[gpiney]

I have hit another hurdle. I am trying to figure out how to do the gear leg alignment on my -8. I have read Vans instructions. I have searched this site for posts and gone to a number of websites looking for a simple, step-by-step way to set the alignment. For some unknown reason, I can't picture the geometry in my head.

Thanks in Advance,

 

[nzrv8]

I think the Van's method is overly complicated..

The two important things to achieve are -

1 - The faces of the gear legs where the axles bolt on need to be parallel in relation to each other.
2 - The axles need to be the same distance from the rear of the fuselage.

The way I did it (Borrowed from VAF forums, of course!) was to drill and loosely mount the gear legs using the single bolt as per Vans instructions, I then took two 4ft pieces of angle and matched drilled them in the centre to the axle mounting bolt holes, then bolted the axles and the angles to the legs (The longer the angle, the more accurate the result - 6ft seems to be the most common, I used what I had).
Then I picked a central point on the rear bulkhead (Tail wheel spring mount is a good place, if you have this mounted already), and used this point to measure up to each gear leg using a taut tape measure. I then moved the legs around until they were parallel with each other, by measuring the distance between the clamped angle pieces at the front and the rear, and the same distance from the rear of the fuselage.
This method I think is the most simple, and doesn't require the fuselage to be level. I leveled my fuselage anyway, and double checked my results using the Vans plumb bob method, but turns out I didn't need to . Gear leg alignment for me was a non-event, thanks to the info on this forum! Good luck!
Hugh

 

[Berchmans]

Gear alignement

I did the same as the previous post but went on step further. I cut a piece of plywood to the exact dimension between the gear legs and dropped that into the angle iron. I then I proceeded to drill the holes. With the ply in place the gear legs cannot move while you are working drilling the holes.

 

[don.olandese]

for gosh sakes get this right!

i flew a CAP D-model bird dog years ago on a skinny little runway in california and during rollout the **** thing headed for the weeds with no warning and no apparent crosswind. i almost lost it, and probably would have, but my instructor powered out of the near-disaster and the only result besides my deflated ego was a bunch of people coming out of the tiny terminal building to see what had almost rattled the shingles off the roof. we later discovered this bird dog was more squirrelly than all the rest for the most mundane of reasons: wheels were badly out of alignment. i now trust smarter people than me to get these details right.

 

[gpiney]

The Deed is Done

Well, I managed to align my gear legs. All by myself. I didn't take any photos, but I may go back tonight and take some. I will try to do a 'step-by-step' explanation here.

Tools Required:

2- 3ft pieces of Aluminum angle. I bought at Home Depot. 1.5"x1.5"x3' $10
3 - Plumb Bobs. I like the expensive Brass ones. Easier to see the point.
2 - 3" C-clamps
1 - Torpedo level. Mine is a Craftsman Digital I got for $20
2 - Tape measures. One should be 20+ft, the other 6+ft
1 - Rubber mallet
1 - Step Stool. Once the gear is on, it is up there. And I am 6'3".
1 - Sharpie and notepad

OK, on to the job at hand. This assumes you have followed Vans instructions completely up until the 4 plumb bobs. You don't need 4 plumb bobs. I did level the fuse per plans.

1. Measure and draw a center line on both pieces of angle. All the way around.
2. Position each angle on the outside of the gear legs flush with the top (bottom) of the leg. The centerline of the angles should show through the
axle hole. Get them as close to centered as possible and clamp them to the legs. I clamped them on this way _| |_.
3. Level the angles.
4. Measure the distance between the angles, fore and aft. This is at the most forward and rearward point of the angles. In my case, the 'fore' distance was shorter than the aft.
5. With the mallet, lightly tap each gear in the direction of the Longer measurement. I tapped mine 'aft'.
6. Repeat steps 4 and 5 until you get equal measurements fore and aft. My final measurement was 65-3/16". Your gear is now parallel.

Now we need to make sure the legs are equidistant to the tail (square to the fuselage).

7. Attach plumb bobs. I strung from the forward lower axle mount hole on the legs and the 'tooling' hole in the tail per Vans.
8. Measure each distance. On my first pass, the right side was 13' 10" and the left was 13" 10-1/2". I split the difference and my goal was 13' 10-1/4".
9. Tap the short leg forward and the long leg aft.
10. Repeat steps 8 and 9 until each side measures the same. Mine are actually about 1/16" apart.

11. Now go back and repeat steps 4 and 5 to make sure they are still parallel. I got real lucky and they were still 65-3/16" fore and aft. If you do have to make adjustments, you have to repeat steps 8 and 9 again after they are parallel..

12. Use a sharpie to mark around the gear leg on the bottom skin per plans.

13. Tighten down the installed gear bolt so the legs won't move. Per plans.

14. You are Done.

I hope this helps all future -8 builders.

 

[TerryWighs]

I have pictures on my builder website that shows this step. You don't need to fabricate the angles everyone seems to be using? Check out the fuselage link date 9-12-10... If you have questions send me an email and I will explain further. Took me a while to figure this one out. My accuracy came within 1/32th of an inch.

 

[gpiney]

Everything is Square with the Angles

Terry,

The one thing that the angles do for you is to guarantee that the gear legs are absolutely parallel to each other. Vans method assumes they are.

 

[scsmith]

Wait! This is not good enough...

The two important things to achieve are -

1 - The faces of the gear legs where the axles bolt on need to be parallel in relation to each other.
2 - The axles need to be the same distance from the rear of the fuselage.

There is one other criterion that must be met. You want the angles to be parallel to the centerline of the fuselage. By following the procedure outlined here, this is not guaranteed. You can easily end up with the left gear toed outward by two degrees, and the right gear toed inward by two degrees (parallel to each other) and equidistant from the tail wheel, but now both wheels are two degrees off of fuselage center.

You would notice this flying. And it is easy to end up this way because Van's gear legs are not perfectly formed and are slightly twisted. Ask me how I know this can happen!

I worked very hard to get the axles equidistant from the tail wheel, and compromised on the two angles being parallel, to get both angles closer to exaclty perpendicular to the fuselage centerline. I ended up with about a half-degree of toe-in on one, and one degree of toe-out on the other, and then I shimmed both of them to get them both straight. My alignment ended up perfect, confirmed by measurements, uniform and minimal tire wear, and rolls straight.

 

[gpiney]

I think Vans expects minor toe-in/toe-out issues. That is why they sell the shims.

Before I drill my first hole, I am going to get my Tech counselor over to 'check my math'.

 

[TerryWighs]

Greg,
There is no assumption here with the legs. The outer leg plumb lines are dropped from the leading edge/corner of the gear. Both of these outboard plumb lines must be dropped from the exact same location on right and left gear. This forward gear leg surface is flat. Put them on table top, and you will see that there is no taper. The critical plumb line is the outside one on the forward corner of the legs. Distance from these lines to the rear bulkhead center hole plumb line must be exactly the same distance. This "squares" the legs. The toe-in-toe-out issue is resolved by making sure the forward four plumb lines fall exactly on a straight line on the floor. The inner leg plumb lines just need to dropped from the same forward surface of the leg, and don't necessarily have to be the same distance from the outboard plumb lines. It goes without saying that the further apart these inboard plumb lines are dropped from each outboard leg lines...more accuracy results. Draw this out on paper...it works. I am not familiar with the popular modifications with the Grove gear, but the ones I have seen online appear to have tapering surface on forward and aft surfaces. You would have to use the angle method on these types of gear modifications. I am not the best writer and hope this makes sense.