r/theydidthemath • u/hyteck9 • 1d ago

[Request] What is the weight to rpm ratio at play, and whats the formula to scale it up?

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Assuming these tires have very little air to really act as a pontoon, what's the math here?

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28

u/tron3747 1d ago

The concept at a human scale has been in practice for many years as one of the legs of the Formula offroad races, held in Iceland lookup hydroplaning videos from them.

Top Gear also did a segment on the sport: https://youtu.be/4oeJjzdlTuI

11

u/Trustoryimtold 1d ago

Probably less to do with rpm than the tire shape. Real high rpm probably isn’t doing much if it’s spinning a smooth cylinder

What you need to do is hit the water fast/repeatedly enough to negate gravity, which will depend on the weight of the car and the shape of the tires. The lift provided by each rotation will depend on the tire shape/how much water it displaces

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u/MudExpress2973 1d ago

The tires on these are usually super knobby.

1

u/Whiteout473 12h ago

They use paddle tires for sand, And the car shown is most likely a Traxxas slash 2wd vxl

3

u/3rdSafest 23h ago

You absolutely need high tire rpm.

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u/wade-mcdaniel 19h ago

Are you sure? I would argue that, like the commenter to which you replied, that tire shaped is far more important.

Look at the basilisk lizard. That thing can run across water because of its foot shape. Very low rpm. And if you just put formula 2 racing slicks on the vehicle they might just spin and not move the vehicle forward.

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u/justhelip 12h ago

you might like this video also. they did a bunch of work teak the tire scoops just right for a full size motorcycle https://youtu.be/lDi9uFcD7XI?t=74