Re: [COUPERS-TECH] SPRING TYPE LANDING GEAR

[Hartmut Beil]

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Wayne.
Good job finding someone that was involved designing the Aircoupe.


I mean we are all having a hard time to get some of the data from Univair.


I am referring to this text here:

Now shouldn't we invite hime to our discussion board so we are having another authority on board? How good would it be when we could ask a person that was actually designing parts of the planes? aerodog Aeronautics) -http://www.eng-tips.com/userinfo.cfm?member=aerodog 24 Feb 05 21:21

     Drkwing











Hartmut





To: <[EMAIL PROTECTED]>
Cc: <tech@ercoupers.com>
Sent: Tuesday, March 21, 2006 4:53 AM
Subject: Re: [COUPERS-TECH] SPRING TYPE LANDING GEAR

In 1964, I designed spring main gears for the Alon Aircoupe. They deflected aft towards the tail. The design replaced the original struts which used Bellville springs. The Bellville's acted as both springs and shock absorbers. For the first flight, the test pilot was able to log one take off and eight landings. Boing...Boing...Boing, well you get the idea, a pogo stick with wings. There was no damping (shock absorber) in the system. After we sorted thru the problem, we slimmed down the strut near the axle, so that on landing, the strut would twist causing the tire to scrub and dampen the rebound. The most interesting aspect of the project was the industrial espionage it took to acquire Cessna's spec on their spring gear. It was a special steel alloy purchased in mill runs. The gears were formed, heat treated to 220,000 psi then shot peened if my memory serves. ----- Original Message ----- From: <[EMAIL PROTECTED]>

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LR,


the Alon A2.  If it was a factory option, I would think that an A&P could

and balance form would have to be updated, because the spring gear is

route as far as paperwork goes.

As far as I know, the bolt hole pattern is the same on both types of gear

when mounting the gear legs.  The bolts are special NAS146-35 internal

of them.  (John at Skyport could probably supply them.)  Also, when you

bolt heads.  The washers go under the nuts.  These bolt heads have a small

legs have a beveled edge cut into the bolt holes.  The radius on the bolt

to use under the heads of these type bolts, but none are supposed to be
installed for this application.)


earlier than mine, and he had a gear leg fall off the plane after landing

bolts were cracked and had signs of being cracked for a while prior to the
incident.  Luckily the plane had only minimal damage.  He said that he had
noticed some unexplained vibration on a few landings before the failure.


destroyed, but I don't know what happened to them.  Buyer beware!


be a good idea to have the gear legs magnaflux inspected before installing

was no liability and no paperwork involved, they did both legs for me for

broken gear leg.

A couple of other opinions - While I prefer the spring steel gear over the

however, lighter in weight, almost zero maintenance, and I think they look

the side.

Another thing to look at is the condition of the metal between the axle

gear legs that I took apart, the block had started to corrode where it was

the road (gotta plan ahead, you know).


these gear legs for Alon.  It is pretty interesting reading, if you are

realized how these gear legs really work!  That's sort of scary in a way.

http://www.eng-tips.com/viewthread.cfm?qid=116349&page=7

Let me know if you want any digital pictures of the fittings, bolts, gear
legs, attach points, etc.

As always, all of this is just my opinion, so check with your licensed
mechanic before using any of this info.

Best Regards,

Wayne DelRossi
Alon N5618F
Hours logged since restoration: 114.0

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I'm just speculating here, but the spring steel gear was a factory option on remove the old gear, install the new, and just sign it off with a 337. The weight reportedly lighter than the original gear. I understand that one of the lady Alon owners did the opposite a few years ago - replaced the spring gear with trailing link gear, so if you could find out who that was, maybe you could go the same legs, so bolting them on should not be a problem. I would use all new hardware wrenching socket head type bolts (new P/N is MS20006-22). When I removed mine, the bolts didn't look too bad, but they did have some light rust on them and showed some signs of wear. If you need a source for them, let me know and I'll look up where I bought mine from. I think that they were about $45.00 for the six install the gear legs, note that there are not supposed to be any washers under the radius between the shoulder of the bolt head and the shank of the bolt. The gear fits into the bevel on the gear leg hole. Putting a washer under the bolt head will not allow the bolt to seat properly. (There are special washers available A few weeks ago I talked to a guy from PA who has an Alon two serial numbers because the bolts cracked and broke. I don't know how this could happen short of crash landing the plane, but he said that's what happened to his. He said the A while back, I bought a set of the spring steel gear legs off of E-Bay, and when they arrived I immediately saw that they were bent. One of them had a single bolt stuck in a bolt hole, and that bolt was sheared off from a crash landing. I returned these legs to the seller, and he said that he was going to have them fixed by a certified shop, or if they couldn't fix them he was going to destroy them. I would have felt better about it if I knew that they were If you are thinking about putting spring steel gear on your plane, it might them. I have heard of two gear legs breaking due to cracks in the steel. (One was the lady owner that I mentioned above.)When I rebuilt my plane, I took the gear legs to a local inspection lab and had them magnafluxed. I explained to the shop manager that I didn't need any official paperwork on the inspection, but that I just wanted to make sure that they weren't cracked. Because there $80.00 while I watched. Money well spent, considering the possible results of a original gear, I personally do not think that the spring steel gear legs are quite as rugged as the original type gear legs. I don't think that they will withstand the same level of side loading abuse as the originals will. They are better. Also they don't have issues with parts wearing and causing the tail to droop. I'm not sure that I would want a set of spring steel gear legs on an Alon without the rudder pedals. I'm always extremely careful with my plane not to touch down unless I'm lined up straight down the runway and not drifting to attachment fitting and the gear leg. The axle is held on with a machined metal block that attaches to the gear leg with six bolts. On one set of spring steel bolted to the gear leg. The corrosion cleaned up OK, but if left alone, it would have gotten progressively worse and might have caused a failure 100 years down And finally, below is a link to a posting from the guy who evidently designed interested in these gear legs. He mentions that the shock absorbing action (as opposed to the spring action) of the gear leg is provided by allowing the gear leg to twist upon impact, and the shock absorbing is due to the tire "scrubbing" on the pavement when the gear leg twists. This is why the bottom portion of the gear leg is so thin compared to the top portion - so that it can twist. I thought that this was a pretty good example of why one should not assume that one knows all about something on the plane just because he has looked at it and studied it. I could have studied these gear legs for 10 years and never

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