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  1. #1
    RC Racer
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    Fastest Motor on 3s?

    Hello all,

    I'm trying to build a 1/16th Traxxas that can go upwards of 90mph. I recently put in a castle 4600kv motor and ran it on a good 3s battery. However, the 4600kv got pretty hot today. I don't have a temp gun, but I couldn't keep my finger on it for more than two seconds. I let it cool down, but I am really confused as to why it got so hot. (gearing is also pretty normal, 26/50) When I roll the car, it sounds a little rough, like there is a bad bearing in the tranny, so I'll take it apart and see if that is the case. However, this brings me to the question of the thread. I need to go with a higher kv motor for speed, but if the 4600kv gets that hot on 3s, will other motors such as Castle's 5700kv just burn up?

    If you have any suggestions, please let me know!

  2. #2
    RC Racer
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    With 3s, 3500kv is the max you want to go. Anything higher and you start to lose efficiency. Meaning the power you're pulling from your battery starts to turn into heat, in your motor and esc. What you need to is either try a lower kv and gear up, or get a larger motor also with a lower kv and gear up. The larger motor is your better option, if you can. I know the titan is a 550, so I'm assuming at least a 3660 would fit. A 3670 or 3675 would be best, in about 3200kv, I just don't know how long of a can you can get in there. So figure out the largest motor you can, and then start gearing up till you reach either your desired speed or the motor starts getting hot.

    Sent from my SM-G970U using Tapatalk

  3. #3
    RC Racer
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    Quote Originally Posted by Steve g View Post
    With 3s, 3500kv is the max you want to go. Anything higher and you start to lose efficiency. Meaning the power you're pulling from your battery starts to turn into heat, in your motor and esc. What you need to is either try a lower kv and gear up, or get a larger motor also with a lower kv and gear up. The larger motor is your better option, if you can. I know the titan is a 550, so I'm assuming at least a 3660 would fit. A 3670 or 3675 would be best, in about 3200kv, I just don't know how long of a can you can get in there. So figure out the largest motor you can, and then start gearing up till you reach either your desired speed or the motor starts getting hot.

    Sent from my SM-G970U using Tapatalk

    Thanks for the reply!

    One of the only reasons that I wanted to put a higher kv motor in is because these mini models have limited gearing. I believe the max is 31/45 and I'm only doing 40 mph with 26/50. Wouldn't a lower kv mean I would have to gear it past 26/50 in order to achieve the same 40mph? If that's the case, I wouldn't be able to go much faster just because of limited gearing. I could end up putting in something like a castle 1515, but that would only be useful on 4 and 6s, and I know that the stock drivetrain can't handle that power, let alone 3s. I do have alot of space for a bigger motor, but I'm not sure that the gearing will allow me to achieve the speeds I want if I go lower on the kv.

  4. #4
    RC Racer
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    Yeah the gearing would have to go up to match the speed with a lower kv. You're over heating and only hitting 40 mph? Is this on road? There are some 3800kv and even 4300kv 550 sized motors you can try. Larger cans so will run cooler then the standard 540 ones. Lighter narrower tires will help with heat, and a good heat sink and fan. Thermal paste makes a difference between the motor and the heat sink too, so use some of that as well. Being limited on gearing i guess you gotta work with what you can.

    Sent from my SM-G970U using Tapatalk

  5. #5
    RC Turnbuckle Jr. Squeegie's Avatar
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    Too bad Greg’s photos no longer show, but you can read about this speed rig here:
    https://forums.traxxas.com/showthrea...ighlight=Nuibe

    Here’s another speed MERV:
    https://forums.traxxas.com/showthrea...-1-16th-E-Revo
    Creativity is intelligence having fun. -Einstein

  6. #6
    RC Champion grizzly03's Avatar
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    I think your best way of trying to make a speed run 1/16 mini is by going higher than 3s. You could go higher using the two battery compartments. Turn the punch down or accelerate slowly. Even loosening the slipper to help with the increased power. Trying to hit your goal is going to be hard to do on only 3s.

    If you use a high Kv motor it's possible to get more speed on 3s, but your not going to be able to make multiple passes without letting the motor cool down.

  7. #7
    RC Racer
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    Quote Originally Posted by Steve g View Post
    Yeah the gearing would have to go up to match the speed with a lower kv. You're over heating and only hitting 40 mph? Is this on road? There are some 3800kv and even 4300kv 550 sized motors you can try. Larger cans so will run cooler then the standard 540 ones. Lighter narrower tires will help with heat, and a good heat sink and fan. Thermal paste makes a difference between the motor and the heat sink too, so use some of that as well. Being limited on gearing i guess you gotta work with what you can.

    Sent from my SM-G970U using Tapatalk

    Yes, this is on road. It wasn't overheated, but I wasn't comfortable running it any longer. I took it home, and I re-adjusted the gear mesh, and the slipper. I ran it earlier this morning on 3s, and it seems to be doing ok now. I think it'll cool down even more once I get a fan and get a bearing replacement kit.

  8. #8
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    im consistently getting 84-86mph with a castle 4600/sv3 combo. running 2, 3s 1000mah 35c lipo's in parallel. gearing was 36t pinion and 45t spur. using proline trenchers.

    i also got 93mph with a 41t pinion/45t spur, but i did send a grub screw into orbit before the end of the run. im hoping for 100mph+

    no idea on temps. i never check. general bashing i use a 32/45 gearing which is good for about 65ish and warmish motor/esc?

  9. #9
    RC Racer
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    Seems like condor99 isn't having any heat issues, so once you get your bearings and fan, sounds like you'll be ok on your current motor. A bad bearing or 2 can cause big heat issues, and isn't always apparent when running the truck. So hopefully you'll be all set soon. Keep us posted on progress.

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  10. #10
    RC Racer
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    Quote Originally Posted by Condor99 View Post
    im consistently getting 84-86mph with a castle 4600/sv3 combo. running 2, 3s 1000mah 35c lipo's in parallel. gearing was 36t pinion and 45t spur. using proline trenchers.

    i also got 93mph with a 41t pinion/45t spur, but i did send a grub screw into orbit before the end of the run. im hoping for 100mph+

    no idea on temps. i never check. general bashing i use a 32/45 gearing which is good for about 65ish and warmish motor/esc?

    Those are really great speeds! I read online that the absolute biggest pinion that people managed to fit was a 31t. Did you have to modify the motor mount /motor mount plate to fit such large gearing?

  11. #11
    RC poster
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    i only make a few passes at a time with the tall gearing. you would absolutely have heat issues if you ran a full pack through it. even on road. but ive never gone into thermal shut down with the smaller gearing.

    bearings are quite important to stay on top of in these little cars. im personally not a big fan....of fans. ha. i honestly can't see them making any amount of different when the whole chassis is pretty open, even with a body. maybe if the body fully enclosed the chassis then sure, fan would probably help.

    i use the traxxas 550 motor mount. no modification needed. 41t is pretty tight, could maybe fit something slightly bigger? but i havent found one bigger than 4t1 to try. id really like to find a 40t spur if anyone knows one that would fit.

    @minisummit50mph ill PM you a link to the pinions i use.

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