What's the thinking behind a torque sensor?

[330rcs]

torque sensor works based on how hard you press on your pedals right? This is great if you're just starting your ride and feeling fresh and full of energy but, when you're tired and legs are getting sore, you can't pedal that hard anymore. To me this is where I should need the most assistance. But if you have a torque sensor you're not going to get as much power if you can't pedal as hard anymore right? I don't understand the point of this. Or maybe I am misunderstanding the purpose?

 

[fooferdoggie]

if you crank up the assist you can get more help with less work. if I am in turbo mode undoing 20+ mph I am only putting out maybe 80 watts. at eco I am doing about 180 watts. the other two levels are between those two.

 

[JRA]

As mentioned that is what the different levels of assist that up the % of motor output is for. However when you are tired and legs getting sore it usually means you have been out for awhile and depending on what level of % you have been using your voltage has dropped as well which makes the battery weaker and not able and going to higher assist levels can be disappointing. At that point you just need to HTFU but it is best to know your limits and also the bikes to avoid an uncomfortable ride back to the barn whether you have cadence, torque or throttle assist.

 

[theemartymac]

Depending on your bike and interface, you may also be able to tune the torque inputs for each PAS level as well. So theoretically, you could have PAS 3 with normal torque ranges like 20% assist at 20lb force, and 100% assist at 50lb force, and then set PAS 4 to be 80% and 100% respectively (or less) so that level is more aggressive and requires less pressure to achieve the max assist, without significantly increasing the top speed cutout.

 

[330rcs]

Thanks for the replies. I understand all the workarounds ie: increasing assist % etc. I was just curious as to why the torque sensor works based on how hard you pedal due to the reasons mentioned. I wasn't asking what I should do about it. I already have my assist setup accordingly. I'm just wondering why the concept of torque sensor works the way it does. i have both bikes with cadence and torque and I feel that when I'm tired it's still easier and more comfortable to keep going at a decent speed with the cadence sensor. Even though the cadence sensor bike is 750w and the mid drive with torque sensor is 1500w. I definately notice my power being lost when I'm tired on the torque sensor bike and having to rely more on throttle/assist. Whereas on the rear hub with cadence sensor I can continue pedaling comfortably to keep my speed up. I get less tired and can go farther. I still like both bikes I'm not saying that I prefer one or the other they are both a lot of fun in their own ways. I am just curious as to why torque sensor works the way it does. It seems only useful when you have the energy to push hard and is not as helpful when you're tired. When I feel when you're tired is when you need the most assistance.

 

[theemartymac]

Well the low initial input can make the launch much smoother, and reduce or eliminate the surging that can come from a cadence sensor. I have both systems, and the torque certainly lends itself to casual cruising with the ability to make a quick pass or attack a hill without adjusting anything. The Cadence bike takes a little more planning, and definitely provides more perceptible motor feedback as it cycles.

 

[EmotionLynx6Pro]

Take both types on singletrack trails and you will see the purpose of a torque sensor. Singletrack trail does not mean rails to trails, greenways and the like.

 

[Luto]

It is to tune the bike assist dynamically and precisely. The Bosch 4 Preform CX have been get more sophisticated assist. The obvious is eMTB mode, but there is more FINE tuning there. For instance the newest software update has a "slide over tree root" tuning buff.

On my non CX Bosch 4 I can tell it is trying to read my cadence when out of the saddle up hills. Sometimes it misses, but I am getting better in tune with it. I expect the next software release will get it better.

 

[Stefan Mikes]

A good mid-drive motor can utilise up to as many as six different sensors to make the ride natural and efficient. For instance, it is not necessarily torque to be taken into account only; controllers in my Specialized and Giant e-bikes actually like me to spin the cranks instead of mashing it. As the rider's power input is the torque multiplied by angular speed of the cranks (related to the cadence), a good e-bike will rather translate the rider's power input into provided motor assistance than torque alone. And yes, the Assistance Levels in mid-motor e-bike are responsible for multiplying the rider's effort (the max amplification in my Vado is 320%, and it is 360% in my Trance E+).

The torque sensor alone is not the only sensor used to determine the necessary motor assistance! (Unless we're talking cheap motors).

 

[AHicks]

Thanks for the replies. I understand all the workarounds ie: increasing assist % etc. I was just curious as to why the torque sensor works based on how hard you pedal due to the reasons mentioned. I wasn't asking what I should do about it. I already have my assist setup accordingly. I'm just wondering why the concept of torque sensor works the way it does. i have both bikes with cadence and torque and I feel that when I'm tired it's still easier and more comfortable to keep going at a decent speed with the cadence sensor. Even though the cadence sensor bike is 750w and the mid drive with torque sensor is 1500w. I definately notice my power being lost when I'm tired on the torque sensor bike and having to rely more on throttle/assist. Whereas on the rear hub with cadence sensor I can continue pedaling comfortably to keep my speed up. I get less tired and can go farther. I still like both bikes I'm not saying that I prefer one or the other they are both a lot of fun in their own ways. I am just curious as to why torque sensor works the way it does. It seems only useful when you have the energy to push hard and is not as helpful when you're tired. When I feel when you're tired is when you need the most assistance.

You mention torque sensing 1500w mid drive, and that you believe you have your assist set up correctly, so I'm going to assume you have a Bafang Ultra. As an Ultra owner that also messed with those settings, I'm going to remind you that the Ultra has both cadence AND torque sensors and suggest you might want to revisit your settings.

Not sure how you arrived at your settings, but if you followed somebody else's hot set up, after studying several of those prior to getting my feet wet, I found those all over the ball park. Very little in the way of a general consensus on what worked right between them. I found I'm far further ahead focusing on what I wanted MY bike to do. This vs. setting up with somebody else's preferences. E.g. I ride in kind of a hybrid 50/50 on/off road cruiser mode, generally at speeds of anywhere from 6 to 14 mph, so my focus was all about slow speed response, which I was able to set up pretty easily as I focused on just those parameters, leaving all the high speed stuff alone. Noteworthy is the fact I was riding a 1000w cadence sensing geared hub bike prior to the Ultra equipped bike. I loved it! It was also programmable (KT controller) - but not to the degree the Ultra is capable of. Point here is, I was able to arrive at what I think is a great torque/cadence sensing balance.

This, vs. using settings that somebody might prefer when riding a road bike, or maybe somebody with a hard mountain bike riding style, or whatever. Basically, somebody with a totally different set of riding priorities/expectations.

Biggest point being, I don't beleive there's a generic set of settings that all are going to enjoy. If you have the patience, focusing on one issue at a time, I think you can come up with a set of parameters of your own that'll put a great big smile on your face.... -Al

 

[fooferdoggie]

Learning to spend and not mash so much will even out your effort so your not so dead at the end too.

 

[6zfshdb]

torque sensor works based on how hard you press on your pedals right? This is great if you're just starting your ride and feeling fresh and full of energy but, when you're tired and legs are getting sore, you can't pedal that hard anymore. To me this is where I should need the most assistance. But if you have a torque sensor you're not going to get as much power if you can't pedal as hard anymore right? I don't understand the point of this. Or maybe I am misunderstanding the purpose?

Perhaps I don't get your point. A torque sensor is just that. It measures the amount of torque you apply to the pedals. It has no way of knowing how tired you are. That's why most bike controllers have adjustable PAS levels. If you get tired or your battery voltage drops, just crank up the PAS to a more comfortable level. Another option for throttled bikes is to set the speed you want and apply a comfortable amount of pedal pressure. That way, you are assisting the bike rather than it assisting you. I find this the best way to deal with fatigue.

That being said, I agree that torque sensors leave a lot to be desired. I've tested a fair number of bikes and these sensors perform differently on every one. Since my bike has both torque and cadence sensors as well as a throttle, I can use the one that best suits riding conditions. Between the three, I can always get a comfortable ride.

 

[Bruce Arnold]

I never found that it got harder to pedal my torque-sensing bike when I got tired. It was not that dependent on the torque-sensing. Backing off on pedal-pressure a bit meant the cadence sensors took over. For me, torque sensing was for acceleration, not for cruising. Maybe it's just the way I ride, or the way my CCS handled the combination of torque and cadence sensors.

That being the case, the question itself is puzzling to me. Reading the above comments, I can see that different bikes and set-ups might lead to different outcomes and conclusions. I had no idea there was that much variance in torque sensing applications.

 

[fooferdoggie]

yes they are different. a bosch powered bike does not give you less assistance as the battery drains. its even till it the battery cuts off. every company has their own way of setting up their bikes it gives you options.

 

[330rcs]

I never found that it got harder to pedal my torque-sensing bike when I got tired. It was not that dependent on the torque-sensing. Backing off on pedal-pressure a bit meant the cadence sensors took over. For me, torque sensing was for acceleration, not for cruising. Maybe it's just the way I ride, or the way my CCS handled the combination of torque and cadence sensors.

That being the case, the question itself is puzzling to me. Reading the above comments, I can see that different bikes and set-ups might lead to different outcomes and conclusions. I had no idea there was that much variance in torque sensing applications.

I have the Ripcurrent S and thats the bike that I'm referring to which is more comfortable to pedal at higher speeds when I'm tired. It might just be rear hub vs mid drive then what I am noticing. On my 1500w mid drive I feel like I'm going slower and notice more loss of power/speed when I'm tired unless I crank up the assist even then it's a noticeable difference to me. I was thinking it has to do with torque sensor. The manufacturer of my mid drive bike (even though it's supposed to have both cadence and torque sensor also) said this:

"The biggest difference you're noticing is because the Ultra is powered by a torque sensor while the hub motor is powered by a cadence sensor. This means that on the ultra, the motor looks at how hard you're pedaling to determine how it helps while the cadence sensor merely looks at how often you're pedaling. So this means that on the cadence bike if you simply move your legs, the assist kicks in whereas on the torque sensor bike, if you don't apply pressure on the pedals, it won't assist as much. Just like riding a regular bike."

So based on the reply it just made me wonder what the reasoning behind the torque sensor is that it operates that way that you get more power when you're not as tired vs when you actually need it. I understand ramping up assist and throttling it to make up the difference. I was just curious about the concept of it. It's kind of like it only helps to go faster if you are already going fast but if you're slow (tired) you will stay slow. Instead of when you're slow/tired getting the assistance.

However now that I think about it, wouldn't make sense to have it in the opposite configuration (to give you assist when you're going easy (tired) on the pedals) by that logic if you're going slow because you need to go up a curb or up a mountain and if the motor all of a sudden kicks in with intense power because it thinks you're tired and need help vs just going slow intentionally because you're being cautious/careful nobody would want that lol

 

[330rcs]

yes they are different. a bosch powered bike does not give you less assistance as the battery drains. its even till it the battery cuts off. every company has their own way of setting up their bikes it gives you options.

Interesting, didn't know that.