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  1. #1
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    E-Maxx 3908 and 775?

    I have a 3908 e-maxx that was suppose to have the mamba in it and I decided to run the Summit 775 motor because of the torque. After modifying the motor plate and a little grinding on the tranny, I now have the question of what gearing I should run. The stock 68t spur wont reach the pinion unless they make a large one. I'm also running Big Joe series 40 tires. Any help on the gearing for decent speed and torque without overheating?

  2. #2
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    Big motors like that typically need a 22T Pinion or larger to reach the spur gear. Make sure you get one that is 32 pitch. I'm not sure what the motor shaft size is, I think it may be a 5mm shaft.

    Bigger question that comes to mind is what ESC are you going to use with that brushed motor? Brushless ESC's don't or can't run a brushed motor. I've read that some brands of ESC can be put into a "Brushed" mode but I'm not sure about the Castle ESC's

  3. #3
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    Try the 70t nitro rustler pinion with an 18t spur. I had that with my summit tires and 775 motor. This will give you some clearance issues, you'll have to dremel...

    If its too slow, try 21/68 but that may be too much with those tires.
    70/18


    68/21
    Last edited by Redsawacs; 12-04-2012 at 08:06 PM.

  4. #4
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Quote Originally Posted by M n M View Post
    Big motors like that typically need a 22T Pinion or larger to reach the spur gear. Make sure you get one that is 32 pitch. I'm not sure what the motor shaft size is, I think it may be a 5mm shaft.

    Bigger question that comes to mind is what ESC are you going to use with that brushed motor? Brushless ESC's don't or can't run a brushed motor. I've read that some brands of ESC can be put into a "Brushed" mode but I'm not sure about the Castle ESC's
    The EVX2 is more than ready for the task.

    Castle's guide has directions as to how to operate a brushed motor with their brushless ESC's... more brushless ESC's can run brushed motors than most realize.
    http://www.castlecreations.com/suppo...s_ed_guide.pdf
    Whatever it is I just said... I could be wrong.

  5. #5
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    I was running a 20T pinion on a 68T spur with my 775 motor. After some work in the transmission case I was able to make it work. Not the fastest, but lots of torque.
    Not enough space here

  6. #6
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    Quote Originally Posted by Jimmie Neutron View Post
    The EVX2 is more than ready for the task.

    Castle's guide has directions as to how to operate a brushed motor with their brushless ESC's... more brushless ESC's can run brushed motors than most realize.
    http://www.castlecreations.com/suppo...s_ed_guide.pdf
    Good info Jimmie. I purchased a Hobbywing BL ESC shortly after I switched to LiPo's mainly for the built in LVC and cooling fan. I also had thought about going with a BL motor at some point. At the time I didn't realize that model of ESC would not run a brushed motor (DeWalt 14.4). So now I have a new BL ESC waiting for me to put it in my 1/10 SCT.

  7. #7
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    Thanks for all the info. I am running the EVX-2 in it. I will try starting with a 20t pinion and go from there. Again, thanks everyone.

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