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Getting on the mains - explained for the next guy.

Phil

Well Known Member
I've heard a few folks talk about the painful process of getting the gear installed on the airframe. Typically the pain revolves around getting the gear fully inserted in the tube, getting the holes drilled, then getting the gear out to deburr before going back into the mounts for the final time. I've even heard it involve hair driers to heat up the tubes and use of pipe wrenches (really) to remove them.

This weekend we tackled the task ourselves and were prepared for the worst - but it was actually a great experience.

Here's how it went down:

Prep Work:
1) With the gear legs on the bench, go ahead and ream the hole in both of the gear legs with a 7.9mm reamer.

2) When the time comes for you to insert the legs into the tubes, you'll have no idea where the hole resides and this can make alignment really frustrating. We marked the top of our gear legs with a magic marker to show us the orientation of the hole through the gear leg. This way we could look down the mount tube and align our marked line with the holes in the mount. This eliminated some guessing about where the holes are and if the gear leg became bound in the mount it would allow us to make some reasonable guesses about the direction we needed to twist the mount to bring the holes into alignment.

3) Go ahead and ream the top hole only of the mount. This will leave only the bottom hole of the mount too small.

4) Deburr as required.

5) Go ahead and mount the wheel pants bracket, brake caliper mount, and the wheel/tire assembly to each of the gear legs.
Go Time:
1) We put the fuselage on a workbench that straddled the gear mounts. It'll take 3-4 guys to comfortably lift the fuselage up. My workbench is [corrected height]34.5 inches. I can get the exact measurement tonight if you'd like.

2) The fit between the gear legs and mounts are pretty tight. We wanted to remove all of the rust particles that might cause binding so we polished the gear legs and mounts with scotchbrite. They cleaned up nicely.

3) We lubed the gear legs and mounts with Aeroshell #6 grease.

4) The gear leg slid into the mounts like butter and we could manipulate them very easily. We used a punch to pin the gear legs into position and roughly align the holes.

5) Since the bottom hole of the mount was the only one that needed reamed to size, we decided to sneak up on the correct hole size. We drilled the entire assembly with a "N" size bit.

6) Then we tried to insert the 7.9mm reamer into the hole so we could get to the bottom one. But we found it wouldn't work unless the legs were aligned absolutely perfectly. I ended up using a hunt-n-peck method for getting the hole aligned perfectly. I used an undersized punch to feel my way around the edges of the top hole in the mount. I was feeling for the gear leg and slightly rotating the gear leg until the transition from the mount to the leg was smooth. At that point the 7.9mm reamer dropped right in. It took all of 2 minutes to get each one aligned using this method.

7) We dropped the reamer in, attached the drill, and reamed the hole.

Note: You can't chuck the reamer first and still fit the reamer and drill into the hole. Which is why pre-drilling the top hole and gear leg early in the process is so nice. You can buy back a few inches and drop the reamer all the way to the bottom of the hole and then mount the drill. :)

8) After reaming we removed the gear legs to deburr, but we probably didn't have to. The reamer made them perfectly clean.

9) We re-inserted the legs (like butter again) - and attached them with the hardware.
I didn't have both wheel pants and brake calipers mounted so it took us some extra time. I only had one done at the time of install but if I had all the pre-work done it would have taken about 1.5hrs to get up on the mains.

It was much easier than we anticipated and if I had it to do again I wouldn't change anything. This was a very easy process.

Phil


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1) We put the fuselage on a workbench that straddled the gear mounts. It'll take 3-4 guys to comfortably lift the fuselage up. I think my work bench is around 42 inches. I can get the exact measurement tonight if you'd like.

There is even an easier method. I have standard EAA workbenches that are 36" tall. The nose wheel is only a couple inches off the ground. Just tip the fuselage and rest the weight on the nosewheel. My son and I were able to do this, then my wife simply slid the table out the back. We probably could have rolled the fuselage out further on the nosewheel, but is was 10 degrees outside and I didn't want to open the hangar door.

bob
 
Thanks Phil

Thanks for those tips Phil. I'll be doing this in about 1 month.
 
Thanks, Phil!

I know this post was from awhile back but I wanted to thank you for the write up Phil. We used your method and we had the mains on in less than 30 minutes. I was thinking this would be a big event but it was a piece of cake.

Two of us were able to lift the fuse up onto an EAA bench and from there we just slid the gear legs up into the mounts. They went in nice and easy. Having everything prepped as you suggested was the key.

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I did nearly exactly that and it worked beautifully. My fuselage was up on sawhorses so we had access all around the gear mounts. The hard part for me was aligning the gear leg to the mount tube initially so it would slide in. Once I got it right, in like butter as Phil said. I initially left off the wheels and brake mount bracket but (important!) left the axle nuts on to protect the threads - it's too easy to drop a gear end while trying to move them gently around the fuselage. A blanket on the floor is also good insurance. Once the legs were in, I mounted and drilled the brake mount brackets and installed the bolts so the heads were forward. A side benefit is that the bolts now 'clock' the gear leg to help decide where to drill for the cotter pin even with the legs off the fuselage.

Since this seems like a good place, I'll point to my web page showing how to assemble the wheels. It's not hard but doing it methodically makes it much quicker and easier. Then the wheels can go on and the axles drilled for the cotter pin. On the RV-6A, I drilled them in place with a hand drill, which is no way to do it. I went through several bits and a lot of blue vocabulary. For the 10 I removed the legs and used a friend's mill. Even a drill press is a better option. Here's my writeup in a recent thread. I see I didn't mention why I drilled from both sides; if you try to drill straight through, you're liable to miss the hole in the axle nut on the other side. Drill bits wander slightly.

I put my -10 on the nosewheel at the same time as the mains and I expect others will do so as well. The nose gear assembly is easy and I found no 'gotchas' following Van's instructions with two exceptions. Before assembling the gear leg to the engine mount, ream all the bolt holes on the gear leg. There was also a bit of flashing on the engine mount that I removed with a dremel and then the bushings slid right in. The second problem was getting the elastomers compressed enough to get the WD-1015 in place. I hoisted the tail until the mains were off the ground but without the engine in place, there was simply not enough weight. I ended up adding a ratcheting cargo strap wrapped around the engine mount and gear leg to compress it that final bit.

The last thing I did before installing the wheels was add the brake and wheel-pant mounts. Then the wheels were installed (I used the replacement nosewheel and axle from Matco) and I did the nosegear compression - the wheels acted as cushion in case something slipped. With the tail hoisted for the compression, I simply slipped the remaining sawhorses out from under the fuselage and it was free standing.
 
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