I've nearly finished the reconfiguration of the Propulsion Module for the Little D.
The original pattern, on the right, was configured for being molded as a whole. This shape was made from thick styrene and covered with detail castings. The objective here was to be able to make the propulsion module as one casting so nothing would come apart years later.
The castings were 'slush' castings, meaning resin was poured into the mold, the mold was sealed and rotated in a constant motion until all inside surfaces had been covered and the resin cured. The problem in this case is the part would distort over time, the middle dishing inward slightly, but enough that lines were no longer straight. Very unacceptable.
The alternative I've come up with is to treat the module as 3 parts, each reinforcing the join between its mating neighbor so everything stays nice and straight. The result is the blank, on the left, identical in size and shape as the original styrene blank.
Here you can see how the blank comes apart. The center joint is registered by the hemispheres and the top joint will be a rim joint, where the top part will interlock along the perimeter.
This shows the forward and middle sections completed. I'm still working on the top section.
Here you can see how clean the joint between these two parts is. I have my fingers crossed in the hopes that the castings mate just as cleanly! Please note that what appears here as some misalignment in the detail castings can barely be seen in person. This image is actually larger than the same part on the large Discovery model!
Scott
The original pattern, on the right, was configured for being molded as a whole. This shape was made from thick styrene and covered with detail castings. The objective here was to be able to make the propulsion module as one casting so nothing would come apart years later.
The castings were 'slush' castings, meaning resin was poured into the mold, the mold was sealed and rotated in a constant motion until all inside surfaces had been covered and the resin cured. The problem in this case is the part would distort over time, the middle dishing inward slightly, but enough that lines were no longer straight. Very unacceptable.
The alternative I've come up with is to treat the module as 3 parts, each reinforcing the join between its mating neighbor so everything stays nice and straight. The result is the blank, on the left, identical in size and shape as the original styrene blank.
Here you can see how the blank comes apart. The center joint is registered by the hemispheres and the top joint will be a rim joint, where the top part will interlock along the perimeter.
This shows the forward and middle sections completed. I'm still working on the top section.
Here you can see how clean the joint between these two parts is. I have my fingers crossed in the hopes that the castings mate just as cleanly! Please note that what appears here as some misalignment in the detail castings can barely be seen in person. This image is actually larger than the same part on the large Discovery model!
Scott
