Taxi springs and hydraulic cylinder

cglucas

cglucas

New member
Well guys a 172 didn't show for an annual today so I tackled installing taxi springs and overhauling the hydraulic cylinders that actuate the gear on my 14-19-2. After several calls to friends about one thing or another I started pulling of the lower gear legs. Just under four hours and the gear had been swung five times to get all of the air out and she was back on the ground. I dissassembled and cleaned anything I could get off, installed the new taxi springs and o-rings, polished the shafts on the hydraulic pistons and installed new o-rings in the hydraulic cylinders. It all went really smooth I thought. The new springs were only about 7/16's of an inch taller than the old ones, but the plane site a full 1 3/8 taller at the gear, not only had the old springs became shorter but much less strengh. I now have a huge amount of prop clearance I didn't have before. I have really been putting this project off and now I am sorry I did because it went so well. Don't get me wrong I just threw the shirt away I was wearing today it was so nasty, but not a bad job. So if any of you are about to tackle this job contact me if you have any questions. Oh yeah my bird only has about 1380 hours since new, that may have been part of the reason things went so well...Greg
 
Greg, Make sure the LG overcenter springs are up to snuff and the slide tube is free of rust and old hard grease. Dan
 
One thing that would be valuable is to find out what the proper force is for overcenter springs-how do we test to find out if they are exerting adequate pressure. Someone reported having to rely on them to lower the gear last year and I encouraged him (while the plane was on jacks) to place a bathroom scale against the gear and see what the poundage was as the gear was forced back against the overcenter springs. That way we could have some figure to use in checking the overcenter springs for adequacy at annual time. I suppose just changing the springs every ten years might work also. Peter
 
Try the factory first. I can get them made, just like the Cruisair taxi springs I had made last year. Dan..
 
I have a 14-13 with the Kidwell hyd. conversion. Just found out (Thank You Grant Jordan!) they are 14-19 gear and parts. I had asked the factory earlier about them and they said that if that was so, the springs should exert 80 pounds of force...presumably at the spring. And yes they have them.

My Question: How the heck do you get them off to check them? I tried at my recent annual, but could not compress the thing enough (read any at all) to be happy about removing the bolt at the retract arm (for fear I couldn't get it back on). BTW my gear do not drop and lock on the jacks (or in the air either).
 
A number! 80 pounds. Can that be checked by pushing a bathroom scale against the wheel when the plane is on jacks? Seems like it would be a different number for a Viking than for a taildragger as the viking lowers the gear with the assistance of airflow rather than against airflow. It would be great if we could all measure the resistance of the gear down assist springs (overcenter springs). Perhaps come to a consensus (thought the numbers mean little, because we have no idea if the numbers we all come up with are adequate for the task. I mean at annual we can do simple tests to acertain the safety of many items on the plane. There are limits for just about everything, but these gear down assist springs come without any guide to assure us that they are in the condition such that they will function when called upon (when loosing hydraulic pressure and having to rely on gravity and the springs to overcome the air flow enough to get the gear down an locked). Lacking a windtunnel in my hangar, I can't function test them. If I knew the poundage, I would be able to assure myself that they were ready to soldier on in their duties for another year. Perhaps knowing their nominal height would be an alternative. I suppose on principal, I should just replace them. Also, can the plane fail in such a way that we can't have zero hydraulic pressure in the lines? should we be ready to cut the lines in flight if that's what it takes to lower the gear in an emergency?
 
My breakover springs get tested every time the gear goes down. No hydraulic pressure when the gear lever is pressed down and the gear comes down on its own.
 
I guess my question to you is would they work as well if they had a 70 mph wind blowing against them (real world of flight) If you test the force they have in their last inch of travel, it might give you an idea of whether they would help you in an emergency. That is why I was hoping all of us would take a bathroom scale and press it against the main wheel just before the gear goes "over center" Maybe we can see what various planes have-what is that poundage when the springs are new-how about the poundage of the guy last year who had to have them work when his hydraulic pump failed?
 
I am going to replace my springs, I will see how much force it takes before and after replacement....Greg
 
Still waiting for the springs they had one and ti was going to be four to six weeks to get the other one......Greg
 
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