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Best choice for loose nose leg repair

L

LarryT

Well Known Member
From a search of those who have gone before - the following repair methods for a loose nose gear leg in the engine mount socket were noted.

1. Ream the hole with a #3 B & S tapered reamer and use the appropriate AN tapered pin and special washer.

2. Use an adjustable straight reamer to oversize the hole for a -5 NAS oversize bolt.

3. Drill hole out and use a 3/8" bolt.

This is finally a flying airplane again. I am really reluctant to do major dismantling to make this repair.

Method #1 seems like it would be best suited to new construction and be a permanent solution to the loose gear leg issue - especially if a metal lock nut is used.

Method #3 seems like it would also be difficult to accomplish without significant disassembly and may still require a reamed hole.

Does that leave method #2 or have I overlooked something? I don't have a feel for how tough it is to remove material from the heat-treated gear leg.

Larry Tompkins
N544WB -6A
W52 Battle Ground, WA
 
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Larry, that depends on where the the leg is loose in the socket. Is the bolt still tight? Usually the lower part of the socket will show clearances due to excessive wheel wobble that has not been controlled by good tires and proper adjustment.

To all 6789 with a nose wheel, you should do this at each annual....
Lift the nose clear of the ground and with the tire exposed, pound down on it with your fist. It should be quiet. If you hear anything, you have slop in the lower socket.

Get out your feeler gauges and see how much slop you have at the lower socket. Report back and we can go from there.
 
Replies to #2 and #3

Craig, you delivered the plane, so you know it was purchased because I was (mostly not) building a -7.

Mike, see what I am (mostly not) building above. Some day, I hope to have the time,money and energy to get back to construction.

Larry
 
Best Choice for Loose Nose Gear Leg Repair

Larry

I just did the same repair on my 8A. I used method #2.
Bought the NAS6605-29X oversize bolt from Gahco. It was 0.326 in dia.
Then I bought a 0.3260 in chucking reamer from McMaster-Carr after measuring the bolt dia. reamers are available in 0.0005 in steps.

I had the gear leg out of the mount & had no problem reaming both the leg & mount using plenty of cutting grease. The (lubricated) oversize bolt went in with some help with a soft-faced hammer & is now a zero clearance fit.

I would suggest that it is worth the effort to remove the gear leg to get it right - much easier to do the job right with the leg held in a vice.

I am assuming that the holes have not been worn beyond the o/s bolt dia.

John Moody
RV-8 VH-MKX
 
Loose nose gear leg

It depends how bad the motor mount hole is elongated. If the elongation isn’t too severe,
use the method listed below to fix the problem. I've repaired several now by using this method:

1. Be sure that you have the correct bolt length to attach the gear leg. When fully inserted, just a bit of the shank (not the threaded area) should be seen extending through the motor mount tube. Use a longer bolt with washers (top & bottom) if necessary. If the nut is impossibleto get started onto the bolt, use a 1” rounded dowel and a hammer to indent the firewall so you are able to get the nut started. The wrong size bolt may have been your original issue.

2. Remove the whole gear leg from the motor mount. Clean ALL surfaces with
a de-greaser - inside the whole tube, and the whole upper part of the gear leg.

3. Apply permanent Loctite to the upper inside surface of the motor mount
tube. Use your finger to coat the inside motor mount tube surface thoroughly.

4. Slide the gear leg into the tube partway. Put some axel grease on the lower bearing area.

5. Over insert the gear leg into the motor mount tube such that the upper bearing surface extends towards the firewall. Coat this bearing surface with permanent loctite. Be sure to cover all surfaces that will come into contact with the upper motor mount tube.

6. Lower the gear leg such that you can start the bolt (with washer) into the upper bushing area of the gear leg. Leave the bolt partially out so you can fill the motor mount elongation area with J-B WELD Epoxy Adhesive.

7. Carefully put some J-B WELD Epoxy Adhesive onto the lower part of the motor mount tube where the nut will be installed. Be careful not to get it onto the bolt threads as that will make future repairs much more difficult...

8. Use a washer to squeeze the J-B WELD Epoxy Adhesive into the lower motor mount Tube area, then install the nut and tighten.

If you ever have to remove the gear leg, remove the nut & bolt, then use a torch to heat up the Loctited area and apply a twisting force to the gear leg. It torch will soften the Loctite and enable the Gear leg to be removed.

Good luck

LarryT said:
1. Ream the hole with a #3 B & S tapered reamer and use the appropriate AN tapered pin and special washer.

2. Use an adjustable straight reamer to oversize the hole for a -5 NAS oversize bolt.

3. Drill hole out and use a 3/8" bolt.

This is finally a flying airplane again. I am really reluctant to do major dismantling to make this repair.

Method #1 seems like it would be best suited to new construction and be a permanent solution to the loose gear leg issue - especially if a metal lock nut is used.

Method #3 seems like it would also be difficult to accomplish without significant disassembly and may still require a reamed hole.

Does that leave method #2 or have I overlooked something? I don't have a feel for how tough it is to remove material from the heat-treated gear leg.

Larry Tompkins
N544WB -6A
W52 Battle Ground, WA
Click to expand...
 
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People have had success just replacing the standard AN bolt with a close tolerance bolt. Two people in our hangar, to be specific...

Very easy to try. You wouldn't think a couple thou would make such a difference, but it does.

It all depends on what the problem is - a more detailed description would be helpful.

Good luck!
 
Loose nose Gear leg

Most of the time it isn't the tolerence of the bolt, but the elongation of the motor mount hole, that keeps getting looser and looser. By Loctiting the complete circumference of the upper leg area to the motor mount, there is a lot more holding area than just what the bolt allows for. I would Loctite this area even if I used an over sized bolt solution to fix the motor mount hole elongation. If you use the Loctite, you'll probably never see this issue again....
I've seen some very bad movements repaired with the process I outlined below, that are still movement free after 500 Hrs of additional operation.... And this process is MUCH easier than removing the engine to drill out a new oversized hole, or even putting in a tapered pin...

AlexPeterson said:
People have had success just replacing the standard AN bolt with a close tolerance bolt. Two people in our hangar, to be specific...

Very easy to try. You wouldn't think a couple thou would make such a difference, but it does.

It all depends on what the problem is - a more detailed description would be helpful.

Good luck!
Click to expand...
 
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Here is what I found yesterday...

After uncowling the engine and taking the weight off the nose wheel, I determined that there was rotational movement between the nose gear leg and engine mount socket. I also found that the bolt was loose. No doubt the bolt holes in the engine mount are elongated.

When I retorqued the bolt, the clamp load was sufficient to prevent rotational movement. I believe this is a temporary and not a permanent solution. I further understand that with only one bolt, the socket deforms elliptically, and the clamp area is not 360 degrees. Therefore I appreciate Fred's solution. The looseness is easy to monitor because I back the plane into the hangar using a tow bar (because I'm more interested in going flying than putting the plane away).

My hope is that the looseness won't return during this flying season and I can address the issue late next fall. Currently I am practicing touch and goes to regain my flying proficiency that got rusty during the 2.5 years of inactivity. If the nose gear leg/socket handles this activity, I only anticipate
one takeoff and one landing per an average of 1 - 2 hrs. of flight time the rest of the summer, so I probably will be good until fall. If it loosens up soon, I will pull the gear leg and take a closer look.

Thank you all for your input

Larry
 
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