552transco

My Feedback: (3)

Hi everyone,
My apologies if this thread belongs somewhere else.
I pulled a pair of Rhom Retracts out of my TF Corsair I've had hanging in the garage for the past 15 years or so.
All the air line disintegrated when I touched it. I went ahead an bought some new airline and hooked everything up on a test board I made. The system held air with no leaks. My problem is the cylinder inside the valve needs some kind of lube job. Both gear retract and rotate 90 deg but the left one takes a few seconds to lock into position. I suspect it (and the other one) needs some kind of lube tool.
Does anyone have any suggestions what type, brand, etc. I can use to get this gear back in shape.
I would appreciate any advice.

Thanks,

Wayne

nine o nine

My Feedback: (1)

I use Marvel air tool oil. When I pump air into the system i coat the inside of the fill valve and the oil gets distributed throughout the system. If I change an O ring a drop of the oil on a fingertip does the job.
The manufacturers of the system also recommend refrigerant oil. Mitch

gunny11

My Feedback: (6)

air tool oil or refrigerant oil works.

gunny

552transco

My Feedback: (3)

Thanks Gunny,

I never had the need to look for these types of oil before.
I guess a store like home depot would carry air tool and refrigerant oil.

Thanks again Guys for the tips,


Wayne

paladin

My Feedback: (9)

I’ve used both but the refrigerant lube has stuff in it to treat your o-rings to keep them soft and make them expand a little with each application. I normally fill the air pump hose with about 2 inches of this stuff then insert it through the air intake valve. Robarts intake valve can not be used to inject AC lube into your system because the same stuff that is good for your o-rings is death to the read valve.

If you want to get some AC lube you will find it in any auto parts store. The container it comes in is usually designed for a one time use so I empty it out into a bowl or cup then suck it up into a hobby syringe. That is good for a life time supply.

Good Luck

Joe

Warbirdz01

My Feedback: (1)

Airtool oil works well........just use very little......keeping in mind "wet" lubricants also attract dirt....which will wear out "Orings" in a hurry.........wipe off any excess.....using just enough to keep dynamic components moving freely............Bill......

552transco

My Feedback: (3)

Thanks Joe and Bill for your tips. I am going to take advantage of your experiences and give this a try.

Again, thanks for your comments,

Wayne

Ed

Any tips on finding air leaks in a system, other then soapy water ?

> Jim

gow589

My Feedback: (1)

I always put a little silicone oil (non-petrolium) in my tube before I pump it up. Even when they sit for a long time they still work fine.

Gary

paladin

My Feedback: (9)

Jim, Finding a leak is easy once you eliminate the stuff that works. Does it loose air only while retracted or only while deployed? Does it loose air regardless of retract position.

If it looses air only when the retracts are deployed or retracted then look at the lines that would be charged for that position.

If it looses air in both positions then the leak is in the lines that are always charged, you got it between the tank, valve, and filler. This is assuming the retracts have not been neglected for a number of years of coarse.

Now that you have ruled out two of the three systems in your retracts (deployed, retracted, supply). We can narrow the problem down with a air pump with a pressure gage and a pair of locking pliers. First identify the lines in question and refill them with pressure. As close as possible to the valve clamp one of the questionable lines with the locking pliers and come back in ten minutes. If the charges line did not lost pressure that line is good. Move the pliers to the other line on the valve and repeat the test. If you still get a leak that points to the valve, if you don’t that points to the line you had blocked off. I hope you are getting the idea.

Now that you have narrowed it down to a specific run you eliminate all the parts in that run by clamping off the individual peaces one at a time until the leak stops and you have found your problem.

Using this method I can find and replace bad air line in about thirty minutes at the field if need be.

I hope this is understandable!

Joe Felice

Ed

" Using this method I can find and replace bad air line in about thirty minutes at the field if need be.

I hope this is understandable!

Joe Felice "

OK Joe, I now understand how to isolate the output up, or down systems, but I'm having trouble with your following statement. > " Now that you have ruled out two of the three systems in your retracts (deployed, retracted, supply). We can narrow the problem down with a air pump with a pressure gage and a pair of locking pliers. First identify the lines in question and refill them with pressure. As close as possible to the valve clamp one of the questionable lines with the locking pliers and come back in ten minutes. If the charges line did not lost pressure that line is good. Move the pliers to the other line on the valve and repeat the test. If you still get a leak that points to the valve, if you don’t that points to the line you had blocked off. I hope you are getting the idea." < I now assume that we are on the Input, or Supply side of the valve, is this correct ? Do you use a hand pump, and remove the lines from the fittings, or do you charge the entire system ? I am in the dark here ?

Also, If I understand you correctly, you do not use soapy water at all for detecting the actual leak ? And if a valve leaks, can it be repaired ?

Thanks Joe - Jim

paladin

My Feedback: (9)

Jim, during the entire process the pump with a pressure gage will be attached to the filler valve. We have ruled out two of the three systems (retracted, deployed, or supply) because. If the gage shows a leak with the retracts deployed the leak is in the charged lines when the gear are deployed. If the gage shows a leak with the retracts retracted the leak is in the charged lines when the gear are retracted. If the gage shows a leak with the retracts deployed and retracted the leak is in the supply lines (they are the only lines charged in both retracted and deployed. That much I think you have.

Now we have ruled out two of the systems (retracted, deployed, supply) how do we narrow down the leak to the actual failed component. If you look at what we have, a system with a leak, if I remove the component with the leak the system will hold pressure once again. To do this I need to find the furthest part of my system from the gage and slowly remove the components from the system one by one until it holds air again. Once it holds air the component I just removed it the offending (leaking) part.

So in real life I have a system that leaks when the gear are deployed. I know that the supply system and retracted system work fine because while retracted the system holds pressure. So if I look at my deployed system it goes cylinder / hose / valve / hose / cylinder (it is possible to have a more complicated system and that means more components to check). So in my little sentence of components above I want to remove each component one at a time so I’m going to do this with the locking pliers everywhere there is a “/” I’m going to place the pliers to eliminate that component. So in my example I would recharge the system and clamp off one of the cylinders and it will probably still leak. Then recharge the system and on the same side block off the airline just past the valve. If it still leaks, recharge the system and clamp off the other cylinder. If it still leaks, recharge the system and block off the airline as close to the valve as possible. If it still leaks the problem is the valve, but 95% of the time the system will hold pressure here and that tells me that the last component removed from the system is the one with the leak, or the second run of hose.

I hope this is better than yesterdays description. And I never use soapy water or smoke and mirrors.

Fixing a leaky valve. First let me say that I’m going to be talking about a spool valve mostly because they are most prevalent. Once the leak is narrowed to a valve you need to look very closely at the installation because most likely failure is that the spool was side loaded on one end and the o-ring took a set so when you move the spool to the other position it leaks. Look for that before dismantling the valve or you will be doing this again soon! There are two things I do to repair leaky spool valves: I replace the valve with one that I know works, the system holds air, I know I have the problem fixed in the plane (if with the new valve it still leaks that means start the process again, it could be I missed the real problem and the original valve is still good, or that there is a secondary leak). Any way I now have a system that holds air and there are now side loads on the spool. Remove the spool from the original valve and visually inspect the o-rings. You will see one of two types of failure, it looks like nothing is wrong or a chunk is missing from the o-ring. If it looks like nothing is wrong that is a side load problem the o-ring has taken a set on one side. The fix is to apply refrigerant lube to the spool so it is dripping with the stuff and push it back into place. After wiping the valve down hook up the air pump to all the barbs one at a time pressurize that side then release it and wipe up the excess. Then put it away for a month, the AC lube has stuff in it that will soften the o-rings and make them expand and it should hold air in a month. If a chunk is missing of the o-ring we treated a month ago was to old, dry, etc. and it still leaks you can get replacement parts from Low’s or Home Depot. Remove the old o-ring and bring it with you and you are looking for a 1/16 thick o-ring, you will probably have to order it so get one on either side of the size you think it is. When they come in order a half dozen of the correct size and make the store put the wrong ones into stock the total cost might be $2.00. Or you can order from the manufacturer of your system and pay $15.00 for the same number of them but they come a lot quicker.

Well that is a lot to digest.
Good luck

Joe Felice

TLH101

My Feedback: (90)

Jim,
Here is a step by step manual for troubleshooting leaks by Robart. It is a very simple process:
http://www.robart.com/air_systems/In...leshooting.pdf

Warbirdz01

My Feedback: (1)

Listen for the "Hissing " noise....works every time...........Bill..........

Ed

Thanks Joe, for the time and effort that you took to put all that together, and it won't go to waste. I've stored it in my Retract file, printed it out, and will start putting it to good use this coming Saturday. The way that you described it, it's fool proof, and gotta work.

Thanks again. - Jim

gnome

Not sure where to address this question but here goes. I'm building the Skyshark TBM Avenger. It calls for Springair retracts. I have a set of Rhom airs that are old but have never been used. These were designed to use freon. I was wondering if they could be used wirh compressed air and if so would I need a bigger air tank. .Also could I use the lubricating oil that you mention. would they lift 31/2 inch Du Bro lite wheels? If I could use them it would save me a bundle and I could keep building and would't have to invest in a new set of retracts. Any help you can give me is greatly appreciated. Thanks. Harry

the-plumber

Be careful about refrigeration oils, there are two major flavors and they are utterly incompatible.

Originally we used mineral oil, when the three main refrigerants were R-12, R-22, and R-502.

When EPA discovered the refrigeration industry, everything changed for the worse.

Production of R-12 and R-502 was halted. Other interim lubricants, compatible with the 'new' interim refrigerants like R-409, showed up. These interim lubricants were synthetic alkylate, for the most part.

Then the chemical manufacturers got their act together and gave us R-134a (the stuff in your car these days, which doesn't quite do the job when you're stuck in traffic) and R-404a, and more recently R-410. These newest refrigerants are incompatible with the old refrigerants and are also incompatible with the old lubricants. The lubricant for R-134a and R-404a is either PEG (for 134 in autos) or PolyOl Ester (POE in the trade); both are pure synthetic lubricants.

One way to literally "kill" a refrigeration system is to inadvertently introduct POE into a mineral system or vice versa - the two lubricants are not miscible at all and will form a wax which is liquid at normal room temperature. The wax solidifies at low temperatures, somewhere around 30 degrees, and it will quite literally plug up small tubes and lines.

I work on refrigeration systems daily, and I don't know whether the o-rings in model pneumatic systems are compatible with POE, but I wouldn't bet my model on it.

Further, refrigeration lubricants have no ability to deal with moisture. That's taken care of by the system drier. Which in turn means that refrigeration lubricants will not protect your pneumatics from water-based corrosion.

Air tool oil is compounded to deal with moisture (duh . . .) and is a MUCH better choice for retract lube.