[MOC] Fast Robust Inverted Wheel (+free instructions)

[astyanax]

 

Quite a few people before me have had the brilliant idea of turning Lego treads inside out to make giant wheels. But it's not trivial to connect and drive them in a strong and robust way. The vehicle can easily sag under the weight of its motors and batteries. This is exacerbated by the fast spins that you'll want to do with it!

 

I found a very robust solution:

(1) making the body as narrow as possible (just 7 studs between the wheels);

(2) using small Technic turntables instead of axles to attach the wheels to the body;

(3) using a reinforced liftarm construction inside the wheels.

 

The model is VERY fast on carpet. On a slippery floor, spinning is the name of the game:

 

Piece count: 260

Motors: 2x PF Large

Free building instructions: https://rebrickable.com/mocs/MOC-38946/astyanax/fast-robust-inverted-wheel

 

Edited April 5, 2020 by astyanax

[Jurss]

This is cool!

Why those axles at treads are not other way around?

[astyanax]

  On 4/5/2020 at 10:19 AM, Jurss said:

This is cool!

Why those axles at treads are not other way around?

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Actually the stops are too wide so the axles would stick out of the wheel, causing a bumpy ride! Anyway, the treads are entirely secure in the shown configuration.

[Jurss]

  On 4/5/2020 at 10:45 AM, astyanax said:

the stops are too wide

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I think I understood, they can't pass that thread middle part.

[howitzer]

What a funny contraption. Reminds me of https://en.wikipedia.org/wiki/Tsar_Tank

[SNIPE]

I tried something like this but found that you could never have perfectly parralel holes using these inverted tracks athough you could force an axle (or liftarms like in your case) in them.

This is because the tracks are not precisley 1L thick.

I wonder if your model has perfectly parralel tracks or are the supports forced in a bit?

[astyanax]

  On 4/5/2020 at 12:01 PM, SNIPE said:

I tried something like this but found that you could never have perfectly parralel holes using these inverted tracks athough you could force an axle (or liftarms like in your case) in them.

This is because the tracks are not precisley 1L thick.

I wonder if your model has perfectly parralel tracks or are the supports forced in a bit?

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I don't entirely understand what is supposed to be parallel and why. Note that each wheel is driven independently. And the liftarms inside the wheel don't have to reach exactly up to the inner diameter: the axles that you see sticking out cover the last bit.

Edited April 5, 2020 by astyanax
Typo

[astyanax]

  On 4/5/2020 at 11:49 AM, howitzer said:

What a funny contraption. Reminds me of https://en.wikipedia.org/wiki/Tsar_Tank

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"This project has become known among industrial design students as a catastrophic failure of engineering without proper consideration to design."

Haha yup, this contraption is good for nothing except some mindless racing fun!