New donuts ?

[Hank]

I read somewhere that the original ones that Al Mooney used on the first Mooney where motor mounts from a Mac truck. if you figure they last 10 years it isn't that bad considering leaky struts that may or may not be repairable. but I agree the price is high for what they are

What leaky struts? On Mack trucks? Mooneys ain't got no struts, leaky or otherwise. What we have is a thick stack of donuts on each wheel, nothing else. Oh, yeah, there's a metal shaft goes through the holes, but that's hardly a strut . . .

[RLCarter]

What leaky struts? On Mack trucks? Mooneys ain't got no struts, leaky or otherwise. What we have is a thick stack of donuts on each wheel, nothing else. Oh, yeah, there's a metal shaft goes through the holes, but that's hardly a strut . . .

Hank, chill out and read the post again......Al Mooney used the engine mounts from a Mack truck for the disk in the Mite(from what I have read) the reference to struts is on other brands of aircraft and that you would spend the same amount in maintenance on those over the same time period.

[Mooneymite]

Feasibility of making your own donut would require...

Knowledge of cross linking polymerization chemistry of the proper rubber.

Building a mold for the donut.

Knowledge of the proper recipe. Including temperatures and pressures. The compounding mixer would be the most difficult to source. Look up Banbury mixer for how the rubber industry does this...

This would be a similar task to making your own home made tires.

Finding a rubber company that makes donuts already...then see what they have on the shelf. Unfortunately these won't be FAA approved....

$100 per donut starts looking good when you see what it cost to have somebody meet your specification for a handful of them.

Best regards,

-a-

What I envisioned was a good bit simpler: locate a rubber pad/block of rubber with the approximate hardness/spongyness and use a hole saw of the correct diameter to cut out each donut. Finish each donut off on a buffing wheel, and face with the metal dividers from the old donuts.

Sounded like about $15 in materials and three hours which is probably why I'd never make it as an engineer.

:-)

[MyNameIsNobody]

$100/small rubber disc is a rip-off and a symptom of what is wrong with GA and FAA. A big joke that is not funny.

For those that want readily available boots for Brittain components this is the problem. Hoops that must be jumped through for certification of compounds in rubber and lack of old...not as good 60's compounds that must be used or a tested and certified compound for your rubber....

The cert process is flawed and FAA will not fix it. They won't cede power/control for a BS physical....

[Yetti]

If you are going to do it.  Make them out of urethane.  They wou1d 1ast 1onger.   There is some pretty good info on getting the right hardness.  A fiberg1ass mo1d and you are in business.   Write a spec sheet to fi11 out by owners.Then is an owner suppi1ed part.

[DonMuncy]

Yetti,

Interesting thought. Would you envision;

1) Buying a new donut and somehow testing it for its elasticity properties.

2) Designing a compound formula from existing information

3) Making a mold from the existing donut

4) Turning out a set of urethane donuts

5) Getting and A&P to install them sign them off as being conforming to the originals as owner produced

6) Testing them by doing some landings

7) Publish (or sell) the urethane formula for others to duplicate

The only problems I see are:

1) Assuring that they are strong enough and the right elasticity

2) Getting an A&P to go along

3) Finding someone to test them on his plane.

After that it's all easy.

I'm interested to see if someone will take this on.

I would take on the procuring the donut and making the mold, but I don't have the resources to test or formulate the compound, nor do I have the guts to test them on my plane.

[Mooneymite]

The cert process is flawed and FAA will not fix it. They won't cede power/control for a BS physical....

 

Actually, we have two ways around the high cost of replacement parts: 

 

1.  Owner supplied parts (be careful, y'all!) 

2.  Get rid of your certificated airplane and go experimental.

 

I'm in both the certificated world and the experimental word.  I can tell you for certain, experimental is far less expensive and the technology is overtaking the certified world so fast, I think "certificated" will soon be relegated to the Part 121/135 world.

[Mooneymite]

..... nor do I have the guts to test them on my plane.

 

I think the prudent way to test an owner produced donut would be to install just one in the stack with the old ones and fly around with it for a year.  You'd know pretty soon if it was going to crack/split/fail without catastophic consequences.

 

At least, I don't "think" a failure would be catastrophic.....

[Andy95W]

I think the prudent way to test an owner produced donut would be to install just one in the stack with the old ones and fly around with it for a year.  You'd know pretty soon if it was going to crack/split/fail without catastophic consequences.

 

At least, I don't "think" a failure would be catastrophic.....

Sounds like a plan. You first!

[Shadrach]

If you are going to do it. Make them out of urethane. They wou1d 1ast 1onger. There is some pretty good info on getting the right hardness. A fiberg1ass mo1d and you are in business. Write a spec sheet to fi11 out by owners.Then is an owner suppi1ed part.

My experience with urethane in automotive applications is that it will infact out last rubber, but then so will steel, and the ride will be about the same! I put a urethane engine mount in my Porsche and removed it almost immediately. Perhaps urethane can be engineered to absorb noise, vibration and harshness, but in every application I've experienced, those qualities suffer for the sake of precision and rigidity.

[Yetti]

And yet many suspension upgrades are done with urethane replacement parts for the degraded rubber components. Wou1d be your next step https://en.wikipedia.org/wiki/Shore_durometer    

 

I cou1d a1so see where an oi1 over air shock cou1d be a much better option with a better ride

[Yetti]

For that matter why are we recreating a not so good whee1...  or puck.   Why not get the comfort of air ride.  Firestone makes these in a11 sorts of sized and if they are good enough for an over the road bus.   http://www.summitracing.com/parts/fip-7881?seid=srese1&gclid=CjwKEAjw0NytBRD-1d3QsdHNpR0SJACGXqgREy5iFwXFcQV7sB_TOFAjNFoNfnVm9K27PAZS0o99HhoC0Vvw_wcB

[carusoam]

Firestone made the donuts in the mid 60s...(didn't they?)

Ye11i, you could be onto something...

-a-

[RobertGary1]

I found a place on the web that offers a set for $1100.00 (7 hoses), so asked an A&P/IA buddy where he gets them from and he said just to make them myself. There is a total of (4) IA's that stop by my hangar to check progreshttp://sacramento.craigslist.org/cto/5097736223.htmls and keep me in line. you would one of them would have said something seeing how they all have offered to sign off on my work

Im replacing mine as I feel like spending the time. But the line from the servo to th firewall cost me around $120. That's firesleaved. I'd be surprised if the whole works cost me $1100.

I regret not changing the oil cooler lines when I did the engine. I sent them along with the oil cooler to be flushed of debris and inspected but if I were to do it again I'd have just replaced them.

-Robert

[Yetti]

most if not a11 the hoses have rep1aceab1e ends.  There is a set of mandre1s that make the work go easier.   I bought the who1e set in the upgraded brown si1icone version to get the some space back. $1100.00.   It is easier to rep1ace them a11 with the mags off and the exhaust dropped.

[Yetti]

so urethane with a 80 - 90 hardness wou1d be a p1ace to start  http://www.mooneymite.com/mitetalk_forum/showthread.php?t=52

 

http://www.knr-inc.com/knr_inc_joomla/shoptalk-articles/25-shoptalk/23-200904-does-your-mooney-need-a-chiropractor

[Shadrach]

A lot of the hose on my 20F were not fire sleeved at the factory.  I replaced and sleeved all of them when I hung the engine in 2010.  If I had it to do again, I'd likely go with silicone, though I swear the added insulation makes hot starts easier.

[cnoe]

Firestone made the donuts in the mid 60s...(didn't they?)

Ye11i, you could be onto something...

-a-

 

There are a great number of skateboard companies marketing their own custom (urethane) skateboard wheels in durometers ranging from the mid 70s ("A" range) into the low 100s. They are precision molded and are virtually INDESTRUCTIBLE.

 

Properly spec'd out I'd have absolutely no problem whatsoever using them on my plane. They would likely outlast and outperform all the rubber versions.

 

If a bunch of 70s burn-outs can put something like this together, surely a bunch of PILOTS could figure it out.  If I didn't abhor bureaucratic interaction I'd look at getting an STC for these myself.

[cnoe]

There are a great number of skateboard companies marketing their own custom (urethane) skateboard wheels in durometers ranging from the mid 70s ("A" range) into the low 100s. They are precision molded and are virtually INDESTRUCTIBLE.

 

Properly spec'd out I'd have absolutely no problem whatsoever using them on my plane. They would likely outlast and outperform all the rubber versions.

 

If a bunch of 70s burn-outs can put something like this together, surely a bunch of PILOTS could figure it out.  If I didn't abhor bureaucratic interaction I'd look at getting an STC for these myself.

 

And they typically retail for $30-$35 for 4 wheels. At that price you could re-puck a Mooney for $100 + labor.

[RLCarter]

Get with Mooney tell them you want to manufacture shock disc, they might even hold the cert. paper work and you could built to their specs.....30~40 bucks a piece would be reasonable to me

[Hank]

Had a chat with a rubber product manufacturer rep today. Wondered about the material and hardness. Urethane in the mid-80s, huh?

Already replaced my disks two years ago. Anybody have dimensions on new disks? Outside diameter, thickness, hole size? I was thinking about owner manufactured parts . . .

[Mooneymite]

Had a chat with a rubber product manufacturer rep today. Wondered about the material and hardness. Urethane in the mid-80s, huh?

Already replaced my disks two years ago. Anybody have dimensions on new disks? Outside diameter, thickness, hole size? I was thinking about owner manufactured parts . . .

Hank, I'm liking the way you're thinking!

[Guest]

Lord of Erie PA. charges quite highly for their rubber products, mounts for my Comanche engine are well north of 300.00. At one point I could not even find mounts for a Bravo.

The problem for knock off replacements is the very limited market size. Rapco aircraft tried making replacement gear shock discs and eventually gave up.

Clarence

[Hank]

Eleven could be machined. Trying to make a lot requires building a mold, which is pricey. Eleven at a time shouldn't be difficult or expensive.

How thick is the bronze piece? Same diameter as the puck, I guess. Bet superglue would hold them together very well.

[cnoe]

What if... An individual contracted the manufacturing of 110 urethane toy wagon wheels that just so happened to be the same dimensions and durometer as a Mooney shock disk? It seems like the metal (aluminum?) plates could be reused; why do they need to be bonded to the rubber/urethane? I've no interest in selling aircraft parts but selling wagon wheels might not be a bad small-time venture. Probably not enough CBs out there to make it worth the trouble.

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