Physics Rediscovered #6: My trebuchet is bigger than yours

michaeldominik.substack.com

21 points·thunderbong··8 comments

Burried in hackaday is the work of a newly minted mechanical engineer who designed and built a trebuchet that has supersonic launch velocities. found it https://hackaday.com/2021/12/01/supersonic-projectile-exceed...

Checking: it's 6 tons dropped 2 meters to launch a 100kg payload. If straight up, it could go 6000*2/100 or 120 meters. Visualize a launch for range vs. for height, and guess it can go roughly twice as far horizontally as up.

(The OP ends up at 210 meters.)

the ideal angle for maximum horizontal displacement is 45 degrees

Assuming zero windspeed, I assume?

No, assuming zero air whatsoever :).

With drag, it is less than 45 degrees.

Source: I once upon a time ran a simulation because I was curious. The magnitude of the offset from 45 degrees scales with drag coefficient & frontal area

Yep. But calculating what horizontal distance that implies, in your head, doesn't seem trivial the way my note above was.

(I think the difference between the OP's calculation and my estimate all comes from their 80% efficiency vs. my assumption of 100%. My 'roughly' twice as far as high is actually exact under ideal assumptions. Where the slope of the inverted parabola is -1, the chord is 4 times the height, but in this parabola only half of the launch energy goes into upward motion, accounting for the other factor of 2.)

For superior trebuchet performance, you want a floating arm:

https://en.wikipedia.org/wiki/Floating_arm_trebuchet

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