Sat Mar 26 2011

Parking brake valve mounting and handle

Today I got back to working on the brake lines and parking brake. Previously, I was thinking of mounting the parking brake valve such that the lines would be parallel with the carry through spar and the axis of the rotary lever would be perpendicular to the spar web...well, actually perpendicular to the spar covers which are at a bit of an angle to the web. With this arrangement, it looked like it would be really cramped quarters between the two tubing brackets, so I started looking at other options. The idea I liked best is shown in this image. The valve will be mounted to the side of the fuel selector cover, and the lever will protrude through a slot in the side. You'll see.

I found a scrap piece of 0.040 thick aluminum for a doubler since the cover is only .020 thick.

After quite a bit of layout and drilling, here's the doubler with the valve in the approximate position...except the valve will actually be on the other side of this plate.

I cut a slot for the lever arm. The slot ended up having to be 1/4 inch wide because the arm had a joggle in it. Hrm...I don't think I really like the looks of that crappy joggled arm.

So I searched around for some stock to make a new arm and found this piece of 3/16 thick 2024-T3 bar.

Some cutting, sanding, and filing later and I had the beginnings of a new arm.

I ran out and picked up this piece of 1/2 hinch diameter aluminum rod at Aviation Depot.

The rod is going to become the finger grips for the new lever arm, which meant I needed to drill and tap some holes along the centerline of this rod. Here's what I came up with to do a decent job of drilling on center of the rod. First, clamp a wood block to the table and use the brad point bits to drill a clean 1/2 inch diameter hole.

Cut a couple pieces of rod. I don't know why I bothered being so precise with these as I'm going to shorten them in a few minutes anyway.

Stuff the rod in the wood block in the hole and center drill.

Then drill 5/8 deep for a 1/4-28 tapped hole. I used a 7/32 drill which is a few thousandths larger than the recommended size. Close enough.

After removing the rod from the wood block, I threaded the hole with a 1/4-28 tap.

The rods were cut down on the band saw to just over 3/4 inch long.

...then sanded and polished to final length. Note the nice radius on the corners.

One end of the lever arm was drilled out to 1/4 inch diameter.

While I was out, I also picked up this bolt: 1/4-28 x 1 lg. The die grinder removes bolt heads like a hot knife through butter.


That little stud is holding this assembly together.

After drilling up and then filing the hole in the other end of the lever into a square (no pictures...sorry), I assembled the new lever arm to the parking brake valve. Here's how it's going to look. The slot needs widened about 3/64 inch, but I think it looks much better than the crappy steel lever the valve came with.