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Monday, December 16, 2013

Main landing gear - part 9

Wheel, brake, tire and tube (5.7 hrs)

With the left gear leg cured, and the new MATCO brake shoe in hand, it was time to finish this side.

Additional 3+3 BID plies cured

It took a lot of work just getting the bolts off, but when they went I had a much better shot at trimming and sanding the fiberglass.

A little trimming is in order

After a lengthy sanding session, I made two templates of the brake shoe attachment bracket, and used the sharpened bolts to help me locate them on either side of the leg bottom.

Leg trimmed, and brake pattern being located

Mirror image opposite side

Template in place to aid in trimming the leg end

One last check before the irreversible cutting took place

Then I started cutting and sanding. This was painful on an emotional level (as usual), but also on a physical level this time, since the gear bow is a very tough structure, and cutting/sanding it is not an easy task.

Needless to say, a mistake at this point would have been critical, as the part would likely have become an expansive boat anchor. So, tension was running high until the very end, and progress was slow due in part to the difficulty of the task, and in part to a conscious effort made to avoid cutting too much off at one time.

"Here we go..."

I had to go back and forth countless times in a nearly endless cycle of sanding, mounting the axle, marking areas to be sanded again, removing the axle, and repeat...

Trimming and sanding in increments

Here you can see where a little more sanding was necessary

But eventually I got to the point where the fit was good and the brake housing no longer touched the fiberglass leg, and I snugged all the hardware.

Caliper in their final position

These 6 bolts, and the outer brake pad, need to be removed before the disk brake can get in there.

The only thing left to do was getting tire, tube, and wheel to play nice with each other long enough to put them all together for good. This was not too hard, but it certainly required a methodical approach.

First I sprinkled some baby powder inside the tire, and anywhere rubber touched aluminum. I also put a lot of it, maybe too much, on the tube itself, to help it slide a bit better. I slightly inflated the tube, and slid it in the tire.

The red dot on the tire marks the position of the tube’s inflation valve, to help keep the tire more balanced. Marks on the wheel also require alignment with the red dot.

Valve stem in correspondence of the red dot

Baby powder is used to help things slide in their proper places

One of the issues I ran into was that as soon as I put the tire on its back, the three main bolts would fall out the back of the wheel half, making it impossible to get to them from the top. I found a roll of tape that was just the right size, and used it to rest wheel and bolts on, while I pressed hard on the top half of the wheel and tire trying to close the deal.

Perfect spacer

This will hold the bolts up as I rest the wheel upside down

Now, a little pressure will let the bolt heads through just enough to get washers and nuts on them.

The tire makes for a pretty good spring while trying to squeeze the two wheel halves together, furthermore it is imperative that the tube does not get pinched in between them, or it’s game over. I found this last part to be easier than expected, and the tube was cooperative for the most part.

Mounting the wheel on the gear leg turned out to be an exercise in weirdness though. 

Since the brake pads are mounted on the inside of the rim, first I had to separate the disk brake from the wheel, then I had to remove the 6 bolts that hold the brake pads together, next I removed the outer pad, put the disk brake onto the axle like a freesbe that had been thrown up there, then I reinstalled the outer brake pad with the 6 bolts making sure the disk brake was between the pads. At this point I mounted the wheel on the axle, snugging it down with the main axle bolt, and rotated the wheel until the disk brake lined up with the matching holes in the wheel, then bolted it down.

Removal is the reversal of the assembly.

I sure hope I won’t have to change the brake pads too often!

This wheel/brake/tire combo looks awesome!

The caliper grasps the disk brake from the inside rather than the outside

Grass strips here I come (carefully)!

Right side to go

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