Nose wheel flutter

[BettyFord]

Hi my nosewheel is fluttering  heavily on grass. Shockdisk has been replaced a year ago. Any other reason fort he flutter?

Thanks

[Mjknick@gmail.com]

Steering horn gets worn. Lasar has rebuild and conversion from early to late. Save your $$$$ not cheap but it fixed my shimmy to zero.



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[rbridges]

I was going to suggest steering horn, also. Several threads about it since it's a pretty common part to wear over the years.  

If you knew what "normal'" felt like, you can grab your rudder and see how much play is in it on the ground. Mine really tightened up when the steering horn was replaced. 

[Guest]

4 hours ago, BettyFord said:

Hi my nosewheel is fluttering  heavily on grass. Shockdisk has been replaced a year ago. Any other reason fort he flutter?

Thanks

While SB M20-202 does not apply to your serial number, the concept does and is in the maintenance manual.  

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-202.pdf?t=1524682187863

Clarence

[N201MKTurbo]

You should also look at the pivot bushing on the trunion. Check it for play while up on jacks. If it is worn you can replace the bolt and bushing. If it warn between the bushing and trunion, Laser has oversized bushings.

The nose gear steering should be stable irregardless of how much slop is in the steering horn. A tight steering horn can keep a sloppy steering pivot from shimmying, which is just masking the real problem. 

[rbridges]

6 minutes ago, N201MKTurbo said:

You should also look at the pivot bushing on the trunion. Check it for play while up on jacks. If it is worn you can replace the bolt and bushing. If it warn between the bushing and trunion, Laser has oversized bushings.

The nose gear steering should be stable irregardless of how much slop is in the steering horn. A tight steering horn can keep a sloppy steering pivot from shimmying, which is just masking the real problem. 

I think that got replaced at my last annual.  Cole ordered a bushing from LASAR because it was worn.

[carusoam]

Aside from all good advice you have gotten so far...

For additional background there is a maintenance piece written by DMax called the eight second ride... it details the wear issues described in this thread.

The title is a reference to riding a bull...

 

How well is your 2200’ grass strip working out?

Best regards,

-a-

[BettyFord]

Thanks, next month is the annual...let's see what the maintenance guys say.
The grass strip works out fine so far......the surface is smooth and with a weight in the midrange you never need more than half the rwy.
On takeoffs almost fully loaded with light winds and not too hot no problems as well.
Only taxiing to the hangar the ride gets rough and the nosewheel starts to flutters.
So the M20J is a perfect plane to fly on grass and not like some say not usable,  provided you fly the correct speed!
I even went to Helgoland (EDXH 480m or 1574ft)

Great fun so far with my plane

[Shadrach]

I have a new steering horn and and installed the LASAR oversized truss bushing. My linkages are tight but my nose wheel still shimmies noticeably when tire pressure is below spec. The further below spec, the more shimmy.  I'd start there first.  Eyeballing the tires on these aircraft is not an adequate means of determining proper pressure, especially on grass.

I agree with you regarding the airframe working well on short and soft fields.  The inner gear doors are vulnerable, but the airframe is perfectly capable in the hands of a speed conscious pilot.

[INA201]

7 hours ago, rbridges said:

I think that got replaced at my last annual.  Cole ordered a bushing from LASAR because it was worn.

Ditto, Cole took care of the bushing which fixed my shimmy.

[Alan Fox]

As all the experts have spoken , Lasar makes a shim that goes on top of the truss over the tube under the collar , it is 45 dollars , and will stop all shimmying.....But by all means spend 2000 dollars trying to do what everybody says , 

[Yetti]

Also holding back on the yoke will help.  Which should probably be done on grass anyways.

[RobertGary1]

On 10/21/2018 at 7:12 AM, BettyFord said:

.
So the M20J is a perfect plane to fly on grass and not like some say not usable,  provided you fly the correct speed!

M20s do fine on some grass fields as long as the gopher holes are smaller than the nose wheel. 

-Robert 

[ujhan]

On 10/22/2018 at 8:14 AM, Alan Fox said:

As all the experts have spoken , Lasar makes a shim that goes on top of the truss over the tube under the collar , it is 45 dollars , and will stop all shimmying.....But by all means spend 2000 dollars trying to do what everybody says , 

@Alan Fox can you post the link here to that shim please?

[Guest]

7 hours ago, ujhan said:

@Alan Fox can you post the link here to that shim please?

Here you go,

https://cdn2.hubspot.net/hubfs/4147179/technical_documents/service_bulletins/sbm20-202.pdf?t=1541526534194

Clarence