flyingbeaver26

flyingbeaver26

Active Member
Today I got around to test fitting the landing gear. I used 4 plumb bobs like the plans specify. After about 30 minutes of tweaking I felt like I got them perfectly lined up. On the left gear, the rear bolt hole in U-803 bracket is almost totally hidden under the skin and flange for the 6-32 screws to secure the cover plate. I'll need to trim away a bit of material to get access to drill the hole in this area and tighten the bolt. Before I start cutting, I want to see if anyone else out there has had this happen on their build. Is it normal to rim away a bit of material in this area? This fuse is a QB.
Thanks,
Brad
Austin TX.
IMG_3133.JPG
 
flyingbeaver26 said:
Is it normal to (t)rim away a bit of material in this area?
Click to expand...

Brad,

Yes, this appears to be normal. I have the Grove gear, and I had to make large, square notches in the skin out to about where the aft, outboard rivet is in your photo. So it looks like your gear positioning is correct.

Remember that this whole area will be covered with a fairing -- so don't sweat the big notches you have to make in your skin too much.

Good luck, and have fun drilling that steel! (Remember -- use sharp cobalt bits; lots of pressure; and a slow-speed, high-torque electric drill.) :)
 
FB26...

I think you have hit on a common problem with the RV-8 here, and I'd suggest you step back and consider the way ahead before you get that drill out :eek:

From eMail correspondance between myself and Van's:
On a QB trying to attach the Gear Legs to the Fuselage.

The inboard 7/16" hole drilled from the Steel part already built in, and the bolt inserted. Gear can now rotate about this bolt for alignment.

The necessary "plumb lines" attached to the Gear Leg LE Inboard and Outboard. However, to get the 4 plumb lines "in line" (as the instructions require) requires both gear legs rotated "aft" as far as they can go, and when the 803 weldments contact built in structure. The aft bolt is also inaccessible - I can file away material - and it just looks wrong i.e. I would expect the gear leg to fit reasonably centrally in the area provided.

I have attached 2 photos hopefully illustrating the above.

I am unsure if I have misunderstood the plans, done something wrong or whatever?!*!

Please could you clarify what the plans are actually requiring, whether I am going about it the right way etc. The following link seems to relate to a similar problem / query:
http://www.vansairforce.com/community/showthread.php?t=2013
Click to expand...

Edited reply from Van's:
The plumb bobs do make sure that the axles are in the same fore
and aft position, but the other consideration is that the axles are
parallel to each other and perpendicular to the centerline.

If there's a conflict between the fore and aft position and the
parallel/perpendicular requirement, I would incline to favor
whichever one puts the legs more centrally in the skin cut out,as that
will result in better edge distance on the longerons. If that's no
factor, give the benefit of the doubt to the p/p aspect as that
eliminates the need for shims. If one wheel is a little further forward
than the other it won't affect anything.
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Me again:
However, that DWG and your comments above at least make clear what is to be achieved. Given what you say:

* Axles Parallel to each other. See Photo below - I have clamped 2 pieces of angle to the legs (ensuring they are flush against the inboard faces of the legs in the axle area). The angles significantly diverge as you go forward - to an extent of ~2.5 degrees toe-out per leg! This would suggest they legs are angled far too far back... as you and I think. The plumb blob x 4 method is therefore not working - probably somewhere in the way I have set it up.
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Reply:
Using the angles is OK, but I
would shift them to the outside of the leg, not the inside, in case the
thickness of the end of the gear leg varies. Also, be sure to measure
from plumb bobs (fore and aft of the leg on the angles) to the
centerline of the fuselage, as well as from one leg to the other to
ensure that the axles will be perpendicular to the CL.

The misalignment using the plumb bobs on the leg may be because
of variation in the upper bend causing a twist in one or both legs, but
as long as the axles are correctly oriented to the centerline it will be
fine.
Click to expand...

Summary
Using the plumb blobs as per the plans has no logic in what you are trying to achieve, and/or makes some assumptions about the geometry of the gear legs.

The replies from Van's to me make clear (and much clearer than the plans!) what you are trying to achieve in order i.e. 1 is the most important:
  1. The outboard face of the Gear Legs (where the axles will bolt) are parallel to each other
  2. The outboard faces of the Gear Legs are parallel to fuselage centreline
  3. The ends of the Gear legs are the same distance for and aft

I am aware of at least 2 RV-8s in the UK with some "interesting" gear issues. One operates off a hard surface, and the tyres wear in such a way that he has to rotate the tyres inside to out from time to time.
The second, when we do formation takeoffs, requires me to have a very low power setting until we get airborne when I suddenly need to add a bunch of power :confused: We both heard a loud squeal off a hard surface recently as we got airborne - he heard it louder, so we assume it was him :D

Both the above seems to suggest a toe in/out problem and I just wonder if the builders followed the plans and experienced the problems we (and you) got, but pressed on...

Thoughts welcome from others ;)

PS We have ~120 hours, and over 300 landings. Most are on grass, but I'd say 1/3 off concrete. No noticeable wear on our tyres, and certainly not uneven wear... so I think ours are reasonably OK :)

Andy & Ellie Hill
RV-8 G-HILZ

Pictures:
Wrong way I think
GearOn_Wrong.jpg


Better (but move the bars to the outboard of the legs):
GearOn_Better.jpg
 
Also NB Dwg 45 (Finish Kit? Old Kit?) that shows Toe In/Out and a method of measuring it (Section 10 of the book). That is effectively what we ended up doing much earlier, albeit the angles we used "amplify" any error so easier to get nil Toe In/Out...
 
Yep, that picture looks familiar! I had the same problem with my QB 3 years ago and posted some similar pics and questions here; http://www.vansairforce.com/community/showthread.php?p=9971#post9971 Make sure you have proper edge distance on the longerons and press on.

Looking back on my airplane, I'd have to say that the landing gear installation and alignment on my -8 was the biggest pain in the neck on the whole project. I spent lots of time aligning, then re-aligning using both the Van's book method and the angle braces clamped to the gear legs. After measuring what seemed like hundreds of times and thinking everything was perfect, I still ended up with a disparity in the gear legs. One leg is just a bit farther forward than the other and I had to spend a bunch of time using shims to get the wheels parallel.

I was pretty worried about how the ground handling and runway manners would be affected, but I think it worked out okay... no squirrelly handling tendencies and tire wear seems acceptable and even on both sides. Most of my operations are from paved surfaces; I rotated my tires at 170 hours and replaced with new at 340 hours and 500 landings. I guess that'll do.

Good luck!
 
Toe in? or paralell?

Andy, Thanks for your explanation. I will definitely try clamping on a couple pieces of angle to the outside surface to check for parallelism. But they should be parallel right? no toe-in? I guess the toe-in is built in later in the project with shims? I haven't read that far ahead yet. But my next step is to bolt on the axles. So I imagine that is when it will be needed if any. -Brad
 
Brad...

But they should be parallel right? no toe-in? I guess the toe-in is built in later in the project with shims?
Click to expand...
AFAIK there should be no Toe In or Out... Section 10 (p10-1) of the Build Manual states that "..with max 1/4deg toe-in or toe-out". DWG 45 shows 3 diagrams, 1 with toe-in, one with toe-out, both labelled "incorrect", and the 3rd with no toe-in/out labelled as "correct".

I am unsure whether there is some theoretical benefit to some toe-in (or toe-out?), but if so, the Van's plans are pretty clear that they do not subscribe to this theory :eek:

Reading "jbDC9s" post, it seems he had a hard time. We would have done had we tried to maintain what the plans said. It was only after the eMails that we established what we were after, and binned the plans/plumb-bob technique altogether, that we did the fitting/drilling, and it was quite easy, and in the middle of the cutout.

Andy
 
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