All -
So its time to finally put my project on her gear, but I ran into a problem today that has befuddled/concerned me for 4 hours and counting. I'm firing off an email to Sonex Tech Support but would also love to hear what all of you have to say about this!
I successfully got the engine-mount aligned and drilled to the fuselage last week. To get the mount pins to line up per spec, I flipped the fuselage upside-down, measured and marked everything, and then drilled it to the attachment plates/angles. Once that was done, I wound up with the lower-left engine mount attachment being about .041" higher (relative to the lower longeron corner) than the lower-right engine mount attachment. This seemed like a pretty minor difference, and the pins lined up properly so I thought that all was going to be fine. I proceeded to drill the upper main landing-gear attachments (ah, what a fun job that is), and got them in nicely. The gear legs started out the same length and both sit just flush with the upper end of the tubes that they mount in - so I figured they were almost exactly the same distance below the fuselage and everything was still A-OK.
Today I stuck the lower axles & sockets onto the gear legs, slipped the alignment collars over the axles, and taped up some spacers and an alignment bar (i.e. a sturdy wooden stick with angle-aluminum reinforcing it) across both axles. BTW I've read about the wooden U-channel alignment method, but I figured that it would be easier to use the factory method since the fuselage was upside down already. In any case, I got things set up and it looked good - until I started taking detailed measurements... I found that the right side axle was about 3/4" lower than the left axle, when measuring the distance from the center-point of the axle to the lower longeron! And even at its minimum height (i.e. with the legs bottomed out in the sockets), the right side gear is at
least 17.25" below the lower longeron (about 1/2" longer than the plans call for) :shock: I also found that there was a 1/2" difference between the axles in the fore/aft dimension! I triple-checked to make sure the whole setup wasn't skewed off to one side (i.e. not tracking down the centerline of the fuselage); but I couldn't find any evidence of this. After monkeying with a few different setups, I confirmed all of these measurements in multiple ways. I then went back and experimented with pulling the left side axle socket out from the end of the gear leg (to lengthen the overall leg). I eventually moved the left axle/socket 7/8" down the gear leg, which resulted in all of the left & right side measurements agreeing
except for the fact that the left axle is now 3/4" further away from centerline than the right axle...
So I have multiple concerns here:
- I'm trying to figure out how the geometry got so goofy in the first place. Is it possible my (factory-supplied) engine mount warped while being welded together, and my gear leg tubes are not at the same relative angle?
- Leaving 7/8" of empty/unsupported space in the left axle socket seems like a really big gap. Should I fill it with something? Or cut down the right gear leg 7/8" instead? Or at least cut down a bit of the right gear leg so that the space in the left socket won't be so big? (Of course, I'm not sure if my bandsaw will cut titanium, and I'm also worried about ruining the leg)
- Will the fact that the "centerpoint" between the two gear legs is 0.75" off the centerline of the aircraft cause noticeable problems? Obviously the spacing means the left gear leg will take more weight during ground ops (compounded by the fact that I'll be sitting on the left side flying it solo a fair bit), but are there any other foreseeable problems with this setup (despite having the wheels aligned to the centerline of the aircraft)?
Photos showing my setup:
https://www.flickr.com/photos/noel_wade/albums/72157679752596096 Has anyone else had this much of a mismatch in gear leg length/alignment when they initially bottomed out their gear legs in the lower sockets? Any thoughts or suggestions of things I've been overlooking?
Thanks a bunch,
--Noel
Sonex #1339