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  1. #1
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    is aftermarket motor needed for undergive gearing?

    Hi,
    I recently bought Summit 1/16 (not VXL, hope I can put it here). I think about undergive gearing (found some threads about it here as well), but there is one thing I don't understand. In the user manual there is Gearing Compatibility Chart. It says that when I go for a really small pinion gear I need to replace the stock motor (Titan 12T 550) by aftermarket 540. Do I need to replace it when I go for undergive gearing as well, as in both cases I increase the gear ratio?

    What is the reason for replacing it (when replacing pinion gear) anyway? I think I understand the need for second battery when decreasing gear ratio (engine stressed more, draining more power from batteries) but when I increase it?

  2. #2
    RC Turnbuckle Jr. pavmentsurfer's Avatar
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    Can you explain what you mean by "undergive" gearing? Ive never heard that term before.

    Smaller pinion will make your throttle feel smoother but your top speeds will be lower. They suggest going to a 540 motor because you can get higher RPM 540 motors to make up for the lower gearing. You would only want to do this if you wanted to maintain your stock speeds. If your trying to improve low speed crawling and dont mind the truck going slower at top speed you dont need to change the motor. Just gear it lower.

    If you gear lower you wont necessarily draw more power from the battery. If you INCREASE your gear ration (make it higher) you WILL be putting more strain on the motor and you will drain your packs faster. Using 2 packs in PARALLEL is the key, NOT series. Series increases the voltage for more speed but I dont believe it will work on the brushed ESC.
    Pede, Summit,
    ERBE, Rally,
    Motley Crew, 1SQ

  3. #3
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    Quote Originally Posted by pavmentsurfer View Post
    Can you explain what you mean by "undergive" gearing? Ive never heard that term before.
    *FACEPALM* I mean underdrive gearing, sorry. When I find out how to edit I will fix it at least in question body.

    Quote Originally Posted by pavmentsurfer View Post
    They suggest going to a 540 motor because you can get higher RPM 540 motors to make up for the lower gearing.
    How is the gear ratio defined? From Gearing Compatibility Chart or http://traxxas.com/forums/showthread...=1#post4049990 (thread about transmission and gear switch) I thought that lower gearing means faster car, higher gearing means more torque. According to you and wikipedia it seems that it is the opposite.

    Quote Originally Posted by pavmentsurfer View Post
    If you gear lower you wont necessarily draw more power from the battery. If you INCREASE your gear ration (make it higher) you WILL be putting more strain on the motor and you will drain your packs faster.
    When I go for higher car speed I put more strain on the motor. When I go for high torque I basicly put less strain. The only reason why high RPM motor is required here is to maintain the stock speed, so I can safely switch gears in transmission to achieve slow car with plenty of torque. Is this correct?

  4. #4
    RC Racer
    Join Date
    Jan 2012
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    Are you trying to make it slow for crawling or to learn to drive? If your doing it for crawling, the torque isnt gonna help much unless you lock the diffs. I have plenty of torque to climb stuff stock provided all the wheels get traction. As for your gearing question, i wouldnt bother with calculating ratios. If you increase pinion teeth car goes faster than a lower tooth. Increase spur gives slower car. Thats only really necessary to change if you need a really low tooth pinion and cant find it. On your motor/tranny question. If you flip the tranny, you are gonna loose most of your high end. I believe it will top out around 18mph (thats with the vxl so the brushed motor would likely be even slower). Yes you could switch out the tranny if you wanted to go back to having speed, but that seems like a pain to do. I guess if where you are planning on driving, you are only gonna slow the whole time, that might be ok.
    Last edited by stingeragents; 01-06-2013 at 10:20 AM.

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