Pointed arch Gantry

Last crawled date: 3 years, 2 months ago

20/11/2020

I recently imagined that the vertical part of the running gear could have been telescopic by means of a possible truss system between each foot to compensate the increase in the lever arm (if necessary: depends on the height of deployment and the rigidity of the inflatable structure).

18/11/2020
Small additional informations on the ideas that guided me and thoughts after the fact ...
1) Why a pointed arch with shell architecture? The idea was to use as little gas as possible by maximizing the inertia of the beam / column, in the same way that one uses H or I sections rather than hollow cylindrical sections.
The pointed arch is for its part the most efficient to support a vertical load (slenderness factor: base / height ratio / load minupulation area).
At the same time, and afterwards, I realized that I should have opened the angle at the feet instead of having them parallel in order to eliminate the instability in flexion at this level. Ropes could also have been put between the weights to stabilize the whole, with a catapult and a catcher in the manner of a sewing machine shuttle to recover the rope, in order to free the space between the feet to get out of the lander.
2) Why drop-stitch panels?
So that this shell architecture (or skin) is foldable, deployable and that the webs of the beam have a certain rigidity in order to sufficiently make the lower section in reinforced fabric work in tension. Thus, the part working in compression mainly supports the payload and to a lesser extent the forces resulting from bending relating to the offset of the load. We can thus estimate that for a tube of 20cm in diameter and a pressure of 1 bar ablsolute, this is already 314 daN per foot (x4 = 1256 daN => G1.622 +/- 7500kg) + the compression linked to the offset.
3) Why a memory foam?
I mentioned memory foam mainly to help the structure unfold, but also to keep it in its shape in the absence of gas pressure. Afterwards, I said to myself that this foam, under certain conditions, could act like a muscle: if the pressure in a panel is suddenly increased and this foam has a certain resistance to the penetration of gas, the panel (the muscle) will suddenly inflate with a minimal amount of gas. This may allow a bent panel to be straightened out or force a violent effort. When the gas has penetrated slowly, we will have a stabilized pressure. As vacuum pumps have more and more difficulty pumping as the gas becomes scarce, the fact that the foam releases the gas slowly is therefore not a major problem.
4) Why running gear with two uncoupled wheels?
I admit that I considered that we could use a relatively high pressure in order to straighten the structure ... which is perhaps not the case because I had not thought of the weight that the auxiliary equipment would make. (batteries, photovoltaic panel deployment system, gas tanks ...) in all cases, they should be placed low enough to reduce the leverage during erection. For the tanks, I think if they are carbon or other composites and the gas used is of the correct molecular size, they should not be very heavy.
Also, the wheels should be large enough in diameter so as not to sink and maintain traction when they drag the equipment on the ground before inflation. It is also considering this that I planned that they could be articulated on 3 axes in order to find the ground presenting the best traction or to use only an inclined wheel to sink further into the ground.
Not having drawn the auxiliary equipment, I did not plan to protect them when they will be dragged ...
5) Why a rigid apex.
It is necessary to see the modes of collapse of the vaults (https://fr.wikipedia.org/wiki/Fichier:Rupture_de_voute.JPG) Certainly it is not rubble that will be used, but one can understand that the collapse at the apex will be done inward.
This "pyramidion" should therefore be large enough to distribute the force elsewhere on the structure (lower than what is drawn) and that it be articulated like the ribs of an umbrella to facilitate folding.
6) Other remarks.
The strips of anti-spacing fabric that I have placed between the panels can, if they are sufficiently stretched, serve as rungs to access the winch (which is not drawn either ...) and the load. This can be useful if something goes wrong.
I did not consider the interfaces between the different inflatable elements because it is a fairly substantial sewing job which is made even more complex by the fact that everything must be waterproof ...
However, I have in mind the way in which the sails of wood and canvas aircraft are assembled.
I'm sorry I didn't have the time to represent these concepts, but faced with a talented competition that produced quite substantial work, I didn't feel I had the means to compete ...
I hope these lines can be useful and wish everyone the best.

Yellow: drop stitch panel (with memory foam inside?)
Orange: inflatable tubes (compression)
Grey/black: tear resistant stretch fabric.
Magenta: Rope
Olive green: Rigid apex (pyramidion) connected to the lifting rope.

Stretch tear (with specific maximum extension) for reinforcement & stretch ability to make easier the foldability.