Assist vs Torque

[Raffe]

Hi,
I´m riding the Shimano 8000 motor and I want to use the St Unlocker to set up the motor.
Could some please explain the difference between Assist % and Torque? I´m having a hard time wrapping my head around those.
Does Torque have anything to do with a certain power at a certain cadance?

Appreciate if somebody could explain it to me Or guide me to a already existing thread about this topic.

Cheers!

 

[flash]

Torque is the maximum amount of power the motor can put out. Assist is the ratio between how much power the bike puts out compared to the rider input.

Gordon

 

[Raffe]

Torque is the maximum amount of power the motor can put out. Assist is the ratio between how much power the bike puts out compared to the rider input.

Gordon

Thank you Gordon,
I thought that the Watts settings decided how much power motor can put out?
If you have time Please explain like I was a child

 

[Dave_h34]

Torque is the amount of twist the motor is capable of delivering. Power is torque X revs (or cadence for a bicycle). Think diesel car Vs non-turbo petrol performance cars of old, diesels have lots of torque at low revs but ultimately low power as they run out of ability to rev, petrol have low torque but can rev really high so produce high overall power. 2 motors putting out a max of 85NM at 80rpm will produce the same amount of peak power, but if one also puts out 85NM at 50rpm but the other 60NM, the first motor will feel much stronger (but consume more power doing it).

Assist is the multiplier that applies to your input, so something that multiplies your input by 360% will lead to greater overall system power than a one capped at 300%. This is no matter the torque or revs.

Torque is ultimately what propels you up the hill, assist is how much effort you need to contribute. I for example could discern no difference between 100% and 300% assist on 70NM modes with fresh strong legs, but with tired dead legs the difference was massive, the motor doing the work my legs no longer could.

There's lots of additional complications associated with overall system capability but tried to keep it simple. ?

 

[steve_sordy]

Torque is force applied to a lever.
Examples are when you are tightening a bolt. It might say on the bolt 12N-m. This means 12 Newton-metres. That is in the SI system (it came after metric). It means a force of 12 Newtons applied to a one metre long lever, or roughly a 3 pound weight hanging off a lever nearly 40" long. That could equally be a 6 pound weight hanging from a 20" lever or a 12 pound weight off a 10" lever. They are all the same torque.

When torque is applied constantly in a rotary manner, like when you are pedalling then (depending upon the units) torque x revs = power.

When you pedal and feel resistance, you are applying power. The torque sensor in the motor can tell what you are doing and also know how fast you are pedalling, It knows how fast you are going from the wheel sensor. It puts all that together using an algorithm designed by the motor supplier and decides how much extra power to give you on top of what you are applying. That is known as "assist". The various modes like Eco, Trail Boost etc give preset proportions of assist. In addition most bikes allow you to tune the individual modes.

 

[Raffe]

"Torque is ultimately what propels you up the hill, assist is how much effort you need to contribute. I for example could discern no difference between 100% and 300% assist on 70NM modes with fresh strong legs, but with tired dead legs the difference was massive, the motor doing the work my legs no longer could"

Thank you Dave. Specialy for the hands on exemple.

 

[slippery pete]

Does Torque have anything to do with a certain power at a certain cadance?

Yes. You've pretty much guessed the dictionary answer: Power = Torque x Cadence

Assist% is the steepness of the line...

Torque is the value it flattens out at...

Torque that can actually be delivered depends on cadence...

And the power you get out is multiplied by cadence (as per dictionary definition)...

And you don't get something for nothing, so if you deliver less power with your legs but take more from the motor your battery range suffers.

 

[Gyre]

It helps to keep in mind that torque is a measure of (instantaneous) force while power is a measure of work.

 

[Raffe]

Great! Thank you for the explanation ?