Another excellent and highly educational video, thanks Mike!

Thank you - I could never have learned that much from a book and you held my attention for the entire time.

@apfelsnutz

6 жыл бұрын

Peter, you should buy his new book and see,,,, Amazon +- $28 with free Prime shipping.

Thanks for the great discussion on this matter.

Need to remake these videos in HD would be so much better. But great info.

Heating and cooling for interference fits is a waste. Heating charges one part with energy and it is not necessary to complete an interference fit. On the GE90 high pressure turbine, both stages are joined with no bolts and nuts, but by interference and bayonets. We used to heat one part and cool the other until we realized all we were doing was reducing the worktime of the join. After that, we cooled one part with liquid nitrogen and left the other stage at ambient room temp. We found we had a much longer worktime, ensuring a proper connection without having to rush the work.

Thanks great info!!!!

I learned more today...fantastic presentation! A must see!

Have you ever come across a thermal fatigue failure of an intake valve - i.e. a crescent shaped piece breaking off the edge of the intake valve -much like the exhaust valve failures? Had personal experience of this happening on intake valves in 2 separate cylinders of an O-235- L2C - over 10 years ago.

MAN, if that slide at 16:40 doesn't tell you that bringing a cold engine up to temperature GENTLY and slowly is a good idea, NOTHING WILL. The extension of those rings out of that piston when everything is cold borders on SCARY. Would be EVEN worse in VERY cold temperatures, like 30 below, where there is ANOTHER 100 F added. As an engineer that slide gives me the willies. The discussing of shedding exhaust valve heat is interesting, as well. Good talk. This particular presenters almost always are.

Thank you

podrías subirlo en mejor calidad. saludos

2 minutes, I thought you were going to say 2 seconds. What the pilot do get out his checklist?

Stuck valve= Marvel Misery Oil in the oil. 1/2 Qt. every oil change. Great Job mike !!!!

@REDMAN298

4 жыл бұрын

add Marvel Mystery to the fuel where it does the most good.

@apfelsnutz

4 жыл бұрын

I do that also...

@devilsoffspring5519

2 жыл бұрын

What's actually in that stuff? They sometimes sell it at hardware & auto parts stores for use in cars, or at least they used to. Not sure if I'd want "mystery"-anything in an aircraft engine, I wonder what they put in it besides just oil itself.

@apfelsnutz

2 жыл бұрын

@@devilsoffspring5519 I don't know, however, the contents are available on line. i don't know where but, IT WORKS LOL !

@devilsoffspring5519

2 жыл бұрын

@@apfelsnutz Good a reason as any I suppose, but the stuff is supposed to be added to the fuel, not the engine oil! The OP suggested adding it to the crankcase oil, that's a no-go!

19:20 is a leak down test, not a compression test

I had stuck exhaust valve, piston struck and punctured. I put aircraft down in a field. weeks before there seemed some roughness to the engine. Never ignore anything out of the ordinary.

@devilsoffspring5519

2 жыл бұрын

Exhaust valve not closing all the way, allowing leakage and rough running. Finally sticking open and being hit by the piston crown. Possibly caused by tetraethyl lead residue on the valve stem, finally jamming the valve?

@flybobbie1449

2 жыл бұрын

@@devilsoffspring5519 Well known carbon build up on the valve stem. Due to lack of cooling, due poor oil flow. They went back to solid valves as one update. At the time i checked incident reports, had been several that year in the UK. This was about 1991.

@devilsoffspring5519

2 жыл бұрын

@@flybobbie1449 Ok, the solid stem valves caused the problem by running too hot and cooking on the residue? Did they eventually replace them with sodium cooled valves and fix it?

@flybobbie1449

2 жыл бұрын

@@devilsoffspring5519 No i believe the reverse, they went solid.

@devilsoffspring5519

2 жыл бұрын

@@flybobbie1449 Really, that fixed it by running the valve stem near the head hotter, burning off any residue? Or wouldn't that make it worse?

On piston expansion, are the manufacturers using alloys that don't expand very much or is it because the operating temperature fluctuation is hugecompared to automotive use.

@devilsoffspring5519

2 жыл бұрын

Aircraft engines run near full load continuously, whereas car engines normally run at a small fraction of their maximum torque/load. So, aircraft engine pistons run hotter and are installed with more clearance when cold, giving audible piston slap ('clatter') on an engine started from cold.

This is a leak down test, not a compression test, they are very different test. And give different information. Also the tools used are different.

"Always keep CHT below 400°F"?!?! My 0-360 hits 400°F+ on nearly every Summer departure. It would be impossible to get any sort of climb rate if I throttled it back enough to keep the temps below 400°F. #3 regularly hits 430°F by the time I'm 3000ft AGL, no matter how rich the mixture. Even at 1300°F EGT cruise, my mean CHT is typically 380°F. This is on a JPI EDM 700. Now I"m scared...

@keepyourbilsteins

3 жыл бұрын

You get this looked at Jeff? What was the outcome?

@theMazdaManiac

3 жыл бұрын

I've discussed it with 1/2 dozen A&P's and IAs as well at a Lycoming representative and thruway its absolutely normal. Just keep it under 450°. LOL I departed KPRC a week or two ago at a DA of over 9000 and it struggled to get more than 250 ft/min of climb, so I leaned it to avoid becoming a dark spot on the surrounding hills. Temps got well into the 430° range on all cylinders with #3 touching 445°. It yeilded are 500 ft/climb though, so as soon as I could put the nose down, I did. Compression is still 70 or more on all cylinders with no obvious cracks...

@keepyourbilsteins

3 жыл бұрын

@@theMazdaManiac I'd be glad to bounce some ideas off you. I'm not an a&p. Have a few thousand hours in the prop shop with my late grandfather and a few dozen air-cooled builds under my belt

Isn't this really a 'leak' test versus a 'compression' test?

@alexmelia8873

5 жыл бұрын

Yes, the correct term is "leakdown test"

@MrJdsenior

5 жыл бұрын

And it has benefits, like if you lock the crank at certain positions you can check the leakage at various points in the stroke, among others, to locate some specific kinds of problems. They are really BOTH leakage tests, though, when you really get down to it, as the compression is determined by design parameters, both valves closed cylinder volume to final squish volume on the compression stroke minus the leakage during that same stroke. EVERY cylinder leaks to some extent, even when newly broken in. Old worn cylinders leak a lot worse, especially if the wall is scored, the rings are broken, or valves are leaking.

@TheReadBaron91

2 жыл бұрын

The kind we do in aviation are leak down tests

Those engine makers are a lot of hot heads.

The 80 PSI is NOT for historical reasons. The leakdown tester has a metered air hole to the cylinder side pressure gauge that demands a specific pressure to give the correct value. I expect if all flow paths gave equal flow differences for equal pressure drops it wouldn't matter, but they don't. I expect you could conceivably design the leakdown tester for a different pressure (not an aero engineer, electrical), but a specific pressure would still be required for each design. He makes an excellent point about testing when the cylinder geometry is junk by virtue of its coolness. Another MAJOR contributor to noise in compression test readings is the amount of oil on the cylinder wall at the time, dry to wet is MANY percent. In fact it is THE TEST for worn rings in a car engine, add oil if the compression is crap, and if it goes up to near good, it's rings, not valves that are your primary problem. And it's a GOOD test.

@MrJdsenior

3 жыл бұрын

@@filespec Precisely.

So a pilot shouldn't take the girlfriend and the kids up even after you work on his plane? Having said that. I wouldn't take passengers up, after I worked on my plane.

Thank you