I am about to use my first air operated retract system ( 1/5 P-51 with Robarts ) and have a question or two.

1) - Is it a good idea to spray a bit of oil or WD40 in the system from time to time.

2) - Is it OK to grease with Vaseline or something the plastic blocks where the locking mech travels, they seem to stick a bit and make the operation somewhat jerky.

3) - What is the max. air pressure to use, trying them in the shop I pump up to about 120 psi - too much ?????

I think that a light machine oil applied inside one of the air lines, only about two or three drops, before you connect the air lines for the first time should last you for a very long time. When the system is pressurised, the light oil will be distributed throughout the retract system

I have never found a need to externally lubricate the retract mechanism itself. The downside of doing so is that the lube, whatever you use, will attract dirt and grit of all kinds. This will make it necessary to get in there and clean and relube the external mechanism from time-to-time.

120 pounds of pressure is not too much but is probably waaaaay more than you will need for normal operation. 100 pounds will be quite sufficient. Having said that, I have a Jet Model Products T-33 which has JMP retracts designed for the kit. These retracts do not mechanically lock in the up position so it is necessary to use 120-130 pounds of pressure to keep the gear from "sagging" out of the wheel well during a turn. As long as your gear has a mechanical lock-up action, then you do not need this much pressure.

Yes, by all means, do not lubricate externally. I have a set of 10 year old spring airs and every two years I just put a drop or two of marvel mystery oil in the fill valve and air them up after the flying season. This keeps the plunger from sticking over time. No problems after hundreds of flights and crashes. Lucky retracts I guess![sm=lol.gif] Paul

Petroleum based lubricants including vaseline and automotive greases will attack the plastic blocks (nylon) and make them soft, causing the retract mechanism to stick worse than it did. Engine vibrations tend to make the slide pin slowly groove down into the locking slide area, creating a small valley that the pin then has to pop out of for the gear to come down. My fix is to sand the area flat every now and then. Over time, it will make the gear a little loose in the up position, but it helps me avoid gear up belly landings and the resulting repair jobs. Don't know why your new retracts are sticking. Maybe there are small burrs or imperfections that need to be smoothed out.