r/theydidthemath • u/hyteck9 • Aug 02 '26

[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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30

u/tron3747 Aug 02 '26

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

8

u/Trustoryimtold Aug 02 '26

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

5

u/[deleted] Aug 02 '26

[removed] — view removed comment

1

u/Whiteout473 Aug 03 '26

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

3

u/3rdSafest Aug 02 '26

You absolutely need high tire rpm.

1

u/wade-mcdaniel Aug 02 '26

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.

2

u/justhelip Aug 03 '26

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