Main Gear Alignment, part 2 (4)

4 hours

Back at the main gear again.  After some pondering, I decided I might as well use the full length of the gear legs and take advantage of the higher deck angle that they will provide on landings.  I tapped both legs back down to nearly flush with the engine mount, and then started working on setting the alignment.  This is the method I used to set both the toe angle and ride height at the same time:

1. Level the fuselage in both directions.
2. Clamp an 8' piece of angle (I used 1" x 1" x 1/8" aluminum angle from Home Depot) to the bottom of the lower longerons so it extends above both axles.
3. Clamp a ruler vertically to the angle so it extends down to the very center of the outboard end of the axle.
4. Put a level on the angle to check that it's horizontal, and a level on the ruler to check that it's vertical.
5. Measure on the ruler to the top edge of the angle, and that's the dimension that the plans refer to.
6. Repeat on the other side.

So that was how I set my ride height.  For the toe angle, I continued like this:

7. Install the little spacer sleeves on each axle that come in the kit.
8. Make some spacers out of scrap bar stock that are at least as long as the axles (7" was good), and thick enough to offset your straight edge forward from the axle to clear the weldment.
9. Find the most rigid, straight, at least 7' long thing you can (I used 2"x2"x1/8" aluminum angle from Home Depot...  Steel would've been better but they only had it in 6' lengths which isn't long enough).
10. Clamp the spacers to the angle stock, and then clamp the whole thing to the front side of both angles.
11.  Tap the axles forward or back until the spacers on the angle stock touch both the little spacer sleeve and the end of the axle.
12. Check that the angle stock is level in both directions.  Left-to-right probably isn't a big deal, but making sure it's level front-to-back ensures the angle is actually sitting on the front of both axles.

13. Then re-check the ride height again, since rotating the axles will change that measurement.

I went through many iterations of this, until I was satisfied that the ride height was equal on both sides and the toe angle was correct.  I ended up with one leg flush with the top of the engine mount, and the other one about 2mm up from that.  That gave me a floor-to-axle distance of 462mm.  The plans dimension is about 424mm, so that's almost 1.5" of extra clearance!

Here are a bunch of pictures showing the steps outlined above:

Measuring the floor-to-axle distance

The axle weldment is in the way of a straight line from the axle tip to the spacer sleeve, so you need a spacer thick enough to get your straight edge forward of that.  As long as the spacers you use are the same on both sides it won't affect the alignment.

Measuring down to the axle

If this piece of angle is horizontal, and the ruler is vertical, then that's the measurement!

Here's the spacer I used on each side to get my chunk of angle across the front of both axles without touching the weldments

Checking and rechecking everything many times!

If this angle is level front-to-back, that means it's on the front of the axles and not rotated partially underneath them.

I ended up with the right leg flush...

... and the left leg about 2mm up.

With all that geometry finally set, I drilled through the front of the engine mount into the legs.  This was a pain.  I needed a long bit to drill there since the engine mount itself partially block access to the hole, so my choices for drill bits were limited.  I found a random ~6" long 1/4" black oxide bit in my tool box that actually did a decent job, but it was only long enough to drill like three quarters of the way through the leg.  I have a long hex bit extension that worked, but I could only use bits in it with a hex bit on the end.  I tried a titanium "metal" bit that I had with a hex end, but it didn't work very well.  I figured maybe black oxide bits were the best bet, so I went back to HD and bought a long 12" black oxide bit.  That thing didn't work at all!  They had some other "hard metal" cobalt bits there, but they were short and none had a hex bit end so I couldn't use them.

Anyway, what I ended up doing was just use that random bit that actually worked as long as I could, and then suck it up and use the bit with the extension for the last part.  Eventually I finally got both holes drilled, but it took about an hour per hole!

Lastly, I installed the hardware!  I have heard these bolts can eventually break inside the gear leg under some circumstances, so rather than using just a cotter pin and castle nut, I bought bolts that are drilled on both ends (AN4H30), and safety wired both ends together.  Hopefully now if the bolt happens to break it'll at least not fall out.  I will probably do what some others have done and just plan to replace this hardware as part of each 100 hour inspection.  I might do the same thing on the lower bolts too, I just don't have the drilled bolts for that yet.