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4-speed Compact Sequential Transmission

March 23rd, 2015 Leave a comment Go to comments

A 4-speed sequential transmission controlled remotely by a single PF M motor.  Instructions available. Update: instructions replaced with new, improved version.
Many of my transmission designs aren’t very practical – they are either very large, very complex, or require a control system that is complicated, inconvenient to use, and involves many expensive motors. I wanted to develop a design that would address all these issues and this is the result.

This transmission is pretty small, robust and except for the driving rings and catches it is build entirely with basic, common pieces. The 4 speeds offer gear ratios from 5:1 to 1:1 and can be selected by a PF M motor – which can be replaced by essentially any other Lego motor. With many advanced sequential transmission designs floating around, my goal was to strip this one to bare minimum – hence no PF Servo motor, no stepper mechanism, no rubber bands or steering links, literally nothing fancy. The shifting is done in a full cycle, meaning that the transmission can be shifted through speeds 1 to 4 and back to 1 again, or in the opposite direction – there are no “ends” of the cycle. A worm gear is used for shifting to ensure precision and to keep the driving rings locked against torque at all times. The entire unit is somewhat tall, but I specifically kept it just 7 studs wide for easy integration into chassis, between the stringers.

The lack of a stepper mechanism of any kind means that shifting requires some attention – but it can be done perfectly well just by ear, as the 3L driving rings shift with loud, clear “click”. Two “clicks” mean that another speed has been successfully selected. This may prove insufficient with models that are loud, or are meant to work at some distance from the operator. Another disadvantage is that 3rd and 4th speeds add plenty of friction because of how the gears are arranged – enough to slow down a single PF L motor, but not a PF XL one.

All in all, I count this transmission among my most practical and useful designs. It’s not a perfect solution, but it has a long list of advantages and it suits the needs for which I’ve developed it perfectly. It is a good demonstration of the advantages of simplicity, also known as KISS principle (Keep It Simple, Stupid).

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

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  1. Sariel
    April 14th, 2015 at 19:25 | #1

    Owszem, musisz pokryć opłatę celną jeśli deklarowana wartość przesyłki przekracza 45 dolarów. Tak było od zawsze. Ile to wyniesie zależy od paczki, więc nie jestem w stanie powiedzieć – nawet różni celnicy różnie naliczają opłaty.

  2. Psor
    April 14th, 2015 at 18:39 | #2

    Może wiesz,
    odbierając przesyłkę z Bricklinku z Ameryki musisz pokryć jeszcze opłatę celną, (a przynajmniej takie dostałem zawiadomienie). Jak i ile to może wynieść?

  3. Ev3fan
    March 31st, 2015 at 15:53 | #3

    Oh man. This thing makes my own invention – I talked about it here: http://sariel.pl/2015/01/4-speed-servo-rc-transmission/ – completely obsolete.

  4. Sariel
    March 28th, 2015 at 22:50 | #4

    Yes, of course. It will be released this August, and you can expect my video around that time – maybe a little earlier, if I’m lucky.

  5. Shalene
    March 28th, 2015 at 16:41 | #5

    Hey Mr Sariel are you aware of 2h 2015 Lego technic set Arocs truck 42043.Do you know when it is getting released? And when it get released are you going to make a video of it?

  6. Sariel
    March 27th, 2015 at 18:35 | #6

    W mailu powinno być info jak masz zapłacić – przez Paypala czy przelew. Po prostu wchodzisz na Paypala czy stronę banku i płacisz według danych. I nie, nie wyślą dopóki nie zapłacisz.

  7. Psor
    March 27th, 2015 at 18:25 | #7

    Znowu ja, sprawa jest taka:

    Jeśli na Bricklinku po kliknięciu na >complete purchase< dostajesz na maila wiadomość od dostawcy, kontakt i fakturę, a twoje konto jest bezpośrednio skonfigurowane z PayPalem, to jak wygląda proces transakcji?

    pS: A dopóki im nie zapłacisz, to Ci przesyłki nie wyślą?

  8. March 26th, 2015 at 14:44 | #8

    This is absolutely amazing, I’ve been trying to do something similar for months. 🙂

  9. Sariel
    March 24th, 2015 at 10:48 | #9

    Zaskoczę Cię, ale Allegro. A na Bricklinku zwykle ten sklep który ma je w danym momencie najtaniej. Bricklink domyślnie sortuje od najniższej ceny.

  10. Psor
    March 24th, 2015 at 08:27 | #10

    Gdzie najkorzystniej jest nabyć silniki typu PF, żeby móc skompletować zdalne sterowanie, jeśli chodzi o Polskę?

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