Brushless Motors – Turns Vs. Kv Rating

Aug 05, 2011 9 Comments by

In recent days I have come into the situation where I need a new brushless system for my Traxxas Slash RaceSpec. It had a Castle Creations Mamba Max 7,700Kv system.

It’s well over 3 years old, and gave out on me last weekend at the track. I know that this can be a devastating blow for any racer. Next to the RC rig itself, the next biggest expense is the motor and speed control. Yeah ok, the Radio too. But I’m talking power plant here.

With so many choices out there, and different ways to measure the rating of these motors, you can find yourself going bug-eyed and want to hit your head on the desk out of confusion and frustration. I myself was wondering, if I were to get a different setup, what would I get. Do I want to keep top speed, or get more torque. How do I tell the difference between the two??  Turns, KV. I’m not alone.

I realized with my research with these  3 different brushless setups I wasn’t alone in the common question of “What does this motor in KV translate to a motors Turn????

Here is a chart that I made based on hours of research and best accurate information from the manufactures. Here is what I am looking at.

 

*This chart does NOT indicated the  motor limits or types of motors the ESC can handle, this is a reference chart of comparing between two methods of units of measure. (Data collected based on a 7.2v system setup)

Examples:

-Associated LRP Vector X-11 10.5 Turn Censored Brushless Motor and Ai Pro Brushless Electronic Speed Control Combo.
Part# LRP80585

- Novak Havoc 8.5T Sport Brushless Censored ESC and Motor System.
Part# 3038

- DuraTrax 3900kV Brushless Power System.
Part # DTXC3122

-Castle Creations 7,700Kv Brushless System
Part# 010-0066-04

According to the chart with best accuracy comparing the 3 types, and rating system. I found the DuraTrax system (built based on Castle Creations system) was a close comparable to the LRP Vector system. Minus the fact DuraTrax is not a censored system.  The only extreme is the Mamba 7,700Kv system.  Keep in mind, I did compare more less the 1/10-scale off-road truck type systems/SCT. Other systems may not use this type of chart. The reason I wanted a little reference chart like this is so When I read about a turn, and then a KV rating. I can see where the correlation is between them. I also can better judge the price.
I know there are a lot of determining factors when it comes to the Turns of a motor, and why. Also the KV rating of motor isn’t always everything, and you get what you pay for. I know there are good budget systems out there, i’d like to think I focused on a couple of them here.
With a little understanding on where each system sits and on what scale to one another, you can determine yourself what your up against when looking at systems across the board. With in reason of course.  It doesn’t have to be the systems I chose here to look at. With so many other people asking the same such questions as “If I have a 3500Kv motor, how many turns would it be close to??”

Now you know.

 

 

 

Christopher Oswald, Featured News

About the author

- Winnipeg, Mb, Canada - Over the years Christopher has hand built and designed numerous homemade and customized RC projects. He has also built a large number of the top beginner and expert kits in the industry. He has raced RC cars and trucks competitively in his area of Canada, and is always looking for new tracks to check out. In the past, he has worked for one of the largest hobby supply stores in Canada. It services hundreds of hobbyists across Canada and the United States. That job gave him the opportunity to share the hobby with others and help both new and experienced enthusiasts. After leaving the hobby store Christopher went on to pursue an automotive repair career. When he isn’t fixing cars both big and small, and writing for RC Car Action, you can find him relaxing with his wife and three dogs, racing at the local community race track, camping in the summer and bike riding along Canada’s scenic road ways and parks.

9 Responses to “Brushless Motors – Turns Vs. Kv Rating”

  1. HotWheeler69 says:

    Now add in Volts and you get RPM and then if you change scale size like 1/8 then you need a new chart.
    Because if you run more then 7.4V you will need a lower KV and that will raise you turns or you could change your pinion and spur… Now what do I have… :>

    Still too much.. info to think about…

  2. Timbulb says:

    censored? really?

    • Matthew Higgins says:

      Everybody makes mistakes. Plus, I think he may have fallen victim of Auto Correct or Spell Check there.

  3. Christopher Oswald says:

    Timbulb……. and Yes, Matt I fell victim to auto spell check. I have fixed it. I hope you’ll forgive me. ;) At least it was spelt correctly ;) I’ll keep my eye on the wordpress and word transitions a little closer. :) :)

  4. ADAM says:

    i was going to get a madfire 1/8 buggy it has a 2150 kv motor and u can put 2 batterys in it i think 3s or like 11. something volts should i buy that one for 299.70 or the thunder tiger 1/8 2100kv with 1 battery at alittle over 330.00 please let me know also can i find parts for them alum. parts? Thanks alot for ur time and help…. Later.

  5. legal eagle says:

    The biggest obstacle is that turns and kv don’t directly correlate – one company’s 13.5 will have a different kv rating than another company’s 13.5, etc.

  6. Ef why Eye says:

    Turns are how many times the wire is wrapped around the armature. The fewer turns usually the higher KV is. The KV is the number of revolutions or equates to RPM.

    More elaborately…

    More Turns (e.g. 19T) = Higher torque, less rpm, longer battery life. Slower but easier to drive.

    Less Turns (e.g. 12T) = Less torque, more rpm, shorter battery life. Faster but more difficult to drive.
    Number of Winds

    Turns refers to the number of times the copper wire has actually been revolved around the armature. The higher the number of turns greater is the torque generated and hence greater is the power delivered. However that also means less RPM rating for your rc car electric motor. Generally less turns are preferred for making the rc car run faster. Remember that more turns equals more power or torc for crawling or for heavier vehicles. .. And with more power comes more responsibility.

  7. Cookie says:

    Hey but thats for brushed. Theres no armature in a brushless only a rotor(magnets) and the wiring isnt in the middle. Actually to think of it the insides of the two different motors are inveretrd so where armature and winding is its a magnet and so onare

  8. Coyoteman says:

    Extrapolating from the chart the formulas below give the approximate conversions, +/- 5%, when using a 7.4V battery. The extremes in number or turns ( 17.5) are not nearly as accurate. The calculations for turns given kV and kV given turns should be somewhat independent of the battery voltage but the wattage is not.
    T~43000/kV kV~43000/T W~2375/T W~kV/18

Copyright © 2014 Air Age Media. All rights reserved.