The mold was straightforward enough to do. A bit tricky to decide where to put the seams but I think I got it pretty well in the end.
Casting was another beast to handle. I had to cut the mold into a 4 piece mold to make sure that it did not break when the part was removed. I had a lot of trouble getting the small parts of the uplock strut to come out good. A lot of small channels and tweaks had to be cut into the mold to make it work. A late evening indeed…
At the time I had my fourth Truss assembly I had got the failure rate down to about 3:1.
The mold was easy to do. (maybe a bit too easy as I managed to get a bit sloppy round the splittingline)
This time i had a much easier time casting. Relatively simple shapes to cast. The silicon mold for the primary strut could have been a little better. You can see the split in the mold quite clearly on the finished product. That can be sanded down later. And that is still for the birds because it’s going to be wrapped in aluminum and kapton foil anyway. Can’t wait.
The mold was tricky to manufacture because I wanted to conserve the amount of silicone used. (expensive) I ended up modeling it in 3d so that I could get a good estimate of the volume of silicone that it would take to fill the two parts of the mold. being this cheap ended up biting me in the ass when used for casting.
The truss turned out to be extremely hard to get a good cast. The struts are thin and the details of the LM/SLA interface are very fine in places. The molten tin had time to cool of before it reached the bottom of the mold and there was also the issue of getting air out of the mold. This was further complicated by the fact that the mold was rather flexible and hard to keep “shut” due to the fact that I made it so thin. Maybe not such a good idea afterall… Just look at the number of rubberbands used to keep everything in place…
There where a considerable amount of failed trusses cast, sworn over and melted down again. late late at night and a couple of burnt fingertips later I had the four trusses I needed and even one spare if i where to break one during assembly. (I just do not want to use that mold again if possible.)
The primary and secondary struts where made in the same fasion as all the other struts. (Metal rod core, styrene tubes and all conical surfaces out of paper.) details made out of 0,5*0,5 mm styrene strips and 0.3mm styrene sheets.
The deployment truss crossmember was built out of styrene tubes with a metal rod in its core. I then added conical ends out of paper.
The bridge in the middle Is made of a larger diameter tube and detailed with 0,5*0,5 mm styrene strips.
Next i built the deployment struts with their interesting forklike ends out of styrene rods that I carved and sanded and small pieces cut out of styrene sheets. details out of 0,5*0,5 mm styrene strips.
The uplock struts where made in a similar fashion.
Spurred by the success of the RCS thrusters I have decided to make the Lander legs out of tin as well. First I have to make masters for the molds.
Started with the four legged truss with the LM SLA interface. I first built the lower beams out of styrene rods. The upper cone shaped ones are built out of styrene and paper. Paper because it was easily shaped into cones and with some use of CA-glue as coating it becomes rock hard. Then I created a temporary support structure for the beams so that i could build the LM/SLA interface and the slot that holds the primary strut. a bit tricky but the supportstructure made it manageble.
All enginebells are made out of curved .5mm plastic strips. (3d made flat printed and cut as usual)
I then cover them in epoxy-putty and sand them down to make them smooth and nice.
The 5mm long RCS thruster bell was a very tricky little thing to get done. To make the small rings around it I had to glue these thin copper wires around it. It took forever to get it resonably good. And now i need 15 more of that little bugger…