Ian,
I’m not familiar with the term “circlip” but I assume you’re talking about the snap rings, right?
I strongly recommend reading the information on Chris Zavatson’s site (http://www.n91cz.com/) regarding the LNC2 hydraulic system. He provides valuable insight into the system and its pitfalls. He also has several videos at http://www.n91cz.com/Hydraulics/Lancair_Hydraulics.htm that have proven very beneficial to me and others when this system presents issues. I learned a great deal from him supplemented by my own research, tearing into the system, rebuilding my pump and all of my cylinders.
It certainly sounds like you’ve isolated the troublesome cylinder. When you took it apart did you see any noticeably damaged O-rings? A damaged O-ring would indicate a possible burr or roughness that should be resolved.
Are you getting adequate pressure? You should have no less than about 500 psi on the low side and about 1200 psi on the high side. Even so, you should adjust it to about 700/1500 psi respectively.
I don’t know of a shop in my area (Washington, DC) but I haven’t looked for one either. But I’m sure any decent shop should be able to rebuild and test it. Just don’t tell them it’s for an airplane. I believe these cylinders were originally designed for raising and lowering outboard boat engines so check with a boat shop in your area.
I have two spares in my inventory if you’d like to have one but they’re untested. I’d recommend replacing all of the O-rings before installing either one of them just to save time. Lancair has them new at $275 USD the last time I checked. I’ll let you have one for $100 USD but I want your old one in exchange.
Good luck and let me know if you want one of my spares.
Danny
LNC2-360
N 38° 43' 25.7"
W 77° 30' 38.6"
Nothing is foolproof to a sufficiently talented fool.
From: Ian Crowe [mailto:ian.crowe@sympatico.ca]
Sent: Thursday, October 18, 2012 12:41 PM
To: lml@lancaironline.net
Subject: [LML] Re: Hydraulic cylinder main gear Lancair 320
No I did not hone and deburr the cylinders. I have no tool to easily do that and indeed saw no need unless in the way of the circlip grooves.
Would the pump experience a leak across the shuttle valve if it was going to leak and how would you test for that?
Once we blanked off the offending cylinder by a process of elimination the pressure loss stopped. I have gauges on the HP and LP sides to help me.
I too thought the repair was easy and have done more than few in my time but this one is a little perplexing!
Do you know of a good hydraulic shop near you who would repair and test the cylinder?
----- Original Message -----
Sent: Tuesday, October 09, 2012 8:06 AM
Subject: [LML] Re: Hydraulic cylinder main gear Lancair 320
I’m not. I’m just saying they’re easy to repair. When you replaced the seals did you hone & deburr the cylinder? Have you checked the pump for an internal leak?
Danny
LNC2-360, 650 hours
N 38° 43' 25.7"
W 77° 30' 38.6"
Didn't know you were in the cylinder repair business!! It is the actuating cylinder that is giving the problem. I have rebuilt it twice and it lasts for a while and then starts to leak again across the piston. No sign of any other leaks anywhere and we have blanked off all the other cylinders and the pump still cycles. So it must be the cylinder.
I have actually sold the plane to my flying buddy who did all the initial flight testing for me but am helping him with the maintenance now and again
----- Original Message -----
Sent: Sunday, October 07, 2012 6:15 PM
Subject: [LML] Re: Hydraulic cylinder main gear Lancair 320
Ian,
Are you looking for an actuating (gear up & down) cylinder or an oleo suspension (Ong debonger type) cylinder? I have actuating cylinders that can be rebuilt and I’ll even do it for you. I have no oleo struts but if yours need to be rebuilt I’m sure it can’t be difficult.
Danny
LNC2-360, 650 hours
N 38° 43' 25.7"
W 77° 30' 38.6"
Does any one have a spare main gear cylinder for sale?
Does anyone know where they can be repaired successfully or failing that where new ones can be bought?