Roee Kalinsky's RV-7A Project

2009.04.17: (0.0) Refer to DWG 46A.  My engine mount is Van's p/n WD-739-PC, which is for Lycoming dynafocal-1, and for the tricycle landing gear configuration (i.e. includes a socket to mount the nose gear leg).  The engine mount comes from Van's fully welded and powder-coated.

The engine mount attaches to the fuselage at six points using 3/8" (AN6) bolts.  Four of the six points (the four corners) on the fuselage (firewall, and hard points behind it) have also already been drilled to 1/4" at the factory, which is unfortunate, because these holes don't line up very well with the corresponding holes on the engine mount.  I should be able to enlarge the holes in the fuselage to 3/8" and completely encompass the existing 1/4" holes, just barely.  But this will not be easy since the existing 1/4" holes are far from where will be the centers of the final 3/8" holes.  This is another case of Van's (or the QB factory, I don't know which) taking an extra step without thinking, which only makes my life harder.  Had the holes never been drilled at all, this task would be a no-brainer.  Oh well...

I bolted the engine mount to the fuselage with 1/4" bolts and some bushings I made of various diameters to try to keep the holes as close to centered as possible.  And then I'm using 3/8" OD bushings inserted into the engine mount as drill guides to try to gradually enlarge the holes in the fuselage toward their desired centers.  Work in progress.

2009.04.20: (0.0) Finished all six holes to 3/8".  From 1/4", I enlarged them with a size "S" drill guided through a brass bushing (3/8" OD, 0.014" wall thickness) through the engine mount to keep the drill centered.  The drill bit tends to bind when cutting through the stainless steel firewall, but ultimately the results were fine.  Then I reamed them to 3/8" through the engine mount, yielding nice clean concentric holes.  For the two bottom center holes, which thankfully were not pre-drilled, I first drilled them to 1/4" with a bushing (3/8" OD, 1/4" ID) through the engine mount as a drill guide, and then enlarged them same as the other four.

Note that the four corners sit nice and flush on the firewall, but the other two attach points at the bottom center are raised about 0.032" off the firewall.  Other builders have reported the same.  Anyhow, so I'll need to shim this gap.  The pads surrounding each hole on the engine mount are 1.25" in diameter, so the shims should be that diameter or slightly larger.  I'll probably use a AN970-5 washers, which have a 1.375" OD and 0.328" ID (clearance for AN5 bolt), and I'll open up the ID to 0.375" for the AN6 bolts.  Note that this also makes the AN6-24 bolts that are called out in the plans too short, so AN6-25 bolts will be needed.

2011.07.19: (0.0) With the firewall prepped and the fuselage now on the gear, I proceeded to mount the engine.

Following an article on VAF, my first attempt was to do the top bolts first.  But I then couldn't get the bottom bolts in, so I tried again the other way.  Going bottom bolts first, the top bolts were also very difficult.  But by manipulating the engine with the hoist, and pulling it into the mount with some ratchet straps, I was finally able to get it done.







Wow, looks like an airplane!