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JakeBaby (Automotive)
4 May 08 13:25
In a forum Feb. 05, Aerodog described work on spring landing gear for Alon Aircoupe. This gear replaced the Bellville spring suspension gear, which was used on all early "Ercoupe" models and some later Alon "Aircoupe" aircraft.
Question: When alignment issues arise (toe-out, negative camber), is there any provision for re-alignment of the spring gear? In the automotive world, spring "re-arching" is common, but on aircraft, this doesn't seem viable.
No repair manuals or parts manuals contain any information on this type of gear and new replacements are not available. The spring gear is very rare, so used are also unknown.
der8110 (Aeronautics)
4 May 08 20:07
Spring gear is aligned with shims placed between the flat surface at the end of the gear and the hub carrier (with brake caliper). Not familiar with this Ercoupe mod, but probably uses the same shim parts as Cessna, etc.
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JakeBaby (Automotive)
5 May 08 1:12
der8110:
I can understand shimming to correct the toe-out issue. Any ideas on the negative camber? I believe the next step is probably to pull the gear and check for any signs of bending.
Thanks. I'll check the Cessna shims.
der8110 (Aeronautics)
5 May 08 20:26
Camber is probably the least of the issues, if you look at it from behind, you got a suspension geometry almost as bad as the swing arms on a Corvair. Most tires are round, and I might think the only time the hub is perpendicular to the ground (and the tire rides on its true center) is at max take-off weight. An interesting bar bet would be how much tire wear is due to sliding side-to-side as the landing gear squats during landing, and the usual bouncy-bouncy, versus regular wear due to miles of driving. I did hear once there is a particular bacteria that gobbles up all the abraded molecules of rubber from tires; it does not remain as general dust.
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JakeBaby (Automotive)
6 May 08 1:32
New tires were installed about 100 hours ago and are down to the wear indicator depth on the inside half of the tire. The negative camber is very obvious when viewed from front or back. I'm hoping Aerodog logs on to give us his opinion.
Granted, the absorption is a result of lateral movement of the tires on landing, which definitely scrubs the tires. Aircoupes don't exhibit the typical bounce or porpoise tendency that a Cessna does; they just sit down and stay. This does make it difficult to tell when you've had a bad landing, as they all seem fine from the left seat...lol
BTW, I've heard there are similar bacteria that actually eat oil, which was a comfort to me, as the coupe does still return some to Mother Earth.
bf109g (Aerospace)
6 May 08 8:55
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Jake,
Although they don't sell replacement parts for the spring gear, Univair should be able to tell you what the proper rig is and you may be able to sweet talk them into giving you some idea as to the critical dimensions on the gear.
Ask for Craig in engineering.
JakeBaby (Automotive)
6 May 08 13:38
bf109g:
Thanks for the tip. Craig faxed Alon Bulletin #13, which give the procedure for toe measurement and adjustment using tapered shims. I agree with you, the toe issue probably is the most detrimental to tire wear.
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