The gear truss upgrade done earlier in 2021 was in order to be able to handle larger main wheels - specifically 31" Alaska Bushwheels.
Ordered the legs from Langair in January, and the arrived early April. I had a shoulder added to the leg to be able to add a step at a later date.
Drilled a small hole from the top of the gear socket down through the fibreglass (with a very long bit), then opened it up with a unibit, then a small drum sander on the end of a drill.There was some corrosion in the sockets, and some overspray. So again, with a drum sander I very carefully cleaned everything up, and then cleaned out the socket with some WD40, a rag, and a long screwdriver to push it through a few times.
They are REALLY tight. Had to pound them in the last inch with a rubber mallet. Hopefully they come out again :-)
I bought two 100" lengths of 1.5 x 1.5 x 0.25" angle for levelling the legs and setting the toe.
Next step is alignment.
There have been a huge number of posts on this subject.... but here are the goals:
- Level the legs. Each leg needs to be within 1/8" of the top of the socket, and the gear legs need to be level from side to side.
- Set the toe. For tail drawers, we want somewhere between 0.5 and 1 degree toe OUT.
With the fuselage level (by adjusting the tire pressure), I inserted the legs.
The manual states to grease them, which I did. They move steadily with the liberal application of a heavy rubber mallet.
My original plan was to clamp the aluminum angle to the outside of the axles. Yeah, bad idea. Using the forum, turn the axle around (temporarily) and bolt them to the INSIDE. Trimmed the aluminum angle down, and presto
After lots of frustrations with clamps and blocks of wood, I decided to make a platform that the aluminum angle sits on. using various shapes and sizes of wood I had laying around, I lifted the angle into position against the axle.
I achieved the initial goal of having the fuselage level, gear level, and 0 degrees toe. However, I am slightly out on the pilot side gear truss. It needs to be within 0.125 of the top of the socket, and currently it is .142. I need to move BOTH sides up slightly. 8 whacks of the mallet on both sides brought the left side into .121, and the right side is slightly proud. Level shows that the gear legs are 0.05 degrees. I am good with that.
(NOTE: The below procedure did not work. Follow up on the end about what to do to fix it.)
Inserted an .030 shim on the INSIDE of my turned around gear leg on both sides. Bit of mallet work, check level on everything again, and that should give me a little bit less than 0.5 degree of toe out. I am gong to work the math tomorrow to validate, plus I have emailed the forum for double check guidance.
I haven't done much trig in years, but with the help of google I figured it out.
Radius of the tire = 15.5" (31" bush wheels)
Axle length = 4"
At 0 degrees toe (which is 90 degrees for the triangle formula), the hypotenuse is 16.008". Adding shims to the hypotenuse, then solving for the to angle.
0.030 shim = 0.43 degrees / 0.23" of toe (per wheel - 0.46 total),
0.040 shim = 0.6 degrees / 0.32" of toe
0.067 shim = 1 degree / 0.54" of toe
I drilled everything, and pushed it outside, put on the tires and measured the toe. Definitely toed IN (not desired).
Rough toe measurements with tired on (I am going to repeat this again with angle on the ground.
Front: 102"
Back: 104"
According to this, I am about 3 degrees toe IN, which is bad.
With everything apart and back in the garage and levelled, the legs are again slightly toe OUT.
The only good news is the legs are exactly level.
I am going to stop working on the gear at this point. I think once the wings, engine, panel, interior, etc are all installed the toe measurements will again change. So there is no point fighting this now, just to fight it again later. My gut says that once there is weight on the gear, the toe will go out, but I don't know how much. Shims are available to change the toe angle, but I don't know which ones to buy.
Moving on to something else...
