Throttle Quadrant Support Bracket Redo

Time: 4 Hours

Since my arm rests and throttle quadrant are all custom, meaning I deviated from what Van’s calls for, I had to do some engineering that’s unique for the support of the throttle quadrant cables. I took the idea from my buddy Glenn and made a bracket out of some large aluminum angle. I had completed this task and installed it some time ago and moved on to other tasks. Since then I was really happy with how the arms of the quadrant were moving and it felt like there was some binding. So yesterday I decided to investigate and see if I could fix the problem. What I found after a closer look was that I had actually measured the distance from the side skin to where the holes for the cables needed to be by about 3/8″. This meant that as the cables left the quadrant they angled outboard to hit the bracket holes. This caused each cable to cause a torquing action on the levers and caused the mixture and propeller cable ends to actually touch as they went through there motions in one spot. That was not good and needed to be fixed. So I decided to make a new bracket that would extend 3/8″ farther inboard. So I went about removing each cable from the quadrant then removed the two bolts holding the bracket. This allowed me to slide the bracket off of the three cables and remove it. I used it as a template and just extended the arm length by 3/8″. With the new measurements I went about drilling and trimming the angle to create a new bracket. I then did the task of getting the bend of the arm where the two bolts attach the bracket to the angle on the side skin. This was the time consuming part as it’s a little bit of a task to get the cables in and situated while checking the angle. Once that was done I bolted the bracket down and went through the process of setting the correct throw of the cable ends. These all looked good so I removed the bracket and primed/painted it so it would look presentable. Today the paint was dry so I reinstalled the bracket and worked the cables from outside to inside. First was the throttle cable as it’s the outermost cable on the quadrant. Once I had the throw all set and got the throttle arm on the servo to hit the full and idle stops I locked the cable arm in place with the nut and attached it to the throttle lever with the pin and cotter pin. I repeated this process for both the propellor and mixture cable. The propellor arm has given me the most problems part due to the angle that it goes through the bracket and the arm length on the propellor governor. What I ended up with was the prop lever goes to the full forward position on the quadrant and is short of the full aft portion by 3/8″ or so. I’m ok with this as it will never be in that full aft position and only off the full forward position a little as you increase the propellor pitch and reduce the engine RPM. The mixture arm works perfect allowing the full rich and idle cut-off.All three cables operate much smoother and there is no binding at all. I’m happy about that but I’m happy I spent four hours repeat a process but that part of experimental building. One other thing I did was to give the RV-8 some fresh air so I could sweep out the hangar. She really looks good stretching her legs after a long winter being cooped up!

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