Brock,
I was hoping someone would have an opinion on this subject as I have the same questions and concerns. On my SHI kit there are no bushings in any of the parts that make up the Pitch portion of the rotor head. I feel that the aluminum parts rotating on the steel bolt is not an ideal design. On the SHII and III there are bushings in both the Pitch Pivot Plates (part #320-4006) and the Cyclic Control Bar (#320-4055).
A couple of years ago I asked the customer service dept. at GBA about enlarging the holes in both of these parts to accept bushings. My main concern was that the side (Pitch Pivot) plates only have about 3/8" of material above the hole.. and drilling the hole out to accept a (1/2"OD) bushing would reduce the amount of material to 5/16". I was told that the Pitch Pivot Plates on the SHII and III have the same dimensions as the SHI.. so there is less material above the hole in that part on the models that incorporated bushings. Apparently, load and stress analysis determined that the parts are strong enough with that amount of material (my words).
It was pointed out to me that a bushing may not be necessary in the Pitch Plates if the bolt going through the plates does not move (rotate)... that it is probably more important to have bushings in the Cyclic Control Bar that pitches between the plates.
Newer SH models have bushings in the Cyclic Control Bar... but mine does not. On mine, there is about 5/16" of material below the 3/8" bolt hole in the bar and over 1/2" of material above the hole (seems to me it should be the other way around.. if not centered on the bar). If that hole was enlarged for a (1/2"OD) bushing the material below the hole would be reduced to 1/4"... which is less than the material on the side plates... the difference being that the side plates are 1/2" thick and the bar is 1 1/4" thick.
Unless something changes my mind, I believe I will be enlarging the hole in my Cyclic Control Bar to accept bushings and leaving the side plates as they are. I am wondering why the hole in the bar is not centered... and if it would be a good idea, or a bad idea, to enlarge the hole towards the top side to prevent reducing the amount of material below the hole (if you know what I mean).
On the same subject, I have to wonder why the Roll mechanism uses a 1/2" pin (in a bushing with about 1/2" of material above the hole).... while the pitch mechanism uses a 3/8" bolt. I would think both would be the same (1/2") as they both carry the same load.
Thanks,
Greg