Making an “Aliens” Motion Tracker – Part 2

This has been much delayed, I’m sorry about that. Here is the second part of the 3D Printed Motion tracker build, here’s part 1 if you haven’t read that already.

11. The rod thing that slots into the side.

I’ve no idea what this bit is supposed to be, I like to think it’s a heat sink cooling rod maybe. It prints in two halves, glue them together and sand down to a smooth rod. You’ll need to attach a fat cable to one and and insert a thin cable into the other end, you’ll see I’ve put a slight recess in one end to help with this. I often drill a hole in each end and glue in a small bit of steel wire to help seating the cable later. Then you need to sand the inside of the holes on the body so you can slide in the rod thing, remember you’ll be painting both of these items, so make sure you’ve got enough room for those additional layers of paint.

12. Assembling the Viewer

You’ll see this bit has four parts. Ignore the front part (the screen frame) for now, that’s one of the last bits to go together. For now, you need to glue the back on, the lines align along the edges. Then the little wedge on the side, this is to make the viewer plug align flush with the side of the tracker when it’s assembled. Glue it on, make sure the hole is clear, sand it down if necessary. Then, use one of the pegs supplied, and glue it very firmly into the hole, pointing outwards. This is the only thing that holds the viewer onto the Tracker body, so make sure it’s really, really well glued. The first one I made, I didn’t glue it very well and when pushing the Viewer into the Tracker body the peg pushed back into the Viewer body, annoying. There’s a flat section to glue onto the top and bottom of the Viewer module too, the bottom part has little circles for LED lights on the real thing, the top bit has a slider-switch.

13. Attaching the Light Meter and stuff

This bit is nice and easy. Glue/screw this thing on, there’s mounting holes so it’s just aligning those and doing it. The “real” prop has visible screws here, so even if you’re gluing it, you also want to add screws, if only for the look. Glue the little thing on top of the handle here too, this is the bit that you’ll later be attaching the “meter” graphics to. Screw the  big endcap/washer thing in place.

15. Painting

This is pretty simple, I painted it using a green/brown I had mixed up to the RAL number commonly associated with the Aliens paint colours. There’s a whole thing about the colour, so I suggest googling it and deciding what you prefer. Essentially, the props (Tracker, Pulse Rifle, a few other things) are painted BROWN, but because of the type of film and the lighting used, they appear green on screen. So, while a particular shade of brown is correct, it looks wrong because you’re used to seeing the screen version. It’s totally your call. I prefer the green.

Have a look at a reference to see which bits are black and which green/brown. I also paint white under the bits where I put the decals because I print mine on transparent plastic – if you’re using vinyl or paper printed ones, this step isn’t necessary.

16. The things on the side and the knob underneath.

There’s a box thing and a ridged buttony thing. The box thing just glues right on. The buttony thing is a three-part shape. Glue/screw one side on, then glue the top on, then glue the button on. The knob on the underside just screws right on.

17. The sockets for the cables.

I made these to sit in place by friction, but feel free to glue them in too. I hammer them in using webbing to protect them.

18. Add the decals/stickers/print-outs

Just glue/stick these in place. For the viewscreen there’s a flat plate with notches taken out of it that you can use to sit the graphic for the screen on. Then I put a bit of transparent plastic over that, cutting the same notches in it, then sit that into the open end of the viewscreen and glue on the screen frame over the top of it.

19. Cut the cabling to size.

Here, you need to cut cable to the right lengths, use pictures for reference here (there is a few different ones, even in the film the lengths of these differ a little bit), so again, whatever you find most pleasing. I strip the core out of some of the cables, and leave it in others. If you strip the core it’s lighter and can be easier to manipulate, but it’s also more prone to folding rather than bending. Your call, and it totally depends on the cable you’re using. Glue and use heat-shrink on these to hide the joins, I don’t glue them into the sockets in the Tracker body, I just stuff them through, leaves a little more room for movement.

20. Bottom Cap and Trigger.

The bottom cap just screws into place, again, the screws here are visible on the final thing, you can optionally paint them. The trigger just slots into the handle, however I like to round the edges a bit, it makes it easier to fit into the awkward place. You can of course put this in when you assemble the handle and just paint it black afterwards, both work fine, it’s just personal choice.

21. Headphone jack.

Basically the same as the other cable bits, just smaller and more annoying. glue is essential here. You can also use a real headphone jack if you have one the right shape. Heatshrink tubing to clean up the join.

22. Penultimate bit, plugging in the viewscreen.

This is a simple case of plugging the screen into the socket in the side. However, this is designed to be really tight and once it’s in it shouldn’t come out easily. So, go slow and wiggle a lot, sand down a little bit if necessary, it’ll slide home fairly well once it’s the right fit.

23. Sling Loops

For this I use Bisley wood stock loops, you can get them in a pack like this, I buy them from ebay. These are pretty close to the type used on the actual prop. There’s small pilot holes on the handle where these need to go, I made them small to give people the widest choice of fittings. You may be comfortable with drilling them larger, but always remember that the 3D print is basically hollow, and laterally fragile (as in, fragile along the print lines, tends to pop apart), so if you do drill, I suggest using a filler or something to bulk out the holes and give the screws something to thread into. I personally melt them on. Heat up the screw thread of the loop with a blowtorch or similar – it doesn’t need to be too hot, the plastic will melt at around 200 degrees C (ish), so it’s a quick process. Heat them up, slowly screw them in, the plastic will melt around them and form the interior threads at the same time, easy and strong. Unscrew when cold and add glue for extra strength.


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