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Thread: Mike Busch Maintenance Forums

  1. #21

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    That is why I have a timer turn on the preheater 3 hours before I go fly on cold days, and I use oil that contains the Lyco camshaft additive.

    The roller cams in Lycos also address the issue. But you have to have a recently overhauled engine to get those.

    The best option is to fly a lot so that the cam has residual oil on it at the next start.

    Camshafts live a hard life, but most seem to make it to their first TBO with only a little consideration on the part of the operator. But of course some pilots don't make the briefing....

    Best of luck,

    Wes
    N78PS

  2. #22

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    Here is a picture of a Lycoming roller cam with 300 hours and 1 1/2 years old. Engine tear down because of a prop strike when they discovered this. The Lycoming engineers were NOT happy when they saw this! Corrosion kills more engines, by far, than anything else. And the Lycoming additive, LW-16702, does nothing for corrosion.

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    Ed

    Edward Kollin
    Technical Director
    Aircraft Specialties Lubricants

  3. #23

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    That must have had some awful oil in it. Note there is even corrosion in the camshaft bearing journal

  4. #24

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    i'd like to know more details about this engine, and see some photos of the rest of the parts. If the damage was caused by corrosion, then there would likely be similar damage on other parts.I noitce there is no damage in the photo on the side of the cam or on the tan colored part. Why is it only on the polished part, and not on the nose or top of the cam lobe?

    I have seen upper end wear on cam followers and cam faces in Merlins. I have never seen any evidence of corrosion in one, just friction wear, which seems to be mostly from inadequate lube on first start up. And note most Merlins are not flown much during the winter.

    Maybe Lycomings are different and very subject to corrosion.
    Last edited by Bill Greenwood; 08-14-2012 at 10:42 AM.

  5. #25

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    Is that corrosion? Looks more like a failure due to manufacturing. Heat treating done wrong? I agree that there has to be more to the story and that is likely why the Lyco folks are concerned.

    Best of luck,

    Wes
    N78PS

  6. #26

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    Aeroshell W100 changed every 50 hours.

    Ed

    Edward Kollin
    Technical Director
    Aircraft Specialties Lubrcants
    Last edited by 1TJ; 08-14-2012 at 01:29 PM.

  7. #27

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    Quote Originally Posted by Bill Greenwood View Post
    i'd like to know more details about this engine, and see some photos of the rest of the parts. If the damage was caused by corrosion, then there would likely be similar damage on other parts.I notice there is no damage in the photo on the side of the cam or on the tan colored part. Why is it only on the polished part, and not on the nose or top of the cam lobe?

    I have seen upper end wear on cam followers and cam faces in Merlins. I have never seen any evidence of corrosion in one, just friction wear, which seems to be mostly from inadequate lube on first start up. And note most Merlins are not flown much during the winter.

    Maybe Lycomings are different and very subject to corrosion.
    The plane was flown a lot (300hours/1.5 years) but sat for a few weeks at a time. The damage is due to spalling initiated by corrosion. There were rust spots on crank and gears. No rust on the copper covered or unpolished parts of the cam. This type of pattern is quite common because the carburization process, used to harden the cam, makes it quite susceptible to pitting along grain boundaries, which in turn causes the stresses that lead to spalling failure. Chilled cast iron, used in lifters, is also susceptible to this problem.

    Ed

    Edward Kollin
    Techical Director
    Aircraft Specialties Lubricants
    Last edited by 1TJ; 08-14-2012 at 01:30 PM.

  8. #28

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    So a few years ago when I had the choice of what cam to buy for my overhaul, I chose a Superior cam which I understand is a "billet" cam rather than just a case hardened assembly. Does that type of cam resist the situation pictured more than the stock Lyco unit?

    Thanks,

    Wes

  9. #29

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    I'm still bothered by the corrosion on the camshaft bearing journals that should have been protected from corrosion on shutdown by oil retained in the bearings. Something is fishy here.

  10. #30

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    Maybe the Lycoming cams are made cheaply, that is of an inferior metal and/or an inferior hardening process. Obviously price is a big factor in engine cost at the trainer level.

    I know I have never that seen that type of wear, if it is corrosion, in the cam area of a Merlin. Now obviously Rolls Royce and even Packard were trying to produce the best engines, not the cheapest, so maybe their quality is that much superior.

    I have seen friction wear and/or lack of lubrication make rough spots on cams and followers. A follower is sort of like a rocker arm, Merlins don't use lifters as they have overhead cams.

    I heard a story years ago that some American car cam makers tried to grind some new Merlin cams, but when they took a short cut in the heat treating and hardening process, the resulting cam wore out too fast.

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