Ch. 5 - Landing Gear mounts - Part 5

More sanding, more drilling (7.5 hrs)

The small landing gear brackets (front) have to go through the same process as the big ones (rear) did. Basically, drill the mounting holes undersize, ream them to the proper diameter, mill the lightening holes, and sand it all to shape.

The paper templates proved themselves to be quite precise, and the holes I have drilled so far have ended up with the correct placement.

Front-right landing gear bracket lined up behind rear bracket .

Front-left landing gear bracket lined up behind rear bracket.

In spite of this, I decided to use the templates just for initial positioning, and employ the actual brackets for proper alignment of the holes instead. This way any error in the rear brackets would get duplicated onto the front one, guaranteeing parallelism between the LMGA tubes, and the fuselage sides.

I used the table to make sure the brackets lied onto the same plane, and once the hole and the template lined up, I clamped them together.

Immobilizing brackets before drilling.

I then mounted them on the mill vise, and spent some time leveling them precisely, so that the holes would turn out perpendicular to the surface.

Leveling brackets with the help of a dial gauge.

I used the 1/4” reamer fitted to the mill head, to line up with the hole in the rear bracket (the one on top). Then I removed the reamer, and the rear bracket, and used a series of increasing drill bits to bring the hole to 7/32” (5.55 mm). Finally, I enlarged the hole with the 1/4” (6.25 mm) reamer.

Reamer lined up and ready to roll.

If you have never used a reamer before, here’s a short clip of myself reaming one bolt hole. As you’ll see, it’s pretty similar to drilling a hole, except that you need a hole already made to begin with, and you do not want to run the bit in reverse or you’ll risk damaging it. These reamers are pretty delicate tools.

I used this same technique for all the mounting holes, as well as for the lightening cutout.

Aligning 3/4" end mill.

Here’s a video of the milling of the lightening hole. I decided to add it because it’s pretty wild, with lot metal chips twirling about, but it’s also 4 minutes long, so watch it if you’re into that kind of stuff.

Later, I bolted the two front brackets together, and sanded them to shape. Here they are after sanding. 

Completed left and right front brackets.

Finally, I was able to put all of the pieces that will attach to the rear, inner fuselage skin, together to form the main landing gear attachment points. Here are a few pictures of the finished product. 

Complete right assembly.

I used some bolts to join them loosely, to see if the holes would line up. Given all the variables involved, and the cumulative small errors, it’s kind of scary how precisely they mirrored each other.