Gear Leg Inspection - HR-II

With the engine off and the mount looking shabby, I decided a fresh powdercoat would spruce things up. Pulling each gear leg out of the socket provided an unexpected and unwelcome sight. There was some fretting on the leg within a half inch or so of the bottom of each socket, and one leg even had a sharp line cut into the surface through about 180 degrees. This line was sharp enough to catch a fingernail and was directly adjacent to the exit of the socket. The legs are not snug in the sockets and they are wearing with vibration and landing loads. Obviously a major stress riser right at a point of significant applied load - not good!

I was able to blend the damage out of the leg and made sure the socket had no sharp edges. Upon installation I shimmed the leg with a partial wrap of .005 stainless sheet which snugged things back up.

I bring it up because this airplane only has 322 hours total time on it and this is a LOT of wear. This is now a careful inspection item and will probably drive me to pull the legs once a year.

These legs are expensive and dropping the airplane on the belly is even more so.

Just something for the group to think about.

To be clear, the F1 Rockets use a tapered gear leg socket, different from the HRs. The tapered socket, installed correctly, has zero looseness. While no one has designed a perfect engine mount for our RVs and Rockets, but the tapered sockets are pretty darned close.

Nonetheless.. inspect everything. Mike is spot on in making sure that all the hidden, neglected areas of these planes deserve a good look too! HR guys... please heed his advice on keeping an eye on those legs!!

Thanks for clarifying Vince. I like the F-1 design much better.

I also did a subtle change to the stub axles. My airplane had the bolts going through the aluminum axles and threading directly into the stub sockets. This loaded the threads in shear, which is almost always a bad idea.





I reamed 3 of the holes and installed Hi-Lok pins from the inboard side, secured with nuts on the wheel side. Not only are these pins much stronger in shear than the AN hardware that was being used, it is now installed with the threads far removed from any shear plane. I'll sleep better now.

Mine are so tight I needed a welders helper to help twist to and fro.

Also John recommends checking the bolts when cowling off-- IIRC His loosened up or he found them/one loose.

HR2 gear

Like Michael, the gear legs on my Harmon Rocket have some movement where they exit the engine mount. I spoke with John afew years ago about this. He said to check the gear bolt during inspections and do as Michael and add shims if you like. The gear wiggle in the mount sure is disconcerting.

Several years back, we had a midwestern HRII that broke one of the legs. Perhaps Sodbuster will chime in with the details. I don't recall the whole story.