Axles and Brakes

Step 5 INSTALLING AXLES, BRAKES AND BRAKELINES

I didn't do these steps exactly according to plans. Many thanks to Rick Maddy for most of this sequence of steps, he seems to have figured out how to merge the plans and the Matco brakes to make it all work.

I started by making up a an AutoCAD drawing of the Matco wheel and brake assembly (click here if you'd like to see it.) I then printed a copy full size and spray glued it to a piece of plywood as a template. I located three holes in it on the "edges" of the strut then tapped them and inserted long 8-32 bolts. These align the template into the right place. Trace the template and you have marks for bolt holes and the part of the strut that needs to be removed for brake clearance. I can also reverse the bolts for the other side of the strut/other leg.

Here's my contraption for aligning the axles for the right amount of toe-in. I used my laser device used for mounting shelves and so forth. Ladder held it at the right height, plumb bobs per plan help me find the exact center on the board 25 feet away. At that distance, I needed 1 5/16" offset (towards the center) to get a quarter degree.

3 BID layup was done on a piece of wax paper, then cut in half (one for each side) and applied after painting a bit of epoxy on the strut ends.

Here's the 3 BID layup going on the strut ends. This is one of those layups where you spend about 4 or 5 hours getting ready for it, then, do the layup in less than thirty minutes.

Once the 3 BID "pad" was on the strut (you can see that I marked the strut for material removal and hole drilling before I applied this) it was squeegeed and left to tack cure. The lines for the holes and the extra material to be cut off show through the MGS epoxy and 3 layers of BID pretty well.

The plans say to wrap this layup from one side, around the back, then onto the other side. I did this before removing the extra material, and, applied some strips of peel ply to keep the front of the layup from popping up, off the strut, and to help make a nice transition onto the lower (or upper) part of the strut leg without a bump on the strut where the 3 BID layup starts.

I used 2 decent sized pieces of 3/4" plywood and 4 clamps to make the pads. Clamping pressure was pretty easy to adjust this way to get the right toe in.

With the laser pointer one, and the center marked correctly (there is a pencil line under the red laser light you can't see) I could then move the laser out to the ends for alignment adjustment.

This laser device makes a horizontal or vertical line. I used the vertical one (it's not vertical, but, that's not important here) and lined the laser line on top of the board, almost exactly the same height as the clamping pad center, up with the line on the board that indicated the right distance in for correct toe-in. My son read the lines and I adjusted the clamps until we had it right. Once both sides were set, I shut the door and told everyone don't go in for 6 hours or so! I sure hope this turns out right, no chance to change things now without sanding that whole pad off!

Once the 3 BID pads were cured, it was time to drill the holes for the axles. A long 1/4" drill is the way to do this. I did drill smaller holes, starting from well-aligned, center-punched marks but this sort of thing just works better if you finish drill the holes to size with the axle "installed."

My daughter wanted me to take a picture. I have the axles and wheels mounted in this shot, but no brake calipers or discs yet. I'll have to trim the strut first.

I used the template I made for locating the holes for drilling to re-mark the sections of the strut that would need to be removed for caliper clearance. I purposely added all four bolts, and, marked both sides so there was no chance of removing too much material or the wrong sections. If I did, it may mean a do-over on the entire strut....

This job was a pain. The plans say to use a Dremel but I figured that would just melt the strut because I didn't have any sharp bits handy. Instead, I removed the strut from the fuselage (it was darn hard to cut sticking way up in the air like that) and used a combination of a hacksaw (down to the next picture please)

...my Fein sander with the HSS blade installed

(down to the next picture please)

...my belt sander

(down to the next picture please)

...and a couple of different files, like this rat tail. It took a while, but eventually I had the strut end shaped to allow clearance for the brake calipers but left all of the material for the strut that I could for strength.

Here's a shot of the strut end with the caliper installed. I will probably still sand a bit more off the entire cutout to make sure I have plenty of clearance, but, this is far enough for proper functioning of the brake caliper as the pads wear.

Here's a shot of both strut ends, after trimming and drilling, with the strut re-mounted in the fuselage once again. I'm pretty happy with my cutouts, they turned out pretty good. I ended up drilling the holes in the strut to 17/64" rather than 1/4" (it's 1/64" in diameter too big) to allow the bolts to be installed and removed without having to hammer them. 1/4" just doesn't give any wiggle room.

Once the cutouts were complete I re-installed the entire wheel, caliper, disc and axle assembly to make sure everything fit ok. I will need to flox the axles on, after laser aligning them again for proper toe-in, because the 3 BID pad just didn't have enough give to make a flat spot for the axle.

When I do flox on the axles, I will need to also flox on the backing plate. The plans say to make this 2 1/2" square, and I did. The leaves some corners hanging over past the cutouts on the strut. I pencil marked these sections then trimmed the backing plate to the same shape as the cutout.

Given the 3 BID layup didn't have quite enough give to make a pad for the axle with the right toe-in, I needed to make sure the alignment was right when I floxed them on. I used a similar setup as I did in earlier steps, with slight modifications. This shot shows the laser level clamped to the inside of the wheel, and, if you look closely at the other end of the workshop, my spline, with marks penciled onto it, with the red line of the laser shining on it. I had to block the windows to see the laser, but, tightening the front and back sets of bolts until I had correct alignment did the trick.

I re-made the backing plated because I did not like how the squares turned out. I ended up with strange corners and this just didn't look good. These round backing plates fit nicely against the cutout made for the strut for the brake calipers.

I applied a whole lot of flox behind the axle, after covering it with packing tape and covering the bolts in petroleum jelly. The hardware store nuts are acting as spacers to take up the extra bolt length.

I did this assembly with the brake calipers not included, but, I did install the wheels. This allowed easy access to the bolt heads and made a nice surface for the laser level to rest against (both side of the inside rim of the wheel.) Once this assembly cured, I dis-assembled, then re-assembled it, without the packing tape or petroleum jelly on the bolts and did install the discs and calipers.

I will probably stop here on this step. I don't want to install the brake lines until I figure out exactly how they will run up to the brake pedals and cylinders.

That's as far as I have gotten, to date, on this step. Click here for the Landing Brake.