Doing piston pre-assembly this week. I came up with something that should work with the help of an engineer here at the hackerspace. Two 16mm grooves on 18mm shaft (1mm deep cut on a lathe with an equilateral triangle cutter), slip O-rings in both, add a bit of oil, and push inside the piston body. One cable to restrict max. extent, fixed by hex nuts on both ends:
13mm I.D. O-rings, 16mm O.D., 1.5mm wide. Got these from Ace, bulk ordering from Amazon who stock larger quantities (although with 2 week lead time).
This makes it so the shaft is not too lose and not too tight, motion is smooth, and shaft doesn't easily go off-center. In addition it reduces the noise from shaft hitting the inside of the body when running so you don't jingle like a Christmas tree. The metal cable is springy but doesn't allow going past max. extent, which actually makes the pistons feel like they are real, with hydraulic fluid inside. The same engineer suggested experimenting with drilling holes in the cap to get the holy grail whistling noise like when C-3PO moves
Had to order more alum stock and more bearings for the second exosuit:
After the two Elysium exosuits (although not directly after), going to be working on a custom exosuit concept with bigger bones (diamond tread-plate chestpiece) and similar pistons:
This is for my industrial band, where members will wear Slipknot-like leather masks with zippers (resembling various animals), and burlap eye-blinds through which a Matrix Sentinel-like sensor eye-array is poking through). All that in addition to the exoskeletons - should make a good show.
Also, since I'm taking it easy this weekend, I started pre-production on another one of my "next" projects, a Sci-Fi car conversion. It will have all-holographic instrument cluster/infotainment center, doors that open upwards, and an AI that you can ask questions that it will Google or Google-map for you and display on the holo screen. Optical combiner windshield with micro-structures to eliminate extra reflections from the projector, you get the picture.
I acquired a used Ford Taurus to tear it apart and replace the body & insides. This will be just like that Ghostbusters Ecto-conversion thread, but to a custom concept.