Last weekend?s trial fit of the engine to our RV-3 engine mount showed a few things that we needed to work on before we got serious about mounting the IO-320 for good. A few phone calls got the appropriate oil filter spacer, short dip stick, and assorted oil and fuel fittings on their way. The real work was going to be the control cable bracket for the prop governor ? the used one that came with our governor just wasn?t going to fit in the firewall recess. Check of the historical references (Randy Lervold?s RV-3 site) confirmed that he had the same problem, and ?had to modify it to fit?. No pictures though, so we took a few measurements from our trial photos, and began sketching. Here?s a shot of the bracket we had (it was of an RV-4). We needed one that was longer, pointed more vertical, and didn?t tilt as far back from the engine:
A phone call to Van?s gave me the information that the bracket was made out of 0.063? 4130 steel, so I got a 9?x18? sheet on the way from ACS. The first thing I did in the shop was to make a cardboard template, cutting and fitting until I had about the position that I wanted for the cable housing end. I traced the end of the original bracket that attaches to the engine exactly ? no reason to mess with a good fit! I then transferred that to the sheet and cut out the rough form on the band saw:
Once I had the rough form cut out, a little trimming on the grinder and some bending in the vice with the help of a 4X rivet gun, assorted bucking bars, and a BFH produced a basic bracket:
The first iteration copied the original bracket with regards to the cable attachment ? a dumb mistake on my part, since I wasn?t going to use Van?s cables, but rather the A-920 cables from Aircraft Spruce. These don?t have threaded ends and nuts to attach them, but rather a slot in the cables? housing end itself. Naturally, I tried a few different things to make the hole in the bracket work ? but didn?t find anything that seemed up to aircraft standards. Two Adel clamps came close, but the cable end rattled around inside the oversized hole:
I finally dug out the little cable clamps that ACS supplies to go with their cables. Pricey little buggers, but they work ? as long as you have a flat surface roughly parallel to the cable. Of course, I had a surface roughly perpendicular to the cable. A little redesign made use of the fact that the bracket was a little longer than it needed to be ? I put in an additional bend in the right direction, shortening the bracket in the process, and drilled the necessary holes. A 3/16? space made things line up a little better, and after about 4 hours work, I had a bracket that I feel is up to AC43.13 standards ? and should fit the airplane!
As always, building the RV-3 presents us with the fun and challenges of truly ?making it up as you go along?! We?ve been forced to get better at spotting ?unintended consequences?, and making sure that we don?t build ourselves in to a corner. For instance, see how the spark plug wires appeared on the P-Mag in the last picture? That?s because I wanted to make sure that we could get them on and off with the new bracket in place. Planning for maintenance and removal is always a good thing. Once again, I am glad to be building the -3?and glad I built the -8 first!
Paul
RV-3: Engine Control Brackets ? Making it Up!
Linear Mode
