Auto Engines Aren't Designed to Take Full Power for More Than a Few Minutes...

Discussion in 'Ford' started by rv6ejguy, Jun 28, 2014.

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  1. Jan 23, 2020 #181

    Wanttaja

    Wanttaja

    Wanttaja

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    Yep, and by NTSB 830, none of them WERE reportable:

    "Engine failure or damage limited to an engine if only one engine fails or is damaged, [is]... not considered "substantial damage" for the purpose of this part.

    I, too, have known several cases where the incident wasn't reported to the FAA. A couple of them DID meet the reporting criteria, but the owner was too feisty/fast and got the residue hidden before the feds got involved.

    My philosophy is that these are, probably, generally evenly spread among the aircraft and engines of the homebuilt world. True, a CH-701 is much more likely to be able to set down without damage after an engine failure than a Lancair IV, but I think the generalization will hold. And, of course, it affects homebuilts with production-type engines as well.

    Ron Wanttaja
     
  2. Jan 25, 2020 #182

    rv7charlie

    rv7charlie

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    *That* is a perfect example of what Ron referred to as "can't". Given the fact that hundreds, if not thousands, of non-Egg Subarus are flying without failure, the problem is obviously not the engine. It's an engine converter that *can't*. And "can't" is the proper term for the one-off builds that fail, as well. Certainly none of them (at least, not the non-Egg endeavors), intentionally did an improper engine installation. They tried, but didn't get it right.

    To the point that the core engine was failing: When the core engine design is statistically reliable, and there are three failures in the same airframe in short order, that's a good indicator of 'operator error'.

    Charlie
     
  3. Jan 25, 2020 #183

    rv7charlie

    rv7charlie

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    To the question about carb ice: One factor that could affect the numbers in a positive way for conversion engines is that many of them are water cooled. This *can* have a significant effect on icing susceptibility. There is even a significant difference in susceptibility between a Lyc, with the carb bolted to the oil pan, and a small Continental, with the carb isolated from hot oil because it's suspended on the intake 'spider'.

    Other modes I noticed was 'drive system' and 'cooling system'. Both stats make sense; 'drive systems' are virtually non-existent on piston a/c engines, and so, for all practical purposes, are cooling 'systems'. I'd wager that you'll never find an NTSB report that blames ragged baffling or a clogged oil cooler for cracked cylinders or seized bearings in a traditional a/c engine.
     
  4. Jan 25, 2020 #184

    TXFlyGuy

    TXFlyGuy

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    Serious question...how do you tactfully reply to those who tell you, "You want to cruise at 2800-3000 rpm, NOT 4100 rpm. This is for engine longevity and reliability."

    There are misconceptions concerning auto engines, how to run them, and reliability, in many (if not all) corners of the aviation world.
     
  5. Jan 25, 2020 #185

    cheapracer

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    Or the PSRU was doing horrible things to the engine
     
  6. Jan 25, 2020 #186

    BJC

    BJC

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    Serious answer: “For the performance at 4100 RPM, and the pleasure that I get will from it, I will accept whatever reduction in longevity or reliability it may cause.”

    Note that, in two different airplanes, I have operated a Lycoming at 3,200 to 3,350 RPM, including cross-country at 3,000 RPM. You might ask those advising you just how they are operating their engine in their airplane. My experience is that most of them are ready to give advice, but are not flying anything.


    BJC
     
    Last edited: Jan 25, 2020
  7. Jan 25, 2020 #187

    BJC

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    In the case I referenced, of two consecutive new Egg Subes that failed, even Mr. Egg admitted that he had a problem with the ECU (is that the correct term?) programming. No operator error involved, other than dealing with Mr. Egg.


    BJC
     
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  8. Jan 25, 2020 #188

    rv7charlie

    rv7charlie

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    That was the reason for the quotes. In the cases the we're discussing, 'operator' would be the guy operating *on* the engine; not simply running it. In other words, circumstances outside the engine's responsibility or control.
     
  9. Jan 25, 2020 #189

    wsimpso1

    wsimpso1

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    There are two prominent ways this can happen:

    Excess radial and/or angular misalignment between engine crank centerline and PSRU input shaft centerline. Since there are no perfectly machined pieces, the coupler must be executed to accommodate some alignment errors without undue loads on either end or fail the coupler. Design of the PSRU system must keep the misalignment small and well within the crank and bearing capabilities. Exceeding these can quickly trash the weakest of the crank, it's aft main bearing, the PSRU input shaft, and its bearings;

    Excess axial load imposed by the PSRU upon the crankshaft. While automotive crankshafts are designed and proven to stand some loads toward the accessory or front end of the engine, this load is clutch throw out and torque converter level. PSRU design must keep axial loads low. Longitudinal misalignment that puts large thrust loads into the crank will quickly fail the weakest of the engine thrust bearings and the PSRU input shaft bearings.

    System resonance due to poor torsional vibration management is UNLIKELY to cause issues due to the fact that the major engine pieces and system must have their fundamental frequencies safely above 2x max firing frequency. If their fundamental frequencies were within max 2x firing, the engine would quickly self-destruct... Since we know that modern engines stand going to their original redline rpm for long periods, we know that a system operating resonance from PSRU and prop will not excite damaging resonance in the major engine pieces.

    But those first two - yeah, poor alignment can wreck the engine. Eggenfelner systems used a shady alignment scheme including leaving to the builder to select washers to set longitudinal position of the PSRU to the engine. I gotta wonder about how good or bad this was for the engine and rubber isolator.

    Billski
     
    Last edited: Jan 25, 2020
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  10. Jan 25, 2020 #190

    BJC

    BJC

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    OK, thanks for that clarification. My friend who had the unfortunate experience with Mr. Egg was a career military pilot and instructor.


    BJC
     
  11. Jan 26, 2020 #191

    BBerson

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    If Mr. Egg sold a well proven direct drive auto engine conversion I might be slightly more interested.
     

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