Continental metallurgy specs?

[Robert Lees]

I post on the off-chance...would anyone have details of the material (alloy) spec used for the A65 piston and piston pin end cap?

Rob

[45 Tcraft]

Re: Continental metallurgy specs?

Robert,

Not handy - but can determine it for you if you have sample pieces to submit. Might take a few weeks to fit into the schedule and all - and you will not get the parts back. Why are you asking for data like this? Just curious.

Randy

[Robert Lees]

Re: Continental metallurgy specs?

Randy:

I have the items ready to send off to an inspection/analysis lab here in the UK (I brought them back from Oregon!)

The reason is, that I think the people who did an engine overhaul forgot to put a piston pin plug in.

I need a completely independent inspection, by a Certified Lab, to Internationally accepted Standards, of the content of the oil screen debris of my failed engine.

Background: I had an engine failure in my Taylorcraft in Oregon, fortunately with no consequential injury or damage, but the engine required rebuilding later.

The oil filter was full of metallic debris, and it is my suspicion that this debris is from a broken portion of the piston (aluminium alloy). The steel piston pin that connects the piston to the conrod floats in the piston, and has aluminium end cap at each end that lightly rub against the cylinder walls (by design). It is my suspicion that the original engine overhauler neglected to fit one of these plugs, so that the steel piston pin was able to rub directly against the steel walls of the cylinder, leading to failure of the piston.

I must assume that the piston pin end cap and the piston, although both appearing to be aluminium, are of different alloys. Unfortunately, I do not know what those alloys are, but a comparison may provide the information I need.

So I would like supporting proof that the debris contains no significant proportion of the end cap material, so supporting my theory that the end cap was never installed.

Photos attached, thanks for your input!
Rob

[3Dreaming]

Re: Continental metallurgy specs?

Rob, I suggest you go ahead and do your testing, because it will make you feel better.
However I do know that on occasion that the little aluminum plug in the end of the piston pin will decide to turn itself into little metal shavings. My dad's airplane had this happen one time. We were doing an oil change getting ready for Sun'n Fun, to find the screen full of metal and collapsed. When we quizzed an old time A&E he said, it is not common, but does happen from time to time". When we tore the engine down there was just a small ball of aluminum floating in the pin interior. We found no damage except the plug and collapsed screen. On advice from the old A&E we flushed the engine out and re-installed the Cylinder with a used pin plug. The airplane flew like that for quite some time afterwards with no ill effect.

[barnstmr]

Re: Continental metallurgy specs?

Here is one reliable metallurgical lab in Mobile Alabama. It was founded by Bill Faircloth who was a metallurgist at Teledyne Continental Motors for many years.... but probably not all the way back to when the A65 was first designed. His son is now the General Manager. I am not sure if Bill still hangs around the lab, but he was still there as recent as about 3 years ago.


Another fine lab we use here in Texas is here.

[Scott]

Re: Continental metallurgy specs?

looking at the photo of the piston, it looks like something was fretting around (for quite some time) between the piston pin boss and the cylinder wall. Question I have is what was there if it wasn't the plug?

To me the damage to the piston looks consistent with a failure of the plug which subsequently orbited around and around, while still keeping the pin from contacting the cylinder wall. Once the remains of the plug was fretted away I expect the pin contacted the cylinder?

[PA1195]

Re: Continental metallurgy specs?

In picture #4 note the left edge of the pinned steel ring assembly below the wrist pin hole...gone disappeared and hard steel versus the aluminum pin plug. Where did that particle go? Also see the adjacent scoring to the right on the piston's lands. Is that a multi-piece oil control ring? (Edit: appears to be a mono slotted oil control ring).

Wouldn't take much steel to destroy aluminum, and how could the steel ring be abraded by the softer aluminum, perhaps by the adjacent anti-rotation pin after wrist pin plug failure? There is scoring (carbon?) on the other pics of the piston skirt. The faces of the rings indicate adequate break-in cylinder pressures and wear due to ? that penetrated to the broken ring which has a >50% wear surface.

Engine history and time in service? Air cleaner functional? Were the valve seats worn abnormally from intake air abrasion? Was the cylinder cross hatching normal or still rough?

Gary

[Guest]

Re: Continental metallurgy specs?

Randy:

I have the items ready to send off to an inspection/analysis lab here in the UK (I brought them back from Oregon!)

The reason is, that I think the people who did an engine overhaul forgot to put a piston pin plug in.

I need a completely independent inspection, by a Certified Lab, to Internationally accepted Standards, of the content of the oil screen debris of my failed engine.

Background: I had an engine failure in my Taylorcraft in Oregon, fortunately with no consequential injury or damage, but the engine required rebuilding later.

The oil filter was full of metallic debris, and it is my suspicion that this debris is from a broken portion of the piston (aluminium alloy). The steel piston pin that connects the piston to the conrod floats in the piston, and has aluminium end cap at each end that lightly rub against the cylinder walls (by design). It is my suspicion that the original engine overhauler neglected to fit one of these plugs, so that the steel piston pin was able to rub directly against the steel walls of the cylinder, leading to failure of the piston.

I must assume that the piston pin end cap and the piston, although both appearing to be aluminium, are of different alloys. Unfortunately, I do not know what those alloys are, but a comparison may provide the information I need.

So I would like supporting proof that the debris contains no significant proportion of the end cap material, so supporting my theory that the end cap was never installed.

Photos attached, thanks for your input!
Rob

Hi Rob,

What did the cylinder wall look like?

I had a tractor that was assembled without the wrist pin caps.

One result was that a very nice deep groove was "machined" into the cylinder walls on both side of the cylinder because there were no end caps.

Did your's have a groove too?

Dave

[Robert Lees]

Re: Continental metallurgy specs?

It did (well two grooves actually, caused by the wrist pin end contacting the cylinder wall).

[Guest]

Re: Continental metallurgy specs?

For what its worth my groove was a wide as the pin and was about .062" deep.

It had many hours on the engine so lots of time to wear in.

How many hours were on this cylinder?

Dave

[Mark Bowden]

Re: Continental metallurgy specs?

Hi Rob,
I would suggest that I don't think a metallurgical analysis is going to tell you anything. You have Aluminum from 2-3 sources: piston, plug and valve train. No valve train damage there so you are left with piston and plug. If they could do a spectral analysis and there was Si content of less than 0.6% then that would say no piston damage, it's all plug.

Since you have physical evidence both piston damage and a missing plug they can't tell the difference.

Did you collect all the chips?

Before your send anything away....

I would suggest you weigh your old piston and a new one, give you the missing mass. Weigh a new plug.
This is the total possible mass of chips. If your mass of chips exceeds the missing mass of the piston, they put a plug in.

If it is equal or less than the piston missing mass they missed the plug.
Now you're left with, did they reuse an old plug and it worked out? Different issue.

But plug failures happen; since the plug is T4, not as hard, it can both be pressed in and not tear stuff up so bad when it goes bad.

Mark

[Mark Bowden]

Re: Continental metallurgy specs?

To your question,

Continental has an extremely helpful tech support phone line staffed by local USA employees (note, I'm not affiliated, they have been most helpful every time I've called). If you have your SN that starts them on the support path.

Tech support line: 888.826.5465

I had the discussion by giving my SN, which is not in the current online database and probably will not ever be, too old. They indicate the following with a discussion on interpreting a possible oil analysis:

Wrist Pin: AMS 6270. (or AMS6274 or grade 8620-aircraft quality)
Plug: 2017-T4. (or 2024-T4)
Piston: this has a material code of AE109-AXP. Federal Mogul PN of PG2258. This is not an alloy designation and he could not find one other than to see a reference to a process spec. This isn't surprising as the drawing is just going to define physical shape and "make per...spec" the spec will say "cast per xxx with alloy yyy".

Even had him look at O200 info. hoped for new info, it is the same callout. Because the pistons are cast in permanent molds it is likely a 300 series cast alloy, probably A356 or A357. These are current alloys for modern processing. The main difference between wrought chemistry and cast is the 6.5-7.5% Si (Silicon) content vs. the 0.5% Si content in 2017 (blind rivet alloy).

Can't hurt to have it tested though.

Mark

[Mark Bowden]

Re: Continental metallurgy specs?

Just for other reference attached is a Blackstone article that is interesting on a couple points. It shows what an analysis report shows, an A65 example that had valve lapping compound left in and best a DYI section on how to identify chips from the filter.

Mark

[Robert Lees]

Re: Continental metallurgy specs?

How many hours were on this cylinder?
Dave

Less than 100, but those hours over 2-3 years, so "out of warranty" according to the original engine rebuilder.

Did you collect all the chips?

No; it's impossible so to do. But thanks Mark for the other info; that might come in useful.

[PA1195]

Re: Continental metallurgy specs?

Is that the correct piston for an A65? The old parts/overhaul info I have indicates it's normally a 3-ring piston, but maybe an interchange with others like the 5-ring A75 is normal. Wrist pins and end plugs vary across the A>C line.

Edit: Search reveals this has already been discussed: http://vb.taylorcraft.org/showthread...engine+failure

Gary