Landing Gear Oleo

[gusc]

The Champ I'm looking at to buy has had "the right oleo replaced". The p/n in the log is 1-2253 which Wag Aero calls a lower tube. I assume this is the piston part of the oleo and the upper part is the cylinder?

There is no mention of replacing the spring and the result is the RH side is lower and the wing droops to the right.

Wag Aero's LG parts list is pretty confusing to me since I don't have any manuals yet. Every Champ I have looked at had manuals so I don't plan to buy any until I get an airplane.

Does anyone have a MLG parts breakdown and illustration you can post or email to me?

Thanks

[Mikek]

Does anyone have a MLG parts breakdown and illustration you can post or email to me?

Thanks

Try this site:

http://www.hangar9aeroworks.com/Aeronca ... strut.html

Do not see that pn in the manual will keep looking!

Again usually it is a bad spring, for a time they were selling springs that
did not have the set removed. This means once you compress it under
load it took a set and would be shorter in length.

Take a look at the above site alot of good info.

If not the spring, someone might have repaired the gear and atachment
points incorrectly, which does happen.

Mikek

[Captgrumps]

Mike--

Having been in the spring design business at a spring factory years ago I can tell you that any spring that takes a "set" in its required function was designed wrong (or the wrong spring was used)--either the wrong wire (type/size) diameter or the number of coils were wrong. The proper spring in the landing gear should not take a set with the aircraft weight static, taxi or landing. Evidently the spring in question was underdesigned. A spring is designed to compress a required length under a given load in a given space with a safety factor designed in (either wire size or number of coils)..

Some heavier antique airplanes have two springs--a large outter landing spring and a smaller taxi spring with reverse winding to fit inside the larger spring. Out course if you design or have a spring duplicated today you usually have to tell them it goes on farm equipment our you are building a home made buggy. Forget the word airplane.

Doug

[Mikek]

Mike--

Having been in the spring design business at a spring factory years ago I can tell you that any spring that takes a "set" in its required function was designed wrong

Doug

Doug,

Its not the design, they were not made right, set needed to be removed
before grinding to length.

Lets say I remove my old spring and ask you to make me a spring just
like it with both ends ground and 11 1/16 overal length. If you coil it
and make it 11 3/8 so you can grind square the ends and end up with 11
1/16, the first time I compress the spring under load to its soild height It
will not come back to its 11 1/16 length. What needed to be done after it
was coiled it should be but in a press and compressed at least to its working
height one time then grind the ends to the 11 1/16 length. Oh also stress
releave at about 350 F.

All basic steel springs will take a set, after you remove the set by
compressing it to it soild height it is said that the set is removed. the
amount of set that is in springs depends on material, wire size, pitch
and -----.

Mikek

[Tim Juhl]

You need to determine whether you have "standard" or "No Bounce" oleos. The struts shown at <http://www.hangar9aeroworks.com/Aeronca ... strut.html> are standard. NB have a "Knob" on the end that attaches to the axle strut. The NB also show very little oleo below the caseframe when sitting. NB oleos have two springs while standard oleos have one heavier unit. Parts are not generally interchangeable.

In either case, oleos can be a maintenance item, notably when they start leaking or the springs wear out or brake. There is little you can do to assess their true condition without pulling them out. If they need rework the best course may be to send them out and have them rebuilt by a pro.

You should also determine whether the bushings and fuselage attachment points are worn and check the condition of the bushing in the caseframe. Some of the repairs required for these problems can be a pain.

A thorough inspection usually involves jacking the airplane up and removing the oleos and possibly the caseframes and struts (to check for wear.)

I looked at my manuals for the 7AC and 7EC and did not find the part number you mentioned.

If you have standard oleos and find that one of your springs is bad, I do have a good spare.

Good luck!
Tim

[Mikek]

You need to determine whether you have "standard" or "No Bounce" oleos. The struts shown at <http://www.hangar9aeroworks.com/Aeronca ... strut.html> are standard. NB have a "Knob" on the end that attaches to the axle strut. Good luck!
Tim

Tim,

The link below from www.hangar9aeroworks.com now shows the NB Gear.

http://www.hangar9aeroworks.com/Aeronca ... Gear-9.jpg

Usually it is the spring that is weak or broken, but like you say there
are a few good people/places that can rebuild the complete strut & Oelo.

Mikek

[Ron Babos]

Mike: you are absolutely correct on the spring sizing. The last set that I did was coil bind the two new ones that I got from Univair. Coil bind represents a compressed oleo as that is the stop. One was 1" shorter than the other after, but both were shorter afterwards than what they started out as out of the box. The other quirk was while pressing two at the same time, one would bind much sooner than the other. What this tells me is that even with correct lengths the plane will not set level. These things can be a real pain, unless you have the time to match them correctly. It could mean sending a few back until the object is achieved. It would appear that quality control is lacking on these things from aircraft suppliers and I doubt it will ever be resolved. Kinda like those new engine mount rubbers.
Ron

[joea]

Mike--

Out course if you design or have a spring duplicated today you usually have to tell them it goes on farm equipment our you are building a home made buggy. Forget the word airplane.

Doug

Doug,

How true! So many of the parts on these planes came off of old cars or whatever. Just do not tell the parts guy that what you are buying goes on a plane and all will be well.

Joe

[gusc]

Guys, thanks. You kind of lost me there on the tech discussion of springs but the link to hangar 9 was a real rich source.

It appears to me that p/n 1-2253 is shown in the hangar 9 oleo illustration as p/n 3-433, Oleo Strut Assembly. Wag Aero (Pg 94 of my March '05 Catalog) calls it Landing Gear Oleo Strut, Lower Tube.

I think if I ever buy new springs I'll compress them to the normal compressed length and leave them there for a few days before installing.

If you want to see impressive MLG springs just look at the ones on a Staggerwing Beech sometime.