Good Morning All!
I spent pretty much all of Saturday and Saturday night playing on AutoCad and made really good progress on the model. One of the things I did was have a crack at making the Secondary Propulsion Unit, which is the topic of this update.
I started by tracing half of the outline of the SPM (Secondary Propulsion Motor) using part of a circle, a line and an arc. I then mirrored it, joined the two and revolved it around the central axis to get the solid body. The propellers were just made from a single ellipse, which I extruded 0.005”. (The images were uploaded with PostImage because you can upload files all at once instead of one at a time.)
After extruding the ellipse, I switched to the top view, centered the extruded ellipse and rotated it.
I then switched to the rear view, assumed there were 5 blades and rotate/copied the one blade four times, with an offset of 72 degrees each time. After that I started the propeller shroud by again tracing half of the foil, mirroring it, joining the two pieces and revolving the whole thing around the central axis.
Supports for the shroud were next. These again started with just a single foil in the same manner as described before. I then extruded it from one side of the shroud, through the hull, and into the other side of the shroud. When I was happy with it, I rotate/copied it 90 degrees and used the UNION command to join the whole mess together.
The base was next, and for that I went to the main drawing to clip and paste the outline of the cutout as shown on the plans, and etched into the hull. (Note, the red part isn’t in the wrong place, it is straight down from the actual location)
I took the copied shape, positioned it where it needed to be and extruded it 0.02”. The supports are once again foils. In fact, I copied one I had already done and scaled it match the drawing posts.
The one support at the back seemed pretty flimsy to me, so I figured that they had to have had supports on the sides too, so, I added some, and once again they are foil shaped. After that it was just the shaft and collar, Unionization and TADA! It was done and looking pretty good I think.
I just had to put it on the ship, which turned out to be more of an ordeal than I thought, mostly because AutCad was glitching and wasn’t doing what it is supposed to do. I was proving Einstein’s definition of insanity in that I kept trying the same thing over and over expecting different results. Finally, I just turned the &^%%^^ thing off and restated it and it started working again. Oh, computers! The love-hate relationship.
Even without the computer glitch, this was a somewhat tricky proposition. First I made 2 copies of the hull part, SPM, and outline shape off to the side. I extruded the shape through the hull of one of them in the proper location and did an “INTERSECT” command which gave me a chunk of the hull the shape of the outline. I did a couple of things with this. I started by making a copy of it and slicing off a thin section of the outer hull, which I attached to the bottom of the SPM base, so that its outer surface would match the shape of the hull. Using the second piece I copied, so as not to mess with the original, I used one of the chunks and subtracted it from the hull to remove the lower section of the outline. I used another one to remove the upper section. I had to do this because, since the one was such a close fit, AutoCad was leaving one end or the other closed. I kept going back and forth with material on one side, then the other, until it finally dawned on me that I could just subtract it twice in different locations.
I now had a cut out going through the ship, and an SPM with no visible means of support. So, I made a block by extruding a rectangle from one side of the inside of the hull to the other one. The problem is that I want to have the option on whether to display it or not, and if I can figure out a way, make it “adjustable” between deployed and not, so this complicated matters, in that I had to build a little canopy over the SPM and subtract the canopy from the model. I tried to show it in one of the images, but it is difficult to get a good angle at it.
As you can see, the way I designed it, the outer shell of the SPM seats up flush with the hull when in the stowed position. I would really like to make it so you could do either, but the only way I can think of is to put a couple of rods with catches on one side of them, but not on the other. The problem with this is that there would be little plastic screw heads on the hull surface. We’re talking eye glass sized or slightly larger though, so maybe they wouldn’t be too conspicuous.
I hope you enjoyed the update.