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1. 09:43 AM - Re: Help on this situation. (mark_trickel)
2. 10:27 AM - Re: Re: Help on this situation. (Alfred Rosa)
3. 11:31 AM - Re: Re: Help on this situation. (Galin Hernandez)
4. 02:51 PM - Help on this situation. (Owen Baker)
Message 1
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| Subject: | Re: Help on this situation. |
Hello Galin,
Once again you are on the fringes of the unknown. With 1000 plus hours I can only
guess you have at least 2000 landings (maybe more) on the airframe.
Your pictures tell a very compelling story, and there are no hidden secrets. If
I were inspecting your airplane, and saw the washers now in a concave mode I
would immediately throw up a red flag. Looking farther, and noticing the washers
under the bolts show a lot of wear. Either bolt bolts are spinning around in
the holes or somebody has been tightening them as they became lose.
Mark is right the story under those washers is not going to be pretty. All the
glass, and resin under the washers is now completely crushed!
Loads on the main gear-
When the landing gear touches the runway the forces are tremendous. You have the
rate of decent, and the forward momentum of the airplane all converging at once
on those two tiny little bolts on the front end of the main gear attach brackets.
Just imagine the TR-4 near gross weight say 2300 pounds with a bunch of
fuel burned off (oh right, some builders keep increasing the gross weight, what
am I thinking) heading towards the runway at 70 plus miles per hour. There
may be wheels attached to the end of the landing gear leg but the moment it all
touches the runway the forces at hand want to rip the landing gear off the
airframe. And that is quiet evident form the pictures posted - a few more landing
and the bolts would have won. Try googling forces on the main landing gear,
and you will find the engineering formulas are very intense. Its a long subject
better left to smart engineers. Needless to say the set-up we use on our KIS
aircraft have room for improvement
I referred to the TR-4 manual The set-up used on THIS installation is NOT correct.
According to the manual Fuselage section 2, page 23. There is supposed to
be a rudder spacer under the fender washer. What is shown in the pics are a
very thin piece of rubber. That said, even if it did have the proper rudder under
the washer I do not think it would have prevented this occurrence. The way
it is set-up we are trying to place all the landing loads under the two forwards
washers, and the loads are much too concentrated. The loads need to be spread
out farther on each side where the gear attaches.
Another thing that would help is a much larger washer, and one or two smaller washers
in the stack to support the larger washers (a certified airplane is allowed
3 washers in the stack). Possibly even using a piece of 4130 steel plate
connecting to the rear bolt as well. My TR-1 has a X 1 bar that connects both
bolts together. The ultimate set-up would be using two bolt spaced a last 1
apart on the forward main landing gear attachment (would require a special custom
attach bracket (would be worth the price of admission)). That would spread
the load farther out, and really add a sense of security to landing operations,
something every pilot needs. Another idea would be to add a rubber piece on
the bottom side of the landing gear between the gear and the attach bracket.
That would allow for more movement of the main gear The idea of putting rubber
under the washer in the stack and cinching up on it makes no sense in me, putting
rubber on both side of the gear seems like a much smarter way to go.
Doing the composite repairs is not difficult but I do not see any way around supporting
the airplane, and dropping the main gear away. While the fiberglass repairs
could be solely done from the inside of the cockpit, I think I would want
to add plies to the underside of the affected areas, but you would have to
be careful around the flox wedge that cants the main gear forward. Typically you
need to v- out the cracks and scarf the edges and give it plenty of room for
the patches to attach to (8 to 1 scarf should be good use a dremel grinder
and 80 grit sand paper to prep for glass). You only need to overlap the crack
line by 2 inches on each side for a good repair. I would think about 20 to 30
layers of 10 oz. cloth would do, with 6 to 8 plies on the underside.
My2 cent Mark T
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=441806#441806
Message 2
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| Subject: | Re: Help on this situation. |
These radius blocks from GROVE are what I installed. The curved surfaces
allow the aluminum gear to flex easily and not stress the bolts.
On Wed, May 6, 2015 at 12:43 PM, mark_trickel <marktrickel@gmail.com> wrote
:
>
> Hello Galin,
>
> Once again you are on the fringes of the unknown. With 1000 plus hours I
> can only guess you have at least 2000 landings (maybe more) on the airfra
me.
>
> Your pictures tell a very compelling story, and there are no hidden
> secrets. If I were inspecting your airplane, and saw the washers now in a
> concave mode I would immediately throw up a red flag. Looking farther, an
d
> noticing the washers under the bolts show a lot of wear. Either bolt bolt
s
> are spinning around in the holes or somebody has been tightening them as
> they became lose.
>
> Mark is right the story under those washers is not going to be pretty. Al
l
> the glass, and resin under the washers is now completely crushed!
>
> Loads on the main gear-
> When the landing gear touches the runway the forces are tremendous. You
> have the rate of decent, and the forward momentum of the airplane all
> converging at once on those two tiny little bolts on the front end of the
> main gear attach brackets. Just imagine the TR-4 near gross weight say 23
00
> pounds with a bunch of fuel burned off (oh right, some builders keep
> increasing the gross weight, what am I thinking) heading towards the runw
ay
> at 70 plus miles per hour. There may be wheels attached to the end of the
> landing gear leg but the moment it all touches the runway the forces at
> hand want to rip the landing gear off the airframe. And that is quiet
> evident form the pictures posted - a few more landing and the bolts would
> have won. Try googling forces on the main landing gear, and you will find
> the engineering formulas are very intense. It=99s a long subject be
tter left
> to smart engineers. Needless to say the set-up we use on our KIS aircraft
> have room for improvement
>
> I referred to the TR-4 manual =93 The set-up used on THIS installat
ion is
> NOT correct. According to the manual Fuselage section 2, page 23. There i
s
> supposed to be a =C2=BC rudder spacer under the fender washer. What is sh
own in
> the pics are a very thin piece of rubber. That said, even if it did have
> the proper =C2=BC=9D rudder under the washer I do not think it woul
d have
> prevented this occurrence. The way it is set-up we are trying to place al
l
> the landing loads under the two forwards washers, and the loads are much
> too concentrated. The loads need to be spread out farther on each side
> where the gear attaches.
>
> Another thing that would help is a much larger washer, and one or two
> smaller washers in the stack to support the larger washers (a certified
> airplane is allowed 3 washers in the stack). Possibly even using a piece
of
> 4130 steel plate connecting to the rear bolt as well. My TR-1 has a =C2
=BC=9C X 1=9D
> bar that connects both bolts together. The ultimate set-up would be using
> two bolt spaced a last 1 =C2=BD=9D apart on the forward main landin
g gear
> attachment (would require a special custom attach bracket (would be worth
> the price of admission)). That would spread the load farther out, and
> really add a sense of security to landing operations, something every pil
ot
> needs. Another idea would be to add a rubber piece on the bottom side of
> the landing gear between the gear and the attach bracket. That would allo
w
> for more movement of the main gear The idea of putting rubber under the
> washer in the stack and cinching up on it makes no sense in me, putting
> rubber on both side of the gear se!
> ems like a much smarter way to go.
>
> Doing the composite repairs is not difficult but I do not see any way
> around supporting the airplane, and dropping the main gear away. While th
e
> fiberglass repairs could be solely done from the inside of the cockpit, I
> think I would want to add plies to the underside of the affected areas, b
ut
> you would have to be careful around the flox wedge that cants the main ge
ar
> forward. Typically you need to v- out the cracks and scarf the edges and
> give it plenty of room for the patches to attach to (8 to 1 scarf should
be
> good =93 use a dremel grinder and 80 grit sand paper to prep for gl
ass). You
> only need to overlap the crack line by 2 inches on each side for a good
> repair. I would think about 20 to 30 layers of 10 oz. cloth would do, wit
h
> 6 to 8 plies on the underside.
>
> My2 cent Mark T
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=441806#441806
>
>
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===========
===========
===========
>
>
Message 3
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| Subject: | Re: Help on this situation. |
I didn't get Mark K's reply but reading Mark T's reply I realize this is
worse than I originally thought. Here are some more photos of the affected
areas.
Does anybody know of somebody that I can pay to do the repairs. I don't
feel comfortable doing these kinds of repairs.
On Wed, May 6, 2015 at 12:43 PM, mark_trickel <marktrickel@gmail.com> wrote
:
>
> Hello Galin,
>
> Once again you are on the fringes of the unknown. With 1000 plus hours I
> can only guess you have at least 2000 landings (maybe more) on the airfra
me.
>
> Your pictures tell a very compelling story, and there are no hidden
> secrets. If I were inspecting your airplane, and saw the washers now in a
> concave mode I would immediately throw up a red flag. Looking farther, an
d
> noticing the washers under the bolts show a lot of wear. Either bolt bolt
s
> are spinning around in the holes or somebody has been tightening them as
> they became lose.
>
> Mark is right the story under those washers is not going to be pretty. Al
l
> the glass, and resin under the washers is now completely crushed!
>
> Loads on the main gear-
> When the landing gear touches the runway the forces are tremendous. You
> have the rate of decent, and the forward momentum of the airplane all
> converging at once on those two tiny little bolts on the front end of the
> main gear attach brackets. Just imagine the TR-4 near gross weight say 23
00
> pounds with a bunch of fuel burned off (oh right, some builders keep
> increasing the gross weight, what am I thinking) heading towards the runw
ay
> at 70 plus miles per hour. There may be wheels attached to the end of the
> landing gear leg but the moment it all touches the runway the forces at
> hand want to rip the landing gear off the airframe. And that is quiet
> evident form the pictures posted - a few more landing and the bolts would
> have won. Try googling forces on the main landing gear, and you will find
> the engineering formulas are very intense. It=99s a long subject be
tter left
> to smart engineers. Needless to say the set-up we use on our KIS aircraft
> have room for improvement
>
> I referred to the TR-4 manual =93 The set-up used on THIS installat
ion is
> NOT correct. According to the manual Fuselage section 2, page 23. There i
s
> supposed to be a =C2=BC rudder spacer under the fender washer. What is sh
own in
> the pics are a very thin piece of rubber. That said, even if it did have
> the proper =C2=BC=9D rudder under the washer I do not think it woul
d have
> prevented this occurrence. The way it is set-up we are trying to place al
l
> the landing loads under the two forwards washers, and the loads are much
> too concentrated. The loads need to be spread out farther on each side
> where the gear attaches.
>
> Another thing that would help is a much larger washer, and one or two
> smaller washers in the stack to support the larger washers (a certified
> airplane is allowed 3 washers in the stack). Possibly even using a piece
of
> 4130 steel plate connecting to the rear bolt as well. My TR-1 has a =C2
=BC=9C X 1=9D
> bar that connects both bolts together. The ultimate set-up would be using
> two bolt spaced a last 1 =C2=BD=9D apart on the forward main landin
g gear
> attachment (would require a special custom attach bracket (would be worth
> the price of admission)). That would spread the load farther out, and
> really add a sense of security to landing operations, something every pil
ot
> needs. Another idea would be to add a rubber piece on the bottom side of
> the landing gear between the gear and the attach bracket. That would allo
w
> for more movement of the main gear The idea of putting rubber under the
> washer in the stack and cinching up on it makes no sense in me, putting
> rubber on both side of the gear se!
> ems like a much smarter way to go.
>
> Doing the composite repairs is not difficult but I do not see any way
> around supporting the airplane, and dropping the main gear away. While th
e
> fiberglass repairs could be solely done from the inside of the cockpit, I
> think I would want to add plies to the underside of the affected areas, b
ut
> you would have to be careful around the flox wedge that cants the main ge
ar
> forward. Typically you need to v- out the cracks and scarf the edges and
> give it plenty of room for the patches to attach to (8 to 1 scarf should
be
> good =93 use a dremel grinder and 80 grit sand paper to prep for gl
ass). You
> only need to overlap the crack line by 2 inches on each side for a good
> repair. I would think about 20 to 30 layers of 10 oz. cloth would do, wit
h
> 6 to 8 plies on the underside.
>
> My2 cent Mark T
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=441806#441806
>
>
===========
===========
===========
===========
>
>
Message 4
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| Subject: | Help on this situation. |
5/6/2015
Hello Al, Thanks for your input. You wrote:
=9CThe curved surfaces allow the aluminum gear to flex easily and
not stress the bolts.=9D
If the wheel axle is directly below the fore and aft center of the bolts
and if the force applied to the wheel end of the landing gear is
directly vertical, and therefore parallel to the bolts, then you are
correct because the rotation of the landing gear crossbar around the
curved surface of the radius blocks would cause minimal stress both
along the length of the bolts nor in bending of the bolt.
But if the force applied to the wheel end of the landing gear has a
fore-and-aft component to it then the attempted rotation of the crossbar
will stress the bolts. And there is a significant aft component of force
applied to the wheel end of the landing gear every time the non rotating
tire comes into contact with the runway surface while the airplane is
travelling at some significant forward speed.
Also if the landing gear is canted forward then even a directly vertical
load parallel to the bolts at the wheel end of the landing gear will
cause the aft edge of the crossbar to attempt to rotate downward and
thereby place a longitudinal stress on the aft bolts.
I think that the radius blocks are very desirable, I just could not get
the spacing to work our for my KIS TR-1 landing gear cross bar and the
existing bolt hole locations.
OC
PS: Do you have some sort of thin elastomeric sheet between the top of
the landing gear cross bar and the bottom of the fuselage flox bed that
it fits up against? This is required to keep the relatively hard
aluminum cross bar from crumbling any cured flox hot spots,
=====================
From: Alfred Rosa
Sent: Wednesday, May 06, 2015 1:26 PM
Subject: Re: KIS-List: Re: Help on this situation.
These radius blocks from GROVE are what I installed. The curved
surfaces allow the aluminum gear to flex easily and not stress the
bolts.
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