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Old 02-28-2011, 02:24 PM
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Phil Phil is offline
 
Join Date: Nov 2006
Location: Waco, Texas
Posts: 1,656
Default Getting on the mains - explained for the next guy.

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



Last edited by Phil : 02-28-2011 at 04:38 PM.
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