Air cylinders and flow control valve for simulated hydraulic feel, anyone tried this?

[Shawn]

I finally got around to buying a second flow control valve and it did make a slight improvement but it's still not what I was hoping for. The pnuematic cylinder provides far to much pushbac initially but the force dies of quite quickly as the pressure equalizes. I have had some decent success with a diy hydraulic cylinder, I just need to find the time to go by the irrigation place for parts.

How many people have lied to a store employee when asked "what do you need that for" just to avoid the 20 minute explanation of what your building in your basement and why?

[Shawn]

I got to the irrigation store today and had another go at building a hydraulic cylinder for control loading. I need some advice, the cylinder seems to work but I'm getting air pockets inside as the control tube is moved and the water (cleaner for testing purposes) is forced out the top hole. I'm pretty sure the seal and the tube are to tight as I get more pressure moving this even without water than I expected. In a normal hydraulic cylinder how much air pressure would be created without the oil? Should I have a small bypass hole in the seal? Any and all suggestions would be appreciated. I plan to try and seal the top with a short piece of brass tubing glued into the hole in the cap, the clearance between it and the control tube are extremely close.