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As for clevises: The threaded type are a definite failure point. No doubt about, they all fail in the threaded area. But I've used the soldered clevis a lot with 100% success.
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It tested both my Sig/clevis rig and a Veco welded horn with a ball link and both a 3.5 pound (54 ounce) loads test.
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The clevis pin is only 1/16" diameter and is simply spot welded to one of the side arms. That is where they break, not where they attach to the pushrod (mssing pin on left clevis in pic).
The bulkier DuBro (center) doesn't have that issue, and there is a safety clip on the other side of the clevis. The Ultrahobby clevis (right) is bulletproof, and was purposely made for demanding CL apps. It has a screw-in 3/32 pin. Steve Moon, who makes these, says on .35 or smaller planes, the DuBro is OK. If you use a clevis, don't use the spot welded ones.
No one has any real data on clevis pin breakage. Failure rates might be as low 1% in 50 hours of use -- which means you will find many people with 100% success rates.
And a lot of Ty's, Ed's, and Larry's! Keep using them, and you get to join our "club" of "victims".
Static tests don't tell you much about survival of parts in the air. Vibration, line jerks, are the killers. Your test, if set up on a vibrating table, and allowed to run for some number of hours would possibly be meaningful.
The danger of the nylon horn is less breaking than shifting position due to stress and vibration. You may find, in the middle of a flight, full up just became slightly down.
Larry FulwiderEdit: Clarify missing pin in clevis