I flew Louise's RV-6 up to College Station (KCLL) yesterday morning (she lost the coin flip and drove the ground vehicle in which she was ferrying office stuff....better not tell her about my two-headed coin!), and as I was turning base to final and needed a little power, I was surprised the the throttle had become very stiff - almost like I was pushing a spring against a hard stop! I was able to get what I needed, but this was quite troubling.
Upon disassembly, I discovered that somewhere along the way, the hardware attaching the rod-end bearing on the end of the cable to the carb's throttle arm had been "simplified". The bolt still had the big safety washer and washer, castle nut and cotter pin on the other end, but the little spacers that go on either side of the spherical bearing were missing. As the cable twisted a bit through it's travel, this made the rod end bearing jam up, causing the hard point in the middle of the travel.
It is not uncommon for someone other than the builder (without the original drawings) do maintenance on an airplane along the way, and sometimes they don't get all the unusual and unique hardware back where it was. This is why a good A&P working on a certified airplane should be using a model-specific service manual, because there are so many unique configurations. Of course, the Experimental world doesn't have the same books, so it is important to refer back to original drawings, or at least make notes as you disassemble things to make sure they go back the way they were.
In this case, those little spacers give the spherical bearing room to move, making the joint truly flexible. Without them, binding can (and did!) occur...
Paul
Upon disassembly, I discovered that somewhere along the way, the hardware attaching the rod-end bearing on the end of the cable to the carb's throttle arm had been "simplified". The bolt still had the big safety washer and washer, castle nut and cotter pin on the other end, but the little spacers that go on either side of the spherical bearing were missing. As the cable twisted a bit through it's travel, this made the rod end bearing jam up, causing the hard point in the middle of the travel.
It is not uncommon for someone other than the builder (without the original drawings) do maintenance on an airplane along the way, and sometimes they don't get all the unusual and unique hardware back where it was. This is why a good A&P working on a certified airplane should be using a model-specific service manual, because there are so many unique configurations. Of course, the Experimental world doesn't have the same books, so it is important to refer back to original drawings, or at least make notes as you disassemble things to make sure they go back the way they were.
In this case, those little spacers give the spherical bearing room to move, making the joint truly flexible. Without them, binding can (and did!) occur...
Paul
