After the ALICE Backpack Frame approach didn’t work out so well as a torso harness for the exoskeleton, I decided to go in  a different direction and make a Kydex (very similar to ABS) mold of my back.

I then affixed the motor mount to this new custom molded back brace using aluminum stock and offsets created with Instamorph (super moldable thermoplastic you can get on Amazon).

First order of business was to make a plaster cast of my back that I could use to make the harness in Kydex. So I got some plaster cloth (or gauze). I got this one from Amazon because it’s nice and wide for the back. I would have gotten two rolls if I were to do it over as the first one went fast and left the back cast a little thin.

Plaster Cloth for Back Cast

For making the cast, I laid on my stomach and my wife Christina applied the plaster cloth strips. A partner would definitely be recommended for this step! Also lots of vaseline and plastic wrap between the plaster and skin for easy removal.

Back casting with plaster cloth

Casting my back with the plaster gauze

Here’s the cast after the plaster had ample time to dry:

Dried plaster cloth back cast


Plaster back cast

The underside view of the plaster back cast

Side view of back cast

Side view of back cast

Next up was molding the kydex using the back cast.

To do so, I used a  12″ by 24″ sheet of kydex that was .93 inches thick (also available at Amazon).

To get the Kydex to a moldable temp, I put it in the oven at 325 degrees for about 15 minutes on a cookie sheet. The time is somewhat arbitrary and what you’re looking for is for the Kydex to easily fold over onto itself when lifting an edge.

Kydex sheet in oven

Kydex sheet in oven and beginning to get warm...


Kydex sheet in oven getting hot

After some time in the oven, you'll see that the sheet is starting to collapse over the cookie sheet


Kydex heated ready to go

Kydex is folding over on itself without going back to lying flat. Ready to mold!

Kydex sheet over back cast

I took the hot malleable Kydex sheet and draped it over the plaster back cast. I also applied some pressure to smooth it out on the cast.

Kydex sheet on back cast

Another shot of the sheet cooling on the back cast

After the Kydex cooled and hardened on the cast, I moved on to setting up the adapter that the hip motor actuator could be bolted using aluminum stock.

Heating instamorph / shapelock in pan on stove


Forming instamorph adapter

Shaping instamorph on Kydex mold. This was a lot of eyeballing and also I used a piece of alumimum stock to flat out the instamorph

Instamorph cooling on Kydex

Clamps on Instamorph and Kydex

Next I made plastic hardware for the front of the harness also out of Kydex that would hold the velcro straps for securing the harness to the body.

Heating kydex with heat gun

Scored piece of Kydex for buckle

Plastic buckles

Once heated up, I exacto'd out the channels and here are four of the velcro strap buckles. Not pretty but they'll do the job.

Velcro strap and buckle

Kydex plastic back brace harness

The finished product! With the buckles bolted to the main harness

© 2011 OpenExo Suffusion theme by Sayontan Sinha