Retracts are designed so that when in the absolutely open and closed position, there is a mechanical advantage so that air pressure alone isn’t holding the retracts… The mechanical advantage is similar to the locking mechanism on a car door. You can easily turn the key and disengage the lock, but if someone puts even a little pressure on the door lock, you can’t turn the key. When retracts are in the locked position, the air pressure simply holds the lock closed.

The first thing to do when you get your Robart Retract system is to adjust the Needle valves. These valves allow you to adjust the speed at which the retracts open and close by regulating how fast the pressure is released. One needle adjusts the speed of opening, the other of closing. To adjust, loosen the lock nut generously and turn in the needle till it is snug. Do NOT tighten it down… just turn it in til you know you are bottomed out. Then back out the needle 2 full turns. This will be a good starting point. From here turning the needles in will slow the speed, turning out will speed them up. Adjust them in 1/8 -1/4 turn increment. You can even remove them completely for the fastest speed.

A Robart pneumatic retract system also comes with a fill valve and fill chuck… the fill valve is very similar to a tire valve and you can even use pumps made for filling tires. To prevent over-pressurizing the system, Robart offers an optional pressure gauge that indicates when the system is fully pressurized.

The system comes with easy to follow diagrams to assist in 2 and 3 gear installation. We’ll cover the 3 gear since that is what we’re using on our Top Flight Giant Scale P-51 ARF.

First we’ll start with the tank and attach some red pressure line. We have the pressure gauge, so we need to tee off the first line with a red tee. Then we’ll add another tee with the end going to the fill valve. The other end goes to the valve’s Air In Port.

Now we’ll run red pressure from one of the OUT ports and first Tee it off to the back end of the tail wheel retract, then coming off from there, we’ll tee off again and go to the back end of each of the main gear retracts. Basically what we’ve done is get air into the valve and attach one side of the retracts to the out port.

We’re already halfway thru. Now lets get the purple line and setup of the other side of our pneumatic system. It’s setup the exact same way… The purple line comes out of the second valve port and is tee’d off with one side going to the FRONT of the tailwheel retract. The other side of the tee is tee’d once more with pressure line going to the FRONT of both retracts. We now have pressure going to the opposite side of the cylinders in the retracts.

That’s pretty much it! See how simple? Our last step is to setup our servo throw for approximately ¼” to slide the spool fully one way, then the other.

Pressurize the system according to the size air tank being used, and watch your retracts in action. Sure is satisfying to see them operate so smoothly and precisely.