Nosegear creaking - Page 2

Captain Avgas · #11 05-20-2007, 06:03 AM

Quote:

Originally Posted by az_gila

Bob... do you have a source for the oversize bolts?

I tried to find them for a friends RV-6A with not much luck. He was lucky, and said that most of his slop went away when he replaced the bolt. I guess sometimes the mount is heat treated during welding to be harder than the bolt...

I guess an NAS1105- with a -X (1/64 os) or -Y (1/32 os) as a suffix...

gil in Tucson

Hi Gil,
If he replaced the bolt with another AN bolt he might have got a "fat" one....so it could have resulted in a better fit....by luck. AN bolts have a relatively loose tolerance compared to NAS bolts.

I doubt the wear would have been in his original bolt. At 125,000 PSI ultimate tensile strength the steel in the AN bolt would probably be far harder than the steel in the mount.

I don't think that a NAS 1105 is the right bolt. The NAS 1105 is a large head shear bolt. It has the larger head to increase the clamping forces. That is not relevant in this particular application and the large head may not fit through the hole in the firewall. In reality I'm not even sure if the 1105 series comes with oversized shanks. But I wouldn't put my house on it.

The bolt you really need is a NAS6605-X which definitely has a .016 oversize shank.

They're not stocked by everyone but they ARE available through specialist aviation fastener suppliers. Do a Google search.

GAHco · #12 05-20-2007, 08:17 AM

Quote:

Originally Posted by Captain Avgas

Hi Gil,
........

The bolt you really need is a NAS6605-X which definitely has a .016 oversize shank.

They're not stocked by everyone but they ARE available through specialist aviation fastener suppliers. Do a Google search.

He is right, that would be the bolt of my choice.

The next would be NAS6205-(GRIP IN 16THS)X

After that the older NAS2905-(GRIP IN 16THS) (NO X REQUIRED)

I believe these are put in shear, so either would work.

What grip length do you need? (how much material is it going through, include washers)

Let me know and I will check on some for you tomorrow.

We also stock the 1st and second oversize reamers in Regular, Long, and Threaded shank.

http://www.gen-aircraft-hardware.com...on_Reamers.pdf

Bob Martin · #13 05-20-2007, 08:59 AM

Quote:

Originally Posted by GAHco

He is right, that would be the bolt of my choice.

The next would be NAS6205-(GRIP IN 16THS)X

After that the older NAS2905-(GRIP IN 16THS) (NO X REQUIRED)

I believe these are put in shear, so either would work.

What grip length do you need? (how much material is it going through, include washers)

Let me know and I will check on some for you tomorrow.

We also stock the 1st and second oversize reamers in Regular, Long, and Threaded shank.

http://www.gen-aircraft-hardware.com...on_Reamers.pdf

I've been following this thread as my -6 has movement in one gear leg after 550TT. I'm pretty sure the plans call for a plain AN5-21A bolt.
I installed a new bolt and torqued it up and it seems tight, but like the previous poster said, only until until the first landing!
As a buyer, not a builder, I found this problem kinda by accident while servicing the wheels and brakes during the condition inspection. My A&P told me about oversized bolts but I wasn't having much luck finding them until this thread, so I was happy to see it!
Gahco....I found page 13 in your catalog and it helped a lot! Thanks Guys!
So I'm thinking:
NAS6605-21X for first oversized .0156
NAS6605-21Y for second oversized .0312
Thanks

GAHco · #14 05-20-2007, 09:36 AM

Quote:

Originally Posted by Bob Martin

I've been following this thread as my -6 has movement in one gear leg after 550TT. I'm pretty sure the plans call for a plain AN5-21A bolt.
I installed a new bolt and torqued it up and it seems tight, but like the previous poster said, only until until the first landing!
As a buyer, not a builder, I found this problem kinda by accident while servicing the wheels and brakes during the condition inspection. My A&P told me about oversized bolts but I wasn't having much luck finding them until this thread, so I was happy to see it!
Gahco....I found page 13 in your catalog and it helped a lot! Thanks Guys!
So I'm thinking:
NAS6605-21X for first oversized .0156
NAS6605-21Y for second oversized .0312
Thanks

BE CAREFUL!

The dash #'s are not directly interchangeable!

An AN 5-21A Bolt has a 1.688 grip,
but the Part number indicates a 2" + 1/8th" nominal Overall length.
For AN Bolt details http://www.gen-aircraft-hardware.com..._thru_an20.pdf

The NAS bolts of which we speak have dash numbers relative to the GRIP length, NOT, the Overall length.

1.688 x 16= 27.008,

or if you math brain works the other way 1.688 divided by 1/16th = 27.008

So the bolt with the matching grip length in NAS would be the NAS6605-27, and for the first oversize add an (X) IE; NAS6605-27X

Remember that you must verify the amount of material you are going through including the washers before ordering these (They are not cheap)

We do have some NAS6605-28X in stock, (one washer longer than a 27x)

Double check your measurements. This link will help you figure out NAS bolts

The first and the last page will be what you are concerned with.

http://www.gen-aircraft-hardware.com...pdf/nashhb.pdf

Scott Will · #15 05-21-2007, 12:25 AM

Followup:
I pulled the cowl tonight and took the weight off the nose gear. By moving the nose gear leg even slightly I could see the bolt and nut rotating on the engine mount.

How to fix?
First chore is to remove gear leg and get a sense of how enlarged the hole is. Would be good if an NAS close tolerance would work. Then the question is how to ream? Short of removing the engine mount, I had an idea to make an opening in the bottom skin and ream it from the bottom if I could not do it from the top. Then just make a patch for the bottom... hey it's on the bottom.

Other idea is to use a tapered reamer and have a machine shop make a tapered pin for it.

Hate that this happened. Vans should advise the use of a proper reamer and close tolerance bolt. I had a machinist friend of mine drill the gear leg and this still happened.

Bob Martin · #16 05-21-2007, 05:34 AM

Hate that this happened. Vans should advise the use of a proper reamer and close tolerance bolt. I had a machinist friend of mine drill the gear leg and this still happened. [/font][/quote]

I kinda agree that Vans should at least mention this as a possible problem and give the builder the option of doing better, but then again, the builder always has the option to do whatever he wants. I guess the fact that Vans calls for a normal AN bolt makes us think it isn't a problem area.
Being a buyer, not a builder, I now have added, torqueing the gear leg bolts to my condition inspection list. When I found the problem, I found the bolt not tight, so I'm betting if the bolt had stayed tight, it wouldn't had be a problem, as my right gear is still tight. Lucky for me, the bolt on the RV-6 is easy to get to compared to the nose gear of the A model.

The OD of the main gear tube is 1 5/8" or 26-16ths FYI.

"Remember that you must verify the amount of material you are going through including the washers before ordering these (They are not cheap)
We do have some NAS6605-28X in stock, (one washer longer than a 27x)"

Seems the NAS 6605-28X would work, but now I'm wondering if it is big enough to take up all the elongated hole. As GAHco mentioned, these bolts ain't cheap. I may just go to the next standard size up, 3/8 -#6 and drill it with a proper size reamer and a close tolerance NAS bolt. Then keep it tight.
Good Luck.

Jim Ellis · #17 05-21-2007, 05:52 AM

There's an article I wrote a few years ago on the Matronics Wiki that shows another way to approach this problem. Click here.

jonbakerok · #18 05-21-2007, 06:48 AM

I first noticed this problem when I was under 100 hours, so maybe this is only a fix if you catch it soon enough. I simply replaced the nylon insert locknut that comes in the kit with an all-steel lock nut, and over-torqued it a bit. Even though it had wallowed out a little, I haven't had any movement since.

A taper pin is probably the ultimate solution, and if it ever loosens up again, that's what I'll do, but this has worked so far (280 hours). If you're still building, it would be a great idea to use a reamer and a close-tolerance bolt, while you can still get in there to work on it. But use a steel locknut whatever you do.

I can't imagine why they put a nylon locknut in the kit for this application. It sits right over the exhaust stacks and obviously gets way too hot for even high-temp nylon.

chaskuss · #19 05-21-2007, 07:03 AM

snipped

I doubt the wear would have been in his original bolt. At 125,000 PSI ultimate tensile strength the steel in the AN bolt would probably be far harder than the steel in the mount.
snipped

The tensile strength of an AN bolt has no bearing on how hard it is. Common AN bolts are actually more ductile than a grade 7 industrial bolt. The designer's intent is for the bolt to stretch, but not shatter, if it is subjected to an overstress.
Prove it to yourself. Subject both a comman grade 7 hardware bolt and a common AN bolt to a hand file. The file will show you which is harder. A harder bolt would wear better. However, all that will do is transfer the wear to the landing gear mount; not a good thing.
As has been previously mentioned, the landing gear socket bolts are loaded in shear, not tension (tensile strength). Another item critical to this problem is how snug the gear leg fits into the socket. If the fit is sloppy, the joint is more prone to move. Van's instructions SUCK here. They suggest using sandpaper to remove any high or tight spots. I spotted this right away. I purchased an adjustable "import" reamer ($54) from MSC for this job. Next I measured each gear leg and adjusted the reamer for a .001" clearance fit. I chucked the reamer up in a buddy's engine lathe. I placed a center cone in the tail stock of the lathe. The landing gear socket was placed between the reamer and the centering cone in the tail stock.
I turned the chuck of the lathe by hand and slowly reamed the socket, to a size .001" larger than the gear leg which was to go in it. Using this method, you will find that the only "tight" areas, are where the welds are placed. Vans vendor reams the tubes out prior to welding. The welding process causes localized distortion of the tube, causing fitment problems. If the vendor did a clean up ream after the welding, this would not be an issue.
I surmise that some of the builders do not consider how critical it is to maintain a close fit in this area. This leads them to get carried away with material removal from the socket, in an effort to get the gear leg to fit. I called all the other RV builders in my local EAA chapter (133). I let them know I had this tool. I then repeated this process for all the other local builders. The results were excellent for all 5 sets of gear legs done.
I realize that this doesn't help those who have finished this process, but I thought that I'd make everyone aware of it.
Charlie Kuss

chaskuss · #20 05-21-2007, 07:27 AM

Quote:

Originally Posted by ctbecker

Would it make sense to insert grease fittings in these locations?

Charlie Becker
N464CB 8A
Finishing

Charlie
It sure wouldn't hurt, so long as the hole was drilled and tapped in the area between where the gear leg contacts the socket. It sure would reduce the amount of work to ensure that the joint was greased.
I think I might just use your suggestion.
Charlie Kuss