BL turn/Kv conversion

[RaceMod]

Hello everyone, I'm looking to replace the CC 4600 in my SCX10 with a lower Kv motor. Money is a factor, and sensored isn't necessary. Any suggestions?

 

[JeepinDoug]

Speedpassion is great for the price.
Speed Passion America online store

 

[winnerone23]

HH Trailmaster Sport.. Is sensored, built for crawler's, by a crawler company, and the price is hard to beat, no matter how ya look at it!

http://holmeshobbies.com/Holmes-TrailMaster-BL-Sport-540.html

Or a pro for a little more..

 

[GLwagon]

what ESC are you running & is speed or torque a factor?
Easy trail running, or hardcore rock rock crawling?

 

[allanon1965]

HH Trailmaster Sport.. Is sensored, built for crawler's, by a crawler company, and the price is hard to beat, no matter how ya look at it!

Holmes Hobbies LLC

Or a pro for a little more..

+1"thumbsup"

 

[RaceMod]

GLwagon, i'm running the CC sv3 on 2s, low end control and torque outweigh speed as this is a trail truck and easy crawling.

 

[RaceMod]

I'll look into the HH motors, i've heard quite a bit about the quality bang-for-the-buck.

 

[RaceMod]

As I mentioned in the title, is there a way to compare Kv to turns? I saw a tekin redline 25.5 and thought that it might be lower Kv than the CC motor?

 

[winnerone23]

A tekin redline 13.5t is around 3100kv..
So a 25.5t would be Slow....

The Trailmaster BL is 3100kv and a 10.5t.. But that's cause it's not ROAR approved, so JRH can make them HH approved!

 

[GLwagon]

Depending on your comfort level of soldering and modding there are a lot of options.
I am in the process of testing a 1200kv 6pole on a 2s motor in my AX10.
I'll post more on that once tested.
I've been using a 1000kv on a 3s in my CR-01, it is a little slow, but crawls nicely.

Unless you goto a sensored setup a cheep 2pole will never feel right.
Even most 4pole motors can have a hickup...
2830 airplane motors are really nice, and can be found under $20 from the right places.
The motor mount needs an adaptor, and you should not run timing on them.
The gearing is also a little different, but nothing major.
NTM Prop Drive Series 28-30 1200kv / 400w (US Warehouse)
Here is the one I currently have on the bench...

 

[GLwagon]

Here is something I might look into...
http://www.amazon.com/gp/aw/d/B00J2...ref=plSrch&dpPl=1&dpID=31YIcHuhZmL&ref=plSrch
http://www.amazon.com/gp/aw/d/B00J2...i=AC_SX110_SY165_QL70&keywords=4pole+rc+motor

Do a little more reading and see what you can find out on some of these...

 

[GLwagon]

Neewer 550 Class Sensorless Brushless Motor 1400KV for 1/10 RC Racing Car Vehicle:Amazon:Toys & Games

I don't know how great these are, but may be worth a try...

 

[GLwagon]

I did a little research & some have had positive things to say about the Neewer line.
I ordered a 2350kv 550 for testing, it will be way slower than the 3900kv 540 CC motor geared 56/9 I've been using in my AX10.
It looks like it is coming from China so I won't see it for a week.

http://www.amazon.com/Neewer-Sensor...ehicle/dp/B00J21Z7RE/ref=pd_rhf_eetyp_p_img_1

Novak used to have a chart on their website that has a KV to Turn listing.
Brushless Motor Spec Chart
An unsensored two pole motor is a "cog monster" & you really need a 4pole or higher with that ESC.

When comparing voltages & kv's the simple math is:

1000kv x 7.4v = 7400rpm
1200kv x 7.4v = 8880rpm
1000kv x 11.1v = 11,100rpm
1200kv x 11.1v = 13,320rpm
2350kv x 7.4v = 17,390rpm
3900kv x 7.4v = 28,860rpm
4600kv x 7.4v = 34,040rpm

 

[Cmarcan167]

Hobbywing 3656sd. I run a 3400kv and my wraith hauls the mail! And has more torque than anyone I crawl with

 

[RaceMod]

Great advice and ideas GLwagon! Thanks a bunch, I'm confident in my soldering skills and i have heard about using outrunners due to the extremely slow speeds and control. JRH's frankenstien sensored outrunner also looks quite appealing.

 

[Olle P]

As I mentioned in the title, is there a way to compare Kv to turns?

No and Yes.

No, not in general. You can't say that "a motor with Kv X must have Y turns".
Too many design factors play part in the Kv.

Yes, within a specific range of motors with the same can and rotor (but different windings on the armature) you can say that Kv is pretty much the inverse of the turns. You double the Kv by halving the turns.
Notice that torque (power) and efficiency is also influence by the turns.

The more turns the more torque and efficiency, but less motor speed and power (at a given voltage).
For a given power output high turn and high voltage is better than high Kv and low voltage.

 

[RaceMod]

Thanks Olle P, quite a bit of brushless wisdom you got there! "thums sup". That explanation cleared things up to the "N"th degree.

Thanks to all who contributed to this thread. All of the input was greatly appreciated.

 

[JohnRobHolmes]

For a given power output high turn and high voltage is better than high Kv and low voltage.

Once inside the motor coils, the respective voltage and amperage that power is produced from doesn't matter if we keep the amp/turn and copper volume constant. The torque and power can't be changed with a different KV, low KV motors do not produce more torque. They do produce more torque per amp, but they also need higher voltage applied to get it.



Outside of the motor, the copper losses do give higher voltages a small edge if we play within a voltage range of a given FET type. 3s and 6s are good voltages because ESCs use 15v and 30v FETs.



Everything else is simply choosing the right KV for your desired wheelspeed with the voltage and geardown of the system.