Update: I have made a new helmet since the original build, and and so I have uploaded the new pictures.
Step 1: Materials
Materials you will need:
PVC pipe (for my size, I used a 10' long section of 4" PVC DRAIN pipe. It needs to be drain pipe because drain pipe is much thinner than pressure pipe)
Wire that is thick enough to make the hooks and loops, and to connect all the pieces together (or zip ties).
Thin crushable foam cushion about 1/4" thick (optional).
Glue that can be used to glue the cushion on, like hot glue (optional).
Leather (optional, you can use cloth or string).
A piece of wood for the gun (optional).
Tools you will need:
Drill and bit
Heat gun, propane burner, or something to heat the PVC pipe
Something to cut the PVC pipe like a saw, heavy duty scissors, or tin snips
Step 2: Breastplate and Backplate
First you need to cut the PVC pipe lengthwise so that you can unroll it to make it flat. Then you need to heat it up so that it becomes pliable (make sure you have adequate ventilation). After that you need to put it on a flat surface and put something flat on top of it and apply pressure (so that when it cools, it cools in a big flat sheet). Then you need to measure how big you want it, and cut it out. You can use my measurements, but you should measure yourself to make sure it will fit (if in doubt, make it big and then trim it). After cutting it out, heat up the places where it needs to be curved, and hold it there while it cools. If it did not turn out how you want, heat it up and do it again. Repeat for all the curved parts, and the backplate. After that, trim all the edges so that it fits you good. Then if you are going to use a cushion, you will need to glue it in and trim it. To join the breastplate and backplate together, you will need to drill some holes at the top. Then you can use zip ties to loosely join the front and back together (alternatively you can use wire like I did). The hook and loop is very simple. You bend one wire into a hook, and another one you make into the loop. You can see by the picture how to attach the hook and loop.
Step 3: Shoulder Plates and Arm Bands
After you finish the breastplate and backplate and join them together, it is time to move on to the arm pieces. I used a bag if sand as a temporary mould for the shoulder pads, but you can use anything you want to mould it. The shoulder pads are mounted to the breast & backplate by something flexible. String will work, but I used leather scraps. It should be placed far enough from the breastplate that it will not be uncomfortable. To mould the armband, you should find something round that is the right size to mould the PVC around. The two arm band pieces are connected together by zip ties (or wire), and also use the hook and loop to get it on and off. The shoulder pad is connected directly to the armband, so that it is a one piece suit. The shoulder pad needs to connect somewhere, so it connects to the breastplate and armband.
Step 4: Vambraces
The vambraces are slightly tapered, and I made the front bend out to make it more comfortable. You should find something that is round and the right size to mould the PVC around. The bottom piece is longer to protect your elbows, and the top shorter to allow movement. It uses the same hinge style of zip ties (or wire), and also the hook and loop.
Step 5: Knee Pads
The knee pads are like the shoulder pads, so you will need to form it using a mould (like the sand bag). I used leather to make the straps, but you can use cloth or whatever you have. I measured and made the usual hook and loop, but you can use Velcro for this part.