The DS gun from Logan's Run is one of my favorite scifi props.
In the novel the DS gun (or Deep Sleep gun) was a six shot revolver that fired different types of ammunition. Ripper, Nitro, Tangler, Vapour, Needler, Homer.
In the film the gun was some sort of energy beam weapon with just one fire mode which killed runners. It shot a green flame from the muzzle, which was a practical effect and looked really cool.
The TV series used the same props, which were refurbished, with some cosmetic changes made. They also introduced different fire modes (Stun, Kill, Blast).
There has been some great kits of this gun available which I have put together, but I thought I would have a go at making a TV and film version from scratch.
The working props used calcium carbide and water in the rear chamber, which created acetylene gas. This was shot out the front and ignited by a glow plug to create the flame.
Working with acetylene gas in a tube under high pressure was way too dangerous, so I decided to make non-functioning props.
To keep costs down I wanted to make as much of the props as possible by hand, out of aluminium plate and tubes. Some parts would be 3D printed or CNC milled.
The first thing was to make the 3D models. for this I used Autodesk 123D design. This is free to download and is relatively easy to learn to use. Separate parts can be exported as .stl files, which are accepted by on-line 3d printing and CNC milling companies.
I got some 3mm aluminium plate for the side plates and holster clip, 4mm for the trigger and 5mm for the front fin.
For the muzzle I got 32mm tube with a wall thickness of 3mm. The rear gas chamber was made from 28mm tube, with a 1.5mm wall.
The models for the muzzle front, and rear of the gas chamber were modified to fit the tubes I bought. I ordered these from Proto Labs in CNC aluminium. The parts were excellent, but not cheap. It would have been great to get the frames, main body and muzzles as well, but the CNC parts were just too expensive.
To make the cutouts in the muzzle, I started with small pilot holes. I gradually increased the size of the drill bit up to 10mm. Using various round and flat files I finished shaping the cutouts.
Two disks were cut from 5mm aluminium sheet for the end cap of the muzzle. I made them a tight fit so they had to be hammered into place. A chamfer was made on the inside edges, and JB weld epoxy was used before the second disk was put in place.
After doing all this, I realized the end plates were totally unnecessary. The main body was going to be 3d printed. So I just needed to make sure the diameter matched the inside diameter of the muzzle and extend the front of the body to fit inside.
The gas chamber did need blocking up at one end, so I did it the same way using 5mm aluminium plate epoxied on the inside. A threaded rod was epoxied into the gas chamber end cap. A washer was cut from thick black styrene sheet to represent an o-ring.
I decided to get the frames, main bodies and grips 3d printed. I got the frames from Shapeways in their white strong and flexible plastic.
The main bodies and grips were from i.materialise in their white Polyamide, which is the same material that Shapeways call strong and flexible plastic. This material has a textured surface like a fine sponge. It is relatively easy to make smooth using layers of filler primer and sanding.
It is easy to cut threads in this material, and bolts hold very well, so long as you don't over tighten them.
Out of all the 3d printed plastics, I found this the most stable in terms of warping. All the parts were fine except the two frames, which were slightly warped. From experience I suspected these would warp so I made them 0.5mm thicker than necessary. Using a heat gun, I got rid of most of the warp, and finished off by sanding.
I got a set of grips from i.materialise in prime gray resin. They are more expensive than the polyamide, but the surface is almost perfectly smooth. All they need is a light sanding and they're ready for paint. I decided to use this material for the muzzle front, and gas chamber cap for one of the guns.
For the TV version I got the muzzle 3d printed in steel, from i.materialise. I used filler primer and sanding to get the surface smooth. I didn't worry about the fine lines on the inside, but I did glue a thin disk of styrene at the end, as it was quick and easy. The aluminium fin was epoxied in place. I used some steel pins on the join for extra strength.
The side plates, trigger and holster clip were cut from aluminium plate. The holster clip was made with some brass tube and a brass hex standoff pillar.
I modeled a cutout in the main body to accept M4 rivet nuts. Unfortunately, I cut the threaded rod on the gas chambers too short, so they wouldn't engage with the nut as the thread started too far in.
I drilled the thread out and glued in an M4 threaded sleeve rod, which solved the problem.
To spring load the trigger I used a micro switch. A piece of dowel was used to stop the trigger coming out too far.
The fin on the TV gun was held in place by what look like spot welds. To mimic this I modeled a piece which I got printed by Shapways in their frosted ultra detail material.
The film gun had a toggle switch at the front. For the TV series this was replaced by a rear push switch.
When starting the prop I didn't have the correct switch. So I got a small push switch and made a collar from aluminium plate.
I later managed to get what I think is the correct Alco switch. The diameter hole to fit this needs to be 9mm. the frame thickness is only 13mm.
As the frame is plastic, I didn't want to weaken it too much. So I decided to stick with what I already had.
The polyamide material is very strong and not too difficult to get smooth, with a bit of filler primer and sanding.
Where you have fine detail, the prime gray resin from i.materialise is a great alternative. I got a replacement for the main body of the gun (film version) in this material. I think it's worth the extra cost.
Halfords filler primer was used on the Polyamide 3D printed parts. Normal Halfords grey primer was used on the prime gray resin parts.
For the aluminium parts, I firstly sanded them with a relatively course wet and dry paper (400 grit). Then they were cleaned with cellulose thinners. Acid etch primer was used as a base coat.
All the parts were sprayed with Simoniz tough satin black as a top coat.
The finished TV version of the DS gun.
The Movie version.
Here are the .stl files for the Film and TV guns.
Note: the blue parts are for the film version only, the red parts are for the TV version, and the green parts are common to both versions.
The yellow parts are made to fit the aluminium tubes I got, which both have a 25.5mm inside diameter.
The parts "ds film 1" and "ds tv 1" are slightly wider versions of the frames.
The parts "ds common 8", "ds film 11" and "ds tv 11" are different versions where the main body extends to fit inside the muzzle. If you are making the muzzle from aluminium or plastic tube, you would need these versions of the main body.
Whereas all the parts can be 3D printed, it makes no sense for some, like the the side plates, which would very likely warp. It would be better to make them from sheet material, such as Aluminium, acrylic, ABS or styrene.
I think the same goes for the fins, trigger and rear washer. The inner barrel and gas chamber would be better made from aluminium or plastic tube rather than printing.
Of course to finish the guns, you still need glow plugs, switches and screws. I used M3 and M4 screws, as well as M3 and M4 threaded rod. The cutout at the rear of the main bodies is designed to take an M4 rivet nut.
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