The Murphy Builders Site

Hello all.

Re: Super Rebel 3500 / Moose

This last weekend, I installed my main gear legs into the fuselage. I can't help but think about the spectre of the drag loads twisting the gear box. I'm doing a lot of head scratching about the issue, and am weighing all options. One thing that I'm sort of considering, is to build an external drag strut that would attach to the leg via a machined collar, on the gear leg end, and a fitting on the fuselage (that'll be internally braced) on the other end. I'm imagining the strut to be built of concentric tubes, with some sort of hard rubber snubber, internally. The ends of the strut would have rod ends, to accomodate movement. This would work, but will add a bit of weight and won't look as clean. Bear in mind, this is only a 'thought'. I've looked at MAM's mod, and am not much impressed.
I'm very much into building the plane and not 'improving' it, so I am interested in getting as many thoughts on the subject, as possible. Are you guys gonna build as is? How about Al P.?

A buddy of mine, who flies a C-170, expressed surprise that the gear box area wasn't beefier. He's done a bit of work, in his gear box, and indicated that the 170 appears much stouter.

Bill Delcambre
172SR FB

Hi Bill,
I have just placed an order for a Moose fast build kit, I don't believe the gear box ( the drag link mod looks like a waste of time to me) does enough to take care of the braking/drag loads.( I got to inspect a fast build kit at Oshkosh last year)

When the kit arrives, (7-8 months) that will be the area that I will be concentrating on, I am hoping I can organise an internal brace somehow from the box rearward to a hard point further back. This will carry similar loads to the mod I have done to my 0-320 spring gear Rebel.( which is now bullet proof!)

That's my 2 cents worth!

Cheers

Alister

----- Original Message -----
From: Bill Delcambre (bdelcambre@cox-internet.com)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Wednesday, September 25, 2002 4:14 AM
Subject: Main Gear Drag Loads


Hello all.

Re: Super Rebel 3500 / Moose

This last weekend, I installed my main gear legs into the fuselage. I can't help but think about the spectre of the drag loads twisting the gear box. I'm doing a lot of head scratching about the issue, and am weighing all options. One thing that I'm sort of considering, is to build an external drag strut that would attach to the leg via a machined collar, on the gear leg end, and a fitting on the fuselage (that'll be internally braced) on the other end. I'm imagining the strut to be built of concentric tubes, with some sort of hard rubber snubber, internally. The ends of the strut would have rod ends, to accomodate movement. This would work, but will add a bit of weight and won't look as clean. Bear in mind, this is only a 'thought'. I've looked at MAM's mod, and am not much impressed.
I'm very much into building the plane and not 'improving' it, so I am interested in getting as many thoughts on the subject, as possible. Are you guys gonna build as is? How about Al P.?

A buddy of mine, who flies a C-170, expressed surprise that the gear box area wasn't beefier. He's done a bit of work, in his gear box, and indicated that the 170 appears much stouter.

Bill Delcambre
172SR FB

Hi Bill,
Take a look at the P. Ponk web site for how they solved Cessna's gear problem.
Al
http://www.pponk.com/HTML%20PAGES/outbo ... acket.html

----- Original Message -----
From: Bill Delcambre (bdelcambre@cox-internet.com)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Tuesday, September 24, 2002 9:14 AM
Subject: Main Gear Drag Loads


Hello all.

Re: Super Rebel 3500 / Moose

This last weekend, I installed my main gear legs into the fuselage. I can't help but think about the spectre of the drag loads twisting the gear box. I'm doing a lot of head scratching about the issue, and am weighing all options. One thing that I'm sort of considering, is to build an external drag strut that would attach to the leg via a machined collar, on the gear leg end, and a fitting on the fuselage (that'll be internally braced) on the other end. I'm imagining the strut to be built of concentric tubes, with some sort of hard rubber snubber, internally. The ends of the strut would have rod ends, to accomodate movement. This would work, but will add a bit of weight and won't look as clean. Bear in mind, this is only a 'thought'. I've looked at MAM's mod, and am not much impressed.
I'm very much into building the plane and not 'improving' it, so I am interested in getting as many thoughts on the subject, as possible. Are you guys gonna build as is? How about Al P.?

A buddy of mine, who flies a C-170, expressed surprise that the gear box area wasn't beefier. He's done a bit of work, in his gear box, and indicated that the 170 appears much stouter.

Bill Delcambre
172SR FB

I am looking at an internal brace that would bolt on sort of like the 2500 mod brace only bigger. Also may go forward with it but have to work around the lower aileron pulley brackets. Then like Alister says run a channel or something all the way back to the rear door bulkheads. You run into the entry step bulkheads before the aft door ones so would have to carry through that. Then I am going to toss out the inner post skins that I just removed to run the aileron cables and double the thickness (up to .063 I think) and make them full length with a inspection hole below the upper aileron pulley. Would still decrease the rivet pitch per bulletin. May gusset the outside of door post too. I've noticed that many aircraft have external gussets that not only run across the bottom of the fuselage like MAM but they have fingers that run fore and aft to spread the load, so considering that.

I was considering having a one piece bracket machined instead of the two-part bolt together. Now I am leaning toward making a steel bracket that would essentially cap the FUS 310 (bolts would go through the new cross piece too) and would have flanges that run up the sides and bolt into the carry through with two bolts per side. That way I have a back up if either of those two bolts failed and the back up bolts would be in shear instead of tension. Brian has mentioned up sizing the bolts by one to get higher torque, but it is really up two to the 7/16 to get any significantly higher torque. Not sure if there is enough material for that but I think so. Then another steel bracket that runs along the back of the inner main gear bracket. It would cap the gear leg and the main bolt would go down through it and the leg. It would have bolts on side flanges that bolt through the carry through on the sides of the gear box. Sort of a poor mans Pponk type of deal. That way if I make a dorky side load landing it isn't all pushing in on just that one bolt. Then like Steve and Ron up in AK mentioned, use NAS bolts in all instead of AN for higher shear.

All that babble may only make sense to me...still thinking.

Scott
Moose N174SL


-----Original Message-----
From: murphy-rebel@dcsol.com [mailto:murphy-rebel@dcsol.com]On Behalf Of Bill Delcambre
Sent: Tuesday, September 24, 2002 10:15 AM
To: murphy-rebel@dcsol.com
Subject: Main Gear Drag Loads

Hello all.

Re: Super Rebel 3500 / Moose

This last weekend, I installed my main gear legs into the fuselage. I can't help but think about the spectre of the drag loads twisting the gear box. I'm doing a lot of head scratching about the issue, and am weighing all options. One thing that I'm sort of considering, is to build an external drag strut that would attach to the leg via a machined collar, on the gear leg end, and a fitting on the fuselage (that'll be internally braced) on the other end. I'm imagining the strut to be built of concentric tubes, with some sort of hard rubber snubber, internally. The ends of the strut would have rod ends, to accomodate movement. This would work, but will add a bit of weight and won't look as clean. Bear in mind, this is only a 'thought'. I've looked at MAM's mod, and am not much impressed.
I'm very much into building the plane and not 'improving' it, so I am interested in getting as many thoughts on the subject, as possible. Are you guys gonna build as is? How about Al P.?

A buddy of mine, who flies a C-170, expressed surprise that the gear box area wasn't beefier. He's done a bit of work, in his gear box, and indicated that the 170 appears much stouter.

Bill Delcambre
172SR FB

Have there been a lot of main gear failures warranting changing MAM's design to this extent? I know of the Super Rebel failure, but that is being attributed to an improperly torqued bolt which resulted in a Service Bulletin to check torques. I always thought that Murphy's planes were well thought of as tough bush planes, and they have addressed signs of wear or minor buckling with some minor changes, but I didn't think they were responding to complete gear failures.

Mike Kimball
SR#044

----------
From: S & L Aldrich
Reply To: murphy-rebel@dcsol.com
Sent: Tuesday, September 24, 2002 8:09 PM
To: murphy-rebel@dcsol.com
Subject: RE: Main Gear Drag Loads

<<File: ATT00001.htm>>
I am looking at an internal brace that would bolt on sort of like the 2500
mod brace only bigger. Also may go forward with it but have to work around
the lower aileron pulley brackets. Then like Alister says run a channel or
something all the way back to the rear door bulkheads. You run into the
entry step bulkheads before the aft door ones so would have to carry through
that. Then I am going to toss out the inner post skins that I just removed
to run the aileron cables and double the thickness (up to .063 I think) and
make them full length with a inspection hole below the upper aileron pulley.
Would still decrease the rivet pitch per bulletin. May gusset the outside of
door post too. I've noticed that many aircraft have external gussets that
not only run across the bottom of the fuselage like MAM but they have
fingers that run fore and aft to spread the load, so considering that.

I was considering having a one piece bracket machined instead of the
two-part bolt together. Now I am leaning toward making a steel bracket that
would essentially cap the FUS 310 (bolts would go through the new cross
piece too) and would have flanges that run up the sides and bolt into the
carry through with two bolts per side. That way I have a back up if either
of those two bolts failed and the back up bolts would be in shear instead of
tension. Brian has mentioned up sizing the bolts by one to get higher
torque, but it is really up two to the 7/16 to get any significantly higher
torque. Not sure if there is enough material for that but I think so. Then
another steel bracket that runs along the back of the inner main gear
bracket. It would cap the gear leg and the main bolt would go down through
it and the leg. It would have bolts on side flanges that bolt through the
carry through on the sides of the gear box. Sort of a poor mans Pponk type
of deal. That way if I make a dorky side load landing it isn't all pushing
in on just that one bolt. Then like Steve and Ron up in AK mentioned, use
NAS bolts in all instead of AN for higher shear.

All that babble may only make sense to me...still thinking.

Scott
Moose N174SL


-----Original Message-----
From: murphy-rebel@dcsol.com [mailto:murphy-rebel@dcsol.com]On Behalf Of
Bill Delcambre
Sent: Tuesday, September 24, 2002 10:15 AM
To: murphy-rebel@dcsol.com
Subject: Main Gear Drag Loads


Hello all.

Re: Super Rebel 3500 / Moose

This last weekend, I installed my main gear legs into the fuselage. I
can't help but think about the spectre of the drag loads twisting the gear
box. I'm doing a lot of head scratching about the issue, and am weighing
all options. One thing that I'm sort of considering, is to build an
external drag strut that would attach to the leg via a machined collar, on
the gear leg end, and a fitting on the fuselage (that'll be internally
braced) on the other end. I'm imagining the strut to be built of concentric
tubes, with some sort of hard rubber snubber, internally. The ends of the
strut would have rod ends, to accomodate movement. This would work, but
will add a bit of weight and won't look as clean. Bear in mind, this is
only a 'thought'. I've looked at MAM's mod, and am not much impressed.
I'm very much into building the plane and not 'improving' it, so I am
interested in getting as many thoughts on the subject, as possible. Are you
guys gonna build as is? How about Al P.?

A buddy of mine, who flies a C-170, expressed surprise that the gear box
area wasn't beefier. He's done a bit of work, in his gear box, and
indicated that the 170 appears much stouter.

Bill Delcambre
172SR FB





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Hi Mike,
I'm the guy who had the gear failure. At this time the cause is still
unknown as to why the AN365 nut failed, but I know the nut was not over
torqued. The safety bulletin was issued because MAM wants to ensure that
those bolts are torqued properly.
Al
----- Original Message -----
From: "Mike's Email" <mkimball@gci.net>
To: <murphy-rebel@dcsol.com>
Sent: Wednesday, September 25, 2002 1:22 PM
Subject: RE: Main Gear Drag Loads


Have there been a lot of main gear failures warranting changing MAM's design
to this extent? I know of the Super Rebel failure, but that is being
attributed to an improperly torqued bolt which resulted in a Service
Bulletin to check torques. I always thought that Murphy's planes were well
thought of as tough bush planes, and they have addressed signs of wear or
minor buckling with some minor changes, but I didn't think they were
responding to complete gear failures.

Mike Kimball
SR#044

----------
From: S & L Aldrich
Reply To: murphy-rebel@dcsol.com
Sent: Tuesday, September 24, 2002 8:09 PM
To: murphy-rebel@dcsol.com
Subject: RE: Main Gear Drag Loads

<<File: ATT00001.htm>>
I am looking at an internal brace that would bolt on sort of like the 2500
mod brace only bigger. Also may go forward with it but have to work around
the lower aileron pulley brackets. Then like Alister says run a channel or
something all the way back to the rear door bulkheads. You run into the
entry step bulkheads before the aft door ones so would have to carry through
that. Then I am going to toss out the inner post skins that I just removed
to run the aileron cables and double the thickness (up to .063 I think) and
make them full length with a inspection hole below the upper aileron pulley.
Would still decrease the rivet pitch per bulletin. May gusset the outside of
door post too. I've noticed that many aircraft have external gussets that
not only run across the bottom of the fuselage like MAM but they have
fingers that run fore and aft to spread the load, so considering that.

I was considering having a one piece bracket machined instead of the
two-part bolt together. Now I am leaning toward making a steel bracket that
would essentially cap the FUS 310 (bolts would go through the new cross
piece too) and would have flanges that run up the sides and bolt into the
carry through with two bolts per side. That way I have a back up if either
of those two bolts failed and the back up bolts would be in shear instead of
tension. Brian has mentioned up sizing the bolts by one to get higher
torque, but it is really up two to the 7/16 to get any significantly higher
torque. Not sure if there is enough material for that but I think so. Then
another steel bracket that runs along the back of the inner main gear
bracket. It would cap the gear leg and the main bolt would go down through
it and the leg. It would have bolts on side flanges that bolt through the
carry through on the sides of the gear box. Sort of a poor mans Pponk type
of deal. That way if I make a dorky side load landing it isn't all pushing
in on just that one bolt. Then like Steve and Ron up in AK mentioned, use
NAS bolts in all instead of AN for higher shear.

All that babble may only make sense to me...still thinking.

Scott
Moose N174SL


-----Original Message-----
From: murphy-rebel@dcsol.com [mailto:murphy-rebel@dcsol.com]On Behalf Of
Bill Delcambre
Sent: Tuesday, September 24, 2002 10:15 AM
To: murphy-rebel@dcsol.com
Subject: Main Gear Drag Loads


Hello all.

Re: Super Rebel 3500 / Moose

This last weekend, I installed my main gear legs into the fuselage. I
can't help but think about the spectre of the drag loads twisting the gear
box. I'm doing a lot of head scratching about the issue, and am weighing
all options. One thing that I'm sort of considering, is to build an
external drag strut that would attach to the leg via a machined collar, on
the gear leg end, and a fitting on the fuselage (that'll be internally
braced) on the other end. I'm imagining the strut to be built of concentric
tubes, with some sort of hard rubber snubber, internally. The ends of the
strut would have rod ends, to accomodate movement. This would work, but
will add a bit of weight and won't look as clean. Bear in mind, this is
only a 'thought'. I've looked at MAM's mod, and am not much impressed.
I'm very much into building the plane and not 'improving' it, so I am
interested in getting as many thoughts on the subject, as possible. Are you
guys gonna build as is? How about Al P.?

A buddy of mine, who flies a C-170, expressed surprise that the gear box
area wasn't beefier. He's done a bit of work, in his gear box, and
indicated that the 170 appears much stouter.

Bill Delcambre
172SR FB







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Hi Mike,
No there have not been a lot of failures but (in my opinion) I think the
buckling was more than minor. Also the fact that they are getting this with
just normal landings with normal braking with a lot of experience in type
makes me want to look close at it.

I don't think the gear failure was attributed to over torque. Also MAM puts
in their advertising how every thing has a back up. Those bolts don't have
any sort of back up. Don't get me wrong I think the SR/Moose is really great
but I do think the gear needs to be more bullet proof.

Scott

-----Original Message-----
From: murphy-rebel@dcsol.com [mailto:murphy-rebel@dcsol.com]On Behalf Of
Mike's Email
Sent: Wednesday, September 25, 2002 2:22 PM
To: murphy-rebel@dcsol.com
Subject: RE: Main Gear Drag Loads


Have there been a lot of main gear failures warranting changing MAM's design
to this extent? I know of the Super Rebel failure, but that is being
attributed to an improperly torqued bolt which resulted in a Service
Bulletin to check torques. I always thought that Murphy's planes were well
thought of as tough bush planes, and they have addressed signs of wear or
minor buckling with some minor changes, but I didn't think they were
responding to complete gear failures.

Mike Kimball
SR#044

172SR FB






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<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> Al,
I have a 3/16, AN365? fibre nut as received from MAM that had no threads.
So much for QA! So it's possible that there was a problem with your nut. Has the NTSB conducted a metallurgical examination of the nut? If not, and you still have the nut I could try and arrange for some of my accident investigation contacts to conduct an analysis.
Regards,
Warren

Subject: Re: Main Gear Drag Loads

Hi Mike,
I'm the guy who had the gear failure. At this time the cause is still
unknown as to why the AN365 nut failed, but I know the nut was not over
torqued. The safety bulletin was issued because MAM wants to ensure that
those bolts are torqued properly.
Al

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Hello Al,

Really hate that you had the gear problem. Truly disheartening. Got a couple of questions, though.
Was there any perceptible movement of the gear leg, before the pullout? How are you coming with the repairs? Could you post a couple of pictures of the damage to the gear box area? After looking at the Pponk site, I was sorta wondering if you were going to try to emulate their design, in your repair, or something else?

Thanks for the insight.

Bill Delcambre

Bill and Warren,
I have uploaded some pictures of the damaged SR landing gear. I felt no movement in the gear leg prior to the failure.
Repairs are progressing slooowly, the engine has been rebuilt and will be shipped back from Ly-Con next week. The prop was a total loss and the prop shop has not found a 2nd hand replacement yet. The fuselage repairs are being done in Pateros, WA, by Air Metal Fabricators, they do good work and I will be over there next week for a status visit. The .032 door post skins have been replaced by .063 skins. The door channels are also upgraded to .063. The steel flanges that are used in the Moose landing gear box are being used at the rear float fitting to strengthen that area. I also plan to put a doubler around the rear float fitting that goes fore and aft, up and down, to distribute the loads. I have the aileron and wing yet to repair and will assembly back here at Vashon.
I like the P Ponk/Cessna design but don't have the resources to design and build a new landing gear system. I would like to have redundancy and use the existing stock parts. As of now I plan to go straight to amphibs and to use the existing gear only to get over to Libby, Montana to get the floats installed.
The damaged parts have been analyzed and the tensile strengths are: the sheared nut 102ksi, the other nut holding the saddle was 98ksi, and the bolt was 156ksi. A MAM supplied new AN365 nut tested 121ksi. The lab report states, "The new nut was fully spherodized, while the used and sheared nuts contained cold worked ferrite and pearlite". "The microstructure of the new nut appeared to contain a higher carbon cotent, which would account for the higher hardness and hence, higher tensile and shear strengths". Note, the sheared nut and the used nut were not supplied by MAM, they came from my local aircraft hardware supplier, only the new nut came from MAM.
Does anyone have access to a copy of the AN365 standard or know what the tensile strength should be for these parts?
Al
----- Original Message -----

From: Bill Delcambre (bdelcambre@cox-internet.com)
To: murphy-rebel@dcsol.com (murphy-rebel@dcsol.com)
Sent: Thursday, September 26, 2002 6:33 AM
Subject: Re: Main Gear Drag Loads


Hello Al,

Really hate that you had the gear problem. Truly disheartening. Got a couple of questions, though.
Was there any perceptible movement of the gear leg, before the pullout? How are you coming with the repairs? Could you post a couple of pictures of the damage to the gear box area? After looking at the Pponk site, I was sorta wondering if you were going to try to emulate their design, in your repair, or something else?

Thanks for the insight.

Bill Delcambre