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Thread: Mag Mystery

  1. #21
    Mike Switzer's Avatar
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    Quote Originally Posted by Tom Downey View Post
    Would you allow us to know the total bill, to have your mag IRANed ?
    I'd like to know also. The last one I had done (for a restoration project I was working on) was $100 plus parts.

  2. #22
    rosiejerryrosie's Avatar
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    I had two mags rebuilt by Savage a couple of years ago. Cost $1000.00
    Cheers,
    Jerry

    NC22375
    65LA out of 07N Pennsylvania

  3. #23

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    Quote Originally Posted by rosiejerryrosie View Post
    I had two mags rebuilt by Savage a couple of years ago. Cost $1000.00
    Al's bill to me was 850.00 each for 2. but they were as good as new and I sent him junk.

    but please don't send him a slick.

  4. #24

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    Quote Originally Posted by flyingriki View Post
    Thanks Mr. Busch. As you can imagine, I'll be taking your advice over that of taking my mag to John Deer. Unfortunately the moderators find that advice "valuable"....
    Sorry you have to compete with this kind of nonsense. But keep up the good work, please!

    Hal, for crying out loud, do you mean to invite a fabulous contributor like this and then encourage ridiculous input from wackos to contradict him?
    It's time to get your priorities in order. Or is this part of the 'New" EAA that wants to be everything to everybody and to heck with those that really know what they are talking about?
    It's interesting to find someone on a board that is centered around experimentals, call someone else a "wacko" and his input "ridiculous" for suggesting a valid alternative. Especially when the person's reason for disagreeing is ignorance.

    My job is overhauling accessories at a large, well-known shop. The same kind of shop Mr. Busch sends mags out to, with all the proper tools and test equipment. Heck, I've probably done more mags in the last couple of months than he has done in his life.

    Thing is, mags are stupidly simple. If you can read a book and follow instructions, you can repair one. There's too much mystery and magic surrounding such a simple device. Most of the expensive tools for the slicks are to aid in replacing bearings. For the Bendix all you need is a arbor press and a degree pointer. Takes at most four hours to inspect, clean and blast, remagnetize, replace required parts, time, test and paint an S-1200. That's a complete "factory" overhaul.

    If someone has worked on magnetos before, understands the basics of how they operate and how one adjustment affects another, I'd have no problem letting that person fix an aircraft mag. You do realize that there is no requirement for the person doing the repair or overhaul to have an A&P? Only the shop needs to be approved and they can hire whoever they want, including Farmer Joe's mechanic, and probably would given his experience.

    But it is aviation. It's your butt up there and you need to feel comfortable with whatever parts you install. If spending more money to get a fancy piece of paper gives you the warm fuzzies, that's fine. But just like there are people that would never set foot in an experimental, there are people that understand how something works and have a different comfort level. No need to discredit someone not at your same comfort level.


    For Mr. Busch:
    Just a note about the S-1200's. You may already know about this. I've been finding lately that over half the blocks coming in at 500 hours have loose bushings. About a quarter have electrode wear from contact with the gear and a nice film of brass shavings, sometimes contaminating the needle bearing. These are usually after an overhaul where the block wasn't changed, so I'd estimate 900-1100 hours on a new TCM block. Even ones that passed inspection at overhaul have sometimes failed with contact damage in as little as 100 hours. I'd strongly recommend pulling the harness and timing plug and doing a wobble test every 50 hours on any blocks over 500 hours. This is as serious as AD 82-13-01, just with the new brown blocks.

  5. #25
    Mike Busch's Avatar
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    Quote Originally Posted by turtle View Post
    Just a note about the S-1200's. You may already know about this. I've been finding lately that over half the blocks coming in at 500 hours have loose bushings. About a quarter have electrode wear from contact with the gear and a nice film of brass shavings, sometimes contaminating the needle bearing. These are usually after an overhaul where the block wasn't changed, so I'd estimate 900-1100 hours on a new TCM block. Even ones that passed inspection at overhaul have sometimes failed with contact damage in as little as 100 hours. I'd strongly recommend pulling the harness and timing plug and doing a wobble test every 50 hours on any blocks over 500 hours. This is as serious as AD 82-13-01, just with the new brown blocks.
    Can you explain the wobble test? Is it possible to determine if the block bushing is loose without pulling the mag and removing the block?
    Michael D. Busch A&P/IA CFIA/I/ME
    President, Savvy Aviator, Inc.
    President, Savvy Aircraft Maintenance Management, Inc.
    2008 National Aviation Maintenance Technician of the Year

  6. #26

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    Quote Originally Posted by Mike Busch View Post
    Can you explain the wobble test? Is it possible to determine if the block bushing is loose without pulling the mag and removing the block?
    There is no official wobble test. The looseness can usually be felt by wiggling the stem of the gear at the circlip while trying to move the gear up and down through the timing plug port (with something soft to not damage the gear). Should be very little play. Compare with a known good mag. When its loose its very loose, being able to lift the gear 1/8" is not uncommon.

    Ideally, pull the block and remove the gear, it only costs a circlip, no need to remove the mag if if there is room and you can keep the marks lined up.

    For the life of me I can't remember if you can see past the gear to the fish paper. It gets a nice coating of brass when the gear hits the electrodes. For some reason the timing plug doesn't. We're trying the Hartzell blocks but don't have enough data yet to determine if they are better. The good news is even with contact the gear usually survives. Personally I'd make sure my S-1200's had new blocks every 1000 hours, regardless of condition.

  7. #27
    I get it now. So next time I go fly Young Eagles I'll put a sign up that I had a tractor mechanic do the "not official wobble test" on my magnetos and since they are so simple they must be fine. Hop in kids...... yeah that'll go over well.

    I guess if ignorance is bliss I'll just stay stupid, experimental or not. Thanks anyway....

  8. #28

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    Quote Originally Posted by flyingriki View Post
    I get it now. So next time I go fly Young Eagles I'll put a sign up that I had a tractor mechanic do the "not official wobble test" on my magnetos and since they are so simple they must be fine. Hop in kids...... yeah that'll go over well.
    Huh?

    The wobble test I mentioned had nothing to do with your mags. As far as it being "unofficial", owners of Bendix 1200's can go the official way - which is not bothering to look at all until overhaul or wait for a failure in the air, which it seems you'd prefer.

    I'm really not sure what your problem is. Many experimental builders overhaul their engine and accessories. Most with no prior experience. Which is better, someone that has never worked on a mag or someone who has many years of experience building the same thing for a different application? I guess mechanics that worked on 290G generators wouldn't have a clue on how to change a cylinder on a 290 in an airplane.

    Or is it that you think amateur built shouldn't be allowed and everybody should buy and maintain certified?

    Quote Originally Posted by flyingriki View Post
    I guess if ignorance is bliss I'll just stay stupid
    Now I'm starting to understand where you're coming from. Next time you fly Young Eagles, put up a sign with that on it.

  9. #29

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    If the mag is On a EXP home Built, who cares who fixed it ?

  10. #30
    Quote Originally Posted by Tom Downey View Post
    If the mag is On a EXP home Built, who cares who fixed it ?
    Gee. maybe the guy flying it!

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