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  #1  
Old 08-25-2013, 08:08 PM
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tkatc tkatc is offline
 
Join Date: Nov 2007
Location: NJ
Posts: 1,747
Default Landing gear alignment?

Anyone have a good write up of how they did the landing gear alignment? I'm using the grove airfoil gear so it is slightly different than Van's stock gear but very similar. I've searched here and google along with the usual sites but haven't stumbled upon one that fills in all the blanks. "Alignment for dummies".

I have 2 pieces of 8' angle from Home Depot waiting to be put to good use. I plan to clamp them to the gear and start measuring from different points but I DO NOT want to screw up this very critical step. I have zero tailwheel time as it is...the last thing I need is misaligned gear.

I assume I'm only aligning 2 planes:
1. They must be parallel so the wheels are aligned to each other
2. They must also be aligned with the centerline of the fuse.

Do I have that right? Parallel to each other seems easy enough...but parallel to the fuse raises more questions than answers. I've been thinking about running a laser line down the belly of the inverted fuse and take measurements from that...
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Last edited by tkatc : 08-25-2013 at 09:01 PM.
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  #2  
Old 08-25-2013, 08:48 PM
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mannanj mannanj is offline
 
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Location: Mtns of N.E. Georgia
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Quote:
Originally Posted by tkatc View Post

I assume I'm only aligning 2 planes:
1. They must be parallel so the wheels are aligned to each other
2. They must also be aligned with the centerline of the fuse.

Do I have that right? Parallel to each other skins easy enough...but parallel to the fuse raises more questions than answers. I've been thinking about running a laser line down the belly of the inverted fuse and take measurements from that...
Tony:

1. Yes
2. Yes

The 8 wheel allignment is done in the final stages with tapered shims on the axle.

I measured my center line with plumb bobs dropped to the floor from the firewall and the rearmost bulkhead. I then drew an extended center line on the floor and measured from the center line outward to the fore and aft points of the angles that were clamped to the flat part of the gear legs where the axles attatch. You can use plumb bobs for this if your fuselage is upside down. You can get by with two plumb bobs. You probably could get by with only one.

You also want to get the ends of the gear legs the same distance fore and aft by measuring from the same point on the end of each gear leg to a center point somewhere on the tail, making sure both left and right measurements are the same.

Hope this makes sense!
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Last edited by mannanj : 08-26-2013 at 08:05 AM. Reason: Better explanation. (I hope!)
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  #3  
Old 08-25-2013, 09:56 PM
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Bob Ellis Bob Ellis is offline
 
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Location: Pembrokeshire, UK
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Hi Tony

I made a guide with the link at this log entry - hope it helps - flying 15 months with no obvious gear alignment issues.

Agree that final alignment is done with shims - see here
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  #4  
Old 08-26-2013, 07:21 AM
BonitaRV8 BonitaRV8 is offline
 
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Location: Bonita, Ca
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Default Good timing

Good timing on this thread, I just put my main gear legs on yesterday afternoon. Following the instructions I have the inboard U-804 brackets wear plates and gear legs mounted with the 7/16? bolts and the outboard mounts located per the print. I only had one plumb bob so I wrapped it up and had a beer while I pondered the best way to proceed. I?m going to pick up a few more plum bobs tonight and I have Black & Decker laser line thingy but don?t know if I?ll find a good use for it.
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  #5  
Old 08-26-2013, 03:54 PM
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tkatc tkatc is offline
 
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When you get it figured out...come do mine.
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  #6  
Old 08-26-2013, 09:26 PM
David-aviator David-aviator is offline
 
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Tony,

I never did understand Vans 4 string method in the plan narrative. I called and said I did not "get it", how about if I use a 3 string method? After explaining what I intended to do, the guy said that should work.

Here's how I did it.

1. Set a string over the inverted fuselage running fore to aft exactly over the center line of the machine. The string should be about the same height as the gear legs. This can be done by dropping a plumb bob to a center point at each end of the fuselage and adjusting the string on a rod or some other device that will permit moving it to get it over the center line. Attach one end of the string to a spring rather than tying both ends. The spring will keep it tight.

2. Set 2 more strings, one each outside the gear legs exactly parallel to the center line string.

3. Bolt or clamp a 4' straight edge to the outside surface of the gear leg where the wheels will be attached. Adjust the gear leg to get the straight edge parallel between the center string and the string next to it. Its easy to measure the distance from center to the board or from the outside string. Clamp the gear leg in position for a final drill when it is parallel to the strings. This could be done with just the center line string but it is easier to get the gear legs adjusted using 3 strings.

This, in theory, will give you zero toe in-out with no weight on the gear. Final toe in or toe out can be accomplished later with shims if necessary. There is no way of knowing before hand how much weight on the gear will affect toe in/out.
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  #7  
Old 08-27-2013, 07:39 AM
BonitaRV8 BonitaRV8 is offline
 
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I think I figured it out and it is not that difficult. I went and bought 3 more plumb bobs last night so I have a total of 4; a fifth one would be nice but not necessary. I have the fuselage inverted on saw horses and have it leveled in pitch and roll; I checked this with a digital level both on the forward floor like the plans say to do and on the center section of the wing spar. I hung one plumb bob from the tooling hole on the F-812 bulkhead (aft bulkhead on the tail cone; the tooling hole should be in the center of the fuselage). I put a mark on the floor directly under the plumb bob. After marking the floor I reused this plumb bob for one of the gear legs. The forward side (edge) of the landing gear legs are straight (flat) so I hung a plumb bob from farthest out and farthest forward point (fwd corner) of each gear leg and then another one further in along the forward edge of each leg; I hung the inboard ones as close as I could with out the string contacting the fuselage. Now you have four plumb bobs all hanging from your gear legs. Now you want to line up these four plumb lines so they touch the same line on the ground; Vans says to use a string pulled taught on the floor. You need to swivel the legs around on the 7/16? bolt until they are all inline. Once you are happy with the alignment you need to measure from the outboard plumb bob of each leg to the mark on the floor (or fifth plumb bob) back at the tail. You want the distances from the left gear leg and right gear leg to be within a 1/4? of each other. You will have to have to keep moving the gear legs around and lining them up and measuring to get it right. Once you are happy with the alignment you recheck the locations of the outboard brackets (U-805?) and wear plates. I haven?t drilled the holes yet but have the alignment done. I am going to do a sanity check tonight before the final drilling of the holes. Hope this helps! I?ll try to take some photos and post them.

Scott
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  #8  
Old 08-29-2013, 08:28 PM
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tkatc tkatc is offline
 
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Thanks for all the suggestions here guys. I think I've manage to come out of it unscathed. For those that have yet to tackle this....here is my build log describing my method.

http://www.vansairforce.com/communit...=86302&page=10
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  #9  
Old 09-05-2013, 01:10 AM
Berchmans Berchmans is offline
 
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Default Gear Alignment

I took the parallel line approach. I dry fit both legs on the fuselage and through the axle mounting holes I bolted two aluminum angles, about 6 feet long to the gear legs, 3 feet fore and aft. I then lined them up so the end distance was the same at each end of the angles. I then cut a piece of ply wood exactly that width and dropped it between the angles. They weren't going to move after that. With the plywood in place I proceeded to drill the mounting holes. When the axles were installed they were in perfect alignment. I now have 15 hours on the plane and 30 landings. It runs straight and true down the runway...
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  #10  
Old 09-05-2013, 06:30 AM
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Rhino889 Rhino889 is offline
 
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Worked for me.

Regards,

Scott
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