Nose Wheel "Clunk" when landing - help needed

Hey - last couple of times when landing, I felt a "clunk" when the nose wheel touched down and had some shimmy afterwards.

I've been trying to figure out what is going on and am starting to run out of ideas of what to check.

The first thing I did was to remove the nose wheel, clean and repack the bearings, balance the wheel, and check the breakout force (~somewhere between 22 and 25 lbs on a fish scale), and check the air pressure (35psi)

Went flying again, and still had the clunk and shimmy.

Reading through past posts, I found a few folks have had trouble with the bolt that holds the nose gear in the motor mount.

This afternoon, I had my dad come the hanger with me and had him push on the tail to lift the nose wheel off the ground. With the nose up, I pretty vigorously shook the nose leg both front to back and side to side and really did not feel any movement. The slight movement I felt seemed to be the leg itself bending slightly... I did not feel like there was any movement at the upper end in the motor mount.

I took a picture and based on the torque seal, it does not look like the nut has moved at all.

I am looking for any suggestions as what to check next. There is the possibility that I put the nose gear down at a higher than normal speed the last couple of flights... wondering if that could be my issue.

Thanks for any suggestions.

Jason

Remember the 6 posted here had the bolt shear, so put a wrench on it. Walt says always check with a wrench, torque seal only means you probably torqued it originally.

If you are fully panted look where the nose gear fairing touches the cowling, especially where metal plate locks the bottom cowling. Check wheel fairing brackets. Strange sounds can come out of them. Couldn't comment on shimmi might be an isolated issue.

Another possibility is to check the nose gear fairing and the wheel pants. The gap between these two are typically only about .25? and a fore/aft movement on the wheel pants could be hitting the fairing.

The bolt looks like there's a lot of thread protruding from the nut and only the one washer. Could the nut be bottomed out on the threads and not fully tensioning the bolt?

If so, the nut will appear to be completely torqued but it wouldn't be putting a preload on the bolt.

Something to check....

Dave

Did you grease the nose wheel pivot joint? Swing the nose wheel back and forth thru it's full travel then grease it again.

Clunk Sound

UnPossible said:

Hey - last couple of times when landing, I felt a "clunk" when the nose wheel touched down and had some shimmy afterwards.

I've been trying to figure out what is going on and am starting to run out of ideas of what to check.

The first thing I did was to remove the nose wheel, clean and repack the bearings, balance the wheel, and check the breakout force (~somewhere between 22 and 25 lbs on a fish scale), and check the air pressure (35psi)

Went flying again, and still had the clunk and shimmy.

Reading through past posts, I found a few folks have had trouble with the bolt that holds the nose gear in the motor mount.

This afternoon, I had my dad come the hanger with me and had him push on the tail to lift the nose wheel off the ground. With the nose up, I pretty vigorously shook the nose let both front to back and side to side and really did not feel any movement. The slight movement I felt seemed to be the leg itself bending slightly... I did not feel like there was any movement at the upper end in the motor mount.

I took a picture and based on the torque seal, it does not look like the nut has moved at all.

I am looking for any suggestions as what to check next. There is the possibility that I put the nose gear down at a higher than normal speed the last couple of flights... wondering if that could be my issue.

Thanks for any suggestions.

Jason

Click to expand...

Be sure to take off the gear leg fairing and check the gear leg for cracks. You should have the newest gear leg in an RV-7A, but if you inadvertantly nicked it below the mounting area, it may have cracked. A partially cracked gear leg will make a noise when landing......
I had an original RV-6A gear leg do exactly what you are discribing. Unfortunatly I didn't find it until it snapped off, causing a prop strike, and lower cowl damage on a landing...

Fred.Stucklen said:

Be sure to take off the gear leg fairing and check the gear leg for cracks. You should have the newest gear leg in an RV-7A, but if you inadvertantly nicked it below the mounting area, it may have cracked. A partially cracked gear leg will make a noise when landing......
I had an original RV-6A gear leg do exactly what you are discribing. Unfortunatly I didn't find it until it snapped off, causing a prop strike, and lower cowl damage on a landing...

Click to expand...

Fred - thanks for the info....curious what you mean when you say "nicked it".. I will definitely look for a possible crack, but curious what could cause a crack.

Thanks,
Jason

Gear Leg

UnPossible said:

Fred - thanks for the info....curious what you mean when you say "nicked it".. I will definitely look for a possible crack, but curious what could cause a crack.

Thanks,
Jason

Click to expand...

I had put a wood stiffener on the first RV-6A front gear leg, and probably "Nicked it" with a file while shaping the wood. The gear leg cracked on the underside, and was "clunking" on landings due to the gear leg flexing up and down when the wheel touched down. Mine was cracked over 50% through before it finally gave up the ghost! All the time I was looking for something loose, never imagining that a 1" steal rod could have cracked..... Van has since re-engineered the gear leg to be stronger, but that doesn't mean that it can't break.....

Flying without the nosegear fairing(s) would quickly prove or disprove the theory that those are playing a part.

How much free play do you have in the gear leg? Hang some weights from the tail tiedown so the nosegear is elevated, or use a ratchet strap between the tail and a tiedown. You want the nosegear elevated, without somebody hanging on the tail, because you want to take your time evaluating any nose gear free-play in all degrees of freedom.

Try to rotate the nosegear leg back and forth in it's mount (like trying to screw and unscrew the gear from its mount). Is it fixed or does it rotate a couple of degrees? Is there any axial play of the gear leg with respect to it's mount?

When you rotate the nosewheel fork about it's bushed axis, is there any free play there?

It might be a good idea to remove the nose gear and inspect the holes in socket and leg. Replace the bolt with a close tolerance bolt (search these archives for much reading on that topic). The bolt on mine was quite worn after only a few hundred hours.

If there is axial play as Noah suggested, it only takes a few thousandths of an inch to make a clunk.

Another thing to check is the torque on the engine mount to fuselage bolts, especially the inner two bottom ones.

troubleshooting 101

Jason,
since you didn't say how many hours you've flown, let me suggest one more thing us 'low-timers' may not have experienced!
I believe it's pretty well known that some RV's exhibit a pronounced 'poonk!' as the airframe transitions from air to ground loads ( my interpretation)...seems to be the rear fuselage skins oil-canning in or out.
As it resonates throughout the airframe, being a big drum, it may be hard to nail down the source.
If you are feeling thru the floorboards, and hearing this clunk, then you may be right to check everything FWF. If not, just saying, there may be other possibilities!?!?

suggestion.... worth exactly what you paid for it!

Steve said:

Did you grease the nose wheel pivot joint? Swing the nose wheel back and forth thru it's full travel then grease it again.

Click to expand...

I have greased the nose wheel pivot joint, but now that I think about it, it has seemed to get a bit "stickier" over the past few months. While the breakout force is in the low to mid-20's, when I use the tow bar to turn the wheel, it doesn't turn smoothly, it seems to want to move in short "hops."

I wonder if what I am feeling the same "hopping" friction when the wheel straightens out on landing.

I know that there needs to be some resistance (i.e. breakout force),but how smoothly should the nose wheel turn side to side?

Good News! - the clunk is gone!

Not sure what did it, but over the past two weeks, I complete removed the entire front landing gear assembly. I did not really find any "smoking guns".

But to be safe, when I reinstalled the front gear into the motor mount, I used Loctite 680. When I reinstalled the nose wheel, I took more care to lightly grease all the washers that may move against each other.

I set the breakout force to somewhere around 28 lbs, and took her for a ride.
I actually could not tell when the nose wheel came down.....

Very happy that this is taken care of and I can enjoy my plane, just as good weather should be here soon.

Thanks for all your suggestions,
Jason

zerk failure

Jason I am wondering if you seen something like this when you disassembled the fork. I had zerk fitting failure last year and inadequate lubrication caused "sticking" in pivot joint. See how ugly it looked?

Nope - no sign of corrosion. However, I did have an issue with the grease zerk. Don't know if my gun holds it super tight, but the zerk that Vans sent with the kit pulled out when I was removing the grease gun.

The zerk that Vans sends is very shallow... I replaced it with a zerk that threads in a bit more (but still way less then the thickness of the nose gear) and everything is now good.