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  1. #1
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    Throttle Jumps between half and full power (Carmaxx 60SL ESC)

    Hello all,

    I bought a 2nd hand Stampede 4x4 and the throttle is behaving inconsistently. It does not have the original Venileon ESC and motor (unfortunately), but rather a Carmaxx 60SL ESC with Carmaxx 3650SL 4000KV motor.

    When start from standstill the motor seems to run at half speed or power. It doesn't spin the wheels much on dirt, and pulls away slowly. Then once it reaches full speed (which is not very fast), I release the throttle completely and then immediately go full throttle again. Then the motor is suddenly double as loud and the car is double as fast. But this doesn't happen consistently, and sometimes I need to do it a few times to get the car to go full speed.

    I don't hear any whistling sounds, so I doubt it's the clutch. Also as mentioned I can hear the motor spinning faster, which means it's not the clutch slipping when it starts off being slow. My guess is that it's the ESC giving issues. Maybe one of the pole pairs struggle to start up under load. Or maybe the motor is broken?

    I'm using a brand new ... 2S 5000mAh 60-120C battery. So the battery is likely not the issue.

    Do any of you know what could be the problem?

    Thanks!
    Hein
    Last edited by cooleocool; 09-18-2020 at 01:58 AM. Reason: Removed referene to banned brand.

  2. #2
    RC Turnbuckle Jr. olds97_lss's Avatar
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    4000kv is pretty high for a stampede 4x4, especially with a 3650 sized motor. The stock motor is a 3500kv 3660 sized, which likely has considerably more torque. Also, a 60A esc isn't really enough either, so it will likely overheat pretty quick on you unless you gear it as low as possible.

    What gearing are you running? What wheels/tires?

    I ran a max10 sct/3660sl 3200kv in mine and it was barely enough for 3S geared around 45mph. The max10 sct is a 120A esc. It would overheat in the grass, which is where I do most of my running. I tried a 3665/3100kv hobbystar motor which helped as it had a bit more torque.

    When I ran 2S, I had a castle sct sv3/3800kv system in it, was geared for high 30's and it did fine. I just wanted a bit more speed, but gearing higher caused it to stutter off the line (overgeared) which is why I went to 3S and lower gearing with a higher torque motor and more capable esc.
    https://www.youtube.com/c/olds97lss

  3. #3
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    4000kv is pretty high for a stampede 4x4, especially with a 3650 sized motor. The stock motor is a 3500kv 3660 sized, which likely has considerably more torque.
    What do you mean by "pretty high for a stampede"? The 3500kv has more torque than the motor I'm using, which means my motor should put less stress on the stampede. Or am I missing something? As far as I understand it my 4000kv motor is less powerful than stock, so it should not be an issue. That said, my knowledge of motors is fairly limited.

    Also, a 60A esc isn't really enough either, so it will likely overheat pretty quick on you unless you gear it as low as possible.
    The ESC and motor came together in the same box, so I assumed the ESC will be good enough. Also, on my only test drive the motor got very hot, almost too hot to touch, while the ESC seemed fine.

    I ran a max10 sct/3660sl 3200kv in mine and it was barely enough for 3S geared around 45mph. The max10 sct is a 120A esc. It would overheat in the grass, which is where I do most of my running. I tried a 3665/3100kv hobbystar motor which helped as it had a bit more torque.

    When I ran 2S, I had a castle sct sv3/3800kv system in it, was geared for high 30's and it did fine. I just wanted a bit more speed, but gearing higher caused it to stutter off the line (overgeared) which is why I went to 3S and lower gearing with a higher torque motor and more capable esc.
    Over gearing would explain the stutter off the line . I'm not sure what my gearing is, I'll determine that tonight.

    Thank you for your feedback! But it does not explain why my stampede sometimes goes full power, and sometimes not.

  4. #4
    RC Turnbuckle Jr. olds97_lss's Avatar
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    Once it's rolling, the motor pulls less amps to keep going, but from a standstill, if you punch it, it pulls a lot of amps. Likely more than the esc wants to deliver.

    With the weight of the stampede and the 4wd drivetrain, it's a lot of mass, so a lower kv/larger motor can deal with that mass more effectively than a higher kv/lower torque motor.

    You can only gear so low, but on 2S, you can get it pretty low so likely will work with your motor/esc, it will just be slow. I think you can go down to 9/54 gearing. I think the highest I went with the 3800kv was 13/52 on 2S. It would stutter a tiny bit of I punched the throttle at a stand still.
    https://www.youtube.com/c/olds97lss

  5. #5
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    So if I understand correctly as to whats probably happening: from standstill it tries to pull a lot of amps, but the ESC does not want to deliver it, so it doesn't. As it speeds up and the required torque lowers the ESC is still in that state where it does not want to deliver more current, even though it's at full throttle and lower torque requirements. Then, when I release throttle and punch it again, now it takes less torque to increase the motor speed so the ESC is willing to supply it. And then it goes faster. Correct?

    And to solve this you suggest a lower gearing. I don't have any extra gears unfortunately. I'll see what a 9/54-ish gearing would cost.

    But you don't think it's the ESC or motor being faulty?

  6. #6
    RC Turnbuckle Jr. olds97_lss's Avatar
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    I don't think it's that yours is faulty, I just think it's that your asking more of it than it can produce, so what your seeing is it struggling.

    What you described is what I've seen when gearing too high. Eventually, the heat goes too high as well and it thermals, but before that, it hesitates/stutters when I give a lot of throttle.
    https://www.youtube.com/c/olds97lss

  7. #7
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    Okay. I will investigate the gearing then. Thank you so much!

    I have one last question if you don't mind:

    it thermals
    What do you mean by that?

  8. #8
    RC Turnbuckle Jr. olds97_lss's Avatar
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    Overheats and shuts down. Many esc's have thermal protection built in. It's best to gear so you never reach that, but if you do, they go into a limp mode (low power) or shut down and won't let you drive until it cools off.

    Some esc/motor combo's have that as well, usually sensored systems. A non-sensored setup usually doesn't have it unless it's something like the hobbywing max10 sct/3660sl combo. It has a motor temp wire, but it's unsensored.
    https://www.youtube.com/c/olds97lss

  9. #9
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    Okay. I will investigate the gearing then.
    Okay, I counted the gear teeth. It's a 18:54 ratio.

    . I think you can go down to 9/54 gearing.
    I think the gearing is definitely the problem then, since it's double as high as you recommended. I will have to find a new gear.

  10. #10
    RC Turnbuckle Jr. olds97_lss's Avatar
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    Yeah, 18T pinion is way too big, even if your running 2S. The highest I went with the 3800kv 3660 (castle) was 14/54 I believe. That kept it comfortable. I may have only ran 13T in the grass... can't recall, was a while ago.

    However, tires also play a big part. I had 2.8" trenchers most of the time on it. If your running stock talons, you may not have to go clear down to 9T.

    Make sure to order the proper pitch pinion, the stampede uses mod .8/32P gears. Also, get the proper size for your shaft.
    https://www.youtube.com/c/olds97lss

  11. #11
    RC Champion zedorda's Avatar
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    With the 18/54 gearing I wonder if this was originally a brushed truck with the smaller diffs but he does say "does not have the original Venileon ESC and motor (unfortunately)".

    So before guessing I will ask, are you the original owner or did you buy this truck used? If bought used are you sure it was a VXL model?

  12. #12
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    Quote Originally Posted by zedorda View Post
    With the 18/54 gearing I wonder if this was originally a brushed truck with the smaller diffs but he does say "does not have the original Venileon ESC and motor (unfortunately)".

    So before guessing I will ask, are you the original owner or did you buy this truck used? If bought used are you sure it was a VXL model?
    I'm not the original, and I'm not sure how much owners there were before me. Thinking back it was a very risky buy.

    I'm not sure if it was brushless or not. I could not find a serial number on the body to indicate. Would it make a diffence if it was originally a brushed motor?

  13. #13
    RC Champion zedorda's Avatar
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    It changes a few details but are not what is causing the problem just helps to know all the details when diagnosing the problem without the thing right in front of us. Plus many people upgrade their brushed versions up to brushless since all the parts are interchangeable. It will be a matter of inspection to find out which parts are what since there is a good chance someone has had their hands in there.
    Last edited by zedorda; 09-22-2020 at 11:45 AM.

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