YellowJacket RV9

YellowJacket RV9

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So I thought I was doing everything right, reaming my gear and gear weldments to .311, but I have still ended up with a sloppy fit. Part of the issue is that it appears that one hole in the gear weldment was not exactly aligned with the other, resulting in one perfect hole, and one elongated hole. So elongated in fact, that I'm concerned even a twice oversize bolt won't fit (max diameter of the hole is .345). I have ordered a new weldment from Vans to the tune of $300. Maybe not needed, but I'd really rather do this right the first time. I will return it if I get a good fit with a twice oversize bolt...

Also, I have found that even though I reamed the gear legs to .311, they are measuring .320, and the bolts are not a tight fit. I figure I can fix this issue with either close tolerance or oversize bolts. One thought is that maybe the gear leg was not perfectly aligned in the socket when drilling, causing everything to enlarge slightly. If so, any hints on how to get the holes lined up exactly? It is so tight once in place that small adjustments are about impossible. BTW, I have double checked and the reamer is .311.

Also, should I try reaming the two pieces separately, rather than in assembly?
Thanks for any advice!

Chris
 
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Been there, done that. I would absolutely ream them together if you want the best fit. No particular advice other than what you're doing. Mine are definitely oversized with close tolerance (at $30 each!:eek:) fit.

Edit: just saw that you are doing a 9A, but the process is the same.

Greg
 
Chris
Are you 'pulling' the reamer through the hole or pushing it through. I'm not sure it makes much difference, but I inserted the shank through the hole, chucked it to the drill, then pulled the reamer through using lots of lubricant. Came out fine.
 
Thanks for the encouragement. After calming myself for a bit, I went and did the right side, with zero issues. On that one, the fit of the gear in the tube was much looser, and I was able to position the hole exactly. Also, I noticed that the hole in the gear leg was almost exactly the right size already - I could put a bolt halfway through. So I reamed one side of the weldment, put the gear leg in place, and put a bolt through that side and into the leg as far as it would go to hold things in place. Then I reamed from the other side about halfway, and that was all it took. Now the standard AN5 just goes in with a few whacks of the rubber mallet. Perfect.

My left gear leg is already oversize now, but I think if I can get the gear leg a bit looser in the socket, I can follow the same procedure with my new adjustable reamer until I get a good fit on an oversize bolt. Live and learn...

Also, is there any way to repair the weldment with the elongated hole? Maybe either by having a machine shop drill out and install a bushing, or have the hole welded and re-drilled? Or should I just suck it up and buy the new one?

Chris
 
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Gear

Find someone who is an artist with a TIG welder. They can run a weld bead part way around or all the way around the hole in the gear weldment.
No need to close up the hole, that just makes things more difficult. Open up the welded hole a little bit at a time with files or rotary files until you get reasonably close, then run the reamer thru again.
I think I start with a .309 or .310 reamer and then go in increments until the bolts are a tight fit.
I bought a 1/2" capacity electric drill for this. Slower speed and a lot more torque. Straight flute reamers work best for me, some kind of heavy bodied tapping lubricant. Take your time and don't get the metal hot.
Hardware store 5/16" bolt for alignment, cut the head off and file polish the bolt to a light drive fit into the unreamed end of the hole. When the reamer touches the alignment bolt, back the reamer out, remove the alignment bolt and finish ream.
 
Gear

One more suggestion, if you buy a variety of bolts from different suppliers you may find some that are a better fit than others. Up to .0025 variation in bolt diameter, sometimes substantial variation in diameter along the length of a long bolt.
 
It's always a good idea to put a micrometer on your bolts before you pick out a reamer to use. I've found that there can be quite a bit of variation on the standard bolts.
 
I'm not a builder, but I design lots of repairs on aircraft. Is there a reason not to just go up to 3/8" and try again? Use a way undersized ream and work up, as someone said above....
 
Make sure you are supporting the drill when you are doing the reaming. I found that just the weight of the drill itself can cause the reamer to elongate the far hole.
 
gtmule said:
I'm not a builder, but I design lots of repairs on aircraft. Is there a reason not to just go up to 3/8" and try again? Use a way undersized ream and work up, as someone said above....
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I have not heard of this being done, and would think that edge distance issues may be part of the reason, but don't know much about steel so not sure. If anybody has had Vans approve that maybe they can let us know? I know that many people have gone with a 1/64 oversize bolt in this case and it is a Vans approved fix, so will probably go that route.

The piece is at a local welder right now to bring the hole size back down, for $30, and I ordered an adjustable reamer last night at 7:30PM from MSC Direct, and it will be here today - free shipping. Will have to remember them for future tool needs.

As Bruce said, this is a good reason to put a caliper on every important bolt, as mine were a bit undersize already.

Thanks for all the input

Chris
 
YellowJacket RV9 said:
I have not heard of this being done, and would think that edge distance issues may be part of the reason, but don't know much about steel so not sure. If anybody has had Vans approve that maybe they can let us know? I know that many people have gone with a 1/64 oversize bolt in this case and it is a Vans approved fix, so will probably go that route.

The piece is at a local welder right now to bring the hole size back down, for $30, and I ordered an adjustable reamer last night at 7:30PM from MSC Direct, and it will be here today - free shipping. Will have to remember them for future tool needs.

As Bruce said, this is a good reason to put a caliper on every important bolt, as mine were a bit undersize already.

Thanks for all the input

Chris
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10-4. Be CAREFUL with that adjustable reamer, they're not easy to get set to what you want, make TINY changes.

Also; THWG!!!
 
When standard close tolerance bolts are not close enough, you can get some custom machined.

Also, it sounds like (excuse me if I misunderstood) people are lining up the pre-drilled holes in the gear and socket and simply reaming through. I would advise against this as 1) Van's is not perfect and 2) there is some variation possible in your gear alignment using this method. Better to align the pre-drilled holes as a starting point but check the alignment of the axles relative to each other and the airframe before reaming. On my -10, I shifted the axles slightly to get the correct alignment and the pre-drilled holes were still lined up adequately. Also clamp the legs together as well as at the socket; reaming can move them. I had a straight piece of angle iron that was bought for my RV-6A for that purpose and it served me well here; I bought it from a metal shop for about $20. I have been reading another thread about main gear shimmy in the RV-10 and have been wondering if there might be a gear alignment issue there.

For the RV-6A, you'd check the gear alignment by putting the angle across the axles. There was a specified value for toe-in and droop, but you could also see if the angle as perpendicular to the fuselage (one gear not 'ahead' of the other) and parallel to the bottom (so the plane will sit level). If shifting the gear slightly in the mounts won't bring things into alignment, then you may have to adjust the weldments themselves (in the -6A, they were drilled to the spar AFTER aligning them, unlike the pre-drilled mounts in the -10) but I found that the parts I got were close enough.

By the way, and slightly off-topic, but before you bolt those gear legs into place, install the wheels, When you install the axle nut, count the turns and note the orientation you want for your cotter pin holes. Then, remove the wheel, reinstall the nut, and take the leg to a machinist to mill the holes. After my struggles drilling those pesky holes on the -6A, I did this and my machinist was able to do a perfect job in about 10 minutes (mostly setup in his mill). It was well worth it to do it this way; I would never consider trying to hand drill through an axle again.
 
By the way, and slightly off-topic, but before you bolt those gear legs into place, install the wheels, When you install the axle nut, count the turns and note the orientation you want for your cotter pin holes. Then, remove the wheel, reinstall the nut, and take the leg to a machinist to mill the holes. After my struggles drilling those pesky holes on the -6A, I did this and my machinist was able to do a perfect job in about 10 minutes (mostly setup in his mill). It was well worth it to do it this way; I would never consider trying to hand drill through an axle again.
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Does the 6 use solid axles or the same hollow version the 7 and 9 use?
 
One person on here posts every now and then, they have a fix for this, they have bolts and reamers that are .010, .020 ect oversize for this problem, some aircraft fastner company.....
 
bret said:
One person on here posts every now and then, they have a fix for this, they have bolts and reamers that are .010, .020 ect oversize for this problem, some aircraft fastner company.....
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I bought the oversize bolts from general aircraft hardware. I believe that's who your're thinking of. They have 1/64 and 1/32 oversize bolts.

Chris
 
Zuldarin said:
Does the 6 use solid axles or the same hollow version the 7 and 9 use?
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Hollow. My machinist friend opined that it's nearly impossible to get a drill bit to track straight through to drill those holes. Instead, he milled one side, pegged the nut in place, turned it over, and milled the other. The cotter pins on my -6A are a pain to install. The one's on the -10 are a piece of cake.
 
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