matadco

My Feedback: (1)

I installed an old set of Rhom retracts in my Chaos but they would not hold air. I checked all fittings that I could and could not find leaks. I would pump them up and immediately the air would bleed off. The tank was old and small so I purchased a small Robart and installed it only to find the same bleed off of air. I then replaced all piping and connections with no change ordifference in speed of bleed off. Fill it up to 100# and immediately bleeds off to -0-. I then purchased a new set of Robart gears and installed them, pumped up the air and the same speed of bleed off. I replaced the fill valve, pumped up the air and again same bleed off. I replaced the control valve, pumped them up and the same bleed off. I am at a complete loss to understand what in the world is going on. There is no difference in the speed of bleed off of air. It is as iff air is not going into the tank but is staying in the system because it pumps up by hand very fast then bleed right off at a slow rate. This is a whole brand new system of Robarts, tank, lines, valves etc and no change fromt he orgional old Rhoms. Any idea the problem and how to solve it. I know ther is a pin hole leak somewhere but I can not find it since Ihave replaced all air hoses, fittings, valves, etc and same speed of bleed off of air. HELP!!!!

jetmech05

Make sure you didn't miss a t fitting or something......other than that seems like you have a date with a sink full of water

DavidAgar

My Feedback: (108)

With that kind of an air leak, you should be able to hear and or see the leak. You can always get a spray bottle with some soap and water and spray your fitting's. You should see bubbles somewhere. Good Luck, Dave

R8893

My Feedback: (20)

Check to see if the air is blowing right through the cylinders. A bad O-ring inside will do this. One way to check cylinder is to hook up lines to one side, pressurize it, and submerge cylinder in water. If air comes out the other nipple the piston seal is bad. I had this issue with a set of Century Jet retracts this Spring.

You  can cut your looking in half if you can establish that it only leaks in the up or down position.

Chuck

pkoury

My Feedback: (7)

You need to take the system out of the airplane, connect everyting up and submerge the system in water. Pump the system up and see wherethe air bubbles are coming from.I had a similar problem with a brand new Robart setup and found that the fill valve was leakingbadly. No matter what Idid I could not get the valve to seal after removing the air pump fitting, I ended up replacing the brand new valve and my air leaks stopped.

matadco

My Feedback: (1)

Found a leak between the fill valve and tank, which of course was at the very bottom below the rudder and elevator servos. After removing everything, replaced the tee and seemed to slow the leak considerably. However after pumping up to 100psi and operating about 2-3 times, they stop working.. I guess next is to take the entire system out and presurize it under water to see what happens. I found a place to purchase o-rings locally so may replace this new set of $135.00 Robarts with the old Rhoms. I have two other planes with retracts but they are manuel and give absoulty no problem. This is my first experience and probably my last with airs.

dubs1946

Someone had to say the dreaded word,if it was not for retracts i would have a life.!
Over the years i have had many a fight with air retracts, i have yet to see a set that you can put in and forget.
My latest non-working retract problem i resolved quite quickly in about 4 hours.
I have a very old set that i keep resurrecting and swear blind i will bin them if they ever go wrong again, well they did and i did not .
On looking at the system there was air leaking through the Robart air valve and the air tank was emptying and one leg was not working, now i have been here before and know that the air retract systems purge the redundant air from the air cylinders when the legs go up or down through the Robart air valve and that means if it leaks continually when up or down that the O ring on the piston in the cylinder is leaking.
The piston should be sealed no air should get passed the piston O ring it is there to push the redundant air out when there is pressure from either side thus raising or lowering the leg.
So i pulled the cylinder and piston apart. I have 2 boxes of O rings all various sizes and there was about 5 in each box that looked like the correct fit well i tried them all and they all leaked to some degree or other.
You test them by putting the new O ring on the piston a very small amount of Lithium grease, when i say a small amount i mean a small amount otherwise you will spend hours like me in the past trying to find the blocked air passage that to much grease has caused.
Put the cylinder back on and pump the system up i use 120 pounds down and put the Robart air valve in water there should be a purge of air only when the retract go up or down when it is in a up or down position no air should be coming out of the valve.
Well mine did after trying ten different new O rings i dont know what size the O should be but the difference between a seal and none seal must be very small in the hundreds of a millimeter,I took the O ring of the piston and in the groove that the O ring sits in i cut a thin strip of white plumbers Teflon tape used for sealing water pipes. I cut a strip about 3/16" thick and about 6 inches long and wound it around the inside of the groove that the O ring sits on/in, i then put back the O back in the groove on top of the Teflon tape.
The tape has the effect of pushing out the O ring out thus making for a tighter fit inside the piston tube.
Its a bit of a fiddle to get the piston back inside the piston case and past the screw thread, as the o ring is now very tight against the case,but immediately it was in i new it would work as it was a very good fit.
Yes it did work no leaks

matadco

My Feedback: (1)

Thanks for the advise. It is my opinion all birds look better in the air with their legs up, however I agree retracts are more pain then perhaps they are worth. Yesterday, one of our jet flyers made a some what rough landing with his jet and the nose gear collapsed. Tore out the front former in the figerglass fuse. Going to be rough to repair. These are really top of the line, expensive systerms. What happened is somewhere along the way a small screw fell out which caused the collapse of the nose gear. I like you have tried air up/down, air up/spring down, manuel but none are really worth the trouble. I am about to start a new war bird with rotating Robarts. Hopefully some of the learning so far will be cause to make the installation and maintenance better. My try the plumber tape idea to help the 0-rings.

Deadstik

My Feedback: (8)

In the "old" days of pattern when Rhom Airs ruled the main reason for a leak in the system was guys using an xacto knife to cut the air lines from the brass fittings. Even though it didn't look like it, each one of these "cuts" would result in a groove being cut in the fitting and a resulting leak down. Fix was simple.. DON'T CUT THE LINES OFF.... so if you have old Rhom Airs, look at the fittings first. Soap bubbles are a great way to find leaks. Pattern ships without retracts just aren't pattern ships. Yep, I know everything now looks like a pregnant guppy with everthing hanging in the wind.... but then again... pattern doesn't even have a fifth as much participation as it used to.... the way the planes look is probably part of it.

BTW... I also use MK mechanicals as well as Dave Browns which work great with very little maintenance.... but the retracts I treasure are my set(s) of Kraft electrics.... so cool... and I've never had one fail on me.....

take the time and learn to master retracts... it's worth it

Dan
Carolina Custom Aircraft

dhal22

Spring Airs seem to work very well.

dubs1946

Hi, i find that if you pull the tube off the nipple without cutting it soon you will find a nipple pulling out with the tube. The nipples are only a press fit, i clip the tube off leaving enough to get hold off with pliers then carefully cut down the tube thats on the nipple trying not to score the nipple and at the same time pulling with the pliers it will come off no problem.

Steve Collins

My Feedback: (8)

Another trick for getting the air line off easily with no lengthwise scratches is to use wire cutters. Use the wire cutters PARALLEL to the nipple and "nip" off as much of the line as you can on one side. Then pull the line away from the nipple sideways in the direction opposite of where you cut away some of the material.

Cutting the air line in this way makes a weak spot in the line that makes it very easy to remove the air line.

Using old retracts or retracts that haven't been used in a long time is a sure recipe for problems. The "O" rings in the system need periodic lubrication to remain supple and maintain the seal they are supposed to provide. I recommend using this product (or similar)to minimize the chances for cylinder "blow-by":

http://bvmjets.com/Pages/thin_o_lube.htm

A properly setup and maintained air retract system should hold air for a couple of days. I know of some pilots who even make it a practice to safety wire the airline to the nipple to further reduce the chance for air leaks.

All air line tubing is not created equal! If the airline you are thinking of using is several years old, do yourself a favor and throw it away and only use fresh air tubing. Robart tubing is usually what you will find in your LHS and is OK but there is airline available that is much tougher and stiffer that makes a leak from a poor tubing seal a lot less likely. You can get this tubing at a number of different places but here are a couple:

http://www.dreamworksrc.com/catalog/...roducts_id=381

http://bvmjets.com/Pages/Catalog/air.htm

dhal22

i use the sullivan fuel line stainless safety ties on my airlines. makes for great redundancy.

dubs1946

Yes i wire a double loop on all my air connections too, if you dont its called learning the hard way.

dhal22

at least with spring airs you will have wheels down if that happens.

matadco

My Feedback: (1)

In addition to not having to make a belly landing if you loose air with Springair's, there is only one air line to deal with. Also the control valve is much smaller. The down side of Springairs is keeping them retrcted without air, especially when installing.

Edwin

My Feedback: (2)

Yeah, air retracts require more maintenance, but thats what you got if you're into the big ones. Steve is right, been using his method for removing hose from the nipple for years. Over time I started actually doing maintenance instead of just flying. I spend a LOT of time doing the setup, leaving access to all the hose connections and such. You have to do the bubble test after installation to check for leaks and for annual maintenance, a small drop of very light oil for the cylinder O-rings. I found in the past most of my problems were due to using retracts/struts not strong enough, or too cheap for the plane. And my favorite is springairs. Spend the money. Nothing dampens flying fun more than un-ruley retracts.
Edwin

KitBuilder

Does anyone make electric retracts?

matadco

My Feedback: (1)

Check Lado Tech on the net

FILE IFR

Yes. This is the correct way to remove a line from the nipple.

dhal22

i think you can still buy gizendanner (sp?) retracts. also the old kraft electric retracts are still highly prized by classic pattern flyers.

matadco

My Feedback: (1)

Anyone know where you can get a 3-gear set of Krafts, short of my right arm and left leg?

82blackbird

My Feedback: (3)

What is a set of the Kraft's worth now?

dhal22

$100? more if they are NIB perfect condition.

82blackbird

My Feedback: (3)

I've got a set only mounted in a plane, never flown, only cycled in the plane. Don't know that I would take $100 though.