Making Ralph mcquarrie’s concept boba jet pack

[RussWebb]

A project I started about 3 years ago and is still on going with a few failures along the way. Don’t get me wrong this is a relatively simple construction but I’ve made it twice out of poor material choices and this last time around I’ve decided to make a mold of it so I can make casts of it. The molding part has been a partial success. I’m not going to upload all the info and pictures at once but I am going to start from close to the beginning of this third shot and post some of the updates from what I feel is each major step. Probably will update each day until I’m caught up to the current progress. It started off with some patterns I made from the first go a few years ago and it was all cut from 3mm foam expanded pvc. Not sintra brand but the same stuff. This is where I had the main body put together and started fixing the little imperfections and then I’ve added some details and started the rocket cylinder. This part was pretty straightforward and easy.

 

[RussWebb]

Next I decided that I really dig the sideshow statues take on the missile cylinder. So in the prior pictures you can see I started making it with a pvc pipe cut in half length wise but changed it to strips of foam expanded pvc doubled up on thickness and rounded them over a bit. I left them off the side that attaches to the main body of the pack because that seemed like pretty pointless effort.

 

[SofaKing01]

Well done! Looking forward to seeing this!

 

[RussWebb]

Thanks

 

[RussWebb]

With the main sections done Next was figuring out the smaller parts that go on the bottom and top of the pack. Using some sintra I made the little U- shaped box looking thing at the bottom of the cylinder. This part was later molded to make durable resin castings. I took some delrin and machined a taper on the end which was then cut in half length wise for the greeblie on the main pack. Then using stainless steel rod, split flexible wire conduit, super glue and baking soda I made up the tube that connects the cone shaped greeblie to the U-shaped box looking piece. I made multiples of these as opposed to molding and casting. Then made the top slanted box bit on top using mdf on the belt sander puttied over, sanded and painted till smooth. This part was also molded to make resin castings. The bottom pipe was pvc with plugs that I machined down to having hard edges and removed all the words and such and the ID machined out to make it fit on the outside of the pipe it wasn’t designed for. This I felt was the best and cheapest way to get something that worked without looking like just pvc pipe. This also didn’t get molded, each one I’ve made this way.

 

[RussWebb]

One of the things that kind of bugs me about the Macquarie jet pack is that there are no thrusters so its more like a missile pack since it doesn’t seem to fly. So I went through all the concept art by joe Johnson and decided it would be neat to have thruster attached to the pipe on the bottom like the concept shown here. I modeled up my own thruster as opposed to just using the same design jango and boba ended up with. It was made using a plastic ball, sintra and a short piece of pvc pipe. Then I added a couple of detail greeblies that I had made resins casts of a couple of years ago for something else.

 

[RussWebb]

Here’s where I stepped out of my comfort zone, I started a brush on mold of the thruster, missile cylinder and main body. The thruster worked out just fine, I made a jacket mold for it then cut it so each time I can easily pull out the casting. I finished the main body mold and cylinder at the same time but finished the jacket for the main body first. And things went south, I’ve only got pictures of the first coat of silicone but this approach didn’t work at least for the main body. After thinking on it for a couple of weeks I think I did 2 things wrong for sure. First I think not making a wide flange with keys flat on my work surface was the downfall to not being able to insert the mold into the jacket without the edges at the back of it falling inward. This caused me to be unable to even rotate a casting without trying to tape the edges (which didn’t work well) to the jacket. Second, taking it off the model and then later off the first casting the corners tore and then tore worse. I attribute this to not having a firm grasp on the shore hardness of rebound 40. I also had planned to do 2 coats of 40 followed by 2 coats of rebound 25. But I had only ordered 2 trial sizes of 25 thinking a gallon would be way too much. I don’t know if that would have gave it enough flexibility that the inside coats of 40 wouldn’t have torn. So I either need to try a completely different approach or buy a gallon of rebound 25 and try with the flange. But not wanting to waste another $200 of silicone and the $100 of plastipaste I’m at a pause on this project. I still have the second half of the cylinder to make the jacket for to see if it worked but my expectations are low. And I still have a positive update in regards to the small molds but I’m going to take better pictures.

 

[RussWebb]

Today I got a test pull from the missile cylinder mold and while it’s an imperfect pull the mold is a success because I’ll just have to pay more attention to my mold seam before pouring the resin. Next is redoing the main body.