The idea is to make it looks like I'm sitting in a chair riding atop a steam-powered mech that walks on two robotic legs. In reality my seated legs are false, and my real legs power the robot's legs. This is basically a variant on the age-old circus-clown costume where someone looks like they're riding a horse, and is also inspired by Ben Hallert's APU costume and the paintball mech costume called Steel Dawn.
While not fast enough to keep up with 6-year-old trick-or-treaters as they went from house to house, I was still able to walk down the street and show off to passers by. The most common reaction was along the lines of "Wow! That's the coolest costume I've ever seen -- what the heck are you?!? I also got little kids (and some older kids, who really should know better) asking me how the thing was powered, several adults admitting they couldn't figure out how the thing worked, and at least one little girl bursting into tears as she saw me ambling towards her. All in all, I'd say it was a big success :).
Step 1: Build the Frame
Next I built a box frame out of six lengths of Â½"-inner-diameter PVC pipe, two 'T' joints, two 90Â° elbow joints and four 3-way corner joints. Connected to the 'T' joints in back
are two short lengths of Â½" PVC, which fit inside the backpack-frame pipe. My first prototype was just as wide as the backpack frame itself, but that was a little too tight a squeeze so I widened the frame by adding a couple of 120Â° angle joints to each side. Once everything was tested I used PVC cement to secure all the joints, except for the front cross-pipe which I left free to turn. That pipe needed to remain free to turn so I could fold up the leg-holder for easy storage. I made the PVC box frame the right length for a chair such that my knee would
come to the far end (about 21" for my leg-length).
I then drilled a hole through each of the back PVC connectors to match the holes in the backpack frame, so when the backpack was connected to the PVC frame I could use the existing cotter pins to secure them to each other.
Step 2: Mech Feet
three pistons instead of two, thus the extra hole up top, which I later ignored completely.
I used fiberglass resin to strengthen the feet so they could withstand the pressures from walking. If you've never worked with it before, fiberglass resin is basically the daemon-spawn older brother of paper-mache, only instead of paste you use a resin that sticks to everything and has toxic, explosive fumes. And instead of newspaper you use a fiberglass cloth that feathers into these long thin strands that always float into whatever you don't want them to stick to. And since they're fiberglass, they give you nasty little splinters. And then once the resin
dries around them they become sharp little needles poking out of your piece that you need to sand down. It's pretty nasty stuff, but it did protect the feet well. I found the best technique was to essentially upholster my foam-core shell with the fiberglass cloth using a stapler, then paint the resin over the cloth. Use as few pieces as possible to avoid feathering.
Step 3: Pistons / Mech Upper Leg
The piston is a piece of 1"-inner-diameter PVC pipe with a piece of Â½" PVC inside. The inner pipe still leaves some wiggle room, so I wrapped duct tape around the end about eight turns to make a snug fit that would still slide in and out. To the inner pipe I added an elbow joint that was threaded at the other end, which gave me rotation where the piston connects to the frame. To that I attached a snap "saddle joint" which could snap onto the frame itself and yet still be disconnected for easy storage. On the lower end I added an elbow joint which attached to a
length of 1" PVC pipe that went through the top holes in the mech feet. Since the mech feet are tapered, the lower cross pipe for the rear two pistons will be longer than for the two that go in the front.
It might not have been necessary, but just to make sure the piston didn't jam as I was walking I threaded an elastic band down the middle of the inner pipe. At the larger elbow I threaded the elastic through a cork (which fits inside the joint but is too long to go around the turn) and then doubled it back up to the snap saddle, where I tied it off. This made the pistons naturally snap closed, which also made storage easier.
Step 4: Side Walls, Back Wall and Seat
Since I wanted these to be detachable for easy storage, I used a glue-gun to attach a wooden dowel to the back, making sure to leave the ends of the dowel glue-free so I could slip a zip tie behind each end. This way I could attach th dowel to the upper pipe on the main frame with a
zip-tie loop, and simply slide the loops off when I wanted to detach the sides.
At the top of each side wall I added a hole for my side railing (though in retrospect I should have put them further forward, as my arms were a little cramped as it was). These railings just consisted of a couple pipes connected by several right-angle joints.
The back wall is simply another pieced of poster-board, cut to fit the bottom back of the frame area. For decoration I cut the heads off of two slotted-spoon cooking utensils, leaving a little bit of handle remaining. After everything was painted I stabbed the handle stub through
the foam core and hot-glued both spoon-heads in place to look like exhaust vents.
The seat is just the lid from a cardboard banker's box cut to fit over the front half of the main box frame (the back half is where my body fit). I just zip-tied this to the frame bottom on both sides.
Step 5: (Fake) Foot Supports
snugly between dowels 1 & 2 and dowels 3 & 4. To get the correct angle I pushed the top dowels such that they stuck out the other side of the PVC pipe, and then tied down another dowel such that it lay across the exposed ends. That way I could just remove the top dowel and fold the whole foot-support rack under the main frame for easy transport.
Step 6: False Legs
I stuffed the entire package into a white nylon stocking.
For the pelvis, I just used a piece of packing foam that had roughly the right shape, bent it a bit with a strategically-placed rubber band, and inserted the dowels into it. (Men may wish to augment the foam as vanity dictates.) I stuffed the entire thing into a pair of white pants that I had split down the back seam, starting at the belt line and stopping just before the crotch. I recommend picking a pair of pants with a slightly larger waist than your own, since you'll want the belt to be able to go around both the false hip and your own hips.
Wrap a rubber band around the bottom of the pants and stuff them into boots. The boots then get rubber-banded in place with the heel hooked over the PVC pipe at the bottom of the foot supports.
Step 7: Random Gauges
Step 8: Putting It Together
I then get someone to help me put the main frame over my head, placing my arms through the backpack straps as it comes down. I then tighten my belt while my assistant pushes the saddle clips at the top of the pistons through the holes in the side panels and snaps them to the upper of the two side pipes in the PVC frame. After that my assistant puts the false legs onto the seat and rubber-bands the boots into place while I thread my own pants belt through the two sides of the false-leg pants and buckle it in front. (Be sure to stretch the fabric around your own hips as much as possible so they extend below where the side panel shields you from view.) Hook the side-rails over the top of the backpack frame and into the top hole in each side panel and you're good to go!
I found it was pretty easy to walk on level ground with this contraption, but much harder on broken sidewalk and certainly impossible to keep up with 6-year-old trick-or-treaters running from house to house. All in all it was great fun and I loved the reactions â€” but next year I plan to listen to that little voice that tells me "no really, you should have started this project earlier than October first!".