Firewall Forward

December 6-7, 2012

Finishing the Main Gear Legs - 3.0 Hours

As I continue to wrap up little tasks that have to be done before I can hang the engine, the Main Gear Legs came into focus again. I never did get around to setting the tension on the bearings and drilling the holes for the cotter pins that hold the big nuts on. So I wanted to get that done before putting the plane on her gear. It just seems to me it would be easier to do this on the bench than down on the floor. All you have to do is find a way to hold the gear leg tightly to the bench so it won't move while you work on it. I temporarily screwed this block of 2 x 4 to the workbench, and drilled a 3" wood screw through the leg into the block. This held this end of it very securely.

The other end was simply clamped to the workbench with my clamps. This wasn't completely rock solid, but good enough to do the job.

I read the instructions in the Matco booklet very carefully several times, and then proceeded. I've been mulling this over in my mind for a long time. Now all of a sudden, it doesn't seem like such a big deal. Just read the directions and go for it. The idea is to tighten the big nut enough so that the bearings remain stationary on the axle while the wheel turns around them. The bearings are NOT supposed to turn on the axle. It seems to me that part of discouraging the bearings from turning on the axle is to not have any grease under them, on the axle. So after drilling the hole for the cotter pin, I took it all apart and took the wheel off the axle and pulled the bearings out. I checked the grease that we applied a while back to the roller bearings, and then I really cleaned up the axle and the hole through the bearing surface with a rag and some naptha to get all traces of grease off of it. The only grease I wanted in there was on the roller bearings themselves, and on the race in the wheel. I hope that makes sense.

The way I did the drilling was to tighten the big nut while turning the wheel forward and back, I tightened until the bearing wasn't moving on the axle, then went just a bit more. I marked the position, loosened it, and did the procedure again. I did this several times, to make sure I was getting the same stopping point each time, and to make sure the bearing wasn't turning on the axle. There is definitely some drag while you're turning the wheel. But this is normal. Matco's instructions tell you how much drag to expect. I was then confident to go ahead and drill the hole for the cotter pin. I used my 12" long #30 bit. I drilled through one side of the nut, then the other side. After that I removed the nut, took the wheel off and cleaned up from the drilling and checked the holes I had just made. I ran the drill completely through both holes at once this time, and then deburred and carefully filed the burrs off the threads with a fine needle file to clean it up. A fine wire brush, followed by a rag and some solvent, really cleaned it up. I also found that before putting the wheel back on, put just the nut on and turn it way in and then back out several times, to make sure the threads are deburred properly and it doesn't bind up on you. Then put it all together. Here's the finished job, with cotter pin in place.

Then, when this is all done, you wash, rinse, and repeat all of this for the other gear leg. This baby is now ready to go on the plane!

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