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While they're probably nothing really wrong with Unibal, you can't go wrong with Aurora in general, such as their CAM-6 (3/8ths shank, high-angle misalignment).
The cost difference between a merely adequate rod end and an excellent one is only a few dollars (e.g., $8 vs. $4).

Many mfg. bolt in the threaded aluminum sleeves within the aluminum control push tubes.
Sport Copter uses steel tubes and sleeves, and welds in the sleeves.

If there were areas where I'd "overbuild" it would be the rotor and control systems.

Good luck in your project!
Kolibri
 
The main difference between cheaper rod end bearings and more expensive ones is the presence/absence of a non-ferrous lining in which the ball turns. Aircraft-grade rod ends have the linings; commercial-grade ones don't. Sometimes they are distinguished by referring to 2-piece vs. 3-piece bearings.

I like the aircraft-grade units, despite the cost. I have used unlined commercial rod ends, but bought them in bulk and had them individually inspected by magnetic-particle testing. The welds employed in manufacturing these units have proven defective on occasion, resulting in breakage.

Loss of control rods has proven fatal more than once. It's important to use good bearings and to make sure that they do not exceed their maximum mislignment angle throughout the control range (if they exceed this limit, the stems will break off).

Design of the pushrod tubes themselves is a separate topic, in which there can be some non-obvious factors. Steel may or may not be "better" than aluminum in this application.
 
Among all aircraft manufacturers, gyroplanes builders are the ones who care least about useless weight. Because of the low L / D ratio, this should be the opposite.
 
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JM -- I know of accidents of three types that involved rod-end failure.

First was one in which the rod-end bearing was not locked in place by a jam nut, tightened against the threaded insert in the push rod tube. The bearing was able to move up and down slightly in the threaded insert, eventually causing the threads in the insert to strip. The rod end bearing then was no longer attached to the pushrod tube.

Second, the threaded stem broke off the bearing housing (ring). This can be caused by bending loads on the stem. This, in turn, can result from the use of a control fork (upper or lower) that restricts the bearing's tilting action as the controls are moved to their limits.

Third, I have heard of (but never encountered myself) bad welds in the round housing in the 2-piece bearings. The round housing, or ring, breaks in half (for instance, it may break at the 3 o'clock and 9 o'clock positions) releasing the ball.

I have not heard pf a pushrod tube itself breaking. These rods are critical in compression (column loading). Resistance to column loading is more a function of the DIAMETER of the tube than the material it is made of. Example, the Gyrobee plans call for pushrod tubes of 9/16" diameter x .065 wall 4130 steel. Despite the use of steel, these rods are weaker in compression than, say, an Air Command pushrod of 7/8" diameter and .058 wall 6061-T6. Neither rod will withstand more than about 200 lb. of compression without buckling -- the 9/16" steel a little less than 200.
 
Yes, Doug. But as you report, the failures mentioned are never due to insufficient strength of the rod ends. Each time, it is an associated part that fails: breakage of the axis without clevis, unscrewing of the thread, buckling of the tube, exceeding the angular limits.
 
JC and JM -- The only failure of a bearing that I know of that is NOT attributable to misuse is the one in which the bearing housing (the "banjo" or "ring") broke in half through a bad weld. That is a manufacturing defect, not really a case of the load exceeding the bearing's RATED strength.

An installation that imposes a bending load on the stem is probably the most common problem in this area. Again, not really an overload but instead poor installation.

Despite all this, i believe in providing a VERY generous safety factor in control assemblies. The control system experiences a constant 2-rev vibration in flight, plus unpredictable shock loads when taxiing on the ground (especially on unpaved surfaces such as those where I live). For this reason, i use only 3/8" rod ends on my own gyros, despite certain gyro plans that call for 1/4" or 5/16" bearings. Others disagree.
 
Can't find male shank 3/8"-24 thread x 1/4" bore, rod end, looked every where! any one know where to find?
 
J-Bird: Commercial rod-end bearings typically have the same diameter hole and shank. Aircraft grade bearings OTOH are available with 3/8" shank and 1/4" hole. Commercial bearing distributors don't necessarily sell them. They're available through aircraft suppliers such as Wicks, Aircraft Spruce, etc. Hold onto your wallet.

If you're stuck with a 3/8" hole bearing of good quality, you can insert a commercially available 3/8" x 1/4" oilite bushing. Be careful not to distort the bushing; slide it onto a bolt, support the bearing ball with a block of metal with a hole in the middle, and carefully tap the bolt head, as gently as possible. Better to buy the real thing, however.

JM: The "classic" advice regarding control stops has been this: Have stops at both the rotor head and the stick, but adjust them so that the stick stops engage first, just before the head stops. This prevents high stick loads from being transmitted into the pushrods and bearings. The pushrods have plenty of tensile strength, but relatively little compressive (column) strength.
 
Thanks Doug, I just want to add, your amazing knowledge of the gyro-world is well appreciated!!!!!!!!!!!!!
 
J-Bird: No problem. I happened to have looked a bit into rod-end bearing issues when I started selling them through my little ol' gyro-supply biz, back in the day.
 
Maybe others unknown to me use 1/4" eye 3/8" shank rod bearings, but I've seen them OEM only in Sport Copter.
And, yes, they pay a premium for them.
 
How about my stock rod ends (heim) 1/4"x3/8"on my Dominator's push tubes.
 
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