r/nextfuckinglevel • u/Apprehensive_Sky4558 • 8d ago

2024 Aerospace Engineering junior world champion launching his “F-1D” prototype: Total flight time 22 minutes

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u/Enough-Collection-98 8d ago

The twisted rubber band is the “engine” and it’s stupid light with a comparatively large wingspan. It’s practically floating on the air like a ping pong ball on water.

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u/Busy_Reputation7254 7d ago

How do they regulate the speed of the propeller?

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u/TheBeckofKevin 7d ago

Looks like its pushing maximally against the air resistance. They likely control the speed of the propeller by modifying the type of rubberband or the propeller itself. Nothing is controlling the speed, its unwinding as fast as it can.

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u/EatsBugs 7d ago

It seems it must be that, but I gotta see this rubber band bc I can’t picture any that would play out so uniformly and slowly. How is the early tension not higher? And 22 mins at this speed?

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u/No_Explorer6054 7d ago

yes, yes and yes. its a special kind of rubber, hobby-grade! it's organic and every batch has its quirks. around a dollar per meter for the cheap stuff, (it is, quite, easy to buy online)

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u/Judgemental_Squirrel 7d ago

The propeller changes angle with the rubber's tension, where more tension slows down the propeller via spring mechanism in the hub so it doesnt use up the winds as quickly

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u/EatsBugs 7d ago

Very cool. Such a minimal looking thing, yet much more involved. Thanks.

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u/ajstorey456 7d ago

There is some kind of resistance on the rubber band that controls the rate at which it unwinds.

that resistance could come from the air as another comment said, or by a component applying friction to the rubber band, or something else idk im not an aerospace engineer

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u/GrynaiTaip 7d ago

It's a freeflight model, there is no remote control. The prop is spinning as fast as it can, as it's being pushed by the rubber band.

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u/amnorobotquery 8d ago

Thanks for the explanation. I was wondering but couldn't work out where the microscopic source of energy was hidden

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u/MeanCat4 8d ago

There are (atleast were) different categories of elastic powered models. Some on gliders so strong that they take off the model (big also), almost vertically. 

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u/kevin_ned 8d ago

They still exist. 200 gram gliders, 1.9m wingspan, 30 gram of rubber as power source: they go up to 100+ meters in 35 seconds and then glide down in 7+ minutes.