Mooney Landing Gear

[Tracker]

I like my mooney just the way it is ;). But wondering what the design advantages were for using the rubber discs as shock absorbers and not oleos.  Less wet? Smaller size? My apologies is this was answered before?

[MikeOH]

11 minutes ago, Tracker said:

I like my mooney just the way it is ;). But wondering what the design advantages were for using the rubber discs as shock absorbers and not oleos.  Less wet? Smaller size? My apologies is this was answered before?

My guess?  Al Mooney was the original CB  Rubber discs were cheaper than oleos.  Plus, pretty much zero maintenance until worn out. (I don't think the discs cost the ridiculous amount they do now, even adjusted for inflation, when they were originally designed in)

[EricJ]

Given the amount of trouble that friends have with their oleo struts, e.g., leaks, seal replacements, recharging, etc., every time I hear of an issue like that I'm glad for the rubber donuts.   Oleos tend to behave better, but not that much better to make up for the maintenance differences, imho.

 

[cbarry]

Rubber discs have their advantages, but the gear design of our Mooneys, especially the long bodies, are pretty much at their limits.  It is my understanding, a possible design (maybe based on the M22) is in the works as a modification for the long bodies to “beef” up the gear that may add a nice increase in the useful load.  The M22 foregoes the rubber discs…

[carusoam]

Oleos are a nice device when you can’t get your performance to match your expectations… 

Watch the videos of people that fly often… see how perfect their landings are…

Rubber donuts are near failure proof, low tech, low weight…

Perfect for a privately owned aircraft…

They have received one technical update since 1958… when they changed from Firestone to Lord based donuts…

 

Next nearly scheduled update will be for a higher MGTW than the current LBs…

PP thoughts only,

-a-

[Igor_U]

On 8/28/2022 at 7:09 PM, EricJ said:

Given the amount of trouble that friends have with their oleo struts, e.g., leaks, seal replacements, recharging, etc., every time I hear of an issue like that I'm glad for the rubber donuts.   Oleos tend to behave better, but not that much better to make up for the maintenance differences, imho.

 

I never heard complains about oleos from Piper or Bo crowd or such; to my understanding their service is pretty straightforward. 

As Mike mentioned, Al was an original CB. This design was first used (that I know) on Mooney Mite and later on m20 and it's all simple tube welding, with no outsourcing and no SCM of today; it could all be done at Mooney by their welder manufacturing the tubular frame as well . What might worked good  in 50s environment of cheap labor, it becomes quite expansive over more then half the century, hence Mooneys are not built anymore. I think it's was a simple design that factory could build it themselves, albeit quite labor intensive and not that great on hard landing or rough runways... 

[Hank]

The pucks themselves were readily available, inexpensive tractor parts, too, weren't they? Tractors have since advanced, but the FAA won't let GA manufacturing advance, resulting in parts scarcity and higher prices.

[1980Mooney]

4 hours ago, Hank said:

The pucks themselves were readily available, inexpensive tractor parts, too, weren't they? Tractors have since advanced, but the FAA won't let GA manufacturing advance, resulting in parts scarcity and higher prices.

Not exactly. He started with disks from a Mack Truck engine mount. But they were not robust enough for the M20 so he had special ones made. 
This is a great KNR article from 2009. 
https://www.knr-inc.com/25-shoptalk/23-200904-does-your-mooney-need-a-chiropractor

“Al Mooney designed the landing gear shock system on his airplanes differently than did Clyde Cessna, Walter Beach, Pug Piper or Lloyd Steerman. Al wanted something simple yet strong and relatively maintenance free; thus the multi-rubber disc articulating landing gear became part of the Mooney heritage with the certification of the Mooney Mite in 1948. This concept has been used in all subsequent production models.”

According to Mooney historian and all-around good guy, Bill Wheat, Al Mooney discovered that Mac Truck engine mounts worked perfectly for the rubber discs on the Mooney Mite. When the M20 series was developed these discs where too small and a special disc had to be made. This landing gear shock absorption systems has evolved over the years as Mooney aircraft have become heavier, but its still basically the same system Al Mooney came up with over sixty years ago.”

Also he points out the limitations of shock disks compared to oleo struts. “The active shock absorbing components of this system are the tires and the rubber shock discs…..Too high tire pressure will not absorb enough energy thus transmitting the loads onto the rest of the system. The shock discs can’t absorb it all so the wing spar (meaning your fuel tanks) absorbs the energy.”

Besides making our wet wings more leak prone, the shock discs don’t dampen as much as oleo struts and this contributes to greater tendency to bounce and porpoising. 
 

Our landing gear are stuck in the 50’s. 

[MooneyMitch]

21 minutes ago, 1980Mooney said:

According to Mooney historian and all-around good guy, Bill Wheat, Al Mooney discovered that Mac Truck engine mounts worked perfectly for the rubber discs on the Mooney Mite

[Guest]

On my Comanche my oleo struts have 1/2 dozen “O” rings and 2 quarts of hydraulic oil, about $30 in parts.  They don’t take a lot more labour to rebuild than it takes to replace the rubber discs on a Mooney, which are pushing $2000.  If the tail of a long body Mooney sits a little low you can’t pump up the rubber discs, when the tail of an oleo strutted plane goes low, you add some nitrogen.

Id guess that the cost of a welded landing gear is similar to that of a machined oleo strut.

[1980Mooney]

7 hours ago, 1980Mooney said:

Our landing gear are stuck in the 50’s. 

Actually our landing gear are stuck in the 40's....The M20 gear are just a larger version of the Mooney Mite landing gear which was developed in the 1940's and on the market in 1947.  It was a great solution at the time but that was 75 years ago.

12 hours ago, Hank said:

The pucks themselves were readily available, inexpensive tractor parts, too, weren't they? Tractors have since advanced, but the FAA won't let GA manufacturing advance, resulting in parts scarcity and higher prices.

I don't think I follow.  The 1940's Mooney Mite which our landing gear originated from had wooden wings.  Since then we have seen the Mooney go to aluminum wings, steel tubing fuselage mated to aluminum  semi-monocoque rear.  The competition went to planes entirely aluminum semi-monocoque.  More recently we see the domination of composite construction.  The Epic E1000 is now all carbon fiber and sets a new higher standard in composite GA design and manufacturing.  Somehow the FAA has let GA manufacturing advance...

https://epicaircraft.com/wp-content/uploads/2020/07/Epic_Innovation_PR_FINAL.pdf

[EricJ]

1 minute ago, 1980Mooney said:

Actually our landing gear are stuck in the 40's....The M20 gear are just a larger version of the Mooney Mite landing gear which was developed in the 1940's and on the market in 1947.  It was a great solution at the time but that was 75 years ago.

FWIW, Cirrus uses a rubber puck suspension in their current models on the nose gear.   So do RVs.

[GeeBee]

One thing you will never have to worry about on a Mooney is arriving at the airplane and finding a puddle and a collapsed strut. That said, it lacks the rebound dampening that an oleo strut features. The trailing link mitigates the lack of rebound control. If you want to fly a sweet gear, the Commander 112 and 114 with trailing link and oleo is the bee's knees. (Literally if you know bee's knees)  It was adapted by Rockwell from the OV-10 Bronco. Almost impossible to bounce the airplane and very good control in all regimes. In fact when they first were selling Commanders they show a flight test video of it landing with a few dozen 2x4's stretched across the runway. Sadly the nose gear on the airplane was weak. I am hopeful if the GW increase comes out it will feature a trailing link oleo. It will cut down on prop strikes for the LB.

Here is a look at the Commander gear.

 

[flyboy0681]

1 hour ago, GeeBee said:

One thing you will never have to worry about on a Mooney is arriving at the airplane and finding a puddle and a collapsed strut. That said, it lacks the rebound dampening that an oleo strut features. The trailing link mitigates the lack of rebound control. If you want to fly a sweet gear, the Commander 112 and 114 with trailing link and oleo is the bee's knees. (Literally if you know bee's knees)  It was adapted by Rockwell from the OV-10 Bronco. Almost impossible to bounce the airplane and very good control in all regimes. In fact when they first were selling Commanders they show a flight test video of it landing with a few dozen 2x4's stretched across the runway. Sadly the nose gear on the airplane was weak. I am hopeful if the GW increase comes out it will feature a trailing link oleo. It will cut down on prop strikes for the LB.

Here is a look at the Commander gear.

 

Mooney's retraction is sexier.

[Fly Boomer]

27 minutes ago, flyboy0681 said:

Mooney's retraction is sexier.

Oops, I read that wrong on the first pass.

[Guest]

4 hours ago, EricJ said:

FWIW, Cirrus uses a rubber puck suspension in their current models on the nose gear.   So do RVs.

Old info,  current SR22’s use a short stroke oleo on the nose. Older models used rubber discs.

[EricJ]

2 hours ago, flyboy0681 said:

Mooney's retraction is sexier.

You can always tell a hydraulic or electrohydraulic system if the gear goes up or comes down in some weird random order.    Coupled mechanical systems like Mooney, many Beechcraft, Cessna twins, etc., are always uniform.

[Hank]

9 hours ago, GeeBee said:

Here is a look at the Commander gear.

 

Man, that's a long time from first movement to fully retracted!

I posted a video of mine, once upon a time, but can't find it now. Mine went up, paused, then back down in the time it took this nose wheel to retract . . . .

[carusoam]

1980 for today’s historian prize!

The Mooney Mite guys have been looking for new rubber discs for decades….

I had heard of the Mac Truck Engine mounts… but couldn’t re-find the reference…

Like Mooneys… some Mac trucks tend to last forever too….
 

Best regards,

-a-

See if we can pass this on to the mite section….

According to Mooney historian and all-around good guy, Bill Wheat, Al Mooney discovered that Mac Truck engine mounts worked perfectly for the rubber discs on the Mooney Mite. When the M20 series was developed these discs where too small and a special disc had to be made. This landing gear shock absorption systems has evolved over the years as Mooney aircraft have become heavier, but its still basically the same system Al Mooney came up with over sixty years ago.”

[GeeBee]

The nice thing about electro hydraulic other than the Cessna's due to the angled retraction is when you need emergency down, there is nothing to fail. Dump the pressure and the gear drops. Add a spring if you want. The bad thing is it is sloooow.

Back to the GW increase, an ideal system would be trailing link, put a torsion spring inside the link and put an automotive type cartridge absorber for the oleo. Alternatively, put the spring around the absorber. Low maintenance, few leaks and when it does, just swap the absorber with two bolts on and off.