Sealing Hydraulic Cylinders?

[rockNmayhem]

Ok guys I'm calling in the expert and people with all the experience here.

As many have seen and know I've been working on building cylinders for my CAT conversion and I have the size and dimensions down but I'm running into operating problems.

My pump I'm running has no problem throwing out 165PSI all day long at full speed. I can turn it down simply by stick control through my esc. The problem I'm having is not getting my cylinders to seal around the shaft.

I started out with o-rings at the shaft and over sizing the shaft so it was a tight squeeze to get through it and it seemed to work for a bit but I still have some seeping around them. I then found some U-cup seals with the sizes I needed and I finally got one of them assembled and started testing it but I'm getting leaks out the front once again.

So now I'm dreading my options. I can keep experimenting till I get it right and hope they'll hold up or end up buying several cylinders from Rick and shelling out around $300 for the cylinders.

I'm really hoping with your guys help and from those of you who have cylinders already and know how they are assembled and able to seal up well can chime in.

I'm not sure if my tolerances are just too loose causing my leaks or what but I'm leaving less that thousandths at critical points so I'm not sure where to go.

Any help I can get would be greatly appreciated. Pictures do help as well.

Thanks guys,
Tyler