Chris Wrote: I am told the rod end bearings have a habit of cracking and failing
Chris, I too have used the now famous Dr Dean concept, in terms of bearing failures, you needn't worry, (My opinion) been designing control systems with bearings for the better part of 20 years, I could send you some data if you let me know what bearings you are planning to use. In my KR2S I used the MS21151-8 (Now found as AS21151) rod end bearings, greased for life, very low rotational drag and are self aligning, but mostly I picked because I had some laying around. On thing to consider is that most rod end type bearings are designed to take a load in the radial direction (that is perpendicular to the bolt) as such the side load (in line with the bolt) is the weak load path. Care should be taken not to preload the bearings in this direction, the Bearing needs to be clamped to the ear of your fitting, if that's the KR channel type hinge I would recommend that that a slip bushing be used on one side so that when you tighten the bolt it will load the bearing face against the opposite ear. What I have done is used Aluminum angle and simply bolts the rod end to the single leg. The 1/4 diameter bolt size rod ends in my case are serious over kill each having a radial limit load of 1720 pounds. I used 5 on the elevator and 4 on the rudder. They only weighed .10 pound each. Jim Mullen KR2S, Everett Washington
