scsmith
Well Known Member
When I built the RV8, I used the wheel alignment shims that Vans sells to get my wheels as closely aligned as I could. They only go down to 1/2 degree, so you can only get within a 1/4 degree of perfect. I ended up with just a very slight amount of toe-out on one wheel (something like 0.1 degrees), and the other one essentially perfect.
Fast-forward 13 years, and a silly mishap this winter when I got stuck in very soft mud while taxiing across a dirt field. The airplane didn't go all the way onto its nose, but the prop did slice into the soft mud, so -- new prop blades and an engine inspection (dial indicated crank flange, magnetic-particle inspection of crank accessory drive gear, new bolt and pin, even used "food-grade anti-seize" as specified in the AD--we are still laughing about that).
After that misadventure, I noticed right away that the airplane was a lot more skittish directionally. I just told myself I was just rusty. But I even noticed that it was harder to make it go straight on take-off, and landings were more of an adventure than they used to be, for sure. I also noticed that I was starting to see tire wear on the inside edges, whereas my tires have always worn pretty even before.
So, I checked my wheel alignment again and, AH HAH, I had a 1/2 degree of toe-out. Seems hard to believe that a gear strut would have twisted, and all the sheet metal looks normal, so my hunch is that the gear struts just got nudged aft within the bolt clearances. Measuring to the aircraft centerline, almost all of the toe-out was on one side (the side that used to be about 0.1 degree toe-out was now 0.4 degrees)
Anyway, I switched out a 1-degree shim for a 1/2-degree shim, so now I have just a very slight amount of toe-in, about 0.1 degrees.
Now, my RV8 is a pussycat! What a difference!
This isn't to re-hash the debate of toe-in vs toe-out (I believe a slight amount of toe-in is better than a slight amount of toe-out) but rather to say that you should try to get the wheels as close to straight as you can.
Fast-forward 13 years, and a silly mishap this winter when I got stuck in very soft mud while taxiing across a dirt field. The airplane didn't go all the way onto its nose, but the prop did slice into the soft mud, so -- new prop blades and an engine inspection (dial indicated crank flange, magnetic-particle inspection of crank accessory drive gear, new bolt and pin, even used "food-grade anti-seize" as specified in the AD--we are still laughing about that).
After that misadventure, I noticed right away that the airplane was a lot more skittish directionally. I just told myself I was just rusty. But I even noticed that it was harder to make it go straight on take-off, and landings were more of an adventure than they used to be, for sure. I also noticed that I was starting to see tire wear on the inside edges, whereas my tires have always worn pretty even before.
So, I checked my wheel alignment again and, AH HAH, I had a 1/2 degree of toe-out. Seems hard to believe that a gear strut would have twisted, and all the sheet metal looks normal, so my hunch is that the gear struts just got nudged aft within the bolt clearances. Measuring to the aircraft centerline, almost all of the toe-out was on one side (the side that used to be about 0.1 degree toe-out was now 0.4 degrees)
Anyway, I switched out a 1-degree shim for a 1/2-degree shim, so now I have just a very slight amount of toe-in, about 0.1 degrees.
Now, my RV8 is a pussycat! What a difference!
This isn't to re-hash the debate of toe-in vs toe-out (I believe a slight amount of toe-in is better than a slight amount of toe-out) but rather to say that you should try to get the wheels as close to straight as you can.
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