Air retracts
01-08-2012, 10:34 PM
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Air retracts
I have a question for the guys who use air retracts system in there models, when you have gear failure of the main not comming all the way down or locking. What did you find as being the route cause of the problem? What exactly was the repair did you preform to the system and get the gear working correctly?
01-09-2012, 03:25 AM
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RE: Air retracts
If in flight I usually find a loop pull the gear down enough to lock it.
If the gear operates OK but when screwed into the model does not operate well, it usually means the bearers are not paralell and are twisting the retracts bady when the screws are tightened.
Sometimes there are just lacking lubrication.
If it air leaks losing pressure then the soapy water test of all joints, the filler valve is the usual culprit.
But if you can't find a leak in the tubes and joins then it may be the seal in one of the cylinders is leaking.
That's sort of roughly it unless you can give more details.
If the gear operates OK but when screwed into the model does not operate well, it usually means the bearers are not paralell and are twisting the retracts bady when the screws are tightened.
Sometimes there are just lacking lubrication.
If it air leaks losing pressure then the soapy water test of all joints, the filler valve is the usual culprit.
But if you can't find a leak in the tubes and joins then it may be the seal in one of the cylinders is leaking.
That's sort of roughly it unless you can give more details.
01-09-2012, 04:32 AM
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RE: Air retracts
I have found different solutions to each gear actuation problem. Mboland has mentioned many fixes but I am sure there are more solutions to the many different problems. Do the gear work on the bench? Do you keep air pressure overnight? Is there a bind you can feel if manually (by hand) drop the gear? Have you tried loosen the mounting bolts? You may have resistance from the air and speed of the plane so you might want to put a little back pressure on the gear for a manual check.
01-09-2012, 02:17 PM
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RE: Air retracts
If a line pinches or kinks it can cause the gear to not fully lock down or up. The air cylinder moves during the cycle on some units and that could be causing the line to pinch against a spar or rib in the wing. I've run into this on Robarts 150 series units.
I know it seems like a dumb question, but are you loading the system with enough pressure to push the gear down against the airflow during flight? Or is the gear slowed too much at the valve that it doesn't build enough pressure at the retract to push it down against the airflow? Try speeding up the cycle and see if the problem still exists.
I know it seems like a dumb question, but are you loading the system with enough pressure to push the gear down against the airflow during flight? Or is the gear slowed too much at the valve that it doesn't build enough pressure at the retract to push it down against the airflow? Try speeding up the cycle and see if the problem still exists.
01-10-2012, 07:45 AM
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RE: Air retracts
Guys Thank you for the responses, . Im Building a Ziroli 112'' B-25 and I don't want to have issues with the retracts. I'm looking to find out what the majority of the issue that causes the loss of air pressure. I have seen time and time again where you pressurize the system in the pits, cycle the gear everything is working. You get the aircraft in the air and for some reason when you go to land, the gear either don't come out at all or they drop half way and you are forced to belly in.
01-10-2012, 08:10 AM
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RE: Air retracts
ORIGINAL: ascforithobbies
Guys Thank you for the responses, . Im Building a Ziroli 112'' B-25 and I don't want to have issues with the retracts. I'm looking to find out what the majority of the issue that causes the loss of air pressure. I have seen time and time again where you pressurize the system in the pits, cycle the gear everything is working. You get the aircraft in the air and for some reason when you go to land, the gear either don't come out at all or they drop half way and you are forced to belly in.
Guys Thank you for the responses, . Im Building a Ziroli 112'' B-25 and I don't want to have issues with the retracts. I'm looking to find out what the majority of the issue that causes the loss of air pressure. I have seen time and time again where you pressurize the system in the pits, cycle the gear everything is working. You get the aircraft in the air and for some reason when you go to land, the gear either don't come out at all or they drop half way and you are forced to belly in.
Electric retract systems are nice,though Ihaven't used any on my planes yet. But they are not completely bullet proof either,I have seen them fail.
It comes down to personal preference. Either system set-up and maintainedproperly should work just fine and be reliable. Just the same either system installed incorrectly will cause you trouble.
01-10-2012, 07:30 PM
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RE: Air retracts
My Robarts on my two P51 TF GS have always worked.[12yrs] You must have enough pressure in the tank and not to close the valve to make them "too" slow.Keep an eye on your pressure indicator before you fly.I use about 140 # of pressure and after a few flights recharge again.
Good luck.Tom
Good luck.Tom
01-10-2012, 08:14 PM
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RE: Air retracts
My Byron P51 gear are the original set up and I only get to cycle the Door's, gear up and down one time. the mains don't bind at all, I have changed the O-rings, lube it and I even increase the air tank . I'm limited on repairs and there is no electric conversion for the Byron unit's. That is why for the b-25 I like to find out what other problem other guys have had, to avoid it when plumbing the system in this new model.
01-11-2012, 06:35 AM
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RE: Air retracts
ORIGINAL: tevans55
Minnflyer-
I am wondering if you have a video showing a 2 lb. main gear cycling? My B-25 with wheels, brakes and strut are just over 2 lbs.
Minnflyer-
I am wondering if you have a video showing a 2 lb. main gear cycling? My B-25 with wheels, brakes and strut are just over 2 lbs.
[youtube]http://www.youtube.com/watch?v=5l9Z6OxENkc&feature=player_embedded[/youtube]
01-11-2012, 06:35 AM
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RE: Air retracts
ORIGINAL: ascforithobbies
Dynamic If you dont mind what was the mistake in the shop?
Dynamic If you dont mind what was the mistake in the shop?
01-11-2012, 06:22 PM
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RE: Air retracts
Hi i had a failure with only one wheel coming down and that was it and it then would not go up or down, the air tank had rotated in its cradle due to vibration, so make sure if you are using air to secure the tank.
01-12-2012, 05:21 AM
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RE: Air retracts
ORIGINAL: MinnFlyer
Well, I'll put it this way. Mitch Stott (the owner of D&L) says he hasn't come across one yet that they haven't been able to convert.
Well, I'll put it this way. Mitch Stott (the owner of D&L) says he hasn't come across one yet that they haven't been able to convert.
Sierra FW190 tail
as it is hold UP/DOWN only by the air pressure
01-12-2012, 07:52 AM
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RE: Air retracts
Its a matter of careful construction with regards to installation techniques...ie keeping rails parallel and square to eliminate any binding in the frames.
Second, you need to use quality retracts, hoses, tee fittings, and valves, both retraction and fill. Cheap hoses can split and kink, cheap valves leak.
Third, make sure you have enough volume to adequately cycle your gear. I prefer 4 cycles per air charge. Your valve must be able to pass enough air to raise large heavy wheels and brakes. IMO, the Robart valves are not up the task. I would go with a BVM or Sierra high volume valves.
Finally, maintenance. You have to lube the cylinders once in awhile, yearly??? You must keep a check on how flexible your lines are. I have seen planes go for years on the same quality hose, BUT these planes had gear systems that were never disconnected and the hoses did not see UV rays. One of these was a 101" B-25. The wing center section was permanent, so the air system was never cracked open, and the hoses were never exposed to UV rays, so they lasted for the life of the plane. I dont think that plane EVER had a retract failure in the 3 years or so that it was flown. Also, dont be afraid to disassemble cylinders to replace O-rings. Things wear out, or normally, they age out with O-rings. They normally get hard from sitting, or lack of lube, or just plain age. Robart sells rebuild kits for their cylinders, its easy and cheap to do.
Second, you need to use quality retracts, hoses, tee fittings, and valves, both retraction and fill. Cheap hoses can split and kink, cheap valves leak.
Third, make sure you have enough volume to adequately cycle your gear. I prefer 4 cycles per air charge. Your valve must be able to pass enough air to raise large heavy wheels and brakes. IMO, the Robart valves are not up the task. I would go with a BVM or Sierra high volume valves.
Finally, maintenance. You have to lube the cylinders once in awhile, yearly??? You must keep a check on how flexible your lines are. I have seen planes go for years on the same quality hose, BUT these planes had gear systems that were never disconnected and the hoses did not see UV rays. One of these was a 101" B-25. The wing center section was permanent, so the air system was never cracked open, and the hoses were never exposed to UV rays, so they lasted for the life of the plane. I dont think that plane EVER had a retract failure in the 3 years or so that it was flown. Also, dont be afraid to disassemble cylinders to replace O-rings. Things wear out, or normally, they age out with O-rings. They normally get hard from sitting, or lack of lube, or just plain age. Robart sells rebuild kits for their cylinders, its easy and cheap to do.
01-12-2012, 08:50 AM
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RE: Air retracts
ORIGINAL: JeffH
Its a matter of careful construction with regards to installation techniques...ie keeping rails parallel and square to eliminate any binding in the frames.
Second, you need to use quality retracts, hoses, tee fittings, and valves, both retraction and fill. Cheap hoses can split and kink, cheap valves leak.
Third, make sure you have enough volume to adequately cycle your gear. I prefer 4 cycles per air charge. Your valve must be able to pass enough air to raise large heavy wheels and brakes. IMO, the Robart valves are not up the task. I would go with a BVM or Sierra high volume valves.
Finally, maintenance. You have to lube the cylinders once in awhile, yearly??? You must keep a check on how flexible your lines are. I have seen planes go for years on the same quality hose, BUT these planes had gear systems that were never disconnected and the hoses did not see UV rays. One of these was a 101" B-25. The wing center section was permanent, so the air system was never cracked open, and the hoses were never exposed to UV rays, so they lasted for the life of the plane. I dont think that plane EVER had a retract failure in the 3 years or so that it was flown. Also, dont be afraid to disassemble cylinders to replace O-rings. Things wear out, or normally, they age out with O-rings. They normally get hard from sitting, or lack of lube, or just plain age. Robart sells rebuild kits for their cylinders, its easy and cheap to do.
Its a matter of careful construction with regards to installation techniques...ie keeping rails parallel and square to eliminate any binding in the frames.
Second, you need to use quality retracts, hoses, tee fittings, and valves, both retraction and fill. Cheap hoses can split and kink, cheap valves leak.
Third, make sure you have enough volume to adequately cycle your gear. I prefer 4 cycles per air charge. Your valve must be able to pass enough air to raise large heavy wheels and brakes. IMO, the Robart valves are not up the task. I would go with a BVM or Sierra high volume valves.
Finally, maintenance. You have to lube the cylinders once in awhile, yearly??? You must keep a check on how flexible your lines are. I have seen planes go for years on the same quality hose, BUT these planes had gear systems that were never disconnected and the hoses did not see UV rays. One of these was a 101" B-25. The wing center section was permanent, so the air system was never cracked open, and the hoses were never exposed to UV rays, so they lasted for the life of the plane. I dont think that plane EVER had a retract failure in the 3 years or so that it was flown. Also, dont be afraid to disassemble cylinders to replace O-rings. Things wear out, or normally, they age out with O-rings. They normally get hard from sitting, or lack of lube, or just plain age. Robart sells rebuild kits for their cylinders, its easy and cheap to do.
