Big low kv motor vs smaller high kv motor

[TaxpayerTroy]

I swapped the sledge motor for the xo1 motor and it’s great and all being able to gear way up. The question is. If cans are the same kv but different sizes what does that do?? Lower heat and more torque or is there more that I don’t know? The xo1 motor is freakin wild in the sledge

 

[Surchaufeur]

I swapped the sledge motor for the xo1 motor and it’s great and all being able to gear way up. The question is. If cans are the same kv but different sizes what does that do?? Lower heat and more torque or is there more that I don’t know? The xo1 motor is freakin wild in the sledge
View attachment 284281

Lower heat and more torque and believe dus less consumation and more run time.

 

[TaxpayerTroy]

Lower heat and more torque and believe dus less consumation and more run time.

Thank you brother. I’ve been encouraging everyone to switch to the xo1 from the stock sledge motor

 

[MMoelmann]

Lower heat and more torque and believe dus less consumation and more run time.

Sounds like all positives. Isn't this only true if you are running a higher voltage on the lower kv motor? Otherwise you have to gear the motor up.
I'm actually curious about the efficiency if you keep the voltage the same but get a lower kv motor.

 

[morrjr71]

A longer can motor with the same kv might run cooler because there's more surface area for the heat to dissipate. And there might be a slight increase in torque due to a longer rotor.

 

[LibertyMKiii]

There are some good videos that explain this, but you can think about using a lever to move something heavy.
The larger diameter can and longer diameter cans both give the motor more leverage to turn the rotor. This translates to more power.
The larger exterior provides more cooling surface area so you will also see lower temps when geared for the same speed.

 

[MMoelmann]

What about the same size motor can with different kv windings?

 

[Garcbomber]

What about the same size motor can with different kv windings?

If you’re familiar with a combustion engine, think of it as the brain (camshaft change-lift/duration/lobe separation angle) with all cubic inch, head cfm specs and intake/exhaust being similar. The lower KV will have more low end torque and as the kV grows, upper RPM horsepower will as well with the low/midrange power suffering as the powerband increases . (Usually 50k-60k RPM on a 22-30V motor)

There are variables in quality and density but this is how I explain it to my fellow motorsport gearhead’s.

What the ideal kv/size rotor is all dependent on the weight and usage of the application. Putting a Honda F1 v12 in a Semi truck will not be ideal, as is a Dump truck diesel in a smart car. But each engine does fantastic with proper transmission(gearing) in their respective platform.

 

[MMoelmann]

If you’re familiar with a combustion engine, think of it as the brain (camshaft change-lift/duration/lobe separation angle) with all cubic inch, head cfm specs and intake/exhaust being similar. The lower KV will have more low end torque and as the kV grows, upper RPM horsepower will as well with the low/midrange power suffering as the powerband increases . (Usually 50k-60k RPM on a 22-30V motor)

There are variables in quality and density but this is how I explain it to my fellow motorsport gearhead’s.

What the ideal kv/size rotor is all dependent on the weight and usage of the application. Putting a Honda F1 v12 in a Semi truck will not be ideal, as is a Dump truck diesel in a smart car. But each engine does fantastic with proper transmission(gearing) in their respective platform.

Very well put. That analogy makes sense.

 

[LibertyMKiii]

What about the same size motor can with different kv windings?

There are some limits.
This is a TP4070 (40x107mm) motor with 780kv winding.

This 780kv motor is rated for 125 amps and 67 volts. It shows with the tiny wires.
If you try to run this on 6s or 8s at 200+ amps it won't "like that", because the windings are made for low amps and high voltage.

My point of showing this is that you need to get a KV and motor that is rated for the voltage you want to run.
How you run that motor makes a difference too. For example a basher on 6s you want 1600-1900kv. For a speed runner I would go with 2200-2700 kv

 

[TaxpayerTroy]

Sounds like all positives. Isn't this only true if you are running a higher voltage on the lower kv motor? Otherwise you have to gear the motor up.
I'm actually curious about the efficiency if you keep the voltage the same but get a lower kv motor.

Currently running 18/52 gearing on xo1 motor 4985. Seems to be punchy and solid compared to the sledge motor at 13/52

If you’re familiar with a combustion engine, think of it as the brain (camshaft change-lift/duration/lobe separation angle) with all cubic inch, head cfm specs and intake/exhaust being similar. The lower KV will have more low end torque and as the kV grows, upper RPM horsepower will as well with the low/midrange power suffering as the powerband increases . (Usually 50k-60k RPM on a 22-30V motor)

There are variables in quality and density but this is how I explain it to my fellow motorsport gearhead’s.

What the ideal kv/size rotor is all dependent on the weight and usage of the application. Putting a Honda F1 v12 in a Semi truck will not be ideal, as is a Dump truck diesel in a smart car. But each engine does fantastic with proper transmission(gearing) in their respective platform.

Very well said thank you!

There are some limits.
This is a TP4070 (40x107mm) motor with 780kv winding.

View attachment 284350

This 780kv motor is rated for 125 amps and 67 volts. It shows with the tiny wires.
If you try to run this on 6s or 8s at 200+ amps it won't "like that", because the windings are made for low amps and high voltage.

My point of showing this is that you need to get a KV and motor that is rated for the voltage you want to run.
How you run that motor makes a difference too. For example a basher on 6s you want 1600-1900kv. For a speed runner I would go with 2200-2700 kv

Word thank you for that tip!

 

[morrjr71]

There are some limits.
This is a TP4070 (40x107mm) motor with 780kv winding.

View attachment 284350

How you run that motor makes a difference too. For example a basher on 6s you want 1600-1900kv. For a speed runner I would go with 2200-2700 kv

The Vendetta and the Infraction 3s, both designed for fast running, come from the Arrma factory with 3900kv motors installed. I have the infraction 3s, and it's fast out of the box. I've installed a 130A ESC and a 23T pinion (stock is 20T), but I haven't had the opportunity to really test it out yet due to the weather.