Rubber Puck Thickness

[shorrick mk2]

Toying with ideas and projects - does anyone happen to know the thickness of the standard Mooney donut when uncompressed? If someone happens to be up on jacks now or to have one on the shelf, I'd appreciate knowing the measurement.

[N201MKTurbo]

It seems like a reasonable question, but not practal. The only way to make that measurement would be to remove the puck, which is a lot of work.

With the plane on jacks and the gear hanging down the pucks will fill the entire space available to them. If they don't then you should consider replacing them. If it is cold they may not expand to fill the space right away. The worst thing that can happen is the top plate can rotate, which doesn't seem to do any expensive damage.

The pucks are rarely a critical maintenance item, when they start to get stiff they should be replaced in the next few years unless the top plate has rotated then it is time to get some new ones.

[mike20papa]

I've got a couple of old donuts & new ones at my hangar.  Will get you both measurements this weekend.    Joe

[shorrick mk2]

I wasn't thinking of maintenance I was thinking of having actual sprung and unsprung dimensions and get together with a coil and shock specialist see if they can fit anything in that sort of dimension.

[N201MKTurbo]

Hard to imagine anything as cheap, light and reliable as the current rubber pucks. If you did come up with a modification that would work, you would probably have to sell it for about $20,000 per plane to recoup your NRE and certification costs. Who would pay that instead of $1000 for a set of pucks that last 20 years with no maintenance.

 

In 31 years of Mooney maintenance I've never had to pump up my struts, never had leaky seals that dribbled oil all over my tires.

[shorrick mk2]

1000 for pucks sure, but how much for avionics and fuel tank sealing shagged by undampened landings?

[N201MKTurbo]

Never been a problem.

[carusoam]

I agree the Mooney rubber donits are really cool for a 60’s design...

I'm looking forward to hearing from Shorrick's expert.

In the 60s a computer filled an industrial room replete with HVAC...

Today, a more powerful device with tremendous connectivity, replete with a touch screen, fits in my pocket...

I am wondering if an expert in suspension systems already has similar stellar improvements...

Some before and after pictures have been posted around here somewhere. The stack height of the old stiff pucks is visually shorter than the new ones by about a cm. (from old aged memory)

Ask the suspension expert if he can improve the energy absorption to include dropping a long body from the height of a 1/2 meter...

I plan on getting really old while flying this plane, I may need the help....

Best regards,

-a-

[chrisk]

1000 for pucks sure, but how much for avionics and fuel tank sealing shagged by undampened landings?

The landings generally aren't a problem for me.    Take offs on a wavy runway are interesting.   And those light reflecting "dots" on the taxi (just like on the highway) way make for quite a jolt.  --That said, I would not pay to swap anything out, unless it weighed a few pounds less. 

[shorrick mk2]

The Mooney has a great advantage in that it has a trailing link gear - yet it stopped short of awesomeness by going for the pucks (understandable in 1955).

Cirrus had pucks on the nose gear and switched to an oleo - surely they don't charge 20k for it not even as a spare.

With nowadays oleos one can adjust the damping depending on movement amplitude i.e. stiff when cornering and soft when taking a bump. Also damp and rebound rates can be set individually i.e. the oleo will compress faster than it'll extend back. All things that could prove useful - especially if landing on less than perfect grass say.

[M20F]

Take offs on a wavy runway are interesting.

I have that issue at my home base it is even more interesting when you get a good cross wind going.

[N201MKTurbo]

My point was that it cost a pile of money to get a STC and I don't think people are going to be rushing out to upgrade their landing gear.

 

So:

 

Pile of money / not a lot of people = $20,000.00

 

That's if the parts are free!

[Sabremech]

Shorrick mk2,

I think you have a neat idea that's worth some researching. I'd be interested in testing something on my Mooney if you come up with a new product. The cost of the STC will depend on the complexity of the product. Highly unlikely this will hit $20k.

Good luck and let me know if I can help.

David

[N601RX]

We have an instrumentated press at work. It would only take a couple of minutes to generate a graph of deflection vs force if someone has a new and old one I will be happy to provide graphs of both.

[Guest]

It would be quite a challenge to design and build an oleo to fit into the 4-5" which the shock discs occupy.

Clarence