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  1. #1
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    4600kv vs 5700kv Clarification

    So, I am about to purchase the castle sv3 5700kv. I have decided on that motor because I have re-thought what I would be doing with the summit, and I think mostly speed runs with some small bashing. But I read on another forum that the 4600kv can go up to 4s. I know that stock sv3 esc cannot, but they said that the motor could. They also said that the 5700kv could only go up to 3s, but not on 4s. Is there a reason why the 4600 can do 4s, and the 5700 cannot do 4s? I mean, I don't think that I would be doing any running with 4s anyway, but I never know, someday in the future I might want to have extra power.

    Thanks for your help!!!

  2. #2
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    Bearings.
    Basicaly, a 5700kv motor on 4 cells has a theoretical max rpm of 95000... In practice of course it won't reach that, buy even 75% of that is too much. Even with high quality bearings, I've heard you shouldn't run a bl motor above around 60k rpm.

    Another thing to consider is gearing. On the stock 4000kv motor, this truck will overheat on 3 cells if you drive it on anything but smooth surfaces even with low gearing. Speed runs with cooldowns are ok, but no bashing on 3 cells. Go to a higher kv motor and the problem only gets worse. The larger size of a 540 helps, but only to a point. You couldn't fit low enough gearing to run even a 4600kv motor on 4 cells without overheating pretty fast...

    The real reason to go higher in voltage (4-6 cells) is so you can get the watts you are looking for without going crazy high on the amps. You go up a cell or 3 on battery, while going down on the motor kv. The end result is more speed and power, but still at an amp draw your batteries can handle.
    Gearing down can be another option, but I don't think there is a vehicle made that can go to a higher kv motor than stock, plus go up two cells, and still get reasonable amp draws with even the lowest gearing that will fit in said vehicle...

    What it comes down to is, what battery do you plan to run? If you want to run 3 cells, no question go with the 4600. If you plan to run mostly two cells with three occasionally for speed runs, the 5700kv is an option, but I would still go with the 4600. Ultra high speed gets boring fast with a vehicle that does multiple cartwheels at the drop of a hat....
    Dacaur

  3. #3
    RC Turnbuckle Jr. Petertje60's Avatar
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    +1 on what dacaur said.

    The only advantage the 5700Kv has over the 4600Kv, is that it does more rpm on the same voltage. Since the amount of power the Castle 1406 series motors can deliver is more than a mini Summit can get on the road without serious issues, the 4600Kv is the best choice by far.

    In the case that you want real crazy speeds, you can go up to 4S, but not with the Sidewinder (3S max).
    I have used 4S with my 4600Kv in my Merv occasionally, but that is quite insane to drive. Your Summit will be more on it's roof than on it's wheels if you don't have a very gentle throttle finger.
    Nobody is born with experience

  4. #4
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    Thanks for replying. What kind of speeds are you getting with your merv, and the 4600kv on 3s?


    Thanks

  5. #5
    RC Turnbuckle Jr. Petertje60's Avatar
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    Never measured it, but powerwise 60+ will be no problem.
    Nobody is born with experience

  6. #6
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    The quality of your batteries plays nearly as much a roll in your speed as the motor. A single 25c 3 cell pack will probably get you into the low 40's. A pair in parallel probably the high 40's. A pair of 35C+ packs will be needed to break into the high 50's and beyond....
    Dacaur

  7. #7
    RC Turnbuckle Jr. Petertje60's Avatar
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    Good point about the batteries.

    My 3S Lipos are 1500 mAh 30C. A pair of those is good for 1000W peak, good enough for crazy speeds. My 2S ones are 2500 mAh 30C, that is per pair a bit less, but still quite enough.

    Bear in mind that the Summit is the 1/16 Traxxas car with the worst Cw value (most drag), which will cost you top speed compared to for example a Merv. My Mustang easily does 60+ mph with its 800W motor.
    Nobody is born with experience

  8. #8
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    Thank you for replying. I would like to hit 50-60 range. What top speed would I get with a 2s 50c, 2200mah lipo?

  9. #9
    RC Turnbuckle Jr. Petertje60's Avatar
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    That depends on a lot like gearing, tires, motor. If you want an estimate, you can use this calculator.

    The speed you get is a theoretical one which will be more off as speeds get higher and things like drag and ballooning tires become a factor.
    Nobody is born with experience

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