Today's Message Index:
----------------------
1. 03:35 AM - Fw: Re: bolting wings on RV-6A (Rick Galati)
2. 07:18 AM - bolting wings on RV-6A (Emrath)
3. 09:03 AM - Re: Nose wheel shimmy (Robin Marks)
4. 09:44 AM - Re: bolting wings on RV-6A (Chris Hand)
5. 09:49 AM - Re: bolting wings on RV-6A (thomas sargent)
6. 09:51 AM - Re: bolting wings on RV-6A (thomas sargent)
7. 09:55 AM - Re: bolting wings on RV-6A (thomas sargent)
8. 01:18 PM - Nose wheel shimmy (Charles Brame)
9. 01:33 PM - Adjusting Sensenich prop tracking (Joe & Jan Connell)
10. 01:56 PM - Re: Adjusting Sensenich prop tracking (Bruce Bell)
11. 02:54 PM - Re: Adjusting Sensenich prop tracking (Jerry Springer)
12. 04:19 PM - Re: Nose wheel shimmy (linn)
13. 05:21 PM - Re: Nose wheel shimmy (HCRV6@comcast.net)
14. 06:08 PM - Re: Nose wheel shimmy (Denis Walsh)
15. 08:03 PM - Re: Nose wheel shimmy (linn)
16. 08:09 PM - Re: Nose wheel shimmy (linn)
17. 10:29 PM - Re: Nose wheel shimmy (Karl Ahamer)
Message 1
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Subject: | Re: Fw: Re: bolting wings on RV-6A |
--- On Sun, 4/5/09, Rick Galati <rick6a@yahoo.com> wrote:
From: Rick Galati <rick6a@yahoo.com>
Subject: Re: bolting wings on RV-6A
Tom,
-
I'd sure be reluctant to ream the holes. The landing gear weldments are att
ached to the spar mostly with AD3 bolts, NOT-close tolerance bolts.- Th
e fact is, at some point you did drill those holes through the weldments so
at least during that drill out operation the holes lined up.- Note exact
ly which holes don't line up-prompting you to post a message. Then start
the installation process all over by removing the fasteners attaching the w
eldment, including the ones on the fuselage side. When the weldment is comp
letely free,-reinstall it by inserting the first bolt through a hole that
does not now line up. Then, strategically insert a number of the bolts-a
nd/or drift pins into a number of holes-along the weldment leaving-all
loose.- Just barely start a nut on the first thread or two of- the bolt
s and do not run any of then down until you are sure the mismatch has been
worked out.-
-
Rick Galati- RV-6A- "Darla!"
RV-8
Message 2
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Subject: | bolting wings on RV-6A |
Thomas;
If I understand you correctly, these are not the close tolerance bolts in
the center section. If you end up removing the weldment from the plane, you
can have the holes welded shut, then re-assemble and re-drill the holes
using a drill guide and appropriate reamer.
How are you supporting the ship while you mount the wings?
Marty
Time: 05:17:29 PM PST US
From: thomas sargent <sarg314@gmail.com>
Subject: RV-List: bolting wings on RV-6A
I am bolting on the wings for the last time - the electrical system is
done, the engine installed, the fiberglass done and it's even all
painted. I just have to screw it all together, take care of 100
little things and it will fly.
The left gear weldment has about 75% of the bolts in (no nuts on
them) and the rest of the holes in the weldment have locator pins in
place EXCEPT for the two outboard AN3 bolts at the lower edge - right
where the gear leg penetrates the fuselage. These are the most
inaccessible holes. Inserting bolts in these holes from the aft side
of the spar go thru pretty easily and stop hard at the weldment. The
misalignment isn't real obvious, but I can't get the bolts thru or
even drive a tapered pin thru. So, I guess those holes in the
weldment need to be enlarged very slightly.
I could take all the bolts and pins out, remove the weldment and
slightly enlarge or elongate those 2 holes in the weldment and then re-
install. I hate to do all that over again. I noticed that a 3/16
drill bit will slide thru the holes in the spar easily. With a right
angle drill I could just drill out those holes in the weldment. Is
this an acceptable practice, or is it too likely to damage the holes
in the aluminum spar? Or am I barking up the wrong tree entirely?
--
Almost There....
RV-6A N811WT
Marty
Message 3
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Subject: | Nose wheel shimmy |
Kim,
I found that once I upgraded the nose wheel fork on my 6A
per the SB the nose wheel shimmy was much worse (never had a problem
before). I think there might be something in the geometry that makes it
more prone to shimmy. Because I was going on 6 years with the same nose
wheel I decided to replace the tire and at the same time have it
balanced. It made a big difference in the shimmy. I don't believe my old
tire was out of round but probably out of balance. I concur with Carl
that upgrading to the Matco axel is an additional improvement that
should help and for $50.00 it's a no brainer. I have one on my -10 and
plan to put one on my 8A.
BTW this is something you want to resolve soon as when the
shimmy is bad it can really damage the wheel pants quickly.
Good luck
Robin
From: owner-rv-list-server@matronics.com
[mailto:owner-rv-list-server@matronics.com] On Behalf Of Carl Froehlich
Sent: Saturday, April 04, 2009 8:07 PM
Subject: RE: RV-List: Nose wheel shimmy
You may want to use the Matco axle for the nose gear. That way you can
pre-load the bearings just enough - letting the wheel spin easily, but
still fully torque the axle nut.
Here is the link
http://www.matcomfg.com/AXLEASSEMBLYA24125INCH-idv-3657-1.html
Get the wheel balance weights from them as well.
Carl Froehlich
RV-8A (450 hrs)
RV-10 (fuselage)
From: owner-rv-list-server@matronics.com
[mailto:owner-rv-list-server@matronics.com] On Behalf Of
Knicholas2@aol.com
Sent: Saturday, April 04, 2009 10:17 PM
Subject: RV-List: Nose wheel shimmy
I know this has been discussed in the archives, but I need some help.
This winter I replace the nose wheel fork on my RV9A per Van's service
bulletin. Since the install, I have a bad nose wheel shimmy on
landing. I have tried various torque settings on the axel, different
tire pressures and varied the break-out pressure on the nose wheel
"pivot". I still get the shimmy on landing - note that it does not
occur on takeoff, and I have intentionally allowed my take off speed on
the runway to exceed my landing speed. On take off it does not shimmy,
only on landing.
Does anyone have any helpful ideas? I feel like the nose wheel is going
to shake right off of the plane, and it is no fun.
Kim Nicholas
RV9A
Auburn, WA
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04/03/09 17:54:00
Message 4
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Subject: | Re: bolting wings on RV-6A |
How do you have the plane supported while doing this?
I had similar problems but was trying to put the remaining bolts in while
the plane was on the gear with only the side bolts and some of the
weldment/spar bolts installed. I was able to resolve by taking the weight
off that main gear when installing those bolts which allowed just enough
shifting of the weldment to allow the holes to line up as originally drilled
a number of years earlier. There was a difference in hole alignment with
weight on the gear as opposed to upside down in the jig without even the
wheels on when the weldments were drilled to the spar.
With the wheel in the air, the methods described in earlier replies worked
for me (turning and/or pressing in).
Chris
RV-6A, almost done with phase I
http://rv6aproject.ckhand.com/
----- Original Message -----
From: "thomas sargent" <sarg314@gmail.com>
Sent: Saturday, April 04, 2009 5:13 PM
Subject: RV-List: bolting wings on RV-6A
>
> I am bolting on the wings for the last time - the electrical system is
> done, the engine installed, the fiberglass done and it's even all
> painted. I just have to screw it all together, take care of 100 little
> things and it will fly.
>
> The left gear weldment has about 75% of the bolts in (no nuts on them)
> and the rest of the holes in the weldment have locator pins in place
> EXCEPT for the two outboard AN3 bolts at the lower edge - right where the
> gear leg penetrates the fuselage. These are the most inaccessible holes.
> Inserting bolts in these holes from the aft side of the spar go thru
> pretty easily and stop hard at the weldment. The misalignment isn't real
> obvious, but I can't get the bolts thru or even drive a tapered pin thru.
> So, I guess those holes in the weldment need to be enlarged very
> slightly.
>
> I could take all the bolts and pins out, remove the weldment and slightly
> enlarge or elongate those 2 holes in the weldment and then re- install. I
> hate to do all that over again. I noticed that a 3/16 drill bit will
> slide thru the holes in the spar easily. With a right angle drill I
> could just drill out those holes in the weldment. Is this an acceptable
> practice, or is it too likely to damage the holes in the aluminum spar?
> Or am I barking up the wrong tree entirely?
>
> --
> Almost There....
> RV-6A N811WT
>
>
>
Message 5
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Subject: | Re: bolting wings on RV-6A |
Marty:
Yes, you are correct. That would work and be the best from an
engineering standpoint. A lot of time and work, though. I think it's
so close already that I'll try a couple other things first.
The ship is supported on the right side by the landing gear installed
with a wooden "false spar" and on the left with a saw horse under the
bottom edge of the fire wall and another under the left rear wing spar
attach point. The left wing is supported by a saw horse out near the
wing tip with a padded, hinged piece on it. It's all freshly painted,
so I have to take care to protect the paint.
On Apr 5, 2009, at 7:16 AM, Emrath wrote:
>
> Thomas;
>
> If I understand you correctly, these are not the close tolerance
> bolts in
> the center section. If you end up removing the weldment from the
> plane, you
> can have the holes welded shut, then re-assemble and re-drill the
> holes
> using a drill guide and appropriate reamer.
> How are you supporting the ship while you mount the wings?
> Marty
>
>
Message 6
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Subject: | Re: bolting wings on RV-6A |
Sending this again - it went just to Rick and I intended it for the
whole list.
Rick:
The gear weldments were delivered to me with almost all the holes
already drilled. I drilled (or drilled out - it's been years and I
don't remember) some of the holes that go thru the side of the
fuselage, but none that go thru the spar. The holes for the 2 AN3
bolts I wrote my post about can only be drilled from the rear when the
spar is drilled, so these were done by Van's.
I have never understood why the gear weldment holes all line up so
poorly. It's as though they drilled them in the steel parts and THEN
welded the steel parts together to make the weldment and it warped a
bit. I have had to "adjust" nearly all the AN3 holes in the weldment,
as I understand most RV-6A builders have. I've had several
conversations with van's about this in the past. They just told me to
get a small rat-tail file and make them fit. I have never put the 2
AN3 bolts in question in before, so these 2 holes didn't get "fixed".
The method you describe is reasonable and may work, although it would
be time consuming; there's lots of different bolt install sequences
and there may be some that work better . Adjusting the loading on the
gear may shift it slightly too.
I've been at this for 11 years already. I managed to use up that many
calendars by doing things in very time consuming ways. Being this
close to the end I'd rather not give up any ground unless I absolutely
have to.
On Apr 5, 2009, at 3:31 AM, Rick Galati wrote:
> Tom,
>
> I'd sure be reluctant to ream the holes. The landing gear weldments
> are attached to the spar mostly with AD3 bolts, NOT close tolerance
> bolts. The fact is, at some point you did drill those holes through
> the weldments so at least during that drill out operation the holes
> lined up. Note exactly which holes don't line up prompting you to
> post a message. Then start the installation process all over by
> removing the fasteners attaching the weldment, including the ones on
> the fuselage side. When the weldment is completely free, reinstall
> it by inserting the first bolt through a hole that does not now line
> up. Then, strategically insert a number of the bolts and/or drift
> pins into a number of holes along the weldment leaving all loose.
> Just barely start a nut on the first thread or two of the bolts and
> do not run any of then down until you are sure the mismatch has been
> worked out.
>
> Rick Galati RV-6A "Darla!"
> RV-8
Message 7
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Subject: | Re: bolting wings on RV-6A |
Chris:
The wheel is dangling in the air, by only about 1/2", but it's
dangling. The plane's up on saw horses as I described in my last
post. I can put some load on it by shoving a wedge under the wheel.
It also occurred to me that I could deflate the tire, put a thick
board under it and then re-inflate to some degree to adjust the amount
of load it's bearing. I think I'll experiment with that this afternoon.
On Apr 5, 2009, at 9:42 AM, Chris Hand wrote:
>
> How do you have the plane supported while doing this?
> I had similar problems but was trying to put the remaining bolts in
> while the plane was on the gear with only the side bolts and some of
> the weldment/spar bolts installed. I was able to resolve by taking
> the weight off that main gear when installing those bolts which
> allowed just enough shifting of the weldment to allow the holes to
> line up as originally drilled a number of years earlier. There was
> a difference in hole alignment with weight on the gear as opposed to
> upside down in the jig without even the wheels on when the weldments
> were drilled to the spar.
> With the wheel in the air, the methods described in earlier replies
> worked for me (turning and/or pressing in).
>
> Chris
> RV-6A, almost done with phase I
Message 8
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Subject: | Nose wheel shimmy |
I have had exactly the same nose wheel shimmy that you describe. The
shimmy was the result of more than one problem.
I originally had a vertical nose shimmy confirmed by outside
observers. It only occurred after landing. I checked for out of round
and balance and both were perfect. I found that the nose wheel itself
would not spin more than a quarter turn regardless of the torque
setting on the axle bolt. After nose wheel touchdown after landing,
the tight wheel caused the strut to flex aft and rebound, which lifted
the wheel back off the runway. Once off the ground it quickly stopped
spinning and the action repeated itself causing the vertical shimmy
until I slowed considerably. I switched from Van's supplied nose wheel
to a Grove wheel that would spin freely regardless of axle torque.
That solved the vertical shimmy problem.
However, I still occasionally had a lateral shimmy at taxi speeds.
Tightening the strut/fork pivot bolt beyond Van's recommendations
helped, but did not completely solve the problem and the shimmy
gradually got worse. I found that even with the axle bolt torqued to
the max, the nose wheel still had a slight amount of lateral play on
the axle. The answer to that was carefully grinding about a sixteenth
inch off the sleeve between the hubs of the Grove wheel. The wheel now
has zero lateral play and still turns freely.
Lastly, I found that the nose strut itself was rotating in the motor
mount sleeve. The rotation amounted to nearly a quarter of an inch
lateral play at the bottom of the tire. The retaining bolt at the top
of the strut was not tight enough and the NAS bolt had wallowed out
the motor mount holes. A temporary fix was to add a couple of washers
to the bolt and tighten it beyond torque recommendations. So far, that
stopped the shimmy.
The loose strut obviously added to the increased shimmy problems. At
some future time, I'll have to take action to repair the oversized
hole. I suspect that the hole enlargement was caused by the vibration
of the strut which was caused by the other shimmy inducing problems.
Recommendations:
Replace Van's supplied nose wheel with a Grove wheel.
Ensure no lateral play of the nose wheel on the axle.
Ensure the nose wheel will spin a couple of turns easily.
Increase the torque on the strut/fork pivot bolt.
Check for the slightest rotation of the nose strut at the motor mount.
Check the nose strut bolt torque (and continue to check frequently.)
Charlie Brame
RV-6A N11CB
San Antonio
----------------------------------------
Time: 07:17:50 PM PST US
From: Knicholas2@aol.com
Subject: RV-List: Nose wheel shimmy
I know this has been discussed in the archives, but I need some help.
This winter I replace the nose wheel fork on my RV9A per Van's service
bulletin. Since the install, I have a bad nose wheel shimmy on
landing. I have
tried various torque settings on the axel, different tire pressures
and
varied the break-out pressure on the nose wheel "pivot". I still get
the shimmy
on landing - note that it does not occur on takeoff, and I have
intentionally allowed my take off speed on the runway to exceed my
landing speed.
On
take off it does not shimmy, only on landing.
Does anyone have any helpful ideas? I feel like the nose wheel is
going to
shake right off of the plane, and it is no fun.
Kim Nicholas
RV9A
Auburn, WA
Message 9
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Subject: | Adjusting Sensenich prop tracking |
Gentlemen:
I have an RV-9A with and Aero Sport 160 hp O-320 with a Sensenich fixed
pitch prop and a 2 1/4 spacer. Today I hung the prop and spacer on the
engine and torqued the 7/16ths bolts to 40 ft lbs.
I raised the nose strut and rested it on a block to keep the nose from
moving. The top spark plugs were removed.
I set up a heavy camera tripod and attached a probe to touch the aft
edge of the prop about 3 inches from the end of the prop. I've rotated
the prop a number of times and the deviation between the two blades is
.02 inches.
Am I in the ball park on this? I could rotate the spacer 180 degrees to
the prop and try again. I could rotate the prop and spacer in relation
to the engine. Is it normal to be able to get the tracking closer?
Suggestions are welcome - I need to get this squared away before I
proceed too far with the spinner.
Many thanks...
Joe Connell
Stewartville, MN
RV-9A N95JJ
Message 10
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Subject: | Re: Adjusting Sensenich prop tracking |
Question! What does it do at the very tip of the prop? Try that! BBB
----- Original Message -----
From: Joe & Jan Connell
To: RV-List
Sent: Sunday, April 05, 2009 3:29 PM
Subject: RV-List: Adjusting Sensenich prop tracking
Gentlemen:
I have an RV-9A with and Aero Sport 160 hp O-320 with a Sensenich
fixed pitch prop and a 2 1/4 spacer. Today I hung the prop and spacer
on the engine and torqued the 7/16ths bolts to 40 ft lbs.
I raised the nose strut and rested it on a block to keep the nose from
moving. The top spark plugs were removed.
I set up a heavy camera tripod and attached a probe to touch the aft
edge of the prop about 3 inches from the end of the prop. I've rotated
the prop a number of times and the deviation between the two blades is
.02 inches.
Am I in the ball park on this? I could rotate the spacer 180 degrees
to the prop and try again. I could rotate the prop and spacer in
relation to the engine. Is it normal to be able to get the tracking
closer?
Suggestions are welcome - I need to get this squared away before I
proceed too far with the spinner.
Many thanks...
Joe Connell
Stewartville, MN
RV-9A N95JJ
Message 11
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Subject: | Re: Adjusting Sensenich prop tracking |
Joe & Jan Connell wrote:
> Gentlemen:
>
1/16" or less and you are good to go.
> I have an RV-9A with and Aero Sport 160 hp O-320 with a Sensenich
> fixed pitch prop and a 2 1/4 spacer. Today I hung the prop and spacer
> on the engine and torqued the 7/16ths bolts to 40 ft lbs.
>
> I raised the nose strut and rested it on a block to keep the nose from
> moving. The top spark plugs were removed.
>
> I set up a heavy camera tripod and attached a probe to touch the aft
> edge of the prop about 3 inches from the end of the prop. I've
> rotated the prop a number of times and the deviation between the two
> blades is .02 inches.
>
> Am I in the ball park on this? I could rotate the spacer 180 degrees
> to the prop and try again. I could rotate the prop and spacer in
> relation to the engine. Is it normal to be able to get the tracking
> closer?
>
> Suggestions are welcome - I need to get this squared away before I
> proceed too far with the spinner.
>
> Many thanks...
>
> Joe Connell
> Stewartville, MN
> RV-9A N95JJ
> *
>
>
> *
Message 12
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Subject: | Re: Nose wheel shimmy |
Charles Brame wrote:
> I have had exactly the same nose wheel shimmy that you describe. The
> shimmy was the result of more than one problem.
>
> I originally had a vertical nose shimmy
Maybe we can call this 'bounce' to differentiate with shimmy?
> confirmed by outside observers. It only occurred after landing. I
> checked for out of round and balance and both were perfect. I found
> that the nose wheel itself would not spin more than a quarter turn
> regardless of the torque setting on the axle bolt. After nose wheel
> touchdown after landing, the tight wheel caused the strut to flex aft
> and rebound, which lifted the wheel back off the runway. Once off the
> ground it quickly stopped spinning and the action repeated itself
> causing the vertical shimmy until I slowed considerably. I switched
> from Van's supplied nose wheel to a Grove wheel that would spin freely
> regardless of axle torque. That solved the vertical shimmy problem.
>
> However, I still occasionally had a lateral shimmy
True shimmy.
> at taxi speeds. Tightening the strut/fork pivot bolt beyond Van's
> recommendations helped, but did not completely solve the problem and
> the shimmy gradually got worse.
This will happen while the new belleville washers 'wear in' ....... I
guess shimmy would help lessen the wear-in time! :-P
> I found that even with the axle bolt torqued to the max, the nose
> wheel still had a slight amount of lateral play on the axle. The
> answer to that was carefully grinding about a sixteenth inch off the
> sleeve between the hubs of the Grove wheel. The wheel now has zero
> lateral play and still turns freely.
>
> Lastly, I found that the nose strut itself was rotating in the motor
> mount sleeve. The rotation amounted to nearly a quarter of an inch
> lateral play at the bottom of the tire. The retaining bolt at the top
> of the strut was not tight enough and the NAS bolt had wallowed out
> the motor mount holes. A temporary fix was to add a couple of washers
> to the bolt and tighten it beyond torque recommendations. So far, that
> stopped the shimmy.
Boring out the strut/mount for the next size bolt would be a better
'repair'. With the elongated holes, the strut will move back and forth
over time making things worse.
> The loose strut obviously added to the increased shimmy problems. At
> some future time, I'll have to take action to repair the oversized
> hole. I suspect that the hole enlargement was caused by the vibration
> of the strut which was caused by the other shimmy inducing problems.
I think you're right.
> Recommendations:
>
> Replace Van's supplied nose wheel with a Grove wheel
The new axle/hub should do also.
> Ensure no lateral play of the nose wheel on the axle.
> Ensure the nose wheel will spin a couple of turns easily.
This is contrary to what I've been told. 1/2 turn is sufficient
pre-load on the bearings. Otherwise the wheel tends to vibrate (may
take some time) as it slows down.
> Increase the torque on the strut/fork pivot bolt.
> Check for the slightest rotation of the nose strut at the motor mount.
> Check the nose strut bolt torque (and continue to check frequently.)
All good items!
Linn
>
> Charlie Brame
> RV-6A N11CB
> San Antonio
>
>
> ----------------------------------------
>
>
> Time: 07:17:50 PM PST US
> From: Knicholas2@aol.com <mailto:Knicholas2@aol.com>
> Subject: RV-List: Nose wheel shimmy
>
> I know this has been discussed in the archives, but I need some help.
>
> This winter I replace the nose wheel fork on my RV9A per Van's service
> bulletin. Since the install, I have a bad nose wheel shimmy on
> landing. I have
>
> tried various torque settings on the axel, different tire pressures and
> varied the break-out pressure on the nose wheel "pivot". I still get
> the shimmy
>
> on landing - note that it does not occur on takeoff, and I have
> intentionally allowed my take off speed on the runway to exceed my
> landing speed.
> On
> take off it does not shimmy, only on landing.
>
> Does anyone have any helpful ideas? I feel like the nose wheel is
> going to
> shake right off of the plane, and it is no fun.
>
> Kim Nicholas
> RV9A
> Auburn, WA
> *
>
>
> *
Message 13
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Subject: | Re: Nose wheel shimmy |
Linn,
Just curious why you haven't considered using a taper pin (bolt) at the top of
the nose wheel strut. Several folks with the little wheel at the proper end have
had problems with the tail wheel spring working loose at the anti-rotation
bolt (the set up looks like the nose wheel strut only slightly smaller) and corrected
this by reaming the mount hole and installing a taper pin.
Harry Crosby
RV-6 N16CX, 565 hours
----- Original Message -----
From: "linn" <pitts_pilot@bellsouth.net>
Sent: Sunday, April 5, 2009 5:20:50 PM GMT -08:00 US/Canada Pacific
Subject: Re: RV-List: Nose wheel shimmy
Charles Brame wrote:
I have had exactly the same nose wheel shimmy that you describe. The shimmy was
the result of more than one problem.
I originally had a vertical nose shimmy Maybe we can call this 'bounce' to differentiate
with shimmy?
confirmed by outside observers. It only occurred after landing. I checked for out
of round and balance and both were perfect. I found that the nose wheel itself
would not spin more than a quarter turn regardless of the torque setting on
the axle bolt. After nose wheel touchdown after landing, the tight wheel caused
the strut to flex aft and rebound, which lifted the wheel back off the runway.
Once off the ground it quickly stopped spinning and the action repeated itself
causing the vertical shimmy until I slowed considerably. I switched from
Van's supplied nose wheel to a Grove wheel that would spin freely regardless
of axle torque. That solved the vertical shimmy problem.
However, I still occasionally had a lateral shimmy True shimmy.
at taxi speeds. Tightening the strut/fork pivot bolt beyond Van's recommendations
helped, but did not completely solve the problem and the shimmy gradually got
worse. This will happen while the new belleville washers 'wear in' .......
I guess shimmy would help lessen the wear-in time! :-P
I found that even with the axle bolt torqued to the max, the nose wheel still had
a slight amount of lateral play on the axle. The answer to that was carefully
grinding about a sixteenth inch off the sleeve between the hubs of the Grove
wheel. The wheel now has zero lateral play and still turns freely.
Lastly, I found that the nose strut itself was rotating in the motor mount sleeve.
The rotation amounted to nearly a quarter of an inch lateral play at the bottom
of the tire. The retaining bolt at the top of the strut was not tight enough
and the NAS bolt had wallowed out the motor mount holes. A temporary fix
was to add a couple of washers to the bolt and tighten it beyond torque recommendations.
So far, that stopped the shimmy.
Boring out the strut/mount for the next size bolt would be a better 'repair'. With
the elongated holes, the strut will move back and forth over time making things
worse.
The loose strut obviously added to the increased shimmy problems. At some future
time, I'll have to take action to repair the oversized hole. I suspect that
the hole enlargement was caused by the vibration of the strut which was caused
by the other shimmy inducing problems.
I think you're right.
Recommendations:
Replace Van's supplied nose wheel with a Grove wheel The new axle/hub should do
also.
Ensure no lateral play of the nose wheel on the axle.
Ensure the nose wheel will spin a couple of turns easily. This is contrary to what
I've been told. 1/2 turn is sufficient pre-load on the bearings. Otherwise
the wheel tends to vibrate (may take some time) as it slows down.
Increase the torque on the strut/fork pivot bolt.
Check for the slightest rotation of the nose strut at the motor mount.
Check the nose strut bolt torque (and continue to check frequently.) All good items!
Linn
Charlie Brame
RV-6A N11CB
San Antonio
----------------------------------------
Time: 07:17:50 PM PST US
From: Knicholas2@aol.com
Subject: RV-List: Nose wheel shimmy
I know this has been discussed in the archives, but I need some help.
This winter I replace the nose wheel fork on my RV9A per Van's service
bulletin. Since the install, I have a bad nose wheel shimmy on landing. I have
tried various torque settings on the axel, different tire pressures and
varied the break-out pressure on the nose wheel "pivot". I still get the shimmy
on landing - note that it does not occur on takeoff, and I have
intentionally allowed my take off speed on the runway to exceed my landing speed.
On
take off it does not shimmy, only on landing.
Does anyone have any helpful ideas? I feel like the nose wheel is going to
shake right off of the plane, and it is no fun.
Kim Nicholas
RV9A
Auburn, WA href="http://www.matronics.com/Navigator?RV-List">http://www.matronics.com/Navigator?RV-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/contribution
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Subject: | Re: Nose wheel shimmy |
This is as good a run down as I have seen. I have around 4000
landings on my 6A, and can verify all these observations. I, too am
inclined to think the new fork assembly is more prone to shake. I too
like the matco assembly, but am sticking with my old original
Cleveland wheel and axle as furnished in 1994 or so.
I have three things to add:
1. Sometimes just increasing or decreasing the nose tire pressure
will help.
2. VERY IMPORTANT to get an observers notes. Frequently the problem
is main wheel shake, which can start the nose going, or vice versa.
3. Regarding the "upper bolt hogging out the holes at top of strut
mount" problem. Most RVs I have seen eventually develop this
problem. My latest quick fix seems to be working quite well. Got a
fender washer with the right size hole. Put it in a vice and beat it
into a curved radius to match the weldment where the strut goes
through. Installed a new bolt with the big ass curved washer under
the head. torqued it down. \\
I made the curvature a little more than matching to get a springy
fit. Voila I now have a new hole at the top which has a very snug fit
(the washer hole shrunk a little laterally when bent), and the
rotational slop is gone..
Hoping it will last a year or so, then I can replace the washer and/or
install another on the bottom.
On Apr 5, 2009, at 2:17 , Charles Brame wrote:
> I have had exactly the same nose wheel shimmy that you describe. The
> shimmy was the result of more than one problem.
>
> I originally had a vertical nose shimmy confirmed by outside
> observers. It only occurred after landing. I checked for out of
> round and balance and both were perfect. I found that the nose wheel
> itself would not spin more than a quarter turn regardless of the
> torque setting on the axle bolt. After nose wheel touchdown after
> landing, the tight wheel caused the strut to flex aft and rebound,
> which lifted the wheel back off the runway. Once off the ground it
> quickly stopped spinning and the action repeated itself causing the
> vertical shimmy until I slowed considerably. I switched from Van's
> supplied nose wheel to a Grove wheel that would spin freely
> regardless of axle torque. That solved the vertical shimmy problem.
>
> However, I still occasionally had a lateral shimmy at taxi speeds.
> Tightening the strut/fork pivot bolt beyond Van's recommendations
> helped, but did not completely solve the problem and the shimmy
> gradually got worse. I found that even with the axle bolt torqued to
> the max, the nose wheel still had a slight amount of lateral play on
> the axle. The answer to that was carefully grinding about a
> sixteenth inch off the sleeve between the hubs of the Grove wheel.
> The wheel now has zero lateral play and still turns freely.
>
> Lastly, I found that the nose strut itself was rotating in the motor
> mount sleeve. The rotation amounted to nearly a quarter of an inch
> lateral play at the bottom of the tire. The retaining bolt at the
> top of the strut was not tight enough and the NAS bolt had wallowed
> out the motor mount holes. A temporary fix was to add a couple of
> washers to the bolt and tighten it beyond torque recommendations. So
> far, that stopped the shimmy.
>
> The loose strut obviously added to the increased shimmy problems. At
> some future time, I'll have to take action to repair the oversized
> hole. I suspect that the hole enlargement was caused by the
> vibration of the strut which was caused by the other shimmy inducing
> problems.
>
> Recommendations:
>
> Replace Van's supplied nose wheel with a Grove wheel.
> Ensure no lateral play of the nose wheel on the axle.
> Ensure the nose wheel will spin a couple of turns easily.
> Increase the torque on the strut/fork pivot bolt.
> Check for the slightest rotation of the nose strut at the motor mount.
> Check the nose strut bolt torque (and continue to check frequently.)
>
> Charlie Brame
> RV-6A N11CB
> San Antonio
>
>
> ----------------------------------------
>
>
> Time: 07:17:50 PM PST US
> From: Knicholas2@aol.com
> Subject: RV-List: Nose wheel shimmy
>
> I know this has been discussed in the archives, but I need some
> help.
>
> This winter I replace the nose wheel fork on my RV9A per Van's
> service
> bulletin. Since the install, I have a bad nose wheel shimmy on
> landing. I have
>
> tried various torque settings on the axel, different tire
> pressures and
> varied the break-out pressure on the nose wheel "pivot". I still
> get the shimmy
>
> on landing - note that it does not occur on takeoff, and I have
> intentionally allowed my take off speed on the runway to exceed my
> landing speed.
> On
> take off it does not shimmy, only on landing.
>
> Does anyone have any helpful ideas? I feel like the nose wheel is
> going to
> shake right off of the plane, and it is no fun.
>
> Kim Nicholas
> RV9A
> Auburn, WA
>
>
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Subject: | Re: Nose wheel shimmy |
Well, I really didn't think of that ...... and the choice would be
determined by the amount of damage in the wallowed out holes and if
they're different on either side. You could ream from the larger hole
side and not 'waste' any more tube area on the smaller side with the
tapered approach where the standard bolt size increases by 1/16th. And
the fact that I have a drill set/bolts instead of the tapered
reamer/pins would probably drive my decision. Reaming with a straight
reamer would mean that the tapered pin would only align one side of the
tube and cut the torsional strength in half. If I'm missing something
here, please let me know.
Linn
> Linn,
>
> Just curious why you haven't considered using a taper pin (bolt) at
> the top of the nose wheel strut. Several folks with the little wheel
> at the proper end have had problems with the tail wheel spring working
> loose at the anti-rotation bolt (the set up looks like the nose wheel
> strut only slightly smaller) and corrected this by reaming the mount
> hole and installing a taper pin.
>
> Harry Crosby
> RV-6 N16CX, 565 hours
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Subject: | Re: Nose wheel shimmy |
Since I haven't got to the gear on the RV-10 (and I'm not an RV repeat
offender) I gather that there's only one bolt to pin the nose gear. My
Grumman (AA-1B) which uses the same strut/socket attachment has two
bolts. The Grummans don't have an issue with the attachment ...... but
the assembly method requires the strut and socket to be liberally coated
with zinc chromate and installed wet. It could be this 'glue' that
makes the biggest difference.
Linn
Denis Walsh wrote:
> This is as good a run down as I have seen. I have around 4000
> landings on my 6A, and can verify all these observations. I, too am
> inclined to think the new fork assembly is more prone to shake. I too
> like the matco assembly, but am sticking with my old original
> Cleveland wheel and axle as furnished in 1994 or so.
>
> I have three things to add:
>
> 1. Sometimes just increasing or decreasing the nose tire pressure
> will help.
>
> 2. VERY IMPORTANT to get an observers notes. Frequently the problem
> is main wheel shake, which can start the nose going, or vice versa.
>
> 3. Regarding the "upper bolt hogging out the holes at top of strut
> mount" problem. Most RVs I have seen eventually develop this
> problem. My latest quick fix seems to be working quite well. Got a
> fender washer with the right size hole. Put it in a vice and beat it
> into a curved radius to match the weldment where the strut goes
> through. Installed a new bolt with the big ass curved washer under
> the head. torqued it down. \\
>
> I made the curvature a little more than matching to get a springy fit.
> Voila I now have a new hole at the top which has a very snug fit (the
> washer hole shrunk a little laterally when bent), and the rotational
> slop is gone..
>
> Hoping it will last a year or so, then I can replace the washer and/or
> install another on the bottom.
> On Apr 5, 2009, at 2:17 , Charles Brame wrote:
>
>> I have had exactly the same nose wheel shimmy that you describe. The
>> shimmy was the result of more than one problem.
>>
>> I originally had a vertical nose shimmy confirmed by outside
>> observers. It only occurred after landing. I checked for out of round
>> and balance and both were perfect. I found that the nose wheel itself
>> would not spin more than a quarter turn regardless of the torque
>> setting on the axle bolt. After nose wheel touchdown after landing,
>> the tight wheel caused the strut to flex aft and rebound, which
>> lifted the wheel back off the runway. Once off the ground it quickly
>> stopped spinning and the action repeated itself causing the vertical
>> shimmy until I slowed considerably. I switched from Van's supplied
>> nose wheel to a Grove wheel that would spin freely regardless of axle
>> torque. That solved the vertical shimmy problem.
>>
>> However, I still occasionally had a lateral shimmy at taxi speeds.
>> Tightening the strut/fork pivot bolt beyond Van's recommendations
>> helped, but did not completely solve the problem and the shimmy
>> gradually got worse. I found that even with the axle bolt torqued to
>> the max, the nose wheel still had a slight amount of lateral play on
>> the axle. The answer to that was carefully grinding about a sixteenth
>> inch off the sleeve between the hubs of the Grove wheel. The wheel
>> now has zero lateral play and still turns freely.
>>
>> Lastly, I found that the nose strut itself was rotating in the motor
>> mount sleeve. The rotation amounted to nearly a quarter of an inch
>> lateral play at the bottom of the tire. The retaining bolt at the top
>> of the strut was not tight enough and the NAS bolt had wallowed out
>> the motor mount holes. A temporary fix was to add a couple of washers
>> to the bolt and tighten it beyond torque recommendations. So far,
>> that stopped the shimmy.
>>
>> The loose strut obviously added to the increased shimmy problems. At
>> some future time, I'll have to take action to repair the oversized
>> hole. I suspect that the hole enlargement was caused by the vibration
>> of the strut which was caused by the other shimmy inducing problems.
>>
>> Recommendations:
>>
>> Replace Van's supplied nose wheel with a Grove wheel.
>> Ensure no lateral play of the nose wheel on the axle.
>> Ensure the nose wheel will spin a couple of turns easily.
>> Increase the torque on the strut/fork pivot bolt.
>> Check for the slightest rotation of the nose strut at the motor mount.
>> Check the nose strut bolt torque (and continue to check frequently.)
>>
>> Charlie Brame
>> RV-6A N11CB
>> San Antonio
>>
>>
>> ----------------------------------------
>>
>>
>>
>>
>> Time: 07:17:50 PM PST US
>> From: Knicholas2@aol.com <mailto:Knicholas2@aol.com>
>> Subject: RV-List: Nose wheel shimmy
>>
>> I know this has been discussed in the archives, but I need some help.
>>
>> This winter I replace the nose wheel fork on my RV9A per Van's service
>> bulletin. Since the install, I have a bad nose wheel shimmy on
>> landing. I have
>>
>> tried various torque settings on the axel, different tire pressures
>> and
>> varied the break-out pressure on the nose wheel "pivot". I still
>> get the shimmy
>>
>> on landing - note that it does not occur on takeoff, and I have
>> intentionally allowed my take off speed on the runway to exceed my
>> landing speed.
>> On
>> take off it does not shimmy, only on landing.
>>
>> Does anyone have any helpful ideas? I feel like the nose wheel is
>> going to
>> shake right off of the plane, and it is no fun.
>>
>> Kim Nicholas
>> RV9A
>> Auburn, WA
>> *
>> href="http://www.matronics.com/Navigator?RV-List">http://www.matronics.com/Navigator?RV-List
>> href="http://forums.matronics.com">http://forums.matronics.com
>> href="http://www.matronics.com/contribution">http://www.matronics.com/contribution
>>
>> *
>
> *
>
>
> *
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Subject: | Nose wheel shimmy |
The nose gear leg of my 7A was able to rotate slightly at the engine mount
end.
Tightening the bolt would fix the problem for a few landings.
I ended up using LOCTITE 680(and the bolt of course) on the upper and lower
socket and no problem after 90 landings.
Would have to use a heat gun if the leg has to come off again...
Don't know if anyone else has tried this before.
Regards
Karl 7A 60hours
Near Sydney/Australia
Checked by AVG - www.avg.com
10:54:00
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