The really awesome thing about this build is at the con you feel like you're in the game. Most prop guns don't show in your field of vision but this thing sitting on your shoulder looks exactly like what you see in game which makes being a solider even more awesome.
4.5" diameter PVC pipe
2" thick insulating foam
0.5" thick insulating foam
24x36" sheet metal
1/8" craft foam
small piece of 1/2" wood (for the handles)
1/8" wood or other solid material
lots of hot glue
Step 1: Preparing the Foam
The tip of the rocket launcher is the easiest to start with. The pics are for the wooden bit, but the steps are the same for the two parts. Cut three 6"x14" pieces of 2" foam and glue them together. A simple hacksaw works well on foam, plus you can put it at an angle and make some long cuts. Go easy on the glue, the more you add the harder it will be to cut the and the less round your final piece will be. I usually go with one light coat on both sides; let the glue dry for a minute then press the two halves together with some bricks or something heavy. If you're worried about the foam flying apart on the lathe, don't. It doesn't hurt that bad when the pieces hit you. :)
When turning foam, always cut the pieces as wide as your foam is stacked. This way you can make a piece as close to round as possible before putting it on the lathe. It's going to be rough to turn this down to a circle and the closer to round it is starting off the less likely it's going to fly apart or break.
Cut the corners off the glued together block so you end up with an octagon.
Step 2: Get Ready to Cut
Now, this will make a terrible mess. This stuff is like saw dust but lighter so it floats further and will stick to anything with the slightest static charge so a lot of it doesn't even make it to the floor. You will be covered in it and everywhere you walk you will spread a fine pink dust. So go to the bathroom and get everything you need to finish the piece and to clean up your mess before you start.
Also, be sure to wear a mask when doing this, I can't imagine this dust being good for you.
large calipers or something else to measure a large round thing
flat head screw driver
Step 3: Turning Foam
Keep in mind that you can never make this perfectly round; there is too much of a difference between the glued joints and the foam. If you have a CNC machine that might work, but if you're turning by hand just go slow and don't push things too fast. If you do you'll end up bouncing off the glue edges, over correcting and cutting deeper into one part of the foam. The glued edges also catch tools easily so you can't use a chisel properly. Instead always go perpendicular to the piece or at a downward angle. This isn't really the proper way to use a lathe, but the foam is soft enough that it works anyways.
When starting off, look at the edge of the piece and look for ghosting (an area on the edge that looks transparent). This will help you identify parts that aren't round yet and get from an octagon to a circle. Just remember that you won't eliminate all ghosting (about 1/16" of an inch is normal) due to the glue seams.
To mark lines hold a measuring tape up to the piece and use a screwdriver to put a slight groove in the piece. A marker should work also.
When doing straight edges I like the wire brush since you can turn it sideways
Step 4: Cut the Pieces!
When you're done, get some finer sand paper and do a final sanding by hand. You can't get a very good finish on the lathe since the glue joints will make the sandpaper bounce, so just take the extra time and do some sanding by hand. The wood piece doesn't need to be very good, if you leave it roughish it makes a good wood texture.
For the tip of the rocket launcher I didn't have a good way to accurately cut foam so I did a rough job with a drill bit then put a PVC pipe in the end. With a little wood glue to fill the big gaps and some layers of Mod Podge on top it blended in nicely.
Once you're done sanding put some layers of Mod Podge on the pieces. We did 3 or 4 coats on each.
Step 5: Build the Cone
I used an online sheet metal cone generator at http://www.sheetmetalguy.com/cones.htm to create a pattern for the cone. The pattern generator will make a .dxf file, which can be opened by almost any 2D CAD program. You can skip this step by using the attached pictures; the guide lines are 5" apart. We used the image with a projector, shone it on the sheet metal and traced the lines with a perminant marker. You can also try printing the image, pasting the sheets together, and then tracing the cutout. Once you have the pattern marked, cut it out with some tin snips.
Use three rivets to complete the cone.
Cut the foam pieces for the end of the rocket launcher. These are just circles, 15" outer diameter and 10" inner diameter. The small, beveled one is 12" and 9.5" diameter. I used a needle and thread to mark the circles. (stick needle in the middle, tie a string to it, grip a pen with the other end of the string and spin in a circle.)
Next I attached the wood part to the cone, then the cone to the bottom rings, with lots of hot glue.
Step 6: Cut the Handles
You can cut these with a laser cutter, or print the pics on paper, glue them onto wood and cut it with a bandsaw. Use the same methods to cut foam pieces to go around the handles.
The attached .svg file has vector drawings of the handles which can be used by a laser cutter. You can also open it in inkscape and print out copies on paper to trace. I also have included pics with a 1" grid if you'd rather use those.
The second pic shows the end of a completed handle. This was pulled off after the rocket launcher was finished, I would attach the handles to the PVC first, then attach the foam after using hot glue.
Step 7: Attach Handles
The front handle can be installed with a long screwdriver, just be patient and go slow so you don't strip it out right away. I angled my hole so I could do most of the work straight on.
For the back screw you'll have to drill a hole on the outside to let a screw driver through. This will be covered by the heat shield so it won't be that noticeable, just make sure to put the hole on the same side as the shield.
To mark the holes for the screws I found that making a straight line on a pipe by using a flat surface and a ruler worked well. Mark the lines, then place the handles at 3/4" and at 10".
Step 8: Make the Shield
Drill small holes in each corner at 1" away from the long edge and 1.5" away from the short edge. (see pics for a drawing)
Find a smallish pipe and use it to bend the metal. A good way to do this evenly is to tape one side of the metal to the pipe then roll it on a flat surface. Don't worry about getting it perfect, as long as the bend is close the screws will take care of the rest. In my tests, I found it's better to overdo the bend, otherwise it will try to bow up and not stay straight. I used a 2" pipe to roll my metal and it sprung back to an almost perfect bend.
Drill holes for the standoffs; one set is straight above the handles, and the other at 90 degrees. Just look at the end of the pipe and mark the end as well as you can, then use the ruler on a flat surface to mark a line all the way down. Put cross marks on 2" and 14" and drill small holes there. To hold the shield, I used some 1 1/8" standoffs I found in our boneyard. If you can't find standoffs I'd use nylon spacers and some drywall screws or bolts. No matter what you use, I'd try to design it so you can just screw straight into the pipe without having to do anything on the backside.
Step 9: Paint and Assemble
I kept all the pieces seprate for ease of painting. Paint everything in a flat black spray paint. It's ok if you get black paint on the parts that are going to be brown, it will help mask the pink color.
**Don't spray paint any foam that isn't covered in Mod Podge as it will melt the foam!! **
Continue to add as many coats of paint as needed to get full coverage. Let dry.
Next mask off anything that isn't going to be painted brown. I used painters tape, and trash bags. Then spray paint brown, and continue to add as many coats for full coverage, like before.
While waiting for the paint to dry, Mod Poge two 1" strips and one 1.5" strip of black craft foam (make sure that they are long enough to go around the widest part of the wood piece, and right above the cone). Once you have at least two layers of Mod Podge, paint with the same flat black spray paint. After they dry, hot glue them to the rocket launcher with some extra, trim to fit, then glue down.
Step 10: Cut the Sight
Once all the pieces are cut, hot glue the sight base together. For the stand up part, make some foam blocks to fill in the middle then sand them down to match the contour of the wood bits.
Bolt them together, paint and then hot glue to the tip of the launcher on the left hand side.
Step 11: Make Your Own Medals of Honor, Learn to Rocket Jump
Run around making your best PSHEWW PSHEWW sounds and try to rocket jump often (practice makes perfect). At the end of the day make yourself some awards out of cardboard for your bravery and wear them proudly.