STUNT SAFE REPLICA

Proton Pack

My final degree project was a self-supported, self-financed build of a prop of our choosing. In my case, I opted to make a replica of the stunt-safe Proton Packs from the movie Ghostbusters. I would use the original moulding and casting process from the 1984 movie, but I would use modern materials to make the pack itself.

The first two weeks of the project were dedicated to making the various shapes that comprise the Proton Pack. Using paper templates, I reconstruced the basic shape of the pack, and used extruded styrene, polystyrene and plastozote as the main body of pack, and various bits of PVC pipe for other parts. The pack itself would require two separate box moulds for some of the components, whlst the neurtino wand required six box moulds

The whole pack was stuck to a 6mm piece of birch plywood. After each component as complete, it was lightly glued to the backboard. After which, a layer of Rosco Foamcoast was applied to the surface of the polstyrene. This was so the surfaces would be smooth and blemish-free, and also to seal any panel gaps.

After the Foam Coat was cured and sanded, the first layer of silicone was applied. This was a drip layer of PS28 condenation-cure silicon from PS Composites. I chose this silicone for its flexibility and versitility. Once the first layer was applied, all the fine detail would be captured. The next step was to add thixotropic additive to the silicone layers, and build up with wall of the mould all the way around, ideally looking for a 5mm layer. In the more troublesome areas, I used ilicone-soaked sponge to bridge the gaps of the mould, which would make it easier to create a fibreglass jacket.

Once the silicone had cured, I made a two-part fibreglass jacket by running a clay wall down the vetical middle of the proton pack. I built up two layers of fibreglass on one side and let it cure. Once cured, the clay wall was removed, and mould release agent was applied to the vertical wall of fibreglass. The second half of the jacket was then constructed. Once both walls were cured, I drilled holes through the walls to apply guide bolts. The silicone mould itself had a few keys added beforehand. 

The next day, I was able to remove the master sculpt from the silicone mould. I then spent a day tidying and cleaning the mould before I applied the Black Gunn Foam, which would be the main casting material

I chose to use Black Gunn Foam as my casting agent for a few reasons. Firstly, it had a 3:1 expansion ratio, which is a better expansion than other two-part flex rubbers. Secondly, the foam is self-skinning, so all the surface detail would be catred in a tough skin, one that is easly paintable and cutable with a sharp blade. This meant I didn’t have to worry about a latex-foam hybrid or potential zombification due to air pockets. Black Gunn foam is also very hard wearing compared to other soft foams. The only issue I had with the foam is how tempremental t is – it needs to be mixed very quickly and preciesely, and pounred into a mould within 10 seconds of being mixed. It is also expensive, which is why the proton pack has a core of polystyrene encased within the black gun foam. Not only would it keep the weight down, but also the cost.

Black Gunn Foam, like many expanding foams, doesn’t like to expand into crevices. Therefore, when it came to the box moulds, I would brush on a layer of mixed resin to the insides, then fill the mould once the surface layer had cured. 

Once the Black Gunn Foam had cured, I mounted the whole sculpt to an ALICE frame, just like the orginal packs from the movie. The stunt ack I made was comparable to the weight of the original stunt packs, which themselves were 50lbs lighter than the hero packs which weighed a lot more due to battery packs. I wanted to make a stunt safe pack rather than a replica, because I wanted to show that I could think in industry terms. I made a lightweight, inexpensive, disposable version of the hero prop. The purpose of the stunt pcks wasn’t that they would survive filming, it was that they would stand in where the expensive hero packs could not.

The pack itself is finished with various tubes and wiring from electrical and plumbing shops. The orinal components used on the proton packs are sadly no longer made. The wholepack was painted gloss black and later weathered with meatlic bronzes and silver. The warning labels were printed and glued to the foam. 

Overall, the build was four weeks, at a rough cost of £250.

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