 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
billderou(at)yahoo.com
Guest
|
 Posted: Sat Jul 19, 2008 12:51 pm Post subject: Main Landing Gear Fairing Bolt Failure |
 |
|
I landed approximately a dozen times on a long, grass strip in the Idaho wilderness and found the AN4-6 bolt shown on page 46-5 figure 2 sheared at the cotter pin. This is the AN4 that pokes out of the large axel nut to hold the fairing standoff. The port side failed but the starboard MLG fairing could be wiggled and would soon fail.
The strip is pocked with small mounds much like a polo field before the divits are replaced. There were no holes, nor did I hit anything, nor did I land hard. The fiberglass fairing is still pristine. What caused the problem is the fairing jiggling up and down during the roll out.
Tearing the landing gear down for inspection revealed that the current design will not work over time. I believe the failure begins at the 3 U-1008 spacers shown on page 46-4 figure 4. When the fairing bounces about these spacers gall the U-1010L plate and loosen the inboard side of the fairing. Once the inboard side of the fairing begins to move around it has a 5 inch lever arm (U-1004B) from the outboard fairing attachment point that works the AN4 bolt and will shear it at the cotter pin hole. Looking at the sheared bolt endwise the structural area is very small after the cotter hole is drilled and the thread depths are subtracted.
Two items need to be redesigned. The three bolts thru U-1010L cannot be tightened because the tension simply crushes the aluminum spacers. The spacers need to be steel and the joint tightened. I don't have a lathe but do have lots of 4130 tubing .5" OD by .375 ID. I cleaned the inside of the tube with a .375" ream and pressed the aluminum spacer inside. Added a washer between the spacer and the U-1010L and tightened it properly. Now it is much stiffer.
Beefing up the AN4 at the axel nut required much more work. If you only have a hammer then you use a hammer to fix all problems. I created a weldment with a TIG welder but a lathe is the better tool. I used the same steel .5"OD by .375"ID tubing and constructed a standoff with an AN5 stud on one end and an AN4 nut on the other. Drilled out the axel nut for the AN5 and placed the AN5 nut on the inside of the axel nut. Make sure you have clearance when the big cotter pin is inserted thru the axel nut. I am sure there are many more clever approaches but this will work.
BTW there were several flight test engineers at our camp that encouraged me to fly home from Idaho with one MLG fairing on and the other off. This would be more convenient as my RV-10 was stuffed full of camping equipment and there was no room for another MLG fairing. I duct taped the leg fairings in place and took off. They were right. At cruise the cost was 8 mph and 1/4 bubble of rudder. No handling difference.
Bill DeRouchey
N939SB, flying
[quote][b]
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
|
|
|
| Back to top |
|
 |
Tim Olson
Joined: 25 Jan 2007
Posts: 2879
|
| Posted: Sat Jul 19, 2008 2:30 pm Post subject: Main Landing Gear Fairing Bolt Failure |
|
|
Bill,
Were you already using improved axle extensions? These
are what we came up with a couple years ago to fix breakage
at that point.
http://www.myrv10.com/N104CD/upgrades/20070118/index.html
If not, that's a pretty easy way to strengthen that point,
as that stem actually doesn't have enough base to prevent
the hex rod from rocking back and forth.
Did you actually see deformation of those 3 spacers?
From what it sounds like at first glance, you may be going
about it the hard way to fix the problem, but I'd like to hear
more of what damaged parts you found OTHER than the bolt
stem.
Tim
Tim Olson - RV-10 N104CD - Flying
do not archive
Bill DeRouchey wrote:
| Quote: | I landed approximately a dozen times on a long, grass strip in the Idaho
wilderness and found the AN4-6 bolt shown on page 46-5 figure 2 sheared
at the cotter pin. This is the AN4 that pokes out of the large axel nut
to hold the fairing standoff. The port side failed but the starboard MLG
fairing could be wiggled and would soon fail.
The strip is pocked with small mounds much like a polo field before the
divits are replaced. There were no holes, nor did I hit anything, nor
did I land hard. The fiberglass fairing is still pristine. What caused
the problem is the fairing jiggling up and down during the roll out.
Tearing the landing gear down for inspection revealed that the current
design will not work over time. I believe the failure begins at the 3
U-1008 spacers shown on page 46-4 figure 4. When the fairing bounces
about these spacers gall the U-1010L plate and loosen the inboard side
of the fairing. Once the inboard side of the fairing begins to move
around it has a 5 inch lever arm (U-1004B) from the outboard fairing
attachment point that works the AN4 bolt and will shear it at the cotter
pin hole. Looking at the sheared bolt endwise the structural area is
very small after the cotter hole is drilled and the thread depths are
subtracted.
Two items need to be redesigned. The three bolts thru U-1010L cannot be
tightened because the tension simply crushes the aluminum spacers. The
spacers need to be steel and the joint tightened. I don't have a lathe
but do have lots of 4130 tubing .5" OD by .375 ID. I cleaned the inside
of the tube with a .375" ream and pressed the aluminum spacer inside.
Added a washer between the spacer and the U-1010L and tightened it
properly. Now it is much stiffer.
Beefing up the AN4 at the axel nut required much more work. If you only
have a hammer then you use a hammer to fix all problems. I created a
weldment with a TIG welder but a lathe is the better tool. I used the
same steel .5"OD by .375"ID tubing and constructed a standoff with an
AN5 stud on one end and an AN4 nut on the other. Drilled out the axel
nut for the AN5 and placed the AN5 nut on the inside of the axel nut.
Make sure you have clearance when the big cotter pin is inserted thru
the axel nut. I am sure there are many more clever approaches but this
will work.
BTW there were several flight test engineers at our camp that encouraged
me to fly home from Idaho with one MLG fairing on and the other off.
This would be more convenient as my RV-10 was stuffed full of camping
equipment and there was no room for another MLG fairing. I duct taped
the leg fairings in place and took off. They were right. At cruise the
cost was 8 mph and 1/4 bubble of rudder. No handling difference.
Bill DeRouchey
N939SB, flying
|
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
|
|
|
| Back to top |
|
|
billderou(at)yahoo.com
Guest
|
| Posted: Sat Jul 19, 2008 6:19 pm Post subject: Main Landing Gear Fairing Bolt Failure |
|
|
Hi Tim-
I remember the list addressing the AN4-6 bolt issue but I had already mounted my wheels and did not want to back track. Maybe I should have in retrospec.
My extensions were Vans stock with no modifications. The U-1008 spacers were galled at the contact with U-1010L and had dug in approx 1/64". All three spacers/plate showed the same wear and the "wiggle" produced at the forward point of the fairing was very noticable. It was approximately 3/4" top to bottom and 1/2" left to right. Imagine the U-1010L plate mounted on 3 weak standoffs and the little play required to move the forward point of the fairing. Of course, this was with the small shoulder spacer from Vans on the outboard side.
The modification of the axel nut standoff as in your drawing should work very well but it is only half of the problem. It would address and solve wiggle on the outboard fairing attach point but is carrying load that should be disipated by the U-1010L plate. By not shifting load to the U-1010L the big countersunk 1/4-28 screw and the fiberglass at the outboard end of the standoff must be handling a lot of shock when the tire hits a bump.
If anyone flying has wiggle in their MLG fairings I believe it can be traced to galling between U-1008 and U-1010L. Omitting a steel washer created the galling but the inability to properly torque the three bolts is also problematic. I initially torqued the three bolts with a thin washer between the aluminum pieces and watched the spacer puff out. After adding an outer steel sheath and a thin washer to fill-in the indentation of U-1010L the plate torques to a solid mount for the fairing. The difference in U-1010L stiffness between the before and after is huge.
Bill DeRouchey
N939SB, flying
--- On Sat, 7/19/08, Tim Olson <Tim(at)MyRV10.com> wrote:
[quote]From: Tim Olson <Tim(at)MyRV10.com>
Subject: Re: Main Landing Gear Fairing Bolt Failure
To: rv10-list(at)matronics.com
Date: Saturday, July 19, 2008, 3:24 PM
[quote]--> RV10-List message posted by: Tim Olson <Tim(at)myrv10.com> Bill, Were you already using improved axle extensions? These are what we came up with a couple years ago to fix breakage at that point. http://www.myrv10.com/N104CD/upgrades/20070118/index.html If not, that's a pretty easy way to strengthen that point, as that stem actually doesn't have enough base to prevent the hex rod from rocking back and forth. Did you actually see deformation of those 3 spacers? From what it sounds like at first glance, you may be going about it the hard way to fix the problem, but I'd like to hear more of what damaged parts you found OTHER than the bolt stem. Tim Tim Olson - RV-10 N104CD - Flying do not archive Bill DeRouchey wrote: > I landed approximately a dozen times on a long, grass strip in the Idaho > wilderness and found the AN4-6 bolt shown on page 46-5 figure 2 sheared > at the cotter pin. This is the AN4 that pokes out of the large axel nut > to hold the fairing standoff. The port side failed but the starboard MLG > fairing could be wiggled and would soon fail. > > > > The strip is pocked with small mounds much like a polo field before the > divits are replaced. There were no holes, nor did I hit anything, nor > did I land hard. The fiberglass fairing is still pristine. What caused > the problem is the fairing jiggling up and down during the roll out. > > > > Tearing the landing gear down for inspection revealed that the current > design will not work over time. I believe the failure begins at the 3 > U-1008 spacers shown on page 46-4 figure 4. When the fairing bounces > about these spacers gall the U-1010L plate and loosen the inboard side > of the fairing. Once the inboard side of the fairing begins to move > around it has a 5 inch lever arm (U-1004B) from the outboard fairing > attachment point that works the AN4 bolt and will shear it at the cotter > pin hole. Looking at the sheared bolt endwise the structural area is > very small after the cotter hole is drilled and the thread depths are > subtracted. > > > > Two items need to be redesigned. The three bolts thru U-1010L cannot be > tightened because the tension simply crushes the aluminum spacers. The > spacers need to be steel and the joint tightened. I don't have a lathe > but do have lots of 4130 tubing .5" OD by .375 ID. I cleaned the inside > of the tube with a .375" ream and pressed the aluminum spacer inside. > Added a washer between the spacer and the U-1010L and tightened it > properly. Now it is much stiffer. > > > > Beefing up the AN4 at the axel nut required much more work. If you only > have a hammer then you use a hammer to fix all problems. I created a > weldment with a TIG welder but a lathe is the better tool. I used the > same steel .5"OD by .375"ID tubing and constructed a standoff with an > AN5 stud on one end and an AN4 nut on the other. Drilled out the axel > nut for the AN5 and placed the AN5 nut on the inside of the axel nut. > Make sure you have clearance when the big cotter pin is inserted thru > the axel nut. I am sure there are many more clever approaches but this > will work. > > > > BTW there were several flight test engineers at our camp that encouraged > me to fly home from Idaho with one MLG fairing on and the other off. > This would be more convenient as my RV-10 was stuffed full of camping > equipment and there was no room for another MLG fairing. I duct taped > the leg fairings in place and took off. They were right. At cruise the > cost was 8 mph and 1/4 bubble of rudder. No handling difference. > > > > Bill DeRouchey > > N939SB, flying > [quote][b]
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
|
|
|
| Back to top |
|
|
Tim Olson
Joined: 25 Jan 2007
Posts: 2879
|
| Posted: Sat Jul 19, 2008 7:19 pm Post subject: Main Landing Gear Fairing Bolt Failure |
|
|
Hi again Bill,
One more followup... you said "It was approximately 3/4" top to bottom
and 1/2" left to right."
I want to make sure I'm understanding. Are you saying that if you
grab the top of that fairing mounting plate (the big swiss cheese
bent thick aluminum metal plate) that you can rock it back and forth
pulling in/out on it if you're sitting facing the side of the wheel
grabbing it by the top, and if you grabbed it by the aft end of that
plate you could pull it 1/2" in and out? As in, that whole plate
gets wobbly?
I ask because so far, mine is very solid with no slop, at 360 approx
hours. I just mounted those flex brake lines to that plate
not long ago so I recently had it apart, and it's really tight.
I've had the axle extension now for probably the last 2 years
or so though, so I'm wondering if maybe yours loosened over time
maybe partly due to the fact that you hadn't been using the extensions.
That would be a possibility I'd think. Let me know if I'm
misunderstanding how it was loose though.
I do think that the outer end of the fairing mount, where it attaches
to the extension, will naturally have to support quite a bit of
bumping up and down. Even if that plate were solid (and by all means,
making or keeping it solid is a great thing), I think that 1/4-28
stainless screw needs to hold that fairing pretty solidly, as there
is going to be quite a bit of torque from the axle extension to
the axle nut trying to snap that bolt. I know my hex rod, even
after 6-12 months, had rounded the corners over rocking on that
metal washer....so yeah, that bolt in the standard design is
definitely a fracture point waiting to happen. Anything you can
do...any of the various axle extensions that were created, should
help make that bolt snapping much much less of an issue. I personally
think they should be standard parts with the kits, given the size
of the wheel fairings we carry around....and the number of
broken extensions we've seen. I know there are over a half-dozen
or more.
Tim Olson - RV-10 N104CD - Flying
do not archive
Bill DeRouchey wrote:
| Quote: | Hi Tim-
I remember the list addressing the AN4-6 bolt issue but I had already
mounted my wheels and did not want to back track. Maybe I should have in
retrospec.
My extensions were Vans stock with no modifications. The U-1008 spacers
were galled at the contact with U-1010L and had dug in approx 1/64". All
three spacers/plate showed the same wear and the "wiggle" produced at
the forward point of the fairing was very noticable. It was
approximately 3/4" top to bottom and 1/2" left to right. Imagine the
U-1010L plate mounted on 3 weak standoffs and the little play required
to move the forward point of the fairing. Of course, this was with the
small shoulder spacer from Vans on the outboard side.
The modification of the axel nut standoff as in your drawing should work
very well but it is only half of the problem. It would address and solve
wiggle on the outboard fairing attach point but is carrying load that
should be disipated by the U-1010L plate. By not shifting load to the
U-1010L the big countersunk 1/4-28 screw and the fiberglass at the
outboard end of the standoff must be handling a lot of shock when the
tire hits a bump.
If anyone flying has wiggle in their MLG fairings I believe it can be
traced to galling between U-1008 and U-1010L. Omitting a steel washer
created the galling but the inability to properly torque the three bolts
is also problematic. I initially torqued the three bolts with a thin
washer between the aluminum pieces and watched the spacer puff out.
After adding an outer steel sheath and a thin washer to fill-in the
indentation of U-1010L the plate torques to a solid mount for the
fairing. The difference in U-1010L stiffness between the before and
after is huge.
Bill DeRouchey
N939SB, flying
--- On *Sat, 7/19/08, Tim Olson /<Tim(at)MyRV10.com>/* wrote:
From: Tim Olson <Tim(at)MyRV10.com>
Subject: Re: Main Landing Gear Fairing Bolt Failure
To: rv10-list(at)matronics.com
Date: Saturday, July 19, 2008, 3:24 PM
Bill,
Were you already using improved axle extensions? These
are what we came up with a couple years ago to fix breakage
at that point.
http://www.myrv10.com/N104CD/upgrades/20070118/index.html
If not, that's a pretty easy way to strengthen that point,
as that stem actually doesn't have enough base to prevent
the hex rod from rocking back and forth.
Did you actually see deformation of those 3 spacers?
From what it sounds like at first glance, you may be going
about it the hard way to fix the problem, but I'd like to hear
more of what damaged parts you found OTHER than the bolt
stem.
Tim
Tim Olson - RV-10 N104CD - Flying
do not archive
Bill DeRouchey wrote:
> I landed approximately a dozen times on a long, grass strip in the Idaho
> wilderness and found the AN4-6 bolt shown on page 46-5 figure 2 sheared
> at the cotter pin. This is the AN4 that pokes out of the large axel nut
> to hold the fairing standoff. The port side failed but the starboard MLG
> fairing could be wiggled and would soon fail.
>
>
>
> The strip is pocked with small mounds much like a polo field before the
> divits are replaced. There were no holes, nor did I hit anything, nor
> did I land hard. The fiberglass fairing is still pristine. What caused
> the problem is the fairing jiggling up and down during the roll out.
>
>
>
> Tearing the landing gear down for inspection revealed that the current
> design will not work over time. I believe the failure begins at the 3
> U-1008 spacers shown on page 46-4 figure 4. When the fairing bounces
> about these spacers gall the U-1010L plate and loosen the inboard side
> of the fairing. Once the inboard side of the fairing begins to move
> around it has a 5 inch lever arm (U-1004B) from the outboard fairing
> attachment point that works the AN4 bolt and will shear it at the cotter
> pin hole. Looking at the sheared bolt endwise the structural area is
> very small after the cotter hole is drilled and the thread depths are
> subtracted.
>
>
>
> Two items need to be redesigned. The three bolts thru U-1010L cannot be
> tightened because the tension simply crushes the aluminum spacers. The
> spacers need to be steel and the joint tightened. I don't have a lathe
> but do have lots of 4130 tubing .5" OD by .375 ID. I cleaned the
inside
> of the tube with a .375" ream and pressed the aluminum spacer inside.
> Added a washer between the spacer and the U-1010L and tightened it
> properly. Now it is much stiffer.
>
>
>
> Beefing up the AN4 at the axel nut required much more work. If you only
> have a hammer then you use a hammer to fix all problems. I created a
> weldment with a TIG welder but a lathe is the better tool. I used the
> same steel .5"OD by .375"ID tubing and constructed a standoff
with an
> AN5 stud on one end and an AN4 nut on the other. Drilled out the axel
> nut for the AN5 and placed the AN5 nut on the inside of the axel nut.
> Make sure you have clearance when the big cotter pin is inserted thru
> the axel nut. I am sure there are many more clever approaches but this
> will work.
>
>
>
> BTW there were several flight test engineers at our camp that encouraged
> me to fly home from Idaho with one MLG fairing on and the other off.
> This would be more convenient as my RV-10 was stuffed full of camping
> equipment and there was no room for another MLG fairing. I duct taped
> the leg fairings in place and took off. They were right. At cruise the
> cost was 8 mph and 1/4 bubble of rudder. No handling difference.
>
>
>
> Bill DeRouchey
>
> N939SB, flying
>
*
*
|
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
|
|
|
| Back to top |
|
|
billderou(at)yahoo.com
Guest
|
| Posted: Sun Jul 20, 2008 8:19 am Post subject: Main Landing Gear Fairing Bolt Failure |
|
|
Hi again Tim - (its all good discussion)
The wobble measurements of 3/4" vertical and 1/2" lateral was the distance my hand was moving when testing the fairing security during my pre-flight. My hand was on the forward tip of the fairing. So it had an approx 18" of lever arm on the U-1010L plate. Working with just the plate: if you tighten the plate then back off each bolt to create a 1/64" opening it would be equilivant to the plate wiggle that I observed. Thinking about it more it was probably closer to 1/32".
All forces on the fairing need to be transfered back into the axel and the mount acts as a system with attach points at the fairing outboard and inboard. When a weak point develops it "leans" on the other side to accelerate wear at that point. Then they go back and forth destroying each other very quickly.
The standard axel end standoff orbiting about the AN4-6 bolt is the weak point outboard and the U-1008 to U-1010 joint galling is the weak point inboard. Yesterday, I thought the galling was the original sin that broke the AN4-6 bolt but your information indicates that the standoff is the major problem since your U-1010 plate is still secure. If you solve the problem on one side it reduces the forces on the other. It would not surprise me that if one mounted the U-1010 plate as I suggested earlier with a washer and steel spacers the AN4-6 bolt would not break for a thousand plus hours.
If you were smarter than me and deviated from the plans slipping a thin washer between the U-1008 and the U-1010 then you have a good 90% solution that will probably last forever. If not, the joint absolutely will gall and loosen over time. Question is how much time?
I think every weak point needs fixing to keep a system failure from occuring.
Devise any standoff with a large OD that will not orbit and no cotter key through the bolt
Add a washer between the U-1008 and U-1010
Replace the U-1008 with steel spacers and torque properly
Its all about minimizing problems over long service times. Nothing really needs to be fixed until the fairing begins to wiggle. Just check it on your pre-flight.
Bill DeRouchey
N939SB, flying
--- On Sat, 7/19/08, Tim Olson <Tim(at)MyRV10.com> wrote:
[quote]From: Tim Olson <Tim(at)MyRV10.com>
Subject: Re: Main Landing Gear Fairing Bolt Failure
To: rv10-list(at)matronics.com
Date: Saturday, July 19, 2008, 8:14 PM
[quote]--> RV10-List message posted by: Tim Olson <Tim(at)myrv10.com> Hi again Bill, One more followup... you said "It was approximately 3/4" top to bottom and 1/2" left to right." I want to make sure I'm understanding. Are you saying that if you grab the top of that fairing mounting plate (the big swiss cheese bent thick aluminum metal plate) that you can rock it back and forth pulling in/out on it if you're sitting facing the side of the wheel grabbing it by the top, and if you grabbed it by the aft end of that plate you could pull it 1/2" in and out? As in, that whole plate gets wobbly? I ask because so far, mine is very solid with no slop, at 360 approx hours. I just mounted those flex brake lines to that plate not long ago so I recently had it apart, and it's really tight. I've had the axle extension now for probably the last 2 years or so though, so I'm wondering if maybe yours loosened over time maybe partly due to the fact that you hadn't been using the extensions. That would be a possibility I'd think. Let me know if I'm misunderstanding how it was loose though. I do think that the outer end of the fairing mount, where it attaches to the extension, will naturally have to support quite a bit of bumping up and down. Even if that plate were solid (and by all means, making or keeping it solid is a great thing), I think that 1/4-28 stainless screw needs to hold that fairing pretty solidly, as there is going to be quite a bit of torque from the axle extension to the axle nut trying to snap that bolt. I know my hex rod, even after 6-12 months, had rounded the corners over rocking on that metal washer....so yeah, that bolt in the standard design is definitely a fracture point waiting to happen. Anything you can do...any of the various axle extensions that were created, should help make that bolt snapping much much less of an issue. I personally think they should be standard parts with the kits, given the size of the wheel fairings we carry around....and the number of broken extensions we've seen. I know there are over a half-dozen or more. Tim Olson - RV-10 N104CD - Flying do not archive Bill DeRouchey wrote: > Hi Tim- > > I remember the list addressing the AN4-6 bolt issue but I had already > mounted my wheels and did not want to back track. Maybe I should have in > retrospec. > > > > My extensions were Vans stock with no modifications. The U-1008 spacers > were galled at the contact with U-1010L and had dug in approx 1/64". All > three spacers/plate showed the same wear and the "wiggle" produced at > the forward point of the fairing was very noticable. It was > approximately 3/4" top to bottom and 1/2" left to right. Imagine the > U-1010L plate mounted on 3 weak standoffs and the little play required > to move the forward point of the fairing. Of course, this was with the > small shoulder spacer from Vans on the outboard side. > > > > The modification of the axel nut standoff as in your drawing should work > very well but it is only half of the problem. It would address and solve > wiggle on the outboard fairing attach point but is carrying load that > should be disipated by the U-1010L plate. By not shifting load to the > U-1010L the big countersunk 1/4-28 screw and the fiberglass at the > outboard end of the standoff must be handling a lot of shock when the > tire hits a bump. > > > > If anyone flying has wiggle in their MLG fairings I believe it can be > traced to galling between U-1008 and U-1010L. Omitting a steel washer > created the galling but the inability to properly torque the three bolts > is also problematic. I initially torqued the three bolts with a thin > washer between the aluminum pieces and watched the spacer puff out. > After adding an outer steel sheath and a thin washer to fill-in the > indentation of U-1010L the plate torques to a solid mount for the > fairing. The difference in U-1010L stiffness between the before and > after is huge. > > > > Bill DeRouchey > > N939SB, flying > > > > --- On *Sat, 7/19/08, Tim Olson /<Tim(at)MyRV10.com>/* wrote: > > From: Tim Olson <Tim(at)MyRV10.com> > Subject: Re: Main Landing Gear Fairing Bolt Failure > To: rv10-list(at)matronics.com > Date: Saturday, July 19, 2008, 3:24 PM > > --> RV10-List message posted by: Tim Olson <Tim(at)myrv10.com> > > > > Bill, > > Were you already using improved axle extensions? These > are what we came up with a couple years ago to fix breakage > at that point. > http://www.myrv10.com/N104CD/upgrades/20070118/index.html > If not, that's a pretty easy way to strengthen that point, > as that stem actually doesn't have enough base to prevent > the hex rod from rocking back and forth. > > Did you actually see deformation of those 3 spacers? > > From what it sounds like at first glance, you may be going > about it the hard way to fix the problem, but I'd like to hear > more of what damaged parts you found OTHER than the bolt > stem. > > Tim > Tim Olson - RV-10 N104CD - Flying > do not archive > > Bill DeRouchey wrote: > > I landed approximately a dozen times on a long, grass strip in the Idaho > > wilderness and found the AN4-6 bolt shown on page 46-5 figure 2 sheared > > at the cotter pin. This is the AN4 that pokes out of the large axel nut > > to hold the fairing standoff. The port side failed but the starboard MLG > > fairing could be wiggled and would soon fail. > > > > > > > > The strip is pocked with small mounds much like a polo field before the > > divits are replaced. There were no holes, nor did I hit anything, nor > > did I land hard. The fiberglass fairing is still pristine. What caused > > the problem is the fairing jiggling up and down during the roll out. > > > > > > > > Tearing the landing gear down for inspection revealed that the current > > design will not work over time. I believe the failure begins at the 3 > > U-1008 spacers shown on page 46-4 figure 4. When the fairing bounces > > about these spacers gall the U-1010L plate and loosen the inboard side > > of the fairing. Once the inboard side of the fairing begins to move > > around it has a 5 inch lever arm (U-1004B) from the outboard fairing > > attachment point that works the AN4 bolt and will shear it at the cotter > > pin hole. Looking at the sheared bolt endwise the structural area is > > very small after the cotter hole is drilled and the thread depths are > > subtracted. > > > > > > > > Two items need to be redesigned. The three bolts thru U-1010L cannot be > > tightened because the tension simply crushes the aluminum spacers. The > > spacers need to be steel and the joint tightened. I don't have a lathe > > > but do have lots of 4130 tubing .5" OD by .375 ID. I cleaned the > inside > > of the tube with a .375" ream and pressed the aluminum spacer inside. > > > Added a washer between the spacer and the U-1010L and tightened it > > properly. Now it is much stiffer. > > > > > > > > Beefing up the AN4 at the axel nut required much more work. If you only > > have a hammer then you use a hammer to fix all problems. I created a > > weldment with a TIG welder but a lathe is the better tool. I used the > > same steel .5"OD by .375"ID tubing and constructed a standoff > with an > > AN5 stud on one end and an AN4 nut on the other. Drilled out the axel > > nut for the AN5 and placed the AN5 nut on the inside of the axel nut. > > Make sure you have clearance when the big cotter pin is inserted thru > > the axel nut. I am sure there are many more clever approaches but this > > will work. > > > > > > > > BTW there were several flight test engineers at our camp that encouraged > > me to fly home from Idaho with one MLG fairing on and the other off. > > This would be more convenient as my RV-10 was stuffed full of camping > > equipment and there was no room for another MLG fairing. I duct taped > > the leg fairings in place and took off. They were right. At cruise the > > cost was 8 mph and 1/4 bubble of rudder. No handling difference. > > > > > > > > Bill DeRouchey > > > > N939SB, flying > > > > > * > > > * > [quote][b]
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
|
|
|
| Back to top |
|
|
Tim Olson
Joined: 25 Jan 2007
Posts: 2879
|
| Posted: Sun Jul 20, 2008 10:09 am Post subject: Main Landing Gear Fairing Bolt Failure |
|
|
I agree with your comments Bill. I think in an ideal world, if you
fixed it on both sides, you'd never have any issue at all. If
you fix it on either side, you probably lessen your chances of
having problems greatly. If you leave it as-is on the plans,
you probably COULD go a long time, but eventually you'll have
some wear or weakening and when you land on grass you'll have
those original axle extensions break.
For me, I'll just monitor those spacers for now then, because
I'm not seeing that with the heavier-duty extensions that
there's as much flex going on to gall the parts. But, I
may slip in a thin washer next time I'm in that area, to
help prevent wear on the metal plate.
Great that you brought it up and clarified it. Certainly if
there were that 3/4 and 1/2" movement on the metal plate, that
would be really severe....at least those measurements were
at the fairing tips. Still not good, but now I see why the
number was larger than I expected.
So far it looks to me like the 2 most "faulty" or in-need-of-fix
areas on the plane are probably those axle extensions and spacers
on the mains that we're talking about, and the spacer system up
on that nosewheel. Other than that, the plane is adding up
lots of good hours with no major issues.
Tim Olson - RV-10 N104CD - Flying
do not archive
Bill DeRouchey wrote:
| Quote: | Hi again Tim - (its all good discussion)
The wobble measurements of 3/4" vertical and 1/2" lateral was the
distance my hand was moving when testing the fairing security during my
pre-flight. My hand was on the forward tip of the fairing. So it had an
approx 18" of lever arm on the U-1010L plate. Working with just the
plate: if you tighten the plate then back off each bolt to create a
1/64" opening it would be equilivant to the plate wiggle that I
observed. Thinking about it more it was probably closer to 1/32".
All forces on the fairing need to be transfered back into the axel and
the mount acts as a system with attach points at the fairing outboard
and inboard. When a weak point develops it "leans" on the other side to
accelerate wear at that point. Then they go back and forth destroying
each other very quickly.
The standard axel end standoff orbiting about the AN4-6 bolt is the weak
point outboard and the U-1008 to U-1010 joint galling is the weak point
inboard. Yesterday, I thought the galling was the original sin that
broke the AN4-6 bolt but your information indicates that the standoff is
the major problem since your U-1010 plate is still secure. If you solve
the problem on one side it reduces the forces on the other. It would not
surprise me that if one mounted the U-1010 plate as I suggested earlier
with a washer and steel spacers the AN4-6 bolt would not break
for a thousand plus hours.
If you were smarter than me and deviated from the plans slipping a thin
washer between the U-1008 and the U-1010 then you have a good 90%
solution that will probably last forever. If not, the joint absolutely
will gall and loosen over time. Question is how much time?
I think every weak point needs fixing to keep a system failure from
occuring.
Devise any standoff with a large OD that will not orbit and no
cotter key through the bolt
Add a washer between the U-1008 and U-1010
Replace the U-1008 with steel spacers and torque properly
Its all about minimizing problems over long service times. Nothing
really needs to be fixed until the fairing begins to wiggle. Just check
it on your pre-flight.
Bill DeRouchey
N939SB, flying
--- On *Sat, 7/19/08, Tim Olson /<Tim(at)MyRV10.com>/* wrote:
From: Tim Olson <Tim(at)MyRV10.com>
Subject: Re: Main Landing Gear Fairing Bolt Failure
To: rv10-list(at)matronics.com
Date: Saturday, July 19, 2008, 8:14 PM
Hi again Bill,
One more followup... you said "It was approximately 3/4" top to
bottom
and 1/2" left to right."
I want to make sure I'm understanding. Are you saying that if you
grab the top of that fairing mounting plate (the big swiss cheese
bent thick aluminum metal plate) that you can rock it back and forth
pulling in/out on it if you're sitting facing the side of the wheel
grabbing it by the top, and if you grabbed it by the aft end of that
plate you could pull it 1/2" in and out? As in, that whole plate
gets wobbly?
I ask because so far, mine is very solid with no slop, at 360 approx
hours. I just mounted those flex brake lines to that plate
not long ago so I recently had it apart, and it's really tight.
I've had the axle extension now for probably the last 2 years
or so though, so I'm wondering if maybe yours loosened over time
maybe partly due to the fact that you hadn't been using the extensions.
That would be a possibility I'd think. Let me know if I'm
misunderstanding how it was loose though.
I do think that the outer end of the fairing mount, where it attaches
to the extension, will naturally have to support quite a bit of
bumping up and down. Even if that plate were solid (and by all means,
making or keeping it solid is a great thing), I think that 1/4-28
stainless screw needs to hold that fairing pretty solidly, as there
is going to be quite a bit of torque from the axle extension to
the axle nut trying to snap that bolt. I know my hex rod, even
after 6-12 months, had rounded the corners over rocking on that
metal washer....so yeah, that bolt in the standard design is
definitely a fracture point waiting to happen. Anything you can
do...any of the various axle extensions that were created, should
help make that bolt snapping much much less of an issue. I personally
think they should be standard parts with the kits, given the size
of the wheel fairings we carry around....and the number of
broken extensions we've seen. I know there are over a half-dozen
or more.
Tim Olson - RV-10 N104CD - Flying
do not archive
Bill DeRouchey wrote:
> Hi Tim-
>
> I remember the list addressing the AN4-6 bolt issue but I had already
> mounted my wheels and did not want to back track. Maybe I should have in
> retrospec.
>
>
>
> My extensions were Vans stock with no modifications. The U-1008 spacers
> were galled at the contact with U-1010L and had dug in approx 1/64".
All
> three spacers/plate showed the same wear and the "wiggle"
produced at
> the forward point of the fairing was very noticable. It was
> approximately 3/4" top to bottom and 1/2" left to right. Imagine
the
> U-1010L plate mounted on 3 weak standoffs and the little play required
> to move the forward point of the fairing. Of course, this was with the
> small shoulder spacer from Vans on the outboard side.
>
>
>
> The modification of the axel nut standoff as in your drawing should work
> very well but it is only half of the problem. It would address and solve
> wiggle on the outboard fairing attach point but is carrying load that
> should be disipated by the U-1010L plate. By not shifting load to the
> U-1010L the big countersunk 1/4-28 screw and the fiberglass at the
> outboard end of the standoff must be handling a lot of shock when the
> tire hits a bump.
>
>
>
> If anyone flying has wiggle in their MLG fairings I believe it can be
> traced to galling between U-1008 and U-1010L. Omitting a steel washer
> created the galling but the inability to properly torque the three bolts
> is also problematic. I initially torqued the three bolts with a thin
> washer between the aluminum pieces and watched the spacer puff out.
> After adding an outer steel sheath and a thin washer to fill-in the
> indentation of U-1010L the plate torques to a solid mount for the
> fairing. The difference in U-1010L stiffness between the before and
> after is huge.
>
>
>
> Bill DeRouchey
>
> N939SB, flying
>
>
>
> --- On *Sat, 7/19/08, Tim Olson /<Tim(at)MyRV10.com>/* wrote:
>
> From: Tim Olson <Tim(at)MyRV10.com>
> Subject: Re: Main Landing Gear Fairing Bolt Failure
> To: rv10-list(at)matronics.com
> Date: Saturday, July 19, 2008, 3:24 PM
>
>
>
>
>
> Bill,
>
> Were you already using improved axle extensions? These
> are what we came up with a couple years ago to fix breakage
> at that point.
> http://www.myrv10.com/N104CD/upgrades/20070118/index.html
> If not, that's a pretty easy way to strengthen that point,
> as that stem actually doesn't have enough base to prevent
> the hex rod from rocking back and forth.
>
> Did you actually see deformation of those 3 spacers?
>
> From what it sounds like at first glance, you may be going
> about it the hard way to fix the problem, but I'd like to hear
> more of what damaged parts you found OTHER than the bolt
> stem.
>
> Tim
> Tim Olson - RV-10 N104CD - Flying
> do not archive
>
> Bill DeRouchey wrote:
> > I landed approximately a dozen times on a long, grass strip in
the Idaho
> > wilderness and found the AN4-6 bolt shown on page 46-5 figure 2
sheared
> > at the cotter pin. This is the AN4 that pokes out of the large
axel nut
> > to hold the fairing standoff. The port side failed but the
starboard MLG
> > fairing could be wiggled and would soon fail.
> >
> >
> >
> > The strip is pocked with small mounds much like a polo field
before the
> > divits are replaced. There were no holes, nor did I hit anything,
nor
> > did I land hard. The fiberglass fairing is still pristine. What
caused
> > the problem is the fairing jiggling up and down during the roll
out.
> >
> >
> >
> > Tearing the landing gear down for inspection revealed that the
current
> > design will not work over time. I believe the failure begins at
the 3
> > U-1008 spacers shown on page 46-4 figure 4. When the fairing
bounces
> > about these spacers gall the U-1010L plate and loosen the inboard
side
> > of the fairing. Once the inboard side of the fairing begins to
move
> > around it has a 5 inch lever arm (U-1004B) from the outboard
fairing
> > attachment point that works the AN4 bolt and will shear it at the
cotter
> > pin hole. Looking at the sheared bolt endwise the structural area
is
> > very small after the cotter hole is drilled and the thread depths
are
> > subtracted.
> >
> >
> >
> > Two items need to be redesigned. The three bolts thru U-1010L
cannot be
> > tightened because the tension simply crushes the aluminum
spacers. The
> > spacers need to be steel and the joint tightened. I don't
have a lathe
>
> > but do have lots of 4130 tubing .5" OD by .375 ID. I cleaned
the
> inside
> > of the tube with a .375" ream and pressed the aluminum
spacer inside.
>
> > Added a washer between the spacer and the U-1010L and tightened
it
> > properly. Now it is much stiffer.
> >
> >
> >
> > Beefing up the AN4 at the axel nut required much more work. If
you only
> > have a hammer then you use a hammer to fix all problems. I
created a
> > weldment with a TIG welder but a lathe is the better tool. I used
the
> > same steel .5"OD by .375"ID tubing and constructed a
standoff
> with an
> > AN5 stud on one end and an AN4 nut on the other. Drilled out the
axel
> > nut for the AN5 and placed the AN5 nut on the inside of the axel
nut.
> > Make sure you have clearance when the big cotter pin is inserted
thru
> > the axel nut. I am sure there are many more clever approaches but
this
> > will work.
> >
> >
> >
> > BTW there were several flight test engineers at our camp that
encouraged
> > me to fly home from Idaho with one MLG fairing on and the other
off.
> > This would be more convenient as my RV-10 was stuffed full of
camping
> > equipment and there was no room for another MLG fairing. I duct
taped
> > the leg fairings in place and took off. They were right. At
cruise the
> > cost was 8 mph and 1/4 bubble of rudder. No handling difference.
> >
> >
> >
> > Bill DeRouchey
> >
> > N939SB, flying
> >
>
>
> *
>
>
> *
>
*
*
|
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
