kv

[asw27x]

i forget is lower kv more torque and higher is more speed

[guidetti_angelo]

Originally Posted by asw27x

i forget is lower kv more torque and higher is more speed

lower kv more torque

[JohnRobHolmes]

More torque per amp, technically. Higher KV motors can produce more peak torque, and they will also produce more power until saturations occur. 35t motors produce more torque than 55t motors on a given voltage like 2s, but if the 55t is volted up to meet the speed of the 35t they will both produce the same torque and power.


The only time this does not hold constant is for field weakening techniques. When you take a 35t and advance the timing a bit to get more speed, you lose low end torque in exchange for high end power.

[cave-man]

Originally Posted by JohnRobHolmes

35t motors produce more torque than 55t motors on a given voltage like 2s, but if the 55t is volted up to meet the speed of the 35t they will both produce the same torque and power .

This is interesting. If I run my 2.2 on 2s with a 35t, 14t pinion and an 87 spur I have very little torque. When I run the same combo with a 55t I have plenty of torque but obviously no wheel speed.

When I run the 35t on 4s I have lots of wheel speed and pretty decent torque. With the 55t on 4s I have a massive amount of torque and pretty good wheel speed.

This seems to be opposite of what is stated above. I guess what Im saying is on 4s my 55t has way more torque than my 35t. (both motors are new).

For the record Im not calling you out John I take everything you say about electronics and consider it to be the gospel. Im just confused because I always thought higher turn motors produced more torque.

[JohnRobHolmes]

More torque per amp is the key term. The 35t may be pulling more amps than your battery can handle without sagging, thus the 55t will produce more torque with a limited amount of amperage available. What battery is it?

By no means is my word gospel. I welcome questioning. After all, what good am I if I claim to know all and don't care to learn or hear others experience?

[cave-man]

So basically the 55t is pulling less amps and is able to use all or the majority of it's available torque, but the 35t is "amping out" before it's full potential is reached?

Im using Turnigy 2200mah 2s in series. I think they are 30c.

So would higher turn motors be considered "more efficient" since they can use all or more of there available torque while using less amperage? (I hope that makes sense).

[JohnRobHolmes]

Efficiency typically does not correlate with KV, unless we are at the ends of the motor design and it is causing saturation or fill issues. An example would be a one turn 540 motor. They just produce a lot of heat instead of power. Sometimes a particular wind will produce more torque due to copper density advantages. As example, I may only be able to fit 100 turns of wire on an armature using 12ga wire (653000cm of wire). If I want to fit 101 turns I have to use 12.5ga wire (587315cm), and there will be less copper overall. To effectively use the 12.5ga wire I would have to fit 113 winds to equal or better the copper fill.

What can be said is that lower KV motors can produce torque more efficiently for a given system resistance. This would include battery resistance, wire resistance, controller resistance, etc. More amps produces more heat, so if you can produce the same torque at a lower amperage ala lower kv (and typically higher voltage to produce said torque) then the system is indeed more efficient. This is why there is a trend towards higher voltage- for a given power level or torque level they can get by with higher resistance components.

Attached is two "unspecified" motor dynos. As you can see, the faster motor is producing quite a bit more torque too. I have removed battery and controller resistance for the purpose of illustration. If we run into battery or controller resistance issues, there would be a bend in the torque curve as one starts to give out.

[cave-man]

Thanks John, That makes perfect sense.

[KBrog]

Originally Posted by guidetti_angelo

lower kv more torque

I liked that answer better