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  1. #1
    RC poster
    Join Date
    Sep 2011
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    1

    Summit 1/10 - Tekin RX8 & T8 Truggy 1700kv Motor Overheat

    Fellas,

    I got my brand spanking new Tekin RX8 & T8 Truggy 1700kv Motor on my STOCK geared Summit (pinion:14, spur:69) with 2 x 2S 5300 mah Lipos.

    Well 2-3 minutes into the first run it stoped, the motor and ESC overheated. I didn't notice smoke or anything coming out of them but smelled like fried motor and ESC...

    I sent the motor and ESC to Tekin and then emailed them explained the situation. They replied saying the following:

    <you have the motor far too undergeared to run on 4S. The Summit, while Traxxasclaims it is a 1/10 is simply not the case, it weighs more than my 1/8 truggy. The first problem here is that the truck puts a decent load on a motor and controller due to the drivetrain. I have helped people setup Summits before and you are undergeared for the 4S voltage so you can do one of two things; gear up or run 6S. Undergearing a brushless motor will cause excess heat as you are running the motor at a higher RPM than necessary to get the torque output desired. This is not a brushed motor, they react differentlyto gearing and voltage.>

    1-Ok, so is he telling me my setting (Truggy 1700kv motor/pinion:14, spur:69/2 x 2S 5300 mah Lipos) is so out of acceptable range and it fried my motor and ESC in a matter of 2-3 minutes???
    I didn't even bash, I ran it on a flat concrete drive way 2-3 minutes!

    2-The lipo chart on Tekin website indicates you are supposed to use 4S or 5S. I used 4s thinking less stress on the motor and less heat. But the email from Tekin is telling me to use 6S. Why? That's too much voltage according to their lipo chart! How would I know I was supposed to use 6S???

    3-I used the stock pinion to achieve more torque rather than top speed for the weight of Summit. I have a hard time believing using stock gear and driving for 2-3 minutes can overheat to the point it can burn my finger. It's not like I used 8S lipo and drove for an hour straight.

    I told them I think I got defective motor and ESC but Tekin does not think so...

    What do you guys think?

    Thanks.

  2. #2
    RC Turnbuckle Jr. 87 GN's Avatar
    Join Date
    Mar 2010
    Location
    kansas
    Posts
    7,821
    Way to undergeared. I run my Revo 2/2s MMM & 2200 kv 21/54 I might be a little over geared. So with a 1700kv I would start at 21/54. I will play with the speed chart & see what you were running...

    Edit: You were geared for 17.42 mph. 14/68

    4s = 40 mph
    5s = 50 mph
    6s = 60 mph

    1700kv 21/54 = 32.91
    1700kv 25/54 = 39.18 This is what I would run...

    Find AOD's links alot of good info...
    Last edited by 87 GN; 09-28-2011 at 09:47 AM.
    Would you go flip my truck back over??

  3. #3
    RC Turnbuckle Jr. pavmentsurfer's Avatar
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    11,145
    Poco... I think your getting some of the attributes of being under and over geared mixed up. A 1700kv 1/8 motor doesnt spin overly fast on 2S... slower than your brushed motor would. So, on 4S your not loading the motor at all... its just reving like crazy. This is as bad for a brushless motor as having it over geared... they both quickly generate excess heat.

    The fact you were on a smooth, low drag surface was, in this case, an even bigger problem and added to the issue. The guy from Tekin isnt wrong, he just did what most technically inclined RC people do... he gave you the dumbed down version of the problem thinking you couldnt grasp more detail but he missed the important points.

    A low KV brushless motor needs to be geared up to "load" it so it begins to work efficiently. Brushed motors dont work the same way. Try going up on your pinion and/or down on your spur and see how it reacts. Nothing drastic... but enough that the motor has to work harder and youll probably be fine. At only 17-20 mph on 4S that motor was probably spinning almost to its full RPM. Load it up and make it work. Brushless motors like that.
    Pede, Summit,
    ERBE, Rally,
    Motley Crew, 1SQ

  4. #4
    RC Competitor
    Join Date
    Nov 2013
    Posts
    70
    Hi guys,

    I'm considering the same combo for my 1/10 Summit as Poco mentions here. Are you still running the car, Poco? And in case with what gearing?

    Did you try the 21/54 or 25/54 based on the recommendations given here? Had any heat issues since? How does in crawl with this kind of engine/gearing-ratio?

    I am currently driving the stock car, but I really do miss the "little extra" - in terms of some "extra kick", or a little extra torque, when operating at low speeds. Choosing the right BL-solution has proven to be a bit of work..... and I really do not want to spend a lot of extra money on this toy just ending up with a smoked motor.

    Grateful for any reply.

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