Twin-radius Tank Steering System [with INSTRUCTIONS]

[Sariel]

Here's a mechanism for controlling your LEGO tanks that may be considered a good alternative to subtractors. It splits a single driveshaft in two and then puts each of these two shafts through a small 3-speed remotely controlled transmission. This effectively allows to drive at two different speeds and to turn with two different radiuses. It’s also fairly easy to add a transmission and/or a piston engine between the drive motor(s) and the mechanism, and – unlike with a subtractor – they will work both when driving straight and when turning.

The primary advantages of this mechanism are realistic controls (with a PF remote you can operate levers just like in a real T-55 tank) and ability to use a transmission and/or a piston engine at all times. There are no differentials needed, which is another advantage because their inner gears can be broken under high torque. The disadvantages include the need for two PF Servo motors to control the mechanism and a larger size and higher number of specialized pieces when compared to a subtractor.

Free building instructions: http://sariel.pl/downloads/

 

Edited April 24, 2021 by Sariel

[howitzer]

Nice, novel mechanism. The need for 2 PF servos is a serious downside though, except that you should be able to use PU motors quite easily in their place.

[Vectormatic]

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Edited July 1, 2021 by vectormatic
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[Sariel]

41 minutes ago, vectormatic said:

Are you planning on building a proper T-55 Sariel? I'd love to see that.

I think it's a bit too similar to the T-72 which I've already built, so no. I've developed this mechanism for my T-34 model, even though the real T-34 actually uses a simpler steering system, with a differential and brakes.

[Vectormatic]

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Edited July 1, 2021 by vectormatic
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[marshmallow]

Hi Sariel, thank you for posting. Do you think this design would have less resistance/friction in the transmission compared to a subtractor? Specifically by not having all movement go through those three small 12-tooth bevel gears inside the differentials. I'm wondering as that could maybe allow me to use less gear reduction and have the tank run faster.

[Sariel]

I guess, but it's probably a fairly small difference.

[allanp]

I like it! Should be fine for smaller builds. I have found that those wave selector pieces can really struggle to shift when whatever it is trying to shift is under high levels of torque but clearly works fine here.