Gear Collapse, Over Center Gap - Jun 2008

I don't know where you are placing the ruler, but an angle measurement on
the verticality of the lg struts reads 88.5 degrees on my Ximango, with the
struts bowlegged in.

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Date:         Wed, 18 Jun 2008 14:01:30 -0500
Reply-To:     "Ximango Owners Group (XOG)" <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       "Ximango Owners Group (XOG)" <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Ted Gordon <tedjgordon@ATT.NET>
Subject:      Re: gear collapse, over center gap
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Dear John and group:

I don't know where you are placing the ruler, but an angle measurement on
the verticality of the lg struts reads 88.5 degrees on my Ximango, with the
struts bowlegged in.

Best
Ted Gordon

--------------------------------------------------
From: "John Lawton" <Thrmlseekr@AOL.COM>
Sent: Wednesday, June 18, 2008 8:04 AM
To: <XIMANGO@HOME.EASE.LSOFT.COM>
Subject: Re: gear collapse, over center gap

> In a message dated 6/18/2008 8:05:57 AM Eastern Daylight Time,
> bruce@SCHIMMEL.COM writes:
>
> I  understand that if you hold a ruler across it, you get an "over
> center" measurement of 5/16".
>
> Hey Bruce,
>
> Yes, that's what I'm referring to.  I compared mine back in December  to
> make
> sure they were similar. As I recall it was about 5/16" gap between the
> straight edge and the locking arm when holding the straight edge across
> the top  of
> the locking arm. I'll measure mine today with my caliper before I fly,
> get a
> more precise measurement and report back later.
>
> I believe the tilt in the main gear legs is a direct result of  the
> adjustment of the locking arm. Another way to measure the proper locking
> arm
> adjustment might be to put an angle finder on the strut and measure the
> departure of
> the strut from vertical (plumb). Angle finders can be sourced  at most any
> home
> improvement store. Usually, they have a magnetic strip on one  side that
> holds them in place while the measurement is taken. A digital level  could
> also be
> used for this measurement, although I would prefer a mechanical  device
> for
> checking this angle because, in my experience, even the  pricey digital
> levels
> are nowhere near as accurate as a mechanical level. I  found that out the
> hard
> way when I was building my Europa setting the angle of  incidence on the
> wings.
>
> Regards,
>
> John  Lawton
> Whitwell, TN (TN89)
> Ximango #135
>
>
>
> **************Gas prices getting you down? Search AOL Autos for
> fuel-efficient used cars.
> (http://autos.aol.com/used?ncid=aolaut00050000000007)
=========================================================================
Date:         Wed, 18 Jun 2008 20:20:45 EDT
Reply-To:     "Ximango Owners Group (XOG)" <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       "Ximango Owners Group (XOG)" <XIMANGO@HOME.EASE.LSOFT.COM>
From:         John Lawton <Thrmlseekr@AOL.COM>
Subject:      Re: gear collapse, over center gap
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Hello again guys,
 
Adding to what Bruce mentioned, my maintenance manual, dated April 02,  2002,
page 1.31, step 2, says to turn the stop screw 2.5 turns clockwise and  lock
it with the locking nut. It doesn't say 2.5 turns from start or 2.5 turns 
from the screw bottomed out. Since it says "clockwise" and following the "righty 
tighty" rule, I would assume that "2.5 turns clockwise" means from when it 
is initially started into the threaded bushing which is welded to the upper 
articulated strut, as is shown in the exploded diagram on this page of the 
maintenance manual.

For what it's worth, mine is nothing at all like this. Mine looks as it  the
screw was threaded into the bushing all the way, then backed off 
counterclockwise to a distance of between 4 and 5 threads. I don't  know how many turns
that is, but I would reckon at least three and possibly as  many as four turns.
 
I did a more precise measurement on the lower articulated strut (the flat 
part of the over center locking mechanism) by placing a steel ruler on  the top
edge of this part with the other end of the ruler situated on  top of the
threaded bushing that holds the adjusting screw on the upper  articulated strut.
While holding the ruler in place, using an  inside caliper I measured from the
bottom of the ruler to the top of  the center pivot point on top of the lower
articulated strut, where  the upper and lower articulated struts meet. The
right side was .38" and the  left side was .33". I didn't measure the angle of
the landing gear leg to  plumb because the clouds just looked too good to be
fiddling with this  today. By the way, cloudbase was 7500'msl with 6-7 knot lift
and some ridge  lift later in the glass off. Not bad for mid June here.
 
I also looked at a Navion in my hangar that belongs to our resident  A&P/IA
to compare how it is done relative to the Ximango. The landing  gear on the
Navion is almost identical to what the Ximango has, both in terms of  the way it
operates and the relative size of the parts. The only difference is  the
"lower articulated strut" on the Navion is tubular, instead of being made  from
flat bar stock. Both look equally "beefy".
 
It would be nice if we could get a more thorough definition of what is 
acceptable in terms of this adjustment of the upper and lower articulated  strut
alignment. Clearly, mine is not set up as the maintenance manual dictates.  It
appears to me that if it were I doubt there would any  over-centering of these
articulated strut parts and, as such, it wouldn't  lock the gear down.
Assuming I understand the theory of operation here, it seems  to me that this is an
important adjustment. If it is improperly adjusted it  could lead to a gear
collapse, especially in a rough runway situation.  I  think it's important that
these parts over center on their connecting pivot bolt  to properly to lock the
gear leg down.

Comments?
 
Regards,
 
John  Lawton
Whitwell, TN (TN89)
Ximango #135



**************Gas prices getting you down? Search AOL Autos for
fuel-efficient used cars.      (http://autos.aol.com/used?ncid=aolaut00050000000007)
=========================================================================
Date:         Wed, 18 Jun 2008 21:13:17 -0400
Reply-To:     "Ximango Owners Group (XOG)" <XIMANGO@HOME.EASE.LSOFT.COM>
Sender:       "Ximango Owners Group (XOG)" <XIMANGO@HOME.EASE.LSOFT.COM>
From:         Bruce SCHIMMEL <bruce@SCHIMMEL.COM>
Subject:      Re: gear collapse, best metric
In-Reply-To:  <d2f.25111229.358b005d@aol.com>
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John --

Thanks for your careful investigation. I wonder if Ted's metric might 
also be useful. You've said .33" and .38" on the gap. Ted writes: an 
angle measurement on the verticality of the lg struts reads 88.5 
degrees.

Are these two expressions of the same condition?

yrs, B

On Jun 18, 2008, at 8:20 PM, John Lawton wrote:

Hello again guys,

Adding to what Bruce mentioned, my maintenance manual, dated April 
02,  2002,
page 1.31, step 2, says to turn the stop screw 2.5 turns clockwise 
and  lock
it with the locking nut. It doesn't say 2.5 turns from start or 2.5 
turns
from the screw bottomed out. Since it says "clockwise" and following 
the "righty
tighty" rule, I would assume that "2.5 turns clockwise" means from 
when it
is initially started into the threaded bushing which is welded to the 
upper
articulated strut, as is shown in the exploded diagram on this page 
of the
maintenance manual.

For what it's worth, mine is nothing at all like this. Mine looks as 
it  the
screw was threaded into the bushing all the way, then backed off
counterclockwise to a distance of between 4 and 5 threads. I don't  
know how many turns
that is, but I would reckon at least three and possibly as  many as 
four turns.

I did a more precise measurement on the lower articulated strut (the 
flat
part of the over center locking mechanism) by placing a steel ruler 
on  the top
edge of this part with the other end of the ruler situated on  top of 
the
threaded bushing that holds the adjusting screw on the upper  
articulated strut.
While holding the ruler in place, using an  inside caliper I measured 
from the
bottom of the ruler to the top of  the center pivot point on top of 
the lower
articulated strut, where  the upper and lower articulated struts 
meet. The
right side was .38" and the  left side was .33". I didn't measure the 
angle of
the landing gear leg to  plumb because the clouds just looked too 
good to be
fiddling with this  today. By the way, cloudbase was 7500'msl with 
6-7 knot lift
and some ridge  lift later in the glass off. Not bad for mid June here.

I also looked at a Navion in my hangar that belongs to our resident  
A&P/IA
to compare how it is done relative to the Ximango. The landing  gear 
on the
Navion is almost identical to what the Ximango has, both in terms of  
the way it
operates and the relative size of the parts. The only difference is  the
"lower articulated strut" on the Navion is tubular, instead of being 
made  from
flat bar stock. Both look equally "beefy".

It would be nice if we could get a more thorough definition of what is
acceptable in terms of this adjustment of the upper and lower 
articulated  strut
alignment. Clearly, mine is not set up as the maintenance manual 
dictates.  It
appears to me that if it were I doubt there would any  over-centering 
of these
articulated strut parts and, as such, it wouldn't  lock the gear down.
Assuming I understand the theory of operation here, it seems  to me 
that this is an
important adjustment. If it is improperly adjusted it  could lead to 
a gear
collapse, especially in a rough runway situation.  I  think it's 
important that
these parts over center on their connecting pivot bolt  to properly 
to lock the
gear leg down.

Comments?

Regards,

John  Lawton
Whitwell, TN (TN89)
Ximango #135