Front Gear Leg Bolt Hole Wear

Hi All,

I just got done repairing the front gear leg mount bolt hole on my RV-7A a while back. There was a slight bit of wear due to the bolt either loosening and/or the front fork being too tight, causing excessive torque on the gear leg during turns. In any case, there was a slight amount of rotation in the gear leg with the bolt loose, indicating that the bolt holes were slightly oblong...
Here's what I did to fix the problem. First I tied down the tail, and removed the front gear leg. Next, I cleaned both the top mount area and the lower mount area of any grease. I did the same to the gear leg, but re-greased the lower mount area where it comes into contact with the mount. Then I applied permanent Lock-Tight to the inside of the upper mount area, and also coated the top mount area of the gear leg. The gear leg was then inserted back into the mount and the bolt partially re-inserted. (My bolt inserts from the top. The firewall has an indentation for the nut. There is no hole in the firewall for the bolt...).
Next I used a small amount of "Liquid Steel" into the worn areas of the gear leg mounting bolt holes. (Since there was very little wear, I did this instead of drilling out the mount/gear to a larger size bolt, or inserting a taper pin.) The bolt was then torqued normally. I let the assembly dry before testing it for any movement. Solid....
I've flown over 100 Hours after that fix was performed, and still have no movement in the front gear leg upper mount area. I have checked it at every oil change for any signs of movement....
With the history of issues in this are, it would seem prudent to do the final front gear leg assembly with Lock-Tight on the upper mount area. This would prevent the re-occurring issue that we've seen in this area on the -A RV models.... And I've seen it happen to every RV-XA that I've owned....

Which type of loctite?

Dear Fred

Thank you for this interesting information.

Can you give us a more preceise answer which type of loctite you where using?

Loctite are usualy choosen by numbers like 222 is a low friction screw safer, 638 is a more permanent glue to put gears and shafts thogether forever (heat it up to 120?C and there is a chance to take it apart again) and so on. do you have a exact number?

Regards, Dominik

swisseagle said:

Dear Fred

Thank you for this interesting information.

Can you give us a more preceise answer which type of loctite you where using?

Loctite are usualy choosen by numbers like 222 is a low friction screw safer, 638 is a more permanent glue to put gears and shafts thogether forever (heat it up to 120?C and there is a chance to take it apart again) and so on. do you have a exact number?

Regards, Dominik

Click to expand...

Dominik,
I'm not trying to answer for Fred, but for another data point I did almost exactly what Fred did and used Loctite 609. It's labled as "Secures Gears" also.

That was about 150 hours ago an the nosegear leg is still tight.
I noticed mine being loose when I was parking the airplane by hand the nose gear would have a little "pop" sound when given a side load.
Not anymore

I used this stuff back when I worked in industrial maintenance. It really works.

Mark

Fred.Stucklen said:

Hi All,

With the history of issues in this are, it would seem prudent to do the final front gear leg assembly with Lock-Tight on the upper mount area. This would prevent the re-occurring issue that we've seen in this area on the -A RV models.... And I've seen it happen to every RV-XA that I've owned....

Click to expand...

Fred, is there any chance that you might not be able to remove the gear leg in the event that you need to for some reason.

Wondering the same thing.......

Captain Avgas said:

Fred, is there any chance that you might not be able to remove the gear leg in the event that you need to for some reason.

Click to expand...

Guys,
It just takes a little heat to "unstick" the loctite. Just enough heat to ruin the powder coat but not adversely affect the engine mount steel.
Seriously, I'd just warm it up slowly and you might not have to compromise the powder coat before the loctite would loosen up.

I couldn't think of a reason I'd want to remove it anyway. Unless Van's comes out with a new style again.

Mark

I think the builder of my RV-6A went one 'better' than loctite on the main gear legs. I could be wrong but it looks to me like the top of the tubes and the legs are spot welded.

Guess I'll find out as I'm currently gearing up to transform the 6A into a 6.

I think the stuff I used was the 609, but not sure. The container label is gone. The idea is to make the gear leg very difficult to move under loose bolt conditions.
And as others have stated, heating up the gear leg where the locktite was used will allow one to remove the gear leg. At least in theory... I haven't had to remove it yet, and don't plan to in the near future.....
It's interesting that there haven't been any reported instances of the main gear legs having the bolt hole wear problem.....

Fred

Mark Burns said:

Dominik,
I'm not trying to answer for Fred, but for another data point I did almost exactly what Fred did and used Loctite 609. It's labled as "Secures Gears" also.

That was about 150 hours ago an the nosegear leg is still tight.
I noticed mine being loose when I was parking the airplane by hand the nose gear would have a little "pop" sound when given a side load.
Not anymore

I used this stuff back when I worked in industrial maintenance. It really works.

Mark

Click to expand...

Hi Fred, are you still going strong with the loctite solution? Any issues? How many hours has it been now?

I am thinking of doing this. Latest condition inspection reveals nosegear rotation in the mount resulting in about .25" lateral free play measured at the nosegear axle after 320 hours on the Hobbs. I can't be sure whether this has gotten worse, I think there has always been a little free play but I never measured it before. I have used the Loctite/Henkel retaining compounds in other applications and it seemed to work pretty well.

Here is their catalog with a flowchart (on pp.121-125) for selecting the proper adhesive and the 609 looks like the correct stuff if you want to be able to remove it later on.
http://www.henkelna.com/us/content_data/321232_LT3355_ASB_v16_Book_2013__F_LR.pdf

I was tired seeing this two-three times a year.






Last year I put loctite per Fred and it stays frozen. No wear on bolt/hole observed at almost 1K hours. I don't use nosegear on landings anymore.

Thanks Vlad. I think I'll pick up some 609.

Vlad said:

I don't use nosegear on landings anymore.

Click to expand...

Whudyado, put helium in your nosewheel? Hey, that's a good idea!

Close tolerance bolt?

I installed a close tolerance bolt in this location. Have you experienced this play where a close tolerance bolt was used or just the standard ANXXXXX?

Taper Pin?

There's just another thread going on about using taper pins instead of this same bolt in order to prevent wear AND movement
http://www.vansairforce.com/community/showthread.php?t=105870

...post-fix behaviour?

I am curious if anyone who experienced shimmy on a 'properly' torqued nose swivel has noticed any diff after taking the slop out of their socket?
....seems to me that the change in camber ( or whatever you want to call that axis) could allow, or even enhance an oscillation?

Pmerems said:

I installed a close tolerance bolt in this location. Have you experienced this play where a close tolerance bolt was used or just the standard ANXXXXX?

Click to expand...

I don't know about the other guys, but I believe I used the Vans supplied shoulder bolt, which is a close tolerance bolt, I think.

Taper pin retrofit

I thought I might post this about retrofitting my 6A nose gear leg bolt with a taper pin. In general I like a good mechanical fit for longevity vs. the loose fit and locktite approach which was my original plan.

The only way to do this modification without removing the mount was to put the pin in from the top, reverse to the Ellis approach. This might make removal of the pin after time a bit harder but it will be possible. I also did not have to put a hole in the engine mount, but note that others might have to.

The original AN5 bolt was loose in the hole and with the nose wheel off the ground, I could rotate the gear leg in the mount an get some free play, which was bound to get worse over time. I decided to use a taper pin. I sized the taper pin based on the existing bolt size and used an AN386-3-12 pin. Unlike the Matronics/Ellis taper pin which is a -4 diameter, I sized the -3. The small end of the -3 at the OD of the tube is .318" and the large end is .3855", whereas the AN5 bolt is .309" to .310". The allowables for the AN386 pin are higher than the AN5 bolt and the 4130 steel engine mount becomes the weak point. Even so, the larger diameter of the pin should help the engine mount bearing loads overall.

Also, given the challenge of taper reaming the hole on the mount (see numerous other posts on this) , I didn't want to have to enlarge the holes all the way up to the -4 diameters.

The existing leg was already match drilled to the mount, and there was no obvious elongation of either hole so it provided a starting place.

I removed the gear leg, and carefully step drilled the hole using progressively larger drill bits so that the taper ream wasn't having to remove so much material (each larger diameter is drilled with less depth). Then reamed so that the pin fit to the proper depth (must account for the engine mount tube thickness, etc.) This took some real effort even with the step drilling. I started out by hand on a bench where I could apply my full body weight and eventually came to a stop. I decided to move to my 3/4hp drill press which I can get down to 120 RPM. Eventually cut the pin hole size to get the pin depth needed. Taper reaming the gear leg is not easy.

Then went back to the aircraft, using a short drill bit, enlarged the top hole in the mount close enough to the pin size to let the taper ream get a good start. Now it is impossible without a machine shop setup to enlarge the hole in the gear leg perfectly on center, but since we are enlarging the hole in the engine mount, I figured to let the gear leg keep everything aligned as the mount is reamed. Inserted the gear leg and aligned and reamed the mount.

Now the good news about the leg being so hard to ream, was that there was no danger of over reaming the engine mount leg combination while taper reaming by hand. Essentially when the reamer stopped cutting, I was to the same size as the gear leg with a perfect match.

After cleaning everything up, installed the gear leg, taper pin, washer and nut and voila', no play.

I have used taper pins for other applications and unless the bearing loads of the pin on the mount are to high, there should be no play forever, and I can remove the gear leg if necessary without having to deal with the locktite.

I hope this helps someone if they need to do the same thing. I don't have pics of this but not really much to show.

how much Loctite????

Before I go drop $60 on a little bottle of loctite, how much have you guys really used???
there's 1 ml, 10 ml, 50ml, or 250 ml for only $223!!! ( acklands supply!!!)

where can you buy some at a reasonable price????

does a guy just put a thin film on, assemble, and hope you had enough?
can you inject more, or is it too thick for that?

I guess if some oozes out, you're golden.

thx

I bought a mL on Ebay for about $1.50. I haven't done mine yet so I can't tell you whether its enough. But its a small gap and it won't take much. Maybe buy 2 or 3 1 mL containers just to be safe. Or skygeek has 10 mL for $10.76:
http://www.skygeek.com/henkel-locti...Nzzv-Vmat31xwN0EoqoWfWrxVsjdevtS7-2gDck_D_BwE

Just goop it on there and rotate the gear leg a quarter turn as you install it, like gluing PVC pipe together.

Spot Weld Gear in socket?

GrayHawk said:

I think the builder of my RV-6A went one 'better' than loctite on the main gear legs. I could be wrong but it looks to me like the top of the tubes and the legs are spot welded.

Click to expand...

Has anybody else done this? Reasons not to?

Inability to remove it comes to mind.

And play can still continue at the bottom of the socket.

Final solution

The socket had been drilled out to 3/8 by the previous owner. The socket has now elongated to .0400. I was able to locate an oversized 3/8 bolt (NAS6606-30Y) that would fill the void. However, the price for that bolt was $525.00! Yes, one bolt, $525.00. So, I'm looking for alternatives. This plane is an RV6, 1990 build. Back then sockets and legs were drilled by the owner.
Here are my courses of action. Spot weld (TIG) the top of the gear leg and socket and install a new AN6 bolt and use loctite 660 to help keep the gear leg from rotating OR get a new engine mount and gear legs.

Inhot said:

The socket had been drilled out to 3/8 by the previous owner. The socket has now elongated to .0400. I was able to locate an oversized 3/8 bolt (NAS6606-30) that would fill the void. However, the price for that bolt was $525.00! Yes, one bolt, $525.00. So, I'm looking for alternatives. This plane is an RV6, 1990 build. Back then sockets and legs were drilled by the owner.
Here are my courses of action. Spot weld (TIG) the top of the gear leg and socket and install a new AN6 bolt and use loctite 660 to help keep the gear leg from rotating OR get a new engine mount and gear legs.

Click to expand...

An M10 bolt is .394" so pretty close. However, it is quite rare for a hole to grow symmetrically from wear. Far more likely to be oblong in shape. I would consider a taper pin if you have enough room. That leg is spring steel, so pretty tough on bits making this a not so fun option.

The wear is likely to be in the socket hole with the holle in the leg true and round. So, you can weld one socket hole closed. Better to build weld outward to avoid having to clean up bore of socket or weld on a new piece of steel over the hole. Then match drill from opposite side with leg in place. Then repeat for the other hole. The large bits like to grab when they punch through and likely how the builder got to 3/8" in the first place. So best to use a smaller bit with a 3/8" pilot to start the hole.

Thank you for your response and recommendations. The elongation is at the 3 o'clock position of the socket hole. The gear leg measures right at .375. I'll confirm this tomorrow, but the distance between the aft side of the socket and the firewall would make it very challenging to properly drill through. Instead of trying the weld option, I'll drop the gear leg and clean the leg and socket, re-insert the leg and apply loctite 660 to the circumference of the top of the gear leg where it seats against the socket. I'll try and fashion a shimm a from a feeler gauge to fill the elongation void, apply the loctite to the new AN6 bolt and insert and torque it down. I'll then apply a slip mark on the top of the gear leg, let it cure for 24 hours. Cross my fingers and try it out, see if and how long it holds.

Inhot said:

Thank you for your response and recommendations. The elongation is at the 3 o'clock position of the socket hole. The gear leg measures right at .375. I'll confirm this tomorrow, but the distance between the aft side of the socket and the firewall would make it very challenging to properly drill through. Instead of trying the weld option, I'll drop the gear leg and clean the leg and socket, re-insert the leg and apply loctite 660 to the circumference of the top of the gear leg where it seats against the socket. I'll try and fashion a shimm a from a feeler gauge to fill the elongation void, apply the loctite to the new AN6 bolt and insert and torque it down. I'll then apply a slip mark on the top of the gear leg, let it cure for 24 hours. Cross my fingers and try it out, see if and how long it holds.

Click to expand...

I would exercise some caution here. While I have not used 660, I have used a few other sleeve retaining compounds. It is like traditional super glue when used on tight fitting parts. If the clearance is barely a slip fit, the glue starts grabbing long before the parts get put together and a decent force is required to get it to fully seat. With tight fitting parts, the intial grip happens in a second or two. WIth loose fitting parts, you have plenty of time. the grip/cure time is directly related to the gap size. I would do some experimentation to be sure you are going to have enough time to get the bolt hole lined up. If you don't get it right, it WILL NOT be fun getting that leg out of the socket. That stuff is quite strong and there is a LOT of surface area in the leg/socket area. You do not want to be using a propane torch in this area and once cured it will either need heat or pressing tools to get it out.

If you really want something between the leg and socket, I would consider one of the wicking versions. However, most won't accommodate much of a gap and usually not as strong.

Now that's some tinely and much appreciated information right there!
Thank-you.