The purpose of the nose gear is to keep the prop from hitting the ground when you park the aircraft.

That said, rebuilding the shimmy damper and balancing the nose wheel and tire should solve your problem.

Afterward, re-read line one.

I recently rebuilt my shimmy damper on the last annual.  It looked like it had never been touched before and I assumed it had no oil in it.  It would shimmy on landing roll out if I did not maintain enough back pressure on the yoke. 

Upon disassembly I found it was servicable and probably did not need rebuilding.  The paint was stripped and it was repainted.  A new seal kit installed and it was put back on the plane.  Upon flight testing is had the same amount of shimmy as before.  It looked a lot better though.

I would think that the shimmy would be related to the geometry of the nose wheel strut (caster angle etc.) and any wear or play in bushings and pins or bolts.  Regardless a rebuilt damper did not change things.

The shimmy is manageable and I can accept it as normal.  If good landing practices are used there is no problem.  I always treat the nosewheel as tender and land will full or near full up elevator.  Especially with no one in the back seat. 

The plane is a 172K with under 1700 hours TT.

Ron

I have a 2000 model 172 and replaced the shimmy damper with a Lord damper. it made a huge difference in taxi, takeoff & roll out. I highly endorse this product. NO more shimmy at any speed.

The most often cause of the dreaded nose wheel shimmy is the lack of steering collar shimming. I have addressed numerous squawks in my shop that the dampener was just overhauled and it still shimmy's. The nose gear assembly must be removed from the airplane to accomplish this. Two other things that come to mind are the strut pressure and the tire pressure.
-Tom

The nose shimmy is almost always the steering collar shims and / or the torque links having too much slop.  When you replace the steering collar shims there is a washer that looks like a shim, only thicker.  Replace that when you add shims.  The lord shimmy dampener works very well, but even with that you can have shimmy if the collar and torque links are not tight.  We see service life of approx. 600hrs between shimmy events when the collar is re-shimmed and torque links fixed.

I had been having a sometimes vicious shimmy on roll-out, that we could not shim out of the scissor link.  At annual I replaced all the bushing and bolts, about $150 worth, and it has been worth EVERY penny I paid.

My A&P said to grab the scissor link from the back and if it could wiggle it was worn out.  We had rebuilt the dampener 4 months ago, so it was doing as well as it could.

Rod

Hi Lorne;

My 1978 C-172 is 45 psi.  If I don't have an air source with a gauge, I usually raise the nose off of the ground, inflate it, and then set it back on the ground and compress the strut a few times.  If it sits with more that about 3 inches of chrome showing on the strut, I release a little air until it sits at about 3 inches.  This seems to be a good approximation.  Hope this helps.

Jon

Ditto on the steering collar and the torque links. If you grab the torque link assy and feel ANY looseness you are going to get nose wheel shimmy. Replace the bushings in the torque links and also install the shims per the maintenance manual and you will find that your shimmy magically disappears.

After complaining for years about nose wheel shimmy and having my A&E overhaul it at each annual, I installed a Lord mount.  It solved the problem and the (172XP) has been shimmy-free for ten years.

I understand that Cessna is installing the Lord mount on all new 172's.

In the case of shimmy at the lower speeds, it is an effect of spatial rigidity and as such just like a gyro spining down with a tendency to tumble. An imbalance of the nose wheel will aggravate the feel of the shimmy simply because its frequency is less. All that was said to recommend that you check the shimmy damper service and the balance of the wheel.

I found a shimmey dampener on www.aec-inc.com for $795 which was a lot cheaper than Lords.

ron christen Wrote:
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> I like to know different ways things are done,Do
> you have a easy way to remove torque link
> bushings. Thanks


Basically you don't remove them, you drill them out.  First use a drill bit (.375 I think) to align the link on a drill press.  Use a machine vice and blocks, clamps etc to hold the link in place straight.  Gradually increase the size of the drill bit removing a small amount of material each time.  Don't go all the way through both bushings, just do one at a time flip the link over to do the other one.  Don't try to drill out the whole thing, once the bushing is thin enough you can use a punch to collapse the remainder of the bushing inward and then extract with no damage of any kind to the link.