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4-Speed Servo RC Transmission

January 16th, 2015 Leave a comment Go to comments

A 4-speed transmission using new pieces, controlled remotely by two PF Servo motors.  Instructions available.
This transmission is a fairly typical 4-speed transmission, except that it’s using the new 2015 transmission driving ring and two PF Servo motors for remote control. It can be modified for use with the older transmission driving ring, too. Its important characteristics is that it does not stall the motors, allowing them to rotate full 90 degrees in both directions. It thus allows to shift very quickly and without any risk to the motors.


The main advantage of this design is fast and comfortable shifting. The disadvantages, besides the obvious need for two PF Servo motors, is the fact that the transmission driving rings aren’t held in position when engaged by the transmission changeover catch, and the fact that shifting with the basic PF remote requires holding a lever. As the video below demonstrates, this can be made relatively comfortable by combining two remotes in certain way, or by using the PF speed dial remote which works with this transmission perfectly well.

Free building instructions for the gearbox are available in the Downloads section.

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  1. Sariel
    February 11th, 2015 at 15:00 | #1

    I think Sheepo made a brilliant one already?

  2. Artwodeetwo
    February 11th, 2015 at 13:47 | #2

    Hi Sariel, have you ever thought of making a MPS? (Modular Platform System)

  3. EV3fan
    February 8th, 2015 at 15:21 | #3

    Update: I figured out a way to operate the “conventional” 4 – speed gearbox (out of your first book) with two m – motors without a slow stepper mechanism but much faster. It’s using clutch gears and a special lever mechanism and I’ll maybe make a youtube video of it, because I think it is really great: Cheaper than your solution, but with the same insane shifting speed. 🙂

  4. Sariel
    January 19th, 2015 at 14:52 | #4

    I don’t know, but a self-centering valve with PF M motor can be found in my first book.

  5. Artwodeetwo
    January 19th, 2015 at 13:49 | #5

    Would connecting a Servo to an 8 tooth then 24 tooth gears then the pneumatic valve work?

  6. Maras
    January 19th, 2015 at 06:46 | #6

    Hmm, there must be a way of controlling pneumatic valve’s using servo motor’s. Ill need to buy a few to try i think.

  7. Sariel
    January 17th, 2015 at 08:14 | #7

    Yeah, this is basically improved version of the R8’s gearbox.

  8. Artwodeetwo
    January 16th, 2015 at 20:09 | #8

    Is this similar to the design you will us in the R8?

  9. EV3fan
    January 16th, 2015 at 15:03 | #9

    Yes, but this is no problem for me. I want to rebuild this and all I’ll need now are the new transmission parts. 🙂 Obviously that would also solve the problem of having to hold the small remote’s levers in forward/backwards position. And, by the way: You did an awesome job keeping everythink so compact!

  10. Sariel
    January 16th, 2015 at 14:32 | #10

    Yeah, it should be possible, but adjusting the rubber band on the stepper mechanism will take some work.

  11. EV3fan
    January 16th, 2015 at 14:19 | #11

    YEEES!! Fast gearchanges!! I hated it when you changed gears while driving because the model slowed down a lot and then it had to accelerate again, but in a higher gear than before, which is both unrealistic and impractical, as it stops one to make the upper gears higher. so this is a huge step forward. One question: would it also be possible to use m motors with a stepper mechanism (there is one in your first book) allowing the motors to only ake a 90 degrees turn at once?

  12. Daniel
    January 16th, 2015 at 13:52 | #12


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