Nose Wheel Shimmy Dampener - Revision history

Admin: 20 revisions

2010-08-20T18:09:54Z

20 revisions

Bferrell at 16:37, 20 February 2009

2009-02-20T16:37:50Z

Bferrell at 16:36, 20 February 2009

2009-02-20T16:36:26Z

Bferrell at 16:17, 18 February 2009

2009-02-18T16:17:35Z

Bferrell at 16:15, 18 February 2009

2009-02-18T16:15:12Z

Bferrell at 16:10, 18 February 2009

2009-02-18T16:10:14Z

Bferrell at 19:46, 8 May 2008

2008-05-08T19:46:30Z

Bferrell at 19:45, 8 May 2008

2008-05-08T19:45:38Z

Bferrell at 01:06, 8 May 2008

2008-05-08T01:06:50Z

Bferrell at 01:06, 8 May 2008

2008-05-08T01:06:14Z

@@ Line 6: / Line 6: @@
 [[Image:Damper parts_2_c10.jpg|right|thumb|300px|Dampener Parts]]
 [[Image:Damper parts_1_anno_c10.jpg|right|thumb|300px|Dampener Exploded View]]
 [[Image:Damper_1_c10.jpg|right|thumb|300px|Mount]]
 [[Image:Fork, tweaked_c20.jpg|right|thumb|300px|Mount]]

@@ Line 3: / Line 3: @@
 [[Image:shimmy2.jpg|right|thumb|300px|Side View]]
 [[Image:shimmy3.jpg|right|thumb|300px|Dampening Curve]]
 [[Image:Damper parts_2_c10.jpg|right|thumb|300px|Dampener Parts]]
 [[Image:Damper parts_1_anno_c10.jpg|right|thumb|300px|Dampener Exploded View]]

@@ Line 6: / Line 6: @@
 [[Image:Damper parts_1_anno_c10.jpg|right|thumb|300px|Dampener Exploded View]]
 [[Image:Drag test_crop_c10.jpg|right|thumb|300px|Dampener Drag Test]]
 [[Image:Damper_1_c10.jpg|right|thumb|300px|Mount]]
 [[Image:Fork, tweaked_c20.jpg|right|thumb|300px|Mount]]
-[[Image:Single weight_1 (2).jpg|right|thumb|300px|Mount]]
+[[Image:Broken mount_c10.jpg|right|thumb|300px|Broken Lead Weight Damper Mount]]
 <hr/>
 <center>end repeat message (partial)</center>

@@ Line 6: / Line 6: @@
 [[Image:Damper parts_1_anno_c10.jpg|right|thumb|300px|Dampener Exploded View]]
 [[Image:Drag test_crop_c10.jpg|right|thumb|300px|Dampener Drag Test]]
 <hr/>
 <center>end repeat message (partial)</center>

@@ Line 25: / Line 25: @@
 <center>more notes</center>
 <hr/>
 One of the local knowledgeable mechanics reminded me that Cessna for years had a hydraulic shimmy damper on their nosegear.  I examined and took photos of an older 150 and 172 to see how they did it.  The same guy gave me a discarded damper that someone had tried to get apart and essentially ruined (by FAA standards).  I took it apart, honed the bore, filed off the rough edges on the piston, put in new o-rings and snap rings, and filled it with automatic transmission fluid (ATF).  Total cost less than $2.<br/><br/>

← Older revision	Revision as of 18:09, 20 August 2010
(No difference)

@@ Line 1: / Line 1: @@
 Here's the shimmy dampener system that Sid Knox devised.<br/>
 [[Image:shimmy1.jpg|right|thumb|300px|Rear View]]
-[[Image:shimmy2.jpg|right|thumb|300px|Side View]]<br/>
+[[Image:shimmy2.jpg|right|thumb|300px|Side View]]
-[[Image:shimmy3.jpg|right|thumb|300px|Dampening Curve]]<br/>
+[[Image:shimmy3.jpg|right|thumb|300px|Dampening Curve]]
-[[Image:Damper parts_2_c10.jpg|right|thumb|300px|Dampener Parts]]<br/>
+[[Image:Damper parts_2_c10.jpg|right|thumb|300px|Dampener Parts]]
-[[Image:Damper parts_1_anno_c10.jpg|right|thumb|300px|Dampener Exploded View]]<br/>
+[[Image:Damper parts_1_anno_c10.jpg|right|thumb|300px|Dampener Exploded View]]
-[[Image:Drag test_crop_c10.jpg|right|thumb|300px|Dampener Drag Test]]<br/>
+[[Image:Drag test_crop_c10.jpg|right|thumb|300px|Dampener Drag Test]]
 <hr/>
 <center>end repeat message (partial)</center>

@@ Line 37: / Line 37: @@
 and still no shimmy.  Taxied back, made both sharp turns into the hanger
 easily.   This may be a keeper.<br/><br/>
 Q: Whats the turning radius with the damper connected?<br/><br/>

@@ Line 7: / Line 7: @@
 <hr/>
 "Nose wheel shimmy.
-One of the recurring irritations of an otherwise great airplane is the
+One of the recurring irritations of an otherwise great airplane is the nosewheel anti-shimmy scheme. Velocity forum readers may recall this subject comes up periodically, stirs up a few people, and then dies with the generally lame advise to keep the Belville washers clean and tightened to some seemingly arbitrary value and stop whining.<br/><br/>
-To get into my hanger I must make a sharp 120 degree right followed
+To get into my hanger I must make a sharp 120 degree right followed immediately by a left 90. Sometimes I make it and sometimes I end up out in the weeds.<br/><br/>
 After the last time, I finally decided I was pissed enough to try and do
@@ Line 23: / Line 17: @@
 <hr/>
-After two years, no problems... the only thing I would do different next
+After two years, no problems... the only thing I would do different next time would be to make it look a little better.
 <hr/>
 <center>more notes</center>
 <hr/>
-One of the local knowledgeable mechanics reminded me that Cessna for years
+One of the local knowledgeable mechanics reminded me that Cessna for years had a hydraulic shimmy damper on their nosegear.  I examined and took photos of an older 150 and 172 to see how they did it.  The same guy gave me a discarded damper that someone had tried to get apart and essentially ruined (by FAA standards).  I took it apart, honed the bore, filed off the rough edges on the piston, put in new o-rings and snap rings, and filled it with automatic transmission fluid (ATF).  Total cost less than $2.<br/><br/>
-I made up the mounting hardware initially from cereal box cardboard to get a
+I made up the mounting hardware initially from cereal box cardboard to get a general idea of fit and then from thin Al (quick and easy to modify) only strong enough so that I could check geometry.  Finally, I made up what you see in the photos from 1/8 inch mild steel ( I do not have any chrome-moly plate).<br/><br/>
-I took (rotary) drag data for both the original Belview setup and for the
+I took (rotary) drag data for both the original Belview setup and for the Cessna damper.  It became immediately apparent that the ATF was too thin so I replaced it with Shell 100 (50 wt) aircraft oil.  This stiffened it up considerably and that what I am currently using.<br/><br/>
-It was during the initial fit-up process that I discovered that the fork is
+It was during the initial fit-up process that I discovered that the fork is bent bad.  I noticed it when I was pulling (by hand (dump-valve open)) the whole gear up into the nose of the plane to check for fit.  One side of the wheel (lightly) dragged on one of the two alignment "posts" (I don't know the official name for these).  I considered trying to straighten it but I don't have a large enough press to do that sort of work so I ordered a new one.  It has since arrived but I am still experimenting with the original as
- bent bad.  I noticed it when I was pulling (by hand (dump-valve open))
+it works ok... just looks a little strange.  The new fork is considerably stronger than my old original.<br/><br/>
 Ok, time for taxi testing.  Big nut backed-off as before.  Two high-speed
@@ Line 66: / Line 38: @@
 easily.   This may be a keeper.<br/><br/>
-**********<br/><br/>
+<br/><br/>
-> Whats the turning radius with the damper connected?<br/><br/>
+Q: Whats the turning radius with the damper connected?<br/><br/>
-Don't know the aircraft turning radius but the measured swing of the wheel
+A: Don't know the aircraft turning radius but the measured swing of the wheel
 is about 45 deg  left, 30 deg right.  Obviously, I don't have the geometry
 correct but it does what I need.  Between my hanger and the taxiway is a 90
@@ Line 79: / Line 51: @@
 adjustments.<br/><br/>
-> When turning in tight quarters do you bottom out or top out on the damper
+Q: When turning in tight quarters do you bottom out or top out on the damper often?  No worries the damper would break from over extending?
-For the above mentioned turns, I feel no indication that I have hit the
+A: For the above mentioned turns, I feel no indication that I have hit the
 ends.<br/><br/>
-> How big is that damper?  It looks big in the picture,  got a part number?<br/><br/>
+Q: How big is that damper?  It looks big in the picture,  got a part number?<br/><br/>
-It is a damper off of some older model Cessna that a friend had in the scrap
+A: It is a damper off of some older model Cessna that a friend had in the scrap
 pile because someone had "ruined" it (by certified standards) trying to get
 it apart and damaged the piston and bore.  I cleaned it up, got some o-rings