.

 

[AHicks]

A geared hub offers pretty sporty performance right from the time it starts to move. The 5:1 gears in most assure that when compared to direct drive hubs, which seem gutless in comparison (at speeds under 15mph or so anyway). As far as what to expect from the different PAS levels, most are speed based, with voltage to the motor increasing with increased PAS/speed levels.

Would like to be more help here, but not sure what you are after:
"Do internally-geared rear hub motors have more torque (but lower speed) for low PAS settings?"

Are you talking geared vs. direct drive, and how they compare performance wise at low speeds (say under 20mph)?
Or maybe the amount of torque available from the start vs. higher speeds (say 10-12mph)?-Al

 

[Art Deco]

As an engineer, you can appreciate how gearing affects torque and speed. Hub motors (both types) do not use your bikes gears, middrive motors apply power thru the bikes drive chain or belt, using 7 to 12 different gear ratios. Hubs have different advantages as detailed above.

 

[Sierratim]

As an engineer, you can appreciate how gearing affects torque and speed. Hub motors (both types) do not use your bikes gears, middrive motors apply power thru the bikes drive chain or belt, using 7 to 12 different gear ratios. Hubs have different advantages as detailed above.

Art, to me the difference is that hub motors are tied to the wheel speed so as the bike accelerates past the motor's peak on its torque/power curve assistance will drop as the motor's torque/power output drops off. The same drop in torque/power with speed happens with all motors. The only difference with mid-drive ebike motors is that the rider can use the bike's gearing to keep the motor output close to its peak.

 

[Art Deco]

Yeah. But. You can spin closer to the bike's prefered speed. I am a stomper, and need the gearing to keep closer to a cadence that keeps the bike's motor generating power. I am just starting to work on cadence, and right now power at 80 or 90 rpm is useless to me b/c I can't pedal that fast.

 

[Stefan Mikes]

and right now power at 80 or 90 rpm is useless to me b/c I can't pedal that fast.

"Practice makes perfect.
Yes, I can prove it"

 

[RMW]

Thank you to all who posted here. My question was best answered by Sierratim with his graphs of motor torque and power output vs speed.
I was also chatting with a friend who drives a Tesla 3. He explained that the electric motor is designed to have lots of torque at low speed, right where it is needed when beginning to move. That is why the Tesla transmission has no changeable gears to shift.

Happy New Year to all!

 

[Sierratim]

Yeah. But. You can spin closer to the bike's prefered speed. I am a stomper, and need the gearing to keep closer to a cadence that keeps the bike's motor generating power. I am just starting to work on cadence, and right now power at 80 or 90 rpm is useless to me b/c I can't pedal that fast.

Art, I guess that's the thing with geared hub motors, the rider needs to pedal at a cadence that matches the motor's peak output rpm when you need peak assistance.

Realizing that all motors have a fairly narrow rpm/speed range to produce max torque/power, hub and mid-drive ebike motors do have different characteristics that impact the rider.

For hub motors the motor and thus the wheel must rotate over a fairly narrow rpm range for peak output. This equates to a narrow range of speed for the bike for max motor performance. The motor simulator output I linked to in post #11 above illustrates one aspect of this where this hub motor peaks at just 16Nm. This is one reason that Grin Tech recommends hub motors for most recreational riding.

Mid-drive motors must also operate over a fairly narrow range of rpm for max output. With the bike's gearing the rider can maintain a fairly consistent speed/cadence while varying the bike speed to match conditions. This is one reason Grin suggests that mid-drives are preferred for rides with higjly variable trail conditions, like MTB riding.

So, different strokes for different conditions (thought I was going to say 'folks'?)

 

[Art Deco]

Art, I guess that's the thing with geared hub motors, the rider needs to pedal at a cadence that matches the motor's peak output rpm when you need peak assistance.

Realizing that all motors have a fairly narrow rpm/speed range to produce max torque/power, hub and mid-drive ebike motors do have different characteristics that impact the rider.

For hub motors the motor and thus the wheel must rotate over a fairly narrow rpm range for peak output. This equates to a narrow range of speed for the bike for max motor performance. The motor simulator output I linked to in post #11 above illustrates one aspect of this where this hub motor peaks at just 16Nm. This is one reason that Grin Tech recommends hub motors for most recreational riding.

Mid-drive motors must also operate over a fairly narrow range of rpm for max output. With the bike's gearing the rider can maintain a fairly consistent speed/cadence while varying the bike speed to match conditions. This is one reason Grin suggests that mid-drives are preferred for rides with higjly variable trail conditions, like MTB riding.

So, different strokes for different conditions (thought I was going to say 'folks'?)

Also the reason I prefer manual transmissions in cars and trucks ( remember those? ). If you want a manual today it's a special order item for anything besides sports cars.
Noticed that the OP liked your torque curves too. Engineers and TMI. It really is a thing.

 

[Sierratim]

Also the reason I prefer manual transmissions in cars and trucks ( remember those? ). If you want a manual today it's a special order item for anything besides sports cars.
Noticed that the OP liked your torque curves too. Engineers and TMI. It really is a thing.

...and TMT!

 

[legsofbeer]

I guess that's the thing with geared hub motors, the rider needs to pedal at a cadence that matches the motor's peak output rpm when you need peak assistance.

This makes no sense at all. The geared hub's position on any torque curve is a function of the wheel's rotational speed, not pedaling cadence. And the point of a geared hub, is that the internal gearing is selected to provide good torque throughout the range of expected wheel speed, thus the observed performance: the geared hub has good torque from a stop up to a certain speed, beyond which you get diminishing torque and eventually none.

 

[AHicks]

This makes no sense at all. The geared hub's position on any torque curve is a function of the wheel's rotational speed, not pedaling cadence. And the point of a geared hub, is that the internal gearing is selected to provide good torque throughout the range of expected wheel speed, thus the observed performance: the geared hub has good torque from a stop up to a certain speed, beyond which you get diminishing torque and eventually none.

Grin's simulator illustrating that point:

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

-Al

 

[Sierratim]

The geared hub's position on any torque curve is a function of the wheel's rotational speed, not pedaling cadence.

Perhaps my comment was unclear in that I did not include the selected gear ratio. The rider's cadence (multiplied by the selected gear ratio) is the same as the wheel rotational speed and is thus directly related to the hub's position on its torque curve (motor output). OK now?

And the point of a geared hub, is that the internal gearing is selected to provide good torque throughout the range of expected wheel speed, thus the observed performance: the geared hub has good torque from a stop up to a certain speed, beyond which you get diminishing torque and eventually none.

Agreed, to a point. All manufacturers of geared ebike motors, whether they be hub or mid-drives, select internal gearing to provide good torque over the expected bike speeds. This of couree is not the same as peak or uniform torque over the range of bike speed.

I do agree with AHicks that the Grin Tech Motor Simulator can be useful in illustrating the relationship between bike speed (wheel rotation speed in effect) and available motor torque for the motors they have evaluated. The same set of Simulator parameters that AHicks provided shows that the MAC motor has a peak torque of 117.9Nm below a bike speed of ~3mph. Torque drops off after that hitting 59.5Nm at ~15mph and 11Nm at 25mph. So, is this good torque over the expected speed range? Depends on your definition I suppose but it does illustrate my point that achieve the motor's peak torque output the rider must adjust his cadence (x gear ratio). Just sayin'.