Mag Mystery

[flyingriki]

Have a Slick mag on one side of an O-320. EI on the other side. Mag has about
600 hours since new and never removed for inspection yet. Plugs were new a
couple hundred hours ago. They were cleaned and gapped under 100 hours ago.
RPM drop at 1800 RPM runup is only about 60 RPM.

Problem: Lately the engine almost won't run on the mag alone at low RPM and if
low enough will just die. Of course it runs fine on the EI at low RPM. And
runs fine with the mag at high RPM.

Any suggestions? Pulling the mag is my next step but grounds me for as long as
it takes to have it sent off and repaired if necessary. Just wondering about
any other ideas. Wish I had the tools to do it myself. The Service Pro, Joe Logie, from
Champion went over a spare I have (no impulse for it) in about 15 minutes at
OSH.....

Timing has not been checked yet.

[nrpetersen]

Probably just bad points. You could get by with just replacing them if yr aircraft is non-certified.

[Tom Downey]

The Service Pro, Joe Logie, from
Champion went over a spare I have (no impulse for it) in about 15 minutes at
OSH.....


swap the impulse coupling from the one on the engine, 1 cotter key, 1 nut, and pull it.

[flyingriki]

swap the impulse coupling from the one on the engine, 1 cotter key, 1 nut, and pull it.

Different part number. Not worth the risk without confirmation that it is compatible. Champion say no and the engine is too valuable to play around in the acc. case...

Guess Mike was just waiting for me to watch the webinar...... will pull it and get it IRANed this week Mike!

[Tom Downey]

Different part number. Not worth the risk without confirmation that it is compatible. Champion say no and the engine is too valuable to play around in the acc. case...

Guess Mike was just waiting for me to watch the webinar...... will pull it and get it IRANed this week Mike!

Which part number? mag or impulse coupling?

[invntr]

Once the engine is running the impulse coupling is no longer effective, it's only for increasing the starting spark. Fly-weights inside the coupling are forced outward by centrifugal force thus taking the spring action of the coupling out of the system. Slicks are bad about the plastic cam for the points wearing down and decreasing the point opening gap. I've also seen the electrode inside the plastic distributor gear come loose several times and cause the timing to be all over the place. 600hrs is a long time for a Slick mag without inspection. I believe a 500 hrs O/H interval is recommended. Ck your timing with the new Rite-System Kit if you want it to be digitally accurate.

[SteveC]

Mike Busch is really adamant about getting mags IRAN d every 500 hrs. He also stresses sending them to a specialist rather than your friendly mechanic, as there are a number of special tools required not usually present in most A&P's shops.......

[flyingriki]

Mike Busch is really adamant about getting mags IRAN d every 500 hrs. He also stresses sending them to a specialist rather than your friendly mechanic, as there are a number of special tools required not usually present in most A&P's shops.......

As I said, he was probably waiting to see if I'd watch the webinar last night, and I did. So I know what he recommends. And he's right.
But I watched the Champion Customer Service chief who writes the manuals and the ADs open my spare up, clean and inspect it, set e-gap and install a new carbon brush in about 10 minutes. All while explaining what he was doing to the folks at his booth at Oshkosh. The "special" tools are so small you could hold them all with three fingers. So it doesn't take a genius to do the Slick IRAN. And i'ts kind of a drag to see $250-$300 base charges plus parts to IRAN them. But still not worth the couple hundred dollars for the tools, at least to me since I only have one and will probably replace it with another EI next time it comes due.

[Mike Busch]

I watched the Champion Customer Service chief who writes the manuals and the ADs open my spare up, clean and inspect it, set e-gap and install a new carbon brush in about 10 minutes. All while explaining what he was doing to the folks at his booth at Oshkosh. The "special" tools are so small you could hold them all with three fingers. So it doesn't take a genius to do the Slick IRAN. And i'ts kind of a drag to see $250-$300 base charges plus parts to IRAN them.
Yes, he does put on a very entertaining and informative show, and he does know his stuff.

However, a proper 500-hour IRAN involves a great deal more than what he demonstrates at AirVenture. It requires a coil and bearing inspection, a good deal of lubrication at various key points inside the mag, and then putting the mag on a test stand and stress-testing it to make sure it's putting out rated voltage. So it's not quite as quick as what the Champion/Slick guy demonstrates at the booth.

I have done many 500-hour IRANs on Bendix S-1200 mags, and I figure about 2 hours per mag to do the job right (including removal and reinstallation). There are four S-1200 mags on my Cessna twin, so doing the 500-hour IRAN on all four mags takes me a full 8-hour day. And that does not include testing (because I don't have a mag test bench). Having become older and wiser, I no longer do my own mags, I send them out to Aircraft Magneto Service up in Washington state, where Cliff Orcutt (who has been working on mags his entire adult life) does a far better job than I could do.

[Tom Downey]

I send them out to Aircraft Magneto Service up in Washington state, where Cliff Orcutt (who has been working on mags his entire adult life) does a far better job than I could do.

I've been working on mags all my life too, I'll open and take a look, but once the problem has been determined the mag goes away. I don't even do my own mags. I use Al at Savage mag in CA.
here is what you usually find: bad rotor, and a bad distributor block
13981399

[Tom Downey]

Mike, what would you think a IRAN on a Slick 4 cylinder mag will cost with a bad distributor block, bad rotor, bad condenser, bad points, with the labor to pull and replace?

[Mike Busch]

Mike, what would you think a IRAN on a Slick 4 cylinder mag will cost with a bad distributor block, bad rotor, bad condenser, bad points, with the labor to pull and replace?
Too much. ;)

The best mag specialty shops (like Aircraft Magneto Service or G&N Aircraft) will let you know right away if your mag is uneconomical to IRAN, and typically won't charge you anything other than freight to send the mag back to you so you can use it as a core in exchange for a rebuilt mag. This doesn't happen too often in my experience, but it does sometimes. A cracked case or a damaged rotor will typically render the mag uneconomical to repair.

Points, felts and carbon brushes are almost always replaced at IRAN. Ditto with cam on Slick (but not Bendix). Condenser is usually good for at least 5 years. Block sometimes has to be replaced, usually not. Same with the coil assembly, bearings, oil slinger. Slicks are less robust but also considerably cheaper. The Bendix S-1200s I use on my airplane are extremely robust but also quite pricey (and heavy).

We usually figure one hour per mag to remove, pack and ship, re-install and re-time. We typically ship 2-day each way, and figure 2-3 days turn time at the mag shop, so total elapsed time is about one week. If we pull the mags on the first day of an annual inspection (right after the hot compression test), the mags will get back in time not to hold things up.

[Tom Downey]

When you use new mags at overhaul they are designed to go to TBO with minor maintenance. when you do the mag IRAN at 500 hours, it does not require many internal parts, shipping and labor to get $600 involved, do the math it is more economical to run until you have a high mag drop then replace the slick with a new from AS&S at $800 +-

[skywagon]

Mag problems at low RPM's is usually caused by the point gap closing to a bare minimum. This is caused by the fiber points bar on the points that follow the distributor cam action. If the cam gets dry, dirty, etc. it will wear down the rubbing bar. The results are the slow closure of the points gap. At high RM's this closure is less noticible due to other forces working on the points and electrical spark generating system. However, that RPM range will soon have problems also.
Rule of thumb....check the mag points and gap at every 50 -100 hrs. After the points are checked or re-set, the timing should be checked too......

[Tom Downey]

Mag problems at low RPM's is usually caused by the point gap closing to a bare minimum. This is caused by the fiber points bar on the points that follow the distributor cam action. If the cam gets dry, dirty, etc. it will wear down the rubbing bar. The results are the slow closure of the points gap. At high RM's this closure is less noticible due to other forces working on the points and electrical spark generating system. However, that RPM range will soon have problems also.
Rule of thumb....check the mag points and gap at every 50 -100 hrs. After the points are checked or re-set, the timing should be checked too......
The wearing of the cam, or the cam follower will cause the points to open late, and close early, which changes the dwell of the coil induction and results in a weak spark. and of course a large mag drop.

[Mike Switzer]

For an experimental, I'd recommend taking the mag to your local tractor dealer, if they have a mechanic over 40 that knows what it is...

Not that I ever get mine serviced, I've got an Allis Chalmers WD45, a Case SC & a Farmall M, all with mags real similar (or the same) to the ones on our "modern" planes, I never have to do anything to them. I've been mowing with the M for over 10 years with no service to the mags other than a few drops of 3 in one oil in the cups every now & then...

[Drew]

Hi Mike,

I’ve got a Lycoming IO-360-A1B6 attached to a single engine airplane that is about to undergo an owner-assisted annual inspection. The engine has Slick magnetos that were installed new during engine overhaul 10 years and 490 hours ago (time for IRAN). I’ve looked at the Lycoming TCDS and see that I could switch to the TCM-1200 series provided they don’t interfere with my existing accessories or the cowling.

One question: Provided that my Slick magnetos return from IRAN only needing points, capacitor, brush and cam, would you consider it economical to continue running the slicks if we assume that I will keep this aircraft/engine for 20+ years?
Or do you feel strongly that the 1200 series Bendix is a much superior product in terms of reliability that you would recommend replacing the slicks sooner even if they are in a serviceable condition? It appears that the Bendix magnetos are about $1200 a piece.


Also, while perusing the TCDS (1E10), it reads that the timing on my engine should be 25 degrees BTC with an “optional” timing of 20 BTC….hmmm…
The engine data plate only indicates 20 degrees.
Which one takes precedence?
Provided that 25 degrees BTC gives adequate detonation margins, do you know what kind of horsepower increase one could expect at full power with the 5 degree advance in timing, provided that I could keep the CHT’s in check with adequate cooling?

Thanks!

-Drew

[Mike Switzer]

For an experimental, I'd recommend taking the mag to your local tractor dealer, if they have a mechanic over 40 that knows what it is...

OK, since Riki took exception to this & called me out on it in another thread - The same magnetos we use on our aircraft engines were originally used on tractors. For an experimental you don't have to spend X AMU's to get your mag rebuilt if you have a good local tractor mechanic that has rebuilt thousands of them in his lifetime. They use the exact same parts.

[flyingriki]

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?

[Tom Downey]

Would you allow us to know the total bill, to have your mag IRANed ?

[Mike Switzer]

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.

[rosiejerryrosie]

I had two mags rebuilt by Savage a couple of years ago. Cost $1000.00

[Tom Downey]

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.

[turtle]

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.

[Mike 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.
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?

[turtle]

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.

[flyingriki]

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....

[turtle]

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?


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.

[Tom Downey]

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

[flyingriki]

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

Gee. maybe the guy flying it!

[flyingriki]

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?


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.

Your snide remarks tell me you don't quite understand at all. If someone ELSE wants to repair his engine without a clue or supervision - it won't be me in the other seat. If someone wants to do anything foolish or follows the know-it-alls on some forum - good for them. If I knew what shop you worked in I'd be sure never to send anything there with this attitude of yours......

[Tom Downey]

Gee. maybe the guy flying it!

I'll bet they wouldn't care until it didn't work.

[turtle]

If I knew what shop you worked in I'd be sure never to send anything there with this attitude of yours......
See, now I'm not going to say where I work. Just send your mags to a well known and respected shop and pay through the nose like a good pilot. Maybe it will be me that works on them. You won't know.

I hope you are paying someone to install them if you are of the opinion that changing the contacts or brush is too complicated.

[flyingriki]

I'll bet they wouldn't care until it didn't work.

Spoken like a pilot everyone should listen to.......... Makes my point about forum junkies in a nutshell. On to the ignore list - these comments are ridiculous.

[flyingriki]

now I'm not going to say where I work.

I wouldn't either. I've gotten to know the guy that redid my mag and he's certainly not you. Mine works fine now, haven't paid an A&P for years. And you're onto the ignore list with Tom and Mike, who also can't find a post they don't feel required to comment on, no matter how useless (counterproductive, disadvantageous, dysfunctional (http://thesaurus.com/browse/dysfunctional), expendable (http://thesaurus.com/browse/expendable), feckless (http://thesaurus.com/browse/feckless), fruitless (http://thesaurus.com/browse/fruitless), futile (http://thesaurus.com/browse/futile), good-for-nothing, hopeless (http://thesaurus.com/browse/hopeless), idle (http://thesaurus.com/browse/idle), impracticable, impractical (http://thesaurus.com/browse/impractical), incompetent (http://thesaurus.com/browse/incompetent), ineffective (http://thesaurus.com/browse/ineffective), ineffectual (http://thesaurus.com/browse/ineffectual), inept (http://thesaurus.com/browse/inept), inoperative, inutile, meaningless (http://thesaurus.com/browse/meaningless)) the comment. Y'all really need to go out and actually fly something rather than theorize about the craziest ways to suggest others do it. See ya......

[turtle]

no matter how useless (counterproductive, disadvantageous, dysfunctional (http://thesaurus.com/browse/dysfunctional), expendable (http://thesaurus.com/browse/expendable), feckless (http://thesaurus.com/browse/feckless), fruitless (http://thesaurus.com/browse/fruitless), futile (http://thesaurus.com/browse/futile), good-for-nothing, hopeless (http://thesaurus.com/browse/hopeless), idle (http://thesaurus.com/browse/idle), impracticable, impractical (http://thesaurus.com/browse/impractical), incompetent (http://thesaurus.com/browse/incompetent), ineffective (http://thesaurus.com/browse/ineffective), ineffectual (http://thesaurus.com/browse/ineffectual), inept (http://thesaurus.com/browse/inept), inoperative, inutile, meaningless (http://thesaurus.com/browse/meaningless)) the comment. Y'all really need to go out and actually fly something rather than theorize about the craziest ways to suggest others do it. See ya......

Says the guy that has time to separately link each word to an online thesaurus. At least I'm trying to help people instead of telling everybody they are too stupid to work on airplanes.

[Mike Switzer]

Alright, I have been biting my tongue, and I don't know what I did to piss Riki off, and I don't know Turtle, but he sounds like he knows what he is talking about, but Tom has more aviation mechanicing experience than most anyone out there, and while I have not worked on that many airplanes I have rebuilt engines for everything from Model T's to Turbo Cosworths, and I have restored many tractors & classic cars, some of which are in museums. When I replied to this thread my intent was to try to save homebuilders some money, as mags are mags, and if you have a good old mechanic around that understands them you don't have to spend $1000 to get it rebuilt by a certified "aviation" shop. Heck, one of the major Cessna Service centers nearby has a local shop do all their alternator/generator/mag work, they got the FAA paperwork for them because they know what they are doing & they SAVE PEOPLE MONEY.

[Tom Downey]

Heck, one of the major Cessna Service centers nearby has a local shop do all their alternator/generator/mag work, they got the FAA paperwork for them because they know what they are doing & they SAVE PEOPLE MONEY.

Any A&P should be able to do the same thing..

[Tom Downey]

Spoken like a pilot everyone should listen to.......... Makes my point about forum junkies in a nutshell. On to the ignore list - these comments are ridiculous.

Maybe to you, but that comment seems like a comment from sone one with a chip on their shoulder.

[Tom Downey]

[QUOTE=Mike Switzer;10911 but Tom has more aviation mechanicing experience than most anyone out there, [/QUOTE]

Thanks for that, but there a great number of folks posting here that are very versed in aviation. and a few that will take exception to anything.

[raytoews]

Throw that 1940 technology mag in the garbage and buy a Pmag. Problem solved.
And while your at it throw the wires and plugs away and use BR9's with bushing from Pmag.

Ray

[flyingriki]

You have a good suggestion Ray. I have one already on the other side. But finances dictated that I fix this old one now and will dump it next inspection time. Spent the extra on a Dynon and new audio panel. Engine is purring away better than ever for now and it's nice to have some glass and clear radios and intercom.

[58boner]

Wow! To think I stopped surfing this site because it became boring!
If Riki only knew how many "unofficial" tests are employed everyday by experienced mechanics everyday he might never fly again!
There's a popular expression amongst inspectors that goes "If you didn't touch it you didn't inspect it". Experience is the best teacher and often a little wiggle from a deft digit is worth more than a shiny red box full of "Snappys" and a shelf full of manuals.
The feds even recognize the value of experience when inspecting a part for condition and wear to determine "airworthiness"
But I guess if your "Glass" says all's well and the mp-3 player sounds great through the new audio panel...Who needs a good mag.

[flyingriki]

Wow! To think I stopped surfing this site because it became boring!
If Riki only knew how many "unofficial" tests are employed everyday by experienced mechanics everyday he might never fly again!
There's a popular expression amongst inspectors that goes "If you didn't touch it you didn't inspect it". Experience is the best teacher and often a little wiggle from a deft digit is worth more than a shiny red box full of "Snappys" and a shelf full of manuals.
The feds even recognize the value of experience when inspecting a part for condition and wear to determine "airworthiness"
But I guess if your "Glass" says all's well and the mp-3 player sounds great through the new audio panel...Who needs a good mag.

What an idiot. I have no idea what you are talking about. I sent my Mag to one of the best shops in the country. Now want to keep running your mouth? What the hell does that have to do with my panel choices?
I've seen work come out of A&Ps and IAs and some of it was scary! So don't lecture me on how much goes on that I don't know about. I've kept my plane flying quite nicely for several years now. I'd be afraid to leave it with some guy the FAA approves. Like I'd trust them for anything!
Go troll another thread with your snotty, useless comments.

[58boner]

Sounds like somebody needs a hug!