New donuts ?

[RobertGary1]

I see the inspection procedure in section 5-15 of the Mooney Sevice manual. Replacement is determined based on gap measurement between the retaining collar and the plate. No need to look for ways to spend money if they are in spec and not cracked.

-Robert

[Andy95W]

I see the inspection procedure in section 5-15 of the Mooney Sevice manual. Replacement is determined based on gap measurement between the retaining collar and the plate. No need to look for ways to spend money if they are in spec and not cracked.

-Robert

And you don't have to replace your car tires until the tread reaches 1/16". When was the last time you let your tires go that far?

There are Mooneys whose old-style discs still pass the maintenance manual inspection. I doubt there are many people left who don't think those should be replaced.

As I said above, mine passed all required inspections but I replaced them when I took my gear apart this past spring. I'm glad I did. My airplane rides much smoother now.

[Mcstealth]

Ross- sounds like you don't need to change your shock discs. Mine were similar at 20 years old and passed all the tests. I just finished a major tune up of my landing gear including replacement of all bushings and shock discs. Made a BIG and noticeable difference. More than I had expected. New bushings tightened up all of my linkages and the discs made it more "squishy" while taxiing.

"Squishy"

Aviations next and new buzz word.

[ryoder]

Please change the title of this thread. I am going low carb for a vacation and the title kills me.

[RobertGary1]

And you don't have to replace your car tires until the tread reaches 1/16". When was the last time you let your tires go that far?

There are Mooneys whose old-style discs still pass the maintenance manual inspection. I doubt there are many people left who don't think those should be replaced.

As I said above, mine passed all required inspections but I replaced them when I took my gear apart this past spring. I'm glad I did. My airplane rides much smoother now.

I have a couple cars near min on tires. There is a reason it's call min not "beyond min". No problem.

What specifically is your concern with donuts that pass a visual inspection and measurement inspection?

-Robert

[RLCarter]

My 65' E passed the test in the manual as well, took the gear apart for further inspection, found rubber splitting on the center hole and several of the donuts had separated from metal disks molded to them, not to mention they were harder than Chinese arithmetic compared to the new ones.

[RobertGary1]

My 65' E passed the test in the manual as well, took the gear apart for further inspection, found rubber splitting on the center hole and several of the donuts had separated from metal disks molded to them, not to mention they were harder than Chinese arithmetic compared to the new ones.

 

What was the date stamped on the old donuts?

 

-Robert

[Andy95W]

What specifically is your concern with donuts that pass a visual inspection and measurement inspection?

-Robert

Nothing specific. There are some reports that new shock discs are better for fuel tank sealant integrity, but I've never seen anything definitive.

I changed mine because I had the landing gear apart and couldn't see the sense in putting it back together again with discs that were "harder than Chinese arithmetic".

Mine were 20 years old. With my fairly light-weight C model, they probably would have continued to pass all tests and inspections for another 20 years.

You should of course do whatever you want. But it would seem with all of the posts on this thread that talk about a noticeable improvement, I don't think I would call it an unnecessary expenditure.

[RobertGary1]

That makes sense. I would put it in the same category as replacing engine mounts. If they look good and measure good (and aren't 30 years old) I wouldn't bother changing them myself. New ones are smoother but not worth it for most. However, if you already have the engine out it would almost be silly to not change them at that time unless they are already pretty new.

 

-Robert

[RobertGary1]

There is a lot of original rubber in my airplane.

More important than donuts are fuel and oil lines. In pre J's these also run through the firewall directly to instruments. An old line can break and drip fuel or oil on your legs. If you have original rubber I'd focus on those first.

-Robert

[RLCarter]

Robert,

Not sure on the stamped date, logs showed 28+ yrs. and you are correct, the fuel & oil hoses behind the firewall are often overlooked. All my hoses (both sides of firewall) are 2 weeks old  

[RobertGary1]

 

Robert,

 

Not sure on the stamped date, logs showed 28+ yrs. and you are correct, the fuel & oil hoses behind the firewall are often overlooked. All my hoses (both sides of firewall) are 2 weeks old  

 

 

Who did you have make the hoses? We used to have a place in Sacramento that would do it while you wait. Now I have to send off for them from a place in SoCal.

 

-Robert

[Mooneymite]

Everytime I look at a Mooney donuts, I wonder about "owner produced parts".

 

Rubber donuts are not peculiar to Mooneys, though the size may be unique.  I wonder if anyone has looked into modifying a John Deere donut, or cutting a donut out of a block of the appropriate material.

 

Anyone ever look into this?

 

I imagine that a substitute could be made for a lot less than $100 each.  If a Mooneyspace member of the engineering persuasion (Hank?) could figure out what to use as a raw material, he might be able to find a reasonable profit selling it with instructions on how to fabricate these disks.

[Hank]

There's the question of the correct hardness (what Shore number), as well as size (OD, ID, thickness). Then there's the little thin piece of bronze stuck to one side that's a little larger diameter than the puck. Bronze ain't easy or cheap to make.

[Guest]

Hank,

I think its anodized aluminum on each side of the rubber.

Clarence

[RLCarter]

Who did you have make the hoses? We used to have a place in Sacramento that would do it while you wait. Now I have to send off for them from a place in SoCal.

 

-Robert

Made them myself, took about 20~30 minutes per hose (after removal)

[RobertGary1]

Made them myself, took about 20~30 minutes per hose (after removal)

I thought making hoses was a whole special FAA certification. In all of California there is only one place left from what I can tell that can still do it.

-Robert

[Mooneymite]

There's the question of the correct hardness (what Shore number), as well as size (OD, ID, thickness). Then there's the little thin piece of bronze stuck to one side that's a little larger diameter than the puck. Bronze ain't easy or cheap to make.

So is an owner fabricated donut beyond feasability?

Is that $1100 for a set of donuts cheaper than what an owner would invest in material/time/tools?

[RLCarter]

I thought making hoses was a whole special FAA certification. In all of California there is only one place left from what I can tell that can still do it.

-Robert

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 progress 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

[Guest]

So is an owner fabricated donut beyond feasability?

Is that $1100 for a set of donuts cheaper than what an owner would invest in material/time/tools?

Assuming they last an average of 10 years on a lighter Mooney, that's 100$ per year. Hardly worth the effort in my opinion.

Clarence

[RLCarter]

So is an owner fabricated donut beyond feasability?

Is that $1100 for a set of donuts cheaper than what an owner would invest in material/time/tools?

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

[carusoam]

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-

[ryoder]

"Time to make the donuts"

[DonMuncy]

I would bet that if someone could find a manufacturer of rubber products, they could reverse engineer one and turn out a couple of hundred for (WAG) $10 each. The big problem is that in order to sell them, someone would have to get the FAA's blessing, which would almost certainly bring a profitable price up to or near the current price.

I don't claim to have much knowledge about owner produced parts, but my general understanding is that the maker of them would have to work from the formula/specifications furnished by each individual plane owner. Ie. he couldn't produce a hundred of them to sell. And if you, as the owner asked him to make you a hundred of them, you would become a seller, and likely in big trouble.

This is just the system we have in place, and I don't see us getting out of it anytime soon.

[Yetti]

mine are sti11 pretty springy.   I get to count 2 1andings tonight.  No carrier 1andings in a Mooney