What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Toe In/Toe Out Adjustment info

More than likely the gear leg was not aligned properly when it was drilled. All of the early -4's & -6's did not come with pre drilled gear legs, aligning them and drilling was a real chore. I had this problem when I built my -6, it went through tires pretty quick. I eventually swapped the mount and gear legs for a factory drilled set when they became available. I don't know if pre drilled mount/legs were available for the -4.
 
Last edited:
George those new drilled legs would not fit your actual engine mount... if available, call Vans, you?d need new legs and engine mount, advantage would be in getting a reinforced mount.
 
The archives are your friend

There are numerous discussions regarding misdrilled, oversized and worn bolt holes. You would essentially turn the gear leg to proper alignment ( assuming the bolt hole is not too loose.),then weld a split sleeve (with bolt holes) on the mount in the proper orientation.
 
George,
Your problem is a combination of the gear leg AND the engine mount being misaligned during drilling. A pre drilled gear leg ONLY would not solve your problem. As others have suggested, your best bet is to bite the bullet and go for a new pre drilled mount/gear leg combo from Van's. You will get the improved strengthened mount, and you could also upgrade to the tall gear if you wish. Probably due for engine isolators while you're at it.
Good Luck!
 
Caviat !

The mount holes in the fuse were probably transferred from the original mount. There could be some variance that would create excess bolt clearance if/when reamed to the new mount. Maybe the mount fabricator will chime in here regarding " one fixture from the first mount" or not ?
 
In our case, the gear toed out when the engine mount cracked and begun to split apart at the gear leg sockets. The plane became very difficult to push around on paved surfaces.
It still landed fine...
 
Gear

The fix itself is relatively simple. It is very time consuming because the mount must be removed to do the job properly.
The holes in the mount are elongated with a file. Short, heavy wall 4130 bushings are machined to length. 3/8" long is a good size. The gear leg is bolted in place with longer bolts and a bushing on each end. The gear is clamped at the axles to achieve the proper toe and camber. The bushings are then tack welded with tig or mig. One very small tack, then let it cool. Then repeat as necessary. At least two small tack welds on each bushing. If this is done very carefully the heat treat of the gear leg will not be affected.
An alternative to the bushings is to cut "washers" from a piece of heavy wall 4130 tubing. The washers are a bit easier to finish weld than the bushings.
To avoid distorting the gear sockets machine a couple of heavy washers that are a snug fit inside the gear socket. Fit the washers to a short piece of threaded rod, with the washers spaced about 3/4" apart. These will only be used for the finish welding, with one washer on each side of the holes.
The bushings or doublers should be reamed to a snug fit on the AN bolts. This usually requires a reamer .002 under the nominal size. One source for the reamers is MSC Supply.
The Wittman gear is only in perfect alignment at one aircraft weight and fuselage angle. If the gear is aligned with the fuselage level, the toe will change with the fuselage in three point attitude. With a tailwheel as weight is added the wheels will toe out.
 
George, flipping the RVator pages found this advice:
Aligning Gear Legs [10/94]

There is a fix (to a degree) for those whose gear legs did not come out in alignment when drilled. Even though all kits are now supplied with drilled gear legs, there are still many in the field where the builder must drill his own. In other cases, bent gear legs must be straightened, and it is almost impossible to do this so precisely that the original bolt holes still align when the axles are in the right place.

The answer is AN 385-6 taper pins. To install these pins the gear legs must be aligned properly (even if the original holes no longer line up) and reamed with a Brown and Sharpe #2 reamer (available from Aircraft Spruce). Start the process by using a chain saw file to file the hole in the mount until the entire hole in the leg is open. This of course will leave the hole egg shaped. Use the reamer to open the hole in both the leg and the mount until it is completely round on both ends.
 
George, flipping the RVator pages found this advice:
Aligning Gear Legs [10/94]

There is a fix (to a degree) for those whose gear legs did not come out in alignment when drilled. Even though all kits are now supplied with drilled gear legs, there are still many in the field where the builder must drill his own. In other cases, bent gear legs must be straightened, and it is almost impossible to do this so precisely that the original bolt holes still align when the axles are in the right place.

The answer is AN 385-6 taper pins. To install these pins the gear legs must be aligned properly (even if the original holes no longer line up) and reamed with a Brown and Sharpe #2 reamer (available from Aircraft Spruce). Start the process by using a chain saw file to file the hole in the mount until the entire hole in the leg is open. This of course will leave the hole egg shaped. Use the reamer to open the hole in both the leg and the mount until it is completely round on both ends.

Good advice. I've done it on two airplanes. I clamped long pieces of angle iron to the brake discs and compared the distances between them fore and aft and also to a snapped center line. Tweaked gear legs in their sockets til happy with the alignment. I had to take most of the weight off off the gear with an engine hoist hooked up the the engine mount to prevent the gear leg moving up in the socket. Filed and taper reamed holes as above and taper pins fitted. They both taxi and land straight. Before - not so much.

Ed Holyoke
 
As these legs are a combination of two angles, one back and the other one to the side it can be tricky to get all the static load out of the wheels when you are measuring the toe in/out. Jim Winnings used a simple ingenious method to make sure all the "forces" were out of the wheel when you made set your gear legs before drilling.
He took four heavy metal plates, two per side, about 16" square. Oil was added between the plates. Now roll the airplane onto these plates, two each side. Almost immediately you will see the top plate move until all the stresses are out of the gear legs. Now you can set your wheel angle and be confident that it will reflect what is actually happening when the wheels hit the runway. I have a set of plates myself and they really to help in setting gear leg angles before drilling. You will know if you got it right by how easily the airplane pushes around the hangar floor.
I miss Jim Winnings, he was old school brilliant.
 
Last edited:
Back
Top