More Experience with the Nose Gear SB

I just got off of the phone with Harmon Lange and he asked me to relate my experiences with attempting to do the leg gear modifications, so that others might not have to repeat my experiences.

I work at the University of Wisconsin-Madison in Mechanical Engineering. We have a fully equipped machine shop. Before sending the leg to Harmon for rethreading, I asked the machinists and tool makers in our shop about doing the threading. While they all indicated that it could be difficult, the consensus was that with a good die, it should not be a big problem.

So I bought the correct die from MSC for ~$54 . When it arrived, I took it and the gear leg to the shop. When I asked the best method for fixturing the leg prior to doing the threading, before I could protest, one of the guys working at the shop grabbed the leg, put it in a pipe vise, tightened the vise, and damaged the surface of the leg. I was pretty certain that this was a big problem, and would likely preclude the leg from being reused, however, we went ahead with the retheading anyway. More on this later.....

We then proceeded to do the threading. Initially, it went well, however, somewhere during the rethreading, it became impossible to continue to thread, or to get the thread to be of sufficient depth. Perhaps parts of the die itself were embedded in the leg, although this was not observable to the eye.

After three plus hours of cursing and sweating, we gave up. I was already concerned about the scoring on the leg, and so I packed the leg up, sent it to Van's for match drilling of a new leg.

Today during my discussion with Harmon (BTW, he is originally a Cheesehead), he told me that they are very careful with the surface finish of the leg and that it would not be a good idea to use a leg with a nicked-up surface finish.

Sincerely, this was, without question, the worst experience I have had with airplane building, and I would not attempt to do it again.

Same here..

Really sorry to hear about your experience but we had to sharpen the die six or seven times over a whole day to get the threads deep enough....it's really hard on dies. The die can be sharpened with a cylindrical grinder in a Dremel tool...what a pain. I do have a wooden vise on my woodworking bench, so no damage to the leg.

Next time it'll go to Langair.

Regards,

The machining is a lot harder than many people realize. You can end up spending as much or more doing it yourself than just sending it off to a machine shop set up to deal with it.

That said, I took a lot of care making up the crate right down to the kitchen size zip lock bag and sent mine off to Langair. Cost to ship via UPS: $22.47. I should get it back any day now. Interestingly, a buddy just received his reworked gear leg back from Langair....not in the crate he made but in a cardboard box. They told him the crate that Langair specified on their website is not required for most gear legs. My guess is the real reason they sent it back in a cardboard box was that shipping costs were a biting into the profit margin and it turns out a cheaper-to-ship cardboard box is acceptable after all. I guess that's the last time I'll see that crate.

Langair's website has been updated with new shipping instructions

Langair's website has been updated recently with new instructions for shipping the nose gear. www.langair.com UPS has a $10-$15 charge for wooden boxes. I think this was unforeseen in the beginning. You can always use a wooden box and wrap it with cardboard to avoid that extra unnecessary charge. Likely, if you do that, you will receive your nice wooden box back.

Got Mine Back

Mine came back yesterday, in the wooden crate that I built wrapped with cardboard from Langair. Total time gone was 14 days, and I live in the midwest.

Far (VERY far) be it from me to judge someone else's decision, but if you have to spend 54 bucks for a die..and the original shop can do it for 75, that's kind of a no-brainer, isn't it?..Not to mention the time and trouble..I don't want to judge too harshly, however...I've went on the cheap a couple of times..and always lived to regret it..Sorry you had bad experience....

Gear Leg modification

I removed and packed my 6A gear leg up in December and sent it off around December 3rd and it arrived at the factory on the 10th. I went off on vacation because I could not do anything on plane until the gear leg was returned. When I came home on the 24th the gear was waiting for me in its plywood box. The shipping cost me 29.00 from WV to Oregon.

What I have found is that gear leg is so dang hard I have only been able to drill one hole for the cotter pin in the threads. I have not been able to drill the other side with any of my drill bits so I have only put in 1/2 of a cotter key. How are you guys doing in this area? They should drill a couple cotter pin holes in the gear leg for us.

Allan Stern
RV 6A flying

Slow and Oily

Wow, we just did two gear legs last friday in about 4 minutes each using a single bit. With the leg off the plane the forks were installed and the nut tightened to spec. We clamped the fork/leg combo to the bench and using the nut as a guide drilled one side using a #30 bit turning real slow and lots of liquid Boelube. When done flip the fork over on the bench and drill the other hole. Your done. Make sure the bit is new and sharp. Use lots of lube, oil will do. Turn the bit slow with steady pressure.

Hope this helps

Machinist's rule of thumb: Harder material, slow the RPM and increase the feed (pressure.) Use lots of cutting oil like Tap Magic to keep the bit cool.

zilik

Are you talking about threading the leg or just drilling for the cotter pin?

kenmorris said:

zilik

Are you talking about threading the leg or just drilling for the cotter pin?

Click to expand...

Drilling for the cotter pin. Slow speed, steady pressure, and lots of cutting oil. I should have mentioned that as a previous poster had a hard time drilling the cotter key holes. I can tell you that threading the leg was no walk in the park. I don't think I want to thread another leg in the near future.

zilik said:

Wow, we just did two gear legs last friday in about 4 minutes each using a single bit. With the leg off the plane the forks were installed and the nut tightened to spec. We clamped the fork/leg combo to the bench and using the nut as a guide drilled one side using a #30 bit turning real slow and lots of liquid Boelube. When done flip the fork over on the bench and drill the other hole. Your done. Make sure the bit is new and sharp. Use lots of lube, oil will do. Turn the bit slow with steady pressure.

Hope this helps

Click to expand...

I was under the impression that you had to drill the cotter pin holes while the gear leg was on the plane in order to determine the appropriate "break out" pressure. How do you get around that issue if you drill it before installing the leg on the plane?

tonyjohnson said:

I was under the impression that you had to drill the cotter pin holes while the gear leg was on the plane in order to determine the appropriate "break out" pressure. How do you get around that issue if you drill it before installing the leg on the plane?

Click to expand...

The break out pressure is measured with the wheel off the ground - your fish scale doesn't know that the leg is/ain't connected to the plane.

You might try a cobalt drill if you're using a high speed drill. If the drill ever stops producing chips and won't go any farther you probably work hardened the steel. High alloy steel is easy to work harden from the heat the drill bit produces. If that happens stop and go to the other side and drill. Like the others said, slower and cutting oil to prevent heat buildup.Cobalt drills will break easier but will drill harder materials. Just be careful to keep the drill lined up straight. Hope this helps.

Junky drill bits

There are a lot of things out there that look like drill bits, but really aren't. One can find numbered drill sets from Harbor or equivalent that are about 10 bucks or decent ones that are around 80 bucks from a machine tool supplier (or McMaster, Grainger, etc.). The good ones will usually drill a lot better. It seems that many cheap suppliers don't know how to grind the tips correctly.

As has been already mentioned, but is worth repeating, slow rpm with moderate pressure and lots of cutting oil is very important for steel. By slow, maybe 100 to 200 rpm (you can see the bit turning).