Envelope wedge clamps – red

As nearing to our first motorised flight, there are/were still few things to take care of. Probably the one most pressing was the way how the envelope upper wedge was clamped, where using the Ametalin tape shown to be unreliable (tape was ripping off as envelope inflated).

Anyway, so designed new clamp in OpenSCAD which goes through the envelope and provides means to strap both sides together while distributing the load in some convenient way (Eye foundation is 30 degrees bent). Code is pretty simple:

use <ShortCuts.scad>

$fn=100;

module joint(angleIn) {
rotate_extrude(angle = angleIn)
translate([3,0,0])
circle(3);
}

module clamp() {
Ty(13)
cylinder(10, 3, 3);
T(-3,13,0)
R(90,30,0)
joint(30);
Ry(30)
T(0.4,13,-4.5)
cylinder(3, 2, 3);

Ty(-13)
cylinder(10, 3, 3);
T(-3,-13,0)
R(90,30,0)
joint(30);
Ry(30)
T(0.4,-13,-4.5)
cylinder(3, 2, 3);

T(0, 10, 13)
Rx(90)
cylinder(20, 3, 3);

T(0,10,10)
Ry(-90)
joint(90);

T(0,-10,10)
R(0,-90,180)
joint(90);
}

module pads(upper = true) {
D() {
if (upper) {
minkowski() {
cube([1.5,40,0.01], center = true);
cylinder(1.5,10,10);
}
}else{
Tz(-1.5)
minkowski() {
cube([1.5,40,0.01], center = true);
cylinder(1.5,10,10);
}}
T(0.4,-13,-1.55)
cylinder(3.1, 2.05, 3.05);

T(0.4,13,-1.55)
cylinder(3.1, 2.05, 3.05);
}}

module pegs() {
Tz(-0.1)
cylinder(1.1,1,1);
Tz(1)
sphere(1);

T(0,22,-.1)
cylinder(1.1,1,1);
T(0,22,1)
sphere(1);

T(0,-22,-0.1)
cylinder(1.1,1,1);
T(0,-22,1)
sphere(1);
}

clamp();

*pads(false);
*pegs();

D() {
pads(true);
pegs();
}

Resulting rendering:

Now, printed all parts many times (each side of wedge has those distributed every 50 cm + multiplied twice for each envelope). Then lots of gluing and it worked out very well – see our weekend inflation test which demonstrates that that idea works pretty well.

Another part installed was envelope gas relieve vent as deflating envelope through the maintenance opening didn’t work out well.

Installed valves actually brought a nice opportunity to see our envelope from inside for a first time showing some nice details.

Finally we did another inflation test which worked out in envelope bursting out in the front and around one meter long rip through it. Luckily it was anticipated that something like this can happen and we were able to fix quickly with a new weld. Inflated envelope then seemed to be keeping its shape for ~10 minutes without any signs of deflation and we took some nice pictures.

Having the port-side envelope done, the next step is to repeat all this for the starboard one, but that’s for another day. 😉