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Thread: Spur Gear Help

  1. #1
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    Spur Gear Help

    I need help, I would like to know what spur gear and pinion size is recommended to use with the e-revo on grass with 6s lipo batteries (Traxxas 5000 3s Lipo 25C), a spur/pinion combination that would reduce the probabilities of the engine getting too hot and the spur gear going teeth-less.

    Right now I have

    -The stock pinion (I do not even know the size of it)
    and
    - 58T M 0.8 and 68T M 0.8 spur gears.

    Which is the combination recommended for bashing?
    Last edited by bono983; 04-07-2012 at 10:47 PM.

  2. #2
    RC Turnbuckle Jr. 87 GN's Avatar
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    the spur gear going teeth-less.
    if that means striping the teeth off the spur, then that usually only happens with a bad gear mesh or the motor coming loose.

    stock pinion IDB is 18T. So I would prob use the 58 spur. Would be a good start, but still abit under geared.
    try 18/54 or 20 ~ 21/54

    Diff ratio

    BrianG speed chart:
    4s = 40 mph
    5s = 50 mph
    6s = 60 mph

    http://www.scriptasylum.com/rc_speed/top_speed.html

    Import this:

    Differential Ratio: 2.8461538461538463
    Transmission Ratio: 1.8333333333333333
    Other Ratio: 1
    Spur Tooth Count: 54
    Pinion Tooth Count: 21
    Total Voltage: 22.20
    Motor KV: 2200
    Tire Diameter (inches): 5.9
    Tire Ballooning (inches): 0
    Motor Current Draw: 0
    Motor Coil Resistance: 0.006
    Spur/Pinion Ratio: 3 : 1
    Total Ratio: 15.65385 : 1
    Tire Circumference (inches): 18.54 inches (470.8 mm)
    Rollout: 1.18:1
    Total Motor Speed: 48840 RPM
    Vehicle Speed: 54.76 mph (87.97 km/h)
    Effective KV Value: 2200
    KT constant: 0.61 oz-in/A
    Would you go flip my truck back over??

  3. #3
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    Is the stock gear (18/65) under/over geared if I use 6s Lipo 5000 25C?

  4. #4
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    Thanks 87 gn, i learnt a bit from your post. I am trying..I am new at this hobby.

    I do not want my erevo to go super fast at the expense of more stress on the engine.

    I want a combination that offers the less stress using 6s LIpo.

    Pardon if you get a little bit frustrated reading my posts.
    Last edited by bono983; 04-08-2012 at 09:25 AM.

  5. #5
    RC Turnbuckle Jr. 87 GN's Avatar
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    all good^
    18/65 would be under geared. under geared will heat things up just like being over geared, the trick is to find a happy medium. Throttle control is more of a must with 2/3s. Follow the chart above & watch your temps & enjoy....

    temps gun is a must...
    Hot motor + cool esc = under geared.
    Cool motor + hot esc = over geared
    Everything warm just right..

    Motor ~ 180/190*F maximum, ideally 140/160*F, temps can be 10* higher inside the motor
    ESC ~ pretty much same temps / Fan comes on @ 150*F
    Lipo's ~ 140*F max, ideally 100/120*F
    Would you go flip my truck back over??

  6. #6
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    OK, What is the happy medium of the E-Revo, using 6S Lipo?

    I just came back from running my truck, used the 68T spur and 18 pinion and the screws of the motor exterior around the pinion became loose.



    This is where I use my ERBE. Tropical Park Miami.

    I give it full throttle and then I make it jump that hill, it flies very high.
    Last edited by bono983; 04-08-2012 at 11:40 AM.

  7. #7
    RC Turnbuckle Jr. 87 GN's Avatar
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    I just came back from running my truck, used the 68T spur and 18 pinion and the screws of the motor exterior around the pinion became loose.

    you lost me ... the motor mount...

    http://traxxas.com/forums/showthread...=1#post4910702

    stock pinion IDB is 18T. So I would prob use the 58 spur. Would be a good start, but still abit under geared.
    try 18/54 or 20 ~ 21/54
    Would you go flip my truck back over??

  8. #8
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    Thanks

  9. #9
    RC Turnbuckle Jr. 87 GN's Avatar
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    sure what did I do...lol
    Would you go flip my truck back over??

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