Saturday, July 31, 2021

Lander Legs

In designing the lander legs, I wanted them to be fairly modular and cheap in case I needed to change the design (stance and clearance) later to accommodate future design changes. I also wanted them to be pretty flexible to adjustments, generally. I decided to take this time to exercise for laser cutting steel parts, and also try my hand at some TIG welding. Each of the leg rods has a weld nut at the end, and each plate is laser cut and then welded together. These were some of my first welds, and they did not turn out too bad. I did have an issue with warping on the feet, as I did not provide enough heat sink material on the bottom and my weld current setting was a tad high.

Here are some pictures in no clear order of operations:

Notice the center rod uses clevises while the side rods use spherical rod ends.
The center bracket is ground down a little for the clevis to fit through. The look a little off center, but I promise that's just asymmetrical grinding :)

Without nuts on the rod ends:

The council of legs have spoken
honestly, a little proud of these, they look sick

I also fabricated the cross bar for the center rod and clevis to mount to. This was just a 1 inch steel tube with two brackets welded to hold the clevis in plate. I MIG welded this to the chassis at the correct height for the legs, and made sure each side was at the correct height. All the bolts are 3/8"-24. Also don't get any shavings into the threads and then tighten a nut over that -- good recipe for seizure and needed a cutoff wheel :). 

Oh man, and it looks super sick (first picture is through fish-eye):

A Paddy for scale...

Tuesday, July 27, 2021

Lander Airframe and Tank Work

I decided that 2021 will be the year I finish all the structural components, tank components, avionics, and linear actuators for the lander project. We'll see if that happens. This gives me time in 2021 to focus purely on GNC, software development, propulsion, and testing.

My friend Keith helped me out by fabricating the airframe. I did not have access to a welder at this point, so this was a major help. Here are a couple pictures from the process. You can see that he has two of the same types of tanks that I have/will be using. It was cool to get an initial perspective picture like this.

Here is the airframe in my living room after I primed it. You can see one of my fuel tanks in the center, as well as my pressure sphere off to the left. Nalgene for scale.

Here is the airframe with my two tanks laying there prepped and ready to go.

As far as the tanks go -- these are WWII Oxygen tanks from B24 bombers that were initially rated to 500psi. Here they are in their element:

My tanks were not as beautiful when they came in 

After sandblasting and priming:

There is still much work do be done on the tanks. Their feed system needs to be designed, fabricated, welded, and then pressure tested (I should not be using higher than 300psi). I should probably hire a professional welder for this, given how important consistency will be.

Another not-fully-filled-in CAD pick of what the vehicle should look like. Lots more to put into it.