nose shimmy

[Medflyer]

My '67 M20F has developed a nose shimmy over the last couple of months.  I'm new to the Mooney world so of course I looked for a non existent shimmy dampner.  It's in annual now and I told my mechanic to take a look at it.  Up on jacks there is a bit of "wiggle" play in the nosewheel.  He said that Laser (I'm not quite sure what that is) does not make parts any more to be able to fix it.  Has anyone had an issue like this and how did you go about fixing it?

 

Again, as always, thank you in advance for the replies!:)

Bill

[Paul Thomas]

Is the wiggle front to back or side to side? Has he determined where the wiggle is from?

LASAR is a company that sells parts.

[N201MKTurbo]

There are a couple of things to look at. One is the pivot bearing. Laser had an oversized bushing that was reasonable and easy to do. 
 

The other thing is the steering horn. If you cannot get a new one, you can shim up the old one and it will work OK for a while.

[Browncbr1]

If your main gear discs are too far worn, they change the geometry of the nose gear trailing link and can cause the 8 second ride.  If your tail is sagging to the ground, check that.  

[Ragsf15e]

40 minutes ago, Medflyer said:

My '67 M20F has developed a nose shimmy over the last couple of months.  I'm new to the Mooney world so of course I looked for a non existent shimmy dampner.  It's in annual now and I told my mechanic to take a look at it.  Up on jacks there is a bit of "wiggle" play in the nosewheel.  He said that Laser (I'm not quite sure what that is) does not make parts any more to be able to fix it.  Has anyone had an issue like this and how did you go about fixing it?

 

Again, as always, thank you in advance for the replies!:)

Bill

Even when it hasa little wiggle, it shouldn’t necessarily shimmy unless the geometry isn’t right.  It might just have a dead spot in the steering.  There’s an sb and a Don Maxwell article about shimmy or the 8 second ride that you can search for.  It’ll help you find the right geometry.  Fixing the wiggle isn’t usually too hard with shims, bushings or new heim joints.  It needs to be up on jacks , lay under the nose and wiggle it.  You can see where it’s loose.

[Brian2034]

Have you checked the Service Bulletin M20-202?

Also as other have mentioned the steering horn can develop play, which can be seen if someone sits in the plane and slightly moves the left/ right rudder pedals, while you observe the steering horn for movement. (Usually side to side movement on the horizontal sleeve. There are videos on the site showing exactly what you should be looking for. Wear in the pivot shaft (steering shaft) is a little harder to detect, you may have to raise the nose wheel off the ground to see the play in the pivot shaft. Also check your tire pressure as the temperature falls your tires may lose pressure.

[cliffy]

With the nose wheel off the ground rotate it (like its turning the airplane) to see

how much left/right slop there is in the linkages at the top of the nose wheel well

Next push it front to back to see if there is lots of play in the big vertical main bushing

Next be sure to check tire pressures  (low pressure equals shimmy)

Read the above SB and check to see if your caster angle is correct. 

One item not checked by many is the torque of the big vertical bolt that the nose wheel turns on

(it passes through the bushing you checked for play above) There is a required torque to be checked 

every annual that no one does. Be aware the torque value was lowered in a later bulletin than the maintenance

manual specifies. Be sure to check this torque

Order of events-

Check tire pressure and bolt torque (as its up on jacks now)

Check left/right steering slop and fore/aft bolt bushing wear.

Check the SB and hang a plumb bob as specified to check caster setting. 

One of these (or several ) will cure your problem. 

[Fritz1]

there is an idler arm in the nose gear steering mechanism, that arm pivots on a #10 bolt, that bolt may be loose, if so tightening it will take some of the slop out, thread locking compound on that bolt thread cannot hurt, bolt is vertical, your A&P will know where to find it, as stated before, jack it up, wiggle it in all directions and see and feel what moves