I'm going to order material in the next week or two for the plastic robot piston. I'm going to use polypropylene because UHMW may have some strength/leeching issues over 180F.
If anyone wants to help me test this I'm willing to send out a handful for material cost+shipping cost. Once I get set up it should only take me 5-10 min/piston.
The V1 will have no provision for a pressure gauge, and the piston pin will bear directly on the piston. I think the plastic will take it, but it may deform or crack with time. This is the main thing I want to test. Material will be $5/6 per piston depending on yield.

I'm interested.

Finally got the material. I should be able to get 4 pistons out of this, so if anyone else wants one to test let me know. I hope to turn them next weekend.

Finally getting some movement on this project. The fixturing for the arm clearance slot is going to be silly, but it'll work. I need to get to bed, so I'm calling it here for tonight.
On the plus side I'll get five pistons if I don't scrap one.

Nice to see this. I thought maybe you'd given up.