Body Armor Materials:
Moto Cross chest protector
Castin Craft resin/catalyst/green dye/mold release
Body Armor Tools:
Step 1: In the Beginning...
You'll notice that Ratchet's armor has several embellishments including straps, illuminated lines, and one big glowing omni wrench symbol slightly off center on his chest. My goal is to recreate the omni wrench symbol without making it look like some sort of half-assed Ironman knockoff.
I began modifying the body armor I purchased by removing all of the decals and pulling a bit of foam from the inside of the front chest area. Next I decided what size I wanted the symbol to be and scribed a circle on the armor to be cut out. Then I used my Dremel to cut out the circle.
I have this weird thing where I like symmetry...and right angles. Right angles give me happy feelings. I could not bring myself to offset this symbol even though this was going to be a glowing circle in the middle of my son's chest that inevitably some little brat was going to confuse for an Arc reactor.
Step 2: Yay, Resin!
After the resin had solidified, I drilled a 3/16" hole in the center of the back to put an led that would illuminate the symbol. A quick and easy LED assembly that I've used before in another costume came from a bicycle safety light. https://www.instructables.com/id/SIMS-plumbob/. You can remove the rubberized covering from this light and you are left with just the led mounted on a circuit board and simple battery holder.
I inserted the led and took it for a spin. What I found was that too much of the light was being lost through the back of the resin. I solved this by adding reflective foil tape to the back of the resin.
Step 3: Some Other Stuff That I Did...
My omni wrench painting skills aren't as refined as my bowstaff skills, but I think it came out decent.
Next I cut a sort of retaining ring out of some sheet plastic and glued it to some of the foam I pulled off of the chest plate earlier. The retaining ring will help hold the symbol in place since I didn't have the foresight to cast some sort of ridge on the symbol edge to do this.