Landing gear hole .311 + what bolt?

After doing a search to find out why such an odd number, .311", is called out for drilling/reaming the landing gear bolt holes, I'm curious...anyone using close-tolerance bolts, or are you okay with reaming to .311 and using the 5/16 (either -12A or -13A, depending...)? Would there be any advantage either way?

A 7.9mm metric drill bit is .311". I picked one up at a local ACE HW. I would think this was cheaper than buying close tolerance bolts.

You had me going

I had to pull out the drawings to see if I missed anything.

Nope, I did not. The plans call for an AN5 bolt, just like I used and I suspect that is most everyone else used as well.

If you look at the design of the gear leg and gear leg socket, the bolt sees very little load. The bolt's main job is to make sure the gear leg doesn't fall out when there is no load on it. It also keeps it from twisting but I suspect that is secondary.

Many go with Close Tolerance

Many go with Close Tolerance NAS6605.

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

Page 1 & 3 are applicable to this subject, page 2 is not.

I will make the ones for the Nose gear available in singles if someone will let me know what the OD of the outer tube is for what types of aircraft.

I will also get some reamers for the close tolerance fit in steel.

(we already have them for aluminum but they are just a little small for the steel)

I do have some oversize bolts for those who just go at it the first time with what bolt they think will work for the final size.

At this time (depending on response) I am considering making it a kit to meet this ongoing demand.

Please chime in and post if you think this is a good idea, your responses will help me make a decision on this. (don't forget your tube dimesions).

Interested in the kit.

Tom,

I am interested in the Kit. Don't have the tube diameter but will get it for you.

Thanks

Tom - I'm interested in the kit for the 9A nosewheel. I don't have the tube diameter since I don't have my finish kit, but I'm hopeful someone else will post it.

I just used a 5/16 reamer and regular AN5 bolts for the main gears. Hopefully I won't have a problem... my gut feeling is that the main gear legs are a lot less troublesome than the castoring nosewheel.

I can get the main gear tube diameters if you want them.

IowaRV9Dreamer said:

Tom - I'm interested in the kit for the 9A nosewheel. I don't have the tube diameter since I don't have my finish kit, but I'm hopeful someone else will post it.

I just used a 5/16 reamer and regular AN5 bolts for the main gears. Hopefully I won't have a problem... my gut feeling is that the main gear legs are a lot less troublesome than the castoring nosewheel.

I can get the main gear tube diameters if you want them.

Click to expand...

To prevent wear over time, an RV gear leg must have zero motion possible when its rotational loads work against bolt.

All of the AN5 bolts I have ever measured are about .311 instead of the .3125 that would be expected. This allows for .015" clearance (or more) if drilled/reamed 5/16". This is more than enough clearance to allow a very small amount of rotation. Problem is, any amount of rotation (however small) allows wear to begin from day one.
If a round rod style landing gear leg on an RV can rotate any amount at all under load (you can't always feel it when checking with your hands) it will be loose eventually.

Which is what you...

rvbuilder2002 said:

....
All of the AN5 bolts I have ever measured are about .311 instead of the .3125 that would be expected. .....

Click to expand...

...you would expect if you read the actual specifications for AN hardware.

An AN-5 bolt is specified at 0.309 to 0.312 inches diameter.

All of this can be easily checked by checking specifications....

AN hardware bolt numbers here...

http://exp-aircraft.com/library/alexande/hardfig2.html


gil A - still freezing in the English Blizzard of 2009....

Is there actually a problem?

Has there ever actually been a problem with gear leg/socket rotation or wear in an RV that used the recommended 0.311" reamed hole and standard bolts? Never heard any discussions of this before, and have been planning to follow Van's design on this one (and I've been making lots of other mods where I thought Van's design was less than adequate). If this has actually caused problems for people, I'd sure like to know so I can take the necessary steps on my airplane. Otherwise, this might be just a solution to a non-existent problem.

RV-9A main gear mount tube diameter

I measured the outer diameter of my RV-9A main gear leg mount tubes to be just about exactly 1.75 inch. Hope this helps.

Thanks for the info.

Thanks for the info.

The original thread that started all this was

"NOSE GEAR CREAKING"


I am getting some reamer quotes for this and will be getting back to y'all.

For now please give more dimensions of the OD's of different gear configurations.



I will then be able to further asses my capabilities of getting all the close tolerance goodies lined up.

az_gila said:

...you would expect if you read the actual specifications for AN hardware.

An AN-5 bolt is specified at 0.309 to 0.312 inches diameter.

All of this can be easily checked by checking specifications....

AN hardware bolt numbers here...
[/I]

Click to expand...

Gil,
It is not really what I would expect.
I am well aware of the tolerance range for standard A.N. bolts. It is the reason that close tolerance bolts exist.
Here is the problem...measure an AN3 bolt, it is usually right on .1875"
AN4 bolt, pretty much always right at .250".
Measure an AN5, it is always .311"
So why as a standard, have manufacturers chosen to hit the correct dimension on AN3's and 4's but always be at the bottom of the size tolerance for AN5's?
Doesn't really matter...the point is, don't use a 5/16 reamer for the gear leg holes unless you plane to use something other than a standard AN5 bolt.

roee said:

Has there ever actually been a problem with gear leg/socket rotation or wear in an RV that used the recommended 0.311" reamed hole and standard bolts?

Click to expand...

None that I am aware of.
There is nothing special or better about using a close tolerance bolt, since the AN5 bolts do seem to always be made ai a consistent diameter (their is nothing wrong with it either, but I see no reason to make an RV project cost more. A close tolerance bolt is not going to be any better than a properly fitted standard An bolt) The important thing is that you make the hole match the bolt you are using. This is the reason a drill or reamer that will produce a .311" hole is specified to be used for the AN5 bolt that is supplied in the kit.

GAHco said:

Thanks for the info.

The original thread that started all this was

"NOSE GEAR CREAKING"


I am getting some reamer quotes for this and will be getting back to y'all.

For now please give more dimensions of the OD's of different gear configurations.



I will then be able to further asses my capabilities of getting all the close tolerance goodies lined up.

Click to expand...

I think nose gear creaking is related. If the hole was not finished for a tight fit with the bolt, the nose gear leg can move slightly causing the creaking

That is not...

rvbuilder2002 said:

Gil,
It is not really what I would expect.
I am well aware of the tolerance range for standard A.N. bolts. It is the reason that close tolerance bolts exist.
Here is the problem...measure an AN3 bolt, it is usually right on .1875"
AN4 bolt, pretty much always right at .250".
Measure an AN5, it is always .311"
So why as a standard, have manufacturers chosen to hit the correct dimension on AN3's and 4's but always be at the bottom of the size tolerance for AN5's?
Doesn't really matter...the point is, don't use a 5/16 reamer for the gear leg holes unless you plane to use something other than a standard AN5 bolt.
....<snip>...

Click to expand...

...what I have found with AN4 bolts. The specification is 0.246 to 0.249 inches diameter.

If all of your AN4 bolts really measure 0.250, then I suggest you talk to the procurement folks at Vans, since you are not getting actual AN specification bolts.

I'm presently 6000 miles away from my hardware and can't measure them now...... but I do know that I bought surplus 0.248 and 0.249 reamers for accurate holes.

..but as you say, ream the AN5 hole to 0.311 (or even 0.310 for a tighter drive fit) for the nose gear bolt in this particular appluication.

If you get good parts, the specifications work.

If the bolts don't meet specifications in diameter, then I would say that their entire pedigree and physical properties are suspect.

Examine you AN4 bolts and check their pedigree...

az_gila said:

...what I have found with AN4 bolts. The specification is 0.246 to 0.249 inches diameter.

If all of your AN4 bolts really measure 0.250, then I suggest you talk to the procurement folks at Vans, since you are not getting actual AN specification bolts.

I'm presently 6000 miles away from my hardware and can't measure them now...... but I do know that I bought surplus 0.248 and 0.249 reamers for accurate holes.

..but as you say, ream the AN5 hole to 0.311 (or even 0.310 for a tighter drive fit) for the nose gear bolt in this particular appluication.

If you get good parts, the specifications work.

If the bolts don't meet specifications in diameter, then I would say that their entire pedigree and physical properties are suspect.

Examine you AN4 bolts and check their pedigree...

Click to expand...

OK Gil, I give. My arm is hurting real bad.
I should know better than to quote specifics from memory with you checking up on me.
I also wasn't anywhere that I could actually measure some bolts so I went from memory (bad thing for me to do nowadays).

I since have measured some bolts to do a memory refresh. So, what I should have said is...
"that from my experience, (now verified) AN3 and AN4 bolts seem to always be manufactured right at the upper end of the tolerance range, but for some reason AN5 bolts seem to always be manufactured at the bottom end of the tolerance range".

Because of this, an AN5 bolt will fit much looser in a hole drilled to 5/16" than an AN3 or 4 will, if installed in there respective fractional hole sizes. So, (making this post relevant to the thread) this is why using a 5/16" drill or reamer for your gear leg bolts (and the rear wing spar bolt) is a bad idea.