I made up these hi tech shock absorber legs for my grandsons quad we are building. Considering the hours I often spend to find a better design for making copter legs that don't disintegrate on every hard landing, It took me about 10 min to stop laughing from the simplicity of the brilliance of this light bulb moment..
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Hehe, you could place them just under the props and use Coandă effect ;-))
I'm using as legs this kind of stuff. I could not find the English name for it.
They are cheap, light, hard enough to survive most crashes yet flexible enough to compensate hard landings.
Here is my copter standing on those legs.
Have you considered using some smaller bottles? Maybe the 1/2L water bottles. Costco sells some heavier bottles branded "Talking Rain" that seem like they would work really well. I have only one on hand here having saved it from a trip because I could reuse it for travel. Want a photo?
I like the 'progressive' strength of your bottle concept. The cap and neck are stronger and the flare gets lighter and springier. Hard to get simpler.
I think when it takes of there is a bit of wind ground affect blowing back up into the cups and makes it wobble a bit on take off. I now made one modification and cut the bottom of the bottles off and inserted it into those top sections of the bottom. So now it just looks like a very short coke bottle. I flew it around in my lounge room and the wobble is gone and the legs work really well.
I'd be concerned about the aerodynamic properties of these. They seem like they would catch the wind and prop wash. I just used some really light and cheap lengths of pipe insulation. A dollar buys six feet. They're too flimsy by themselves so I put a shorter length of thin wall nylon tubing inside. A photo is better. This is the underside with only the leg on the lower left showing the nylon tube stiffener.
What I like if there is a "mishap" on landing the "broken"leg can be easily removed and replaced with a new one
and they are wide enough at the bottom coming in on a bit of slant it will "self right" and not catch like a spike leg and go cartwheeling across the ground .
Cool, they look like Saturn V exhausts...
Jelle I was thinking to try just putting a few cuts about 3 cm long where you can see the grove going up the neck. This would give a bit more cushioning. @ Jonathan, I don't get what you don't get
very simple indeed!. You might get a little more spring effect if you could leave 3-4 strips material on the bottles which you bend and tie together below