How does torque sensing work?

PianoJohn

New Member
Hi folks,
My bike senses only cadence, and I am wondering how torque sensing would be different. As I understand it, the harder one pedals, the more the motor contributes. But what if you want to pedal only lightly and let the motor do most of the work? Can you do that?

Thanks in advance for any enlightenment.
 

Berry78

Active Member
With the better systems, this is accomplished by simply increasing the assist level. You get more bike's effort, and less you. If you combine a high assist with easier gearing, you will find there is a threshold reached where you have virtually no resistance on the pedals (unless you are going up a steep hill).

I like the "real bike" feeling that torque sensors provide.
 

Rich Reano

New Member
Torque sensing pedal assist is the closest thing to feeling like a bike. The difference is you feel like superman. Cadence sensing on the other hand, just detects whether the pedals are moving and go up to the preset speed depending on the assist level. Torque sensing detects how much power you put on the pedals then amplifies that. The power the motor gives is proportional.

Personally, I would never get a cadence only pedal assist bike.
 

flymeaway

Well-Known Member
how torque sensing would be different.
Torque sensors are strain gages, (variable resistors) that change resistant under varying pressure and output a specific current or voltage based on the resistance value. The important issue to address is what implementation of the sensor is best at accurately transmitting the correct torque. Some sensors are installed in the bottom bracket, some are installed in the crank. The quality of the output varies dramatically. In addition, programing how the controller responds is important. Is there a dwell time after the torque is removed, or does the motor instantly respond? The difference between smooth transitions and abrupt transitions is noticeable.

Court J.
 
Last edited:

George S.

Well-Known Member
The motor output is variable. In theory you can pedal the exact amount you want, and then adjust the motor for exactly the amount of power you want. This is basically what a good throttle does. You set it where you want. You pedal what you want.

A cadence sensor knows you are moving the pedals. So it can apply some amount of power when it senses movement. It can figure out your cadence, the times the pedals turn per minute. But that information isn't that valuable. If you pedal 'fast', it doesn't know why. It can guess, and you can change the amount of power it is applying when it guesses. When you try to start of loose dirt? When you make a turn? If there is a patch of ice? Does it know what to do?

A torque sensor can measure actual force. It knows when you are working hard, and it knows when there is force on the pedals. It can make a better guess, especially with more sensors.

You have to consider all the situations any sensor has to measure. What should it do when the pedals start turning, from a stop? What should happen when you are straining to get up a hill? How often should you have to adjust the assist level, and for what reasons? How programmable should the assist be? There are a lot of complaints about cadence sensor systems with aggressive programming. People don't always know what is going to happen.

Any automated sensor throttle can probably be set for normal cruise, like a commuter cruise. Chinese bikes have cruise controls. You get the speed you want and push the button. It holds the speed, even into wind and up hills. If you pedal harder, the motor lets up a bit. It's cheap, and works with the throttle. For any assist, find some setting where it gives you the power you need to cruise at 20 mph. If you hit a hill, maybe you bump up the assist level.

I'm pretty sure the concept "It feels more like a bike" is subjective. I know I have motors. I want them to do what I want. I didn't walk into the ebike store and say "Wow, I would really like to feel like Superman". I wanted to exercise but not struggle up hills. A throttle makes it feel more like an ebike, to me. I'm in control. And the cruise control automates it.

They could make better throttles, better speed controls. A lot of torque sensing systems cost more than basic motors. If they offered some programming choices through a bluetooth app any pedal assist might work for most people, especially with throttle over-ride.
 

dm nelson

Active Member
The couple ebikes I test rode with torque sensing provided quite a nice "automatic transmission" feeling, relative to the effort I pedaled. While I preferred this experience over my radrover's, cadence pas, the cost difference was significant. In fact, I was able to get 2 rovers for the cost of a nice ready-made torque sensor bike. Perhaps Court or others can refer to inexpensive torque sensing bikes. I've grown quite comfortable using the throttle to assist accelerating while pedaling (or not pedaling). :)
 

PianoJohn

New Member
With the better systems, this is accomplished by simply increasing the assist level. You get more bike's effort, and less you. If you combine a high assist with easier gearing, you will find there is a threshold reached where you have virtually no resistance on the pedals (unless you are going up a steep hill).

I like the "real bike" feeling that torque sensors provide.
Ah, gotcha! That makes sense. Thank you. I just tried several torque sensing bikes. I like them much more than the first time I tried them. I may trade in my Diamondback Lindau this afternoon!
 
I will prefer torque sensor especially if you don't have throttle. Not only for comfort reason also safety. In certain cases where you need to accelerate suddenly cadence won't serve well for you. You will depend on your legs but in torque sensor it is possible to get extra boost from motor.

There is an interesting article about it. Seems very introduction level info but can give you some idea i guess.

(Link Removed - No Longer Exists)
 

flymeaway

Well-Known Member
In certain cases where you need to accelerate suddenly cadence won't serve well for you.
That may be true for certain motor controller combinations. If you are using a Bafang Mid-Drive and have the programming cable you can change the variables that relate to power level on input which can be set to 100% with minimal cadence sensing. Not something I'd suggest but you have the option. You can also program the Cycle Analyst to provide any power profile you want using cadence. So assuming you have the ability to setup the controller via programing about the only situation I see where torque sensing would be an advantage is stopping on a steep hill. Of course gear selection from a stop is important so anticipation is critical, unless you have an IGH that can be shifted from a stop, in that case I don't see an advantage at all.

Court J.