landing gear alignment

[GAHorn]

George, I seem to recall you making a comment a while back that your 170's wheels were "perfectly aligned". After reading all the posts on this topic, I can understand how you could & would make such a comment.
"Perfect" is a subjective term, I guess.

Eric

I got lucky. It came that way. (Of course, Bill Goebel spent 17 years working on it. I guess he should have gotten something right!)
(FWIW: My left axle has two shims of unknown PN, and my right has only one. My definition of "perfect" is: No measureable toe in/toe out and no noticeable camber.)
I will say this, a straight (not warped or "coned") brake disc does indeed make an excellent reference to measure camber. The tire interferes with getting a good straight-edge/level on the wheel itself.

[zero.one.victor]

George, take a closer look at your abacus-- 1/16" equals .0625", not .006" (6 thousandths). You're really blowing holes in your credibility for that "perfectly aligned" claim!

Eric

[GAHorn]

George, take a closer look at your abacus-- 1/16" equals .0625", not .006" (6 thousandths). You're really blowing holes in your credibility for that "perfectly aligned" claim!

Eric

Yeah. Sorry, that was a typo. But the statement is still correct as regards the available shims necessary to change your setup, which was the point. (I had rounded the 0.0625 my calculator gave me off and ,..then misplaced the decimal.)

To say the shim's
sole purpose is to adjust toe-in + camber isn't (I think) quite
telling the whole story.

The measuring procedure isn't that big of a deal. I suppose anyone
who thinks it's not crucial is welcome to that opinion.

I don't recall saying shims had a "sole" purpose. But Cessna certainly doesn't describe any other purpose for them other than for toe in/out and camber.

I don't know why folks keep trying to make it seem I'm saying something I'm not. I didn't say it wasn't crucial. I said it doesn't affect toe in/toe out specifications. Whether you have gear legs that point 'em 10-degrees or even 90-degrees to the right, shims are not the correct fix for such wildly bent gear legs.
Certainly the shims (like any shims) are for correction of minor manufacturing differences, and such corrections are important. Cessna consideres it important enough to even stipulate the weight of the aircraft when taking such measurements. But to suggest that a measurement taken from the tailwheel forward to the axle-line is necessary in order to set toe in/toe out is simply not the case. (In an example just as wild as some presently suggested, a string stretched from the tailwheel to the main wheels makes the assumption that the fuselage has no bend it it whatsoever. Without a "jig" there's still plenty of room for error exceeding that of the intended measurement.)
This entire thread has assumed a personality of it's own, not realistically in tune with the problem. One can take a measurement from the tailwheel pivot-pin and walk that string all the way around a 360-degree circle. Just because that fixed-length measurement happens to meet at the right axle just like it does the left axle...does not mean the airplane is "square". In fact, the mismatched 180 gear legs could pass that test.....all it would take would be for one to be spread out from the centerline farther than the other....and they would both measure equi-distant from the tail reference point.
But my point is: By the time such errors are sufficiently large as to cause handling problems, they are probably quite evident to the naked eye, and ...they are not corrected by shims.

[N170BP]

I don't mean to be argumentative or belabor the point, but
if we are supposed to set our airplanes for just a tiny bit of
toe-in or no toe-in at all, why are there such a wide variety
of shims available? Some of them have significant taper indeed.

The only logical conclusion is the shims are there to adjust
for manufacturing tolerances *and* to fine-tune the toe-in.

That's all any of us are saying, along with the fact that it
might not be a bad idea to see just how straight your
axles are relative to the centerline of the airplane before
you go changing shims and playing with toe-in. Think about
it. You will have the stuff all apart anyway. Not only can you
fine-tune the toe-in per the manufacturers specifications, you
can at least attempt to adjust for whatever has happened to the
airplane over the last 50 years (at the very least, like somebody
putting the shims on backwards, which is probably what happened
to my airplane!).

[ak2711c]

George, amazingly I agree with you 100%.

If the gear alignment (not wheel alignment) is out of wack enough to make a noticible difference in the handling as in the aircraft is traveling down the run way cock eyed, then you have major structural issues that are far beyond a simple shim job. I would agree that from the factory there are small misalignments in the gear, but I would be willing to bet that if the wheels are properly aligned you would not be able to notice any difference in handling between one of these and a perfectly square plane. If it made a major difference Cessna would of said to tiangulate it ether in the manual, SB, SI, SL, or AD.
Having said all that if you want to triangulate, knock your self out. It won't hurt any thing, it may just not make any noticable differences.
Shawn

[inman]

I really have to agree that having a little toe-out is much less exciting than having toe-in. When I first got my 52 B model with the floppy straight legs, I needed to say a prayer before every hard surface touchdown because it wanted to dart off one side or another. I had huge positive camber and about an inch of toe-in on each side. Needless to say my outside tread was so thin you could almost see the air inside the tire. I got my alignment fixed and it made so much difference I couldn't believe it. I have since installed 180 gear and need to do another alignment. We should all take inventory of our extra shims and trade.

Does anyone know where I could buy rent or borrow a 100 series service manual for a couple of weeks?

[mvivion]

Yep, except old Harleys use way more oil per cubic inch than any aircraft engine ever made, including the R-2800.

Fun to listen to, fun to tinker with, but for riding, I'll stick with the Injected 03 Softail, thank you.

Go ahead, call me a weeney if ya like

Mike

[Metal Master]

I really have to agree that having a little toe-out is much less exciting than having toe-in. When I first got my 52 B model with the floppy straight legs, I needed to say a prayer before every hard surface touchdown because it wanted to dart off one side or another. I had huge positive camber and about an inch of toe-in on each side. Needless to say my outside tread was so thin you could almost see the air inside the tire. I got my alignment fixed and it made so much difference I couldn't believe it. I have since installed 180 gear and need to do another alignment. We should all take inventory of our extra shims and trade.

Does anyone know where I could buy rent or borrow a 100 series service manual for a couple of weeks?

You can purchase a 100 series maintenance manual on CD at http://www.mccurtaintg.com/S100CD.htm
Unfortunately even though it says 150 through 185 (1953 through 1962/$20) it does not actually cover the 170 series. They do have a 170 series parts catalog. The 120 through 195 seires manual for $260 which I have puchased does not cover the earlier 1949 though 1953 170 series either. I needed the manual for other airplanes. I am very soon going to be checking wing twist as well as as gear alignment on my 170 A and will be needing a manual that covers the 170 A series. Does the Association have copies of this information available.

[lowNslow]

The procedures used for the 180 in 100 series manual should work for the 170.

[mrpibb]

The 100 series manual has the shim # required for the 170, If anyone wants I can email the excerpt.
I am a big fan of doing a wheel alignments, when I bought my airplane I had zero time in tailwheel and 1 hour pic on a fresh certificate. trying to take off and land was next to impossible to the point that my instructor was commenting that he thought a airplane of this caliber would have better handleing qualitys. A week later I was performing the annual on the airplane when the previous owner walks in and comments on all the mods he's done himself, including the solid axles. When I inquired that when he did it was there the right shim combination to keep the wheels in alignment, well lets say there was a long silence. well 80 dollars worth of shims and a days work this 170 tracks as if it were on rails, landings and takeoffs all all but to easy.

[daedaluscan]

I just measured my 170B on 180 gear. I tied two straight edges to the tires, marked the middle and 75cm forward and aft, and then measured between them. This gave me 11mm more at the aft point which I calculate as 0.36 degrees of toe in. But as pointed out above I have no idea if the wheels are parallel to the a/c centre line.

I did not use grease plates or plastic bags, just as the a/c sat on the tarmac but I am taking it to a set of grease plates next week.

[FredMa]

The way I do it is with a 2x8 board and a carpenter square. Place the board on chocks to hold it off the ground and against the forward side of the both tires then use the square with on side on the brake rotor and the other aligned with the board. If it isn't perpendicular to the board it isn't square. Flip the board and duplicate your readings using the other edge of the board to ensue the board is straight.

[N2255D]

Does anyone know where I could buy rent or borrow a 100 series service manual for a couple of weeks?

Try here for a free copy. Long download. With cable took almost 5 minutes.
http://www.micro-tools.net/pdf/Cessna/1 ... _pre63.pdf