Moose/SR3500 Main Gear.
Posted: Fri Feb 17, 2012 10:59 pm
For those following the 3500/Moose gear discussion. I emailed Jim about the
new gear designed for his. This was the Moose on the front of the
Trade-a-Plane awhile back. He bought the original demonstrator from MAM and
it did not have the 3500 gear beef up mods on it so that would be a
contributing factor to his problem. His notes to me are below.
Scott
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Email #1:
Yes, I am the guy that they have made a new set of gear legs and attachment
points for. I had the inner bridge crack on my Moose.
I bought their original prototype, which is different from your aircraft.
The attachment points for the production kit are put further apart than
mine, a stronger set-up. I also had the tundra tires on the aircraft. My
aircraft did not have the drag link modification, which Murphy recommends.
My aircraft did not have the channels that fit on the outside of the
carrythroughs at the inner bridge station, a crucial part. Furthermore, I
land the aircraft wherever I find a reasonably flat spot. I spot land the
aircraft on a regular basis. I suspect I have put as much stress on the
gear as anyone.
My inner bridge pieces failed because the inboard legs would move forward on
touchdown with the large tire/wheel combination. I did not have this
problem when I had the 8.50 wheels. The gear movement caused the hole in
the inboard aluminum bracket to elongate and eventually crack.
I decided to do a gear box/gear leg/attachment point redesign and scratch
the tundra tires. I spoke with Daryl and he said he would help with the
re-design using his CAD drawings of the kit using my ideas for the new
structure.
My re-design entails a new gear leg that is bent outboard of the fuselage,
passing horizontally through a re-designed outboard bracket and terminating
at a re-designed inboard bracket that is about 12 inches inboard. In
addition, I am beefing up the carrythroughs by sandwiching a 2024 aluminum
plate to the carrythroughs on the inside.
This arrangement is about 50 lbs heavier than the production version. The
attachment points are steel. The legs are significantly longer and thicker
(1"). Each 1/4" plate inside the gear box weighs 6.5 lbs. It is clearly
overkill. I am not an aeronautical engineer, though I do have several years
of university engineering training. This gear will never fail. The
fuselage will deform first.
I think the original design has its shortcomings, especially when used with
the tundra tire kit. That simply places too much stress on the gear legs on
landing. I suspect the original design would survive the FAA's test for
certification which is a two foot drop onto greased plates without
catastrophic damage. Their demonstrator apparently has no signs of these
problems, but it doesn't get landed like mine. Furthermore, in my opinion
the Moose gear legs are too thick and stiff.
Murphy has no plans to offer the gear set-up I am using because they don't
think the aircraft needs it. I think they should offer an upgrade kit to
those of us who are amateur bush pilots.
The Moose is a robust aircraft as is the Cessna 185, but that does not stop
pilots from needing gear beef-up mods on that aircraft.
If I were you and I wanted to beef up the gear, I would do what I did, or
look into the Cessna 185 gear mod STC for a better engineered design. There
is no short cut to use the bent gear arrangement, the carrythroughs must be
solid in order to bolt the inboard attachment point up. The bent gear
arrangement places more twisting moment on the gear box than the straight
leg arrangement which is why I had to go to steel attachments. It was a
large hassle, as I had to replace all the damaged parts, including the
original carrythroughs.
I won't have mine flying for 90 days or so because I don't have the parts
yet and still need
to have my 0-540 AD done.
Sincerely,
Jim
Email #2:
Scott:
I don't mind you ccing your friends. That would be the best way to
broadcast the discussion rather than my e-mailing everyone who is interested
individually.
As far as getting the parts for the upgrade, MAM has shipped the parts to me
and they are enroute. They will be the first thing I install. MAM and I
will work out the kinks. By the way, the gear legs have been thickened to
1" because of the bend put in the legs. I think this is unnecessary and
heavy but it is what MAM specified. I think this needs to be looked into
engineering wise. There is an 6500# Air Tractor across from my hangar with
5 inch wide x 1 1/8" thick gear and a bent configuration. I will see how
much the gear flexes when I land the A/C with the thick gear. I believe the
Moose 7/8" gear is overkill for a 3500# A/C. The 185 gear is 3/4", I
believe. The maximum shock transmitted to the structure is increased
rather dramatically as the gear is thickened. I disagree strongly with
Murphy's engineer on the gear thickness issue but Daryl assures me he has
taken into consideration the additional gear length and narrowed the cross
section to give it the required springiness.
I don't think you should fly with the Tundra tires without a gear upgrade of
some sort. The drag loads simply will overwhelm the inner bridge within a
few hundred landings, no matter how well executed. At a minimum, the inner
bridge needs to be made of steel and needs to be triangular in shape, not
"Y" shaped. The drag load mod and "C" channels on the outside of the gear
box are crucial. I also would be very careful landing on hard surface
runways.
The best way to handle this however is to go to the bent gear. This allows
the gear to be lengthened inside the fuselage.
MAM's position on the gear mod is that the original design works fine for
normal use. Daryl thinks I beat up his airplane but is willing to help get
me out of a jam, and I appreciate the assistance. I bought an experimental
airplane, and a prototype at that. I think that they should offer a gear
upgrade as a kit, however, especially for the users of the tundra tires. I
will have my parts on within a few weeks.
Jim
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new gear designed for his. This was the Moose on the front of the
Trade-a-Plane awhile back. He bought the original demonstrator from MAM and
it did not have the 3500 gear beef up mods on it so that would be a
contributing factor to his problem. His notes to me are below.
Scott
----------------------------------------------------------------------------
Email #1:
Yes, I am the guy that they have made a new set of gear legs and attachment
points for. I had the inner bridge crack on my Moose.
I bought their original prototype, which is different from your aircraft.
The attachment points for the production kit are put further apart than
mine, a stronger set-up. I also had the tundra tires on the aircraft. My
aircraft did not have the drag link modification, which Murphy recommends.
My aircraft did not have the channels that fit on the outside of the
carrythroughs at the inner bridge station, a crucial part. Furthermore, I
land the aircraft wherever I find a reasonably flat spot. I spot land the
aircraft on a regular basis. I suspect I have put as much stress on the
gear as anyone.
My inner bridge pieces failed because the inboard legs would move forward on
touchdown with the large tire/wheel combination. I did not have this
problem when I had the 8.50 wheels. The gear movement caused the hole in
the inboard aluminum bracket to elongate and eventually crack.
I decided to do a gear box/gear leg/attachment point redesign and scratch
the tundra tires. I spoke with Daryl and he said he would help with the
re-design using his CAD drawings of the kit using my ideas for the new
structure.
My re-design entails a new gear leg that is bent outboard of the fuselage,
passing horizontally through a re-designed outboard bracket and terminating
at a re-designed inboard bracket that is about 12 inches inboard. In
addition, I am beefing up the carrythroughs by sandwiching a 2024 aluminum
plate to the carrythroughs on the inside.
This arrangement is about 50 lbs heavier than the production version. The
attachment points are steel. The legs are significantly longer and thicker
(1"). Each 1/4" plate inside the gear box weighs 6.5 lbs. It is clearly
overkill. I am not an aeronautical engineer, though I do have several years
of university engineering training. This gear will never fail. The
fuselage will deform first.
I think the original design has its shortcomings, especially when used with
the tundra tire kit. That simply places too much stress on the gear legs on
landing. I suspect the original design would survive the FAA's test for
certification which is a two foot drop onto greased plates without
catastrophic damage. Their demonstrator apparently has no signs of these
problems, but it doesn't get landed like mine. Furthermore, in my opinion
the Moose gear legs are too thick and stiff.
Murphy has no plans to offer the gear set-up I am using because they don't
think the aircraft needs it. I think they should offer an upgrade kit to
those of us who are amateur bush pilots.
The Moose is a robust aircraft as is the Cessna 185, but that does not stop
pilots from needing gear beef-up mods on that aircraft.
If I were you and I wanted to beef up the gear, I would do what I did, or
look into the Cessna 185 gear mod STC for a better engineered design. There
is no short cut to use the bent gear arrangement, the carrythroughs must be
solid in order to bolt the inboard attachment point up. The bent gear
arrangement places more twisting moment on the gear box than the straight
leg arrangement which is why I had to go to steel attachments. It was a
large hassle, as I had to replace all the damaged parts, including the
original carrythroughs.
I won't have mine flying for 90 days or so because I don't have the parts
yet and still need
to have my 0-540 AD done.
Sincerely,
Jim
Email #2:
Scott:
I don't mind you ccing your friends. That would be the best way to
broadcast the discussion rather than my e-mailing everyone who is interested
individually.
As far as getting the parts for the upgrade, MAM has shipped the parts to me
and they are enroute. They will be the first thing I install. MAM and I
will work out the kinks. By the way, the gear legs have been thickened to
1" because of the bend put in the legs. I think this is unnecessary and
heavy but it is what MAM specified. I think this needs to be looked into
engineering wise. There is an 6500# Air Tractor across from my hangar with
5 inch wide x 1 1/8" thick gear and a bent configuration. I will see how
much the gear flexes when I land the A/C with the thick gear. I believe the
Moose 7/8" gear is overkill for a 3500# A/C. The 185 gear is 3/4", I
believe. The maximum shock transmitted to the structure is increased
rather dramatically as the gear is thickened. I disagree strongly with
Murphy's engineer on the gear thickness issue but Daryl assures me he has
taken into consideration the additional gear length and narrowed the cross
section to give it the required springiness.
I don't think you should fly with the Tundra tires without a gear upgrade of
some sort. The drag loads simply will overwhelm the inner bridge within a
few hundred landings, no matter how well executed. At a minimum, the inner
bridge needs to be made of steel and needs to be triangular in shape, not
"Y" shaped. The drag load mod and "C" channels on the outside of the gear
box are crucial. I also would be very careful landing on hard surface
runways.
The best way to handle this however is to go to the bent gear. This allows
the gear to be lengthened inside the fuselage.
MAM's position on the gear mod is that the original design works fine for
normal use. Daryl thinks I beat up his airplane but is willing to help get
me out of a jam, and I appreciate the assistance. I bought an experimental
airplane, and a prototype at that. I think that they should offer a gear
upgrade as a kit, however, especially for the users of the tundra tires. I
will have my parts on within a few weeks.
Jim
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