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11-09-2008, 11:27 PM
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Join Date: Mar 2006
Posts: 86
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landing gear alignment
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.

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11-09-2008, 11:56 PM
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Join Date: Nov 2006
Location: Rockford, IL
Posts: 501
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Quote:
Originally Posted by flyingbeaver26
Is it normal to (t)rim away a bit of material in this area?
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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.) 
__________________
Buck Wyndham
Northern Illinois
RV-8 N18XL
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11-10-2008, 01:13 AM
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Join Date: Dec 2005
Posts: 976
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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
From eMail correspondance between myself and Van's:
Quote:
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/communit...ead.php?t=2013
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Edited reply from Van's:
Quote:
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:
Quote:
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:
Quote:
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.
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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: - The outboard face of the Gear Legs (where the axles will bolt) are parallel to each other
- The outboard faces of the Gear Legs are parallel to fuselage centreline
- 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  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
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
Better (but move the bars to the outboard of the legs): 
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11-10-2008, 01:37 AM
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Join Date: Dec 2005
Posts: 976
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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...
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11-10-2008, 08:20 AM
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Join Date: Jan 2005
Location: Houston, TX
Posts: 868
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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/communit...=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!
__________________
John Bixby
RV-8 QB sn 82030 - 1750 hrs
O-360-A1D/CS/Pmags
Houston, TX
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11-10-2008, 09:28 AM
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Join Date: Mar 2006
Posts: 86
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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
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11-10-2008, 09:53 AM
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Join Date: Dec 2005
Posts: 976
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Brad...
Quote:
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But they should be parallel right? no toe-in? I guess the toe-in is built in later in the project with shims?
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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
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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11-10-2008, 11:23 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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I suspect your legs are in the wrong place.
Listen to Andy. Forget the plumb bobs. Use the angles. Get them dead parallel with both legs the same distance from the tailwheel spring mount.
There are some drilling tips and a photo here:
http://www.vansairforce.com/communit...ht=brake+lines
Note the photo shows Grove gear with larger brackets. They do need skin cutouts, but steel legs probably don't.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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11-11-2008, 07:27 AM
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Join Date: Jan 2005
Location: Palm Bay, FL
Posts: 420
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Aligning RV-8 Gear legs and axles.
I have photos and text showing the issues you have mentioned and the solution. This photo session is from the second RV-8 builder I have assisted in the Chattanooga, Tennessee area.
http://www.n2prise.org/champ004.htm
__________________
Jerry K. Thorne
Built in East Ridge, TN.
Now in Palm Bay, Florida
RV-9A - - N2PZ
www.n2prise.org
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