Retract valve help needed.
09-14-2009, 07:41 PM
#1
Thread Starter
Retract valve help needed.
Hoping someone can help me figure out an issue I am having with my retract system. I replaced the conrtrol valve that came with the ARF aircraft as it leaked and it has been noted to not be of good quality. Bought a Robart VR valve which I have used before. Hooked it up, opend the two set screw valves two turns per the instructions and put 100 PSI in the tanks. The gear go up and down as they should. However in one position after finishing movement air coninues to leak out of the exhaust hole in one of the the stems. Move the control valve the other way, the gear move as they should and afterwards no more air leaks out.
I reverised the up down lines on the valve and when tried the other stem continuosly leaks out of the exhaust hole. I am thinking the valve is fine and the problem must be somewhre else, however I have checked the cylinders and they do not leak.
If I turn the set screw all the way in on the stem with the air escaping all the time, the air stops. Of course the gear will not cycle in that dierction. The non leaking stem I can turn in or out and the gear rate can be controlled nicely.
Appreciate your help.
John B.
I reverised the up down lines on the valve and when tried the other stem continuosly leaks out of the exhaust hole. I am thinking the valve is fine and the problem must be somewhre else, however I have checked the cylinders and they do not leak.
If I turn the set screw all the way in on the stem with the air escaping all the time, the air stops. Of course the gear will not cycle in that dierction. The non leaking stem I can turn in or out and the gear rate can be controlled nicely.
Appreciate your help.
John B.
09-14-2009, 07:51 PM
#2
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RE: Retract valve help needed.
Hi John,
There is a good chance that the leak is not in the valve but the leg itself.
Pinch each line and you will be able to find which cylinder is leaking in the up and down position
Steve
There is a good chance that the leak is not in the valve but the leg itself.
Pinch each line and you will be able to find which cylinder is leaking in the up and down position
Steve
09-14-2009, 10:19 PM
#3
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RE: Retract valve help needed.
john I had the same issue myself I sent it to Robart and when they tested it they said it was fine[:@],I installed it again, then I noticed when they sent it back one of the adjustment stems broke in shipping and fell out of the valve body, so they sent me a new one it works perfect, I would send it in and ask for a new one the guy who works in the warentee dept is a good dude.
09-14-2009, 10:41 PM
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RE: Retract valve help needed.
Hi John, i had the same problem, i changed the valve and it was the same.
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 piston 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 when the retract is up or down, the O ring on the piston is there to push the redundant air out when there is pressure from either side thus raising or lowering the leg.
You can check by pinching the air lines from the retract one at a time when fully up or down and if the leak stops then air is leaking past that piston back through the retract valve.
Dont forget as the retract go's up or down you will get the redundant air back through the valve so wait until it is fully up or down.
When you find the problem let us know what it is so we can all learn.
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 piston 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 when the retract is up or down, the O ring on the piston is there to push the redundant air out when there is pressure from either side thus raising or lowering the leg.
You can check by pinching the air lines from the retract one at a time when fully up or down and if the leak stops then air is leaking past that piston back through the retract valve.
Dont forget as the retract go's up or down you will get the redundant air back through the valve so wait until it is fully up or down.
When you find the problem let us know what it is so we can all learn.
09-15-2009, 09:01 PM
#5
Thread Starter
RE: Retract valve help needed.
I used clamps to isolate each gear. One works perfect with no leaks up or down. The other has the leak and all signs point to the O ring on the piston. Next task is to dissasemble the cylinder and replace the O ring. When I do this I will check the cylinder edges for any burrs or anything that could scratch the O ring when the piston is inserted into the cylinder. Hopefully this will solve the problem.
John B.
John B.
09-15-2009, 11:26 PM
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RE: Retract valve help needed.
Hi John it can be a problem to get the correct size O ring could be metric or imperial.
One method i have used in the past when i could not get the correct size O ring is 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 1/8" 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 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, but immediately it was in i new it would work as it was a very good fit. don't forget to put a very small amount of rubber grease on the O ring not to much or you will block the air holes.
One method i have used in the past when i could not get the correct size O ring is 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 1/8" 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 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, but immediately it was in i new it would work as it was a very good fit. don't forget to put a very small amount of rubber grease on the O ring not to much or you will block the air holes.
09-16-2009, 12:27 PM
#7
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RE: Retract valve help needed.
John, go to your favorite autoparts store and by AC lub it comes in a spray can for addign to your Car AC system. this has a neopren conditioner in it put enough of it in the cylinder from both ends so it sound soupy, leave it overnight then test it again.
this stuff will make the existing o-ring grow, once the leak has stoped then you need to open the cylinder and air it out to get the conditioner out to stop the groth.
now the 34 cent qestion who's gear is it, some of the gear manufacturers use bimba cylinders that have screw in barbs, if you have these you need to check the barb for leaks, i have this in 4 of my planes and have had to rebarb 4 cylinfers. dish soap and water sprayit on while pumping ot up to see the bubles.
Joe
this stuff will make the existing o-ring grow, once the leak has stoped then you need to open the cylinder and air it out to get the conditioner out to stop the groth.
now the 34 cent qestion who's gear is it, some of the gear manufacturers use bimba cylinders that have screw in barbs, if you have these you need to check the barb for leaks, i have this in 4 of my planes and have had to rebarb 4 cylinfers. dish soap and water sprayit on while pumping ot up to see the bubles.
Joe
