Raider With 15 Turn Quad Brushed Motor-Brushless Equivalent?

[Snaab9-2]

I put a Turnigy 2C 4200mAh shorty lipo in the Raider today after a little encouragement from my Dremel. Wow, what a difference from a 25 year old NiCd! It was actually pretty quick (as was the Ultima with same battery when the diff was working). It could easily break the a back end out and snap oversteer. It was cold out so this may have reduced traction but wow.

It has a Revtech 15x4 brushed motor in it. It made me think, what brushless motor would be it's equal? Something like a 21 turn? Maybe a 17? Just trying to get a feel of how much more power I want. I cannot wait to go brushless at some point but for now I am really enjoying the Turbo Raider! The shorty lipo is so light and I was able to put it on the right side to offset the motor weight on the left! Seems like it is balanced perfect! I am running an old ESC so I only drove it for 10 min and checked the voltage on my new Turnigy Accucel 6 80w charger (which I am really happy with even though it forced me to learn how to solder and get creative with the connectors it came with). It was only down to 8.1 v or so.... i am just going to be conservative for now with run times.

The Raider is so light.... and even more so with the lipo. It is going to fly with a brushless setup if it can keep traction!

[notarex]

Anywhere from 17.5 to 21T is the equiv. of a "stock" brushed motor. Your 15x4 is turning around 27,000rpm, doing the math kv=rpm/v the equiv. brushless would be 3500-3700kv. Depending on the manufacturer, a 10.5-13.5T would get you in that ballpark. I have a sensorless tacon 3500kv that is a ripper, and it was only 25 bucks. If I were you, I'd look for a 13.5 or 3700kv and err on the side of gearbox safety.

[Snaab9-2]

Anywhere from 17.5 to 21T is the equiv. of a "stock" brushed motor. Your 15x4 is turning around 27,000rpm, doing the math kv=rpm/v the equiv. brushless would be 3500-3700kv. Depending on the manufacturer, a 10.5-13.5T would get you in that ballpark. I have a sensorless tacon 3500kv that is a ripper, and it was only 25 bucks. If I were you, I'd look for a 13.5 or 3700kv and err on the side of gearbox safety.

Wow, thanks for the info. I kind of expected that the brushless motors in that range would blow mine out of the water! Good to know.

I am undecided at this point but I may push things a bit..... i would like another 10 mph or so. I was leaning towards a 9.5t Speedpassion sensored combo but idk.... I will cry when i break it and hear I told you so.....

[dldiaz]

In my experience, the mathematic comparisons between brushed and brushless motors (i.e. - comparing their kV values) never seems to explain the true real world performance differences between brushed and brushless.

What I'm trying to say is basically that a high quality, freshly trued, and carefully tweaked 15-turn brushed motor can just barely keep up with an economy priced 17.5 turn (sensored) brushless motor - and after five minutes the brushed motor will be sizzling hot and the brushless will barely be above ambient temperature.

I have never seen any 15-turn brushed motor that runs even close to a 10.5 brushless.


- Just my opinion. I'm only trying to prompt discussion, not trying to discredit anyone else's theories.

[Snaab9-2]

In my experience, the mathematic comparisons between brushed and brushless motors (i.e. - comparing their kV values) never seems to explain the true real world performance differences between brushed and brushless.

What I'm trying to say is basically that a high quality, freshly trued, and carefully tweaked 15-turn brushed motor can just barely keep up with an economy priced 17.5 turn (sensored) brushless motor - and after five minutes the brushed motor will be sizzling hot and the brushless will barely be above ambient temperature.

I have never seen any 15-turn brushed motor that runs even close to a 10.5 brushless.


- Just my opinion. I'm only trying to prompt discussion, not trying to discredit anyone else's theories.

This seems more in line with what I expected but I have no real knowledge so put it out there to see what you guys thought.

I have only run the raider with lipo when the temp was in the 20 but so far the motor has only been warm to touch. A 90 degree day may change things.

[notarex]

I agree the numbers are confusing and don't tell the whole story, RPM isn't the best way to measure the actual power of a motor. I do know that I replaced a 23t brushed motor with a 17.5 brushless, and the power was similar. 10.5t may be stretching things comparison wise- I think anything under 17.5 is going to be quick enough for your needs. The Lipo makes a big difference also, as you've seen.

[Snaab9-2]

I agree the numbers are confusing and don't tell the whole story, RPM isn't the best way to measure the actual power of a motor. I do know that I replaced a 23t brushed motor with a 17.5 brushless, and the power was similar. 10.5t may be stretching things comparison wise- I think anything under 17.5 is going to be quick enough for your needs. The Lipo makes a big difference also, as you've seen.

Yeah, BIG!

The back end of the car is all over the place granted the tires have low traction.... makes it fun. I cannot go WOT until about 10 or 15 mph without lighting up the tires.... hitting it in a corner, forget about it unless you crave spin outs and donuts.