Magneto timing questions.

Gary Ward

Gary Ward

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When the points wear does the magneto timing change?
If so do they retard or advance?
I have 230 hours on a 500 hour inspection and found the timing off.
Maybe I didn’t have it right from the beginning?
I am not sure if I am looking at retarded timing and very confused right now.
I just texted my AP and he is coming by later this afternoon .
 
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Slick magnetos are supposed to wear the points and the follower at an equal rate, cancelling each other out so the timing doesn't change.

Worn points advance the timing, a worn follower retards the timing.
 
Joe my AP/IA came by and confirmed what I was thinking. It was retarded 2 degrees at 23. Not sure how it got like that. Mag was tight and the nuts were still torqued as I checked them before loosing them.
I am working on my annual due next month, mag check, leak down, leaking valve cover gasket replacement, exhaust removal and anti seize etc. swapped the plugs out 34 hours ago so I am reusing them to stay on schedule.
Oil change is not until 7 more hours so holding off on that to keep the oil sample the same frequency.
Next month focus on the airframe.

Discovered why the valve cover was leaking, installation error on my part relating to the spark leads bracket. Washer in the wrong place. Took 684 hours and 4 years to leak.
I only have 45 more hours until my alternator will have 500 hours on it. Got to do something about that.
 
2°is common and unconcerning esp if retarded not advanced.
Most systems are only accurate to one degree. Wear can easily result in 1° change.
 
Thanks and that is what i was thinking. within one degree is about as close as i can get it.
Over tightening will do this.
cover was still flat luckily. look how clean it is from lots of flying.IMG_4493.jpegIMG_4494.jpegIMG_4492.jpeg
 

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Timing to Engine off or Mag Internal Timing?

When dealing with D mags I always replace the Contacts AND

the Impulse Spring when removed from engine.

The ones that break most often seem to be low time.

Low time operating = high time rusting

Rust is terrible for Springs (ask Ford) .

btw - I do not have a Glider Rating!
 
Gary Ward said:
Joe my AP/IA came by and confirmed what I was thinking. It was retarded 2 degrees at 23. Not sure how it got like that. Mag was tight and the nuts were still torqued as I checked them before loosing them.
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2° in 230 hours isn't bad. You're seeing some points rubbing block wear. The larger problem is that the E-gap gets thrown off, and the spark is weakened. The E-Gap is the angle after rotor neutral at which the points open. At the correct angle, or E-gap, the distance the flux falls is maximized and the hottest spark produced. Resetting that is a pain in a TCM/Bendix mag.

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The static flux is the magnetic flux generated in the magneto's core as the magnet in the rotor turns. The resultant flux is the flux in the core due to the current generated in the primary winding; the inductance of that winding keeps the current flowing after the magnet has reached neutral, and that continuing current flow generates a continuing flux. The points open at the E-gap, the flux falls a long way to below neutral, and that rapidly collapsing magnetic field generates the high spark voltage in the secondary winding.

If the points open later, the E-gap moves farther from the 90/270 rotor neutral positions, the flux has been decreasing on its own (see the slight downward curve developing just before points open), the distance it falls is less and the secondary voltage suffers.

While we're at it, we might as well mention the condenser (capacitor). Some think it's to prevent arcing and burning of the points, but just try running without it. If the primary current arcs across the points as they open, that represents continued current flow right when we want to arrest it suddenly to get the rapid collapse of the field. So the flux curves off gradually and you get little or no spark. The condenser will absorb current flow after the points open, but it is soon full, and by that time the points are too far apart to arc, so the currents stops dead and the field collapses.

There is nothing in the mag that doesn't absolutely need to be there.

Pilots that want to know more about the workings of their airplanes should get this book:
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Some pilot shops have it. Amazon has it. If you buy it I can post a corrections page for it, though this issue is newer than the one I used as a textbook for my college class. The mistakes might be corrected.
 

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This is how I do it, always looking for input on how to do it better.
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I can't see it clearly unless I climb up on top. Notice the missing rivets in the cover on my front fairing? Got to remove that and fab a retainer for underneath. All those grass landings do add up to more wear. I don't care I love grass and the look of the wheel fairings.
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Isn't it weird I get great satisfaction from topping off the water in my battery? I know I am old and weird like that. Not a fan of sealed battery's. I just had to replace a $214.00 sealed battery in my RV for an inverter that only lasted 2.5 years. If I didn't have a battery charger for the sealed battery I would have switched back
to a wet cell battery. This battery is 4.5 years old going strong even after going dead twice for 24 hours because I left the main switch on.
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IMG_4407.HEIC

My dog is going blind from cataracts so he knows if he stays close to the plane he won't get left behind.
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Gary, are you showing us in the first image setting/checking the mag to engine timing using external engine markings?
If so, you might consider a digital angle gauge and piston stop - I get much better accuracy with that method.
 
Good suggestion and I have a piston stop, but the digital angle finder I am not clear on.
I do have the old fashioned angle finder cup that mounts on the spinner but it don't fit my spinner(too big or my spinner is too pointy)
I would love to check TDC but unsure how to use digital for that?
 
Gary Ward said:
When the points wear does the magneto timing change?
If so do they retard or advance?
I have 230 hours on a 500 hour inspection and found the timing off.
Maybe I didn’t have it right from the beginning?
I am not sure if I am looking at retarded timing and very confused right now.
I just texted my AP and he is coming by later this afternoon .
Click to expand...
depending on mag flavor (slick / bendix) one has metal cam the other a fiber cam. if cam or follower wears timing will retard. i am not sure (forgot the failure mod for point contacts), but if contact part of points wears i think there would be a different symptom. 230 hrs isn't much, points, condenser and cam (cam on slick mags, fiber) should have been changed with new parts at 500 hr insp. how far out of timing are you talking about? If a degree or two, it probably happened when initially timed to the engine. Just re-time and check in about 10 to 20 hours (roughly) unless you get some indication during operation (mag check etc.). The method used during setting the timing can be critical. I have seen people just scratch a line when removing mags and using that line / mark to re-install, for lack of the proper tools, (obviously not a guarantee for success) and even with experience and the right tools and rushed you can be off a little. And if a bunch of hoses / wires etc. are in the way it can be difficult to hit the mark dead on.
With as little time on them i would re-adjust and check again at some future date.
 
IMG_60061.jpg

I have to look in my small library for that book as I have some other ASA publications.
I understand the basics as I have some engine building experience. Always looking to improve.
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Gary Ward said:
This is how I do it, always looking for input on how to do it better.
Click to expand...
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See that little indent on the starter in line with the 25°BTDC mark on the flywheel? Those are your timing marks. Lycomings are easy that way. Continentals have various dumb ways to do it.
 
Gary Ward said:
Good suggestion and I have a piston stop, but the digital angle finder I am not clear on.
I do have the old fashioned angle finder cup that mounts on the spinner but it don't fit my spinner(too big or my spinner is too pointy)
I would love to check TDC but unsure how to use digital for that?
Click to expand...
I tape this to my spinner, then use the piston stop to find TDC, there is an easy procedure.
Also useful for checking/adjusting control surface deflections against TCDS values.

 
If you are adjusting mag timing on D2000, I suggest you take great care with lock washers and proper torque to keep the nuts from backing off.
 
Skyrys62 said:
Is it the hole in the indent? I'm guessing yes or it would be a bit less precise.
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I think Dan using the starter reference so to locate the timing mark on the ring gear support assembly?
Or does it line up with the starter on that engine?
Dan Thomas said:
View attachment 129570

See that little indent on the starter in line with the 25°BTDC mark on the flywheel? Those are your timing marks. Lycomings are easy that way. Continentals have various dumb ways to do it.
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I wish my markings were facing forward. They are only on the aft side on my ring gear support assembly.
I only have 2 markings that I know of on the aft side. I line up the 25 BTDC line on the support assembly to the parting line on top of the engine case. It is hard to line up looking at it at an angle. So climb on top to look at it. My mechanic said there is something that fastened to the engine to extend the case parting line to get it closer to the support assembly to make easier to line it up?

When I had the mag 500 hr inspection done all this was replaced and 2 sets of instructions were included to help me reinstall with the proper later mag clamp blocks, using the right gasket which was supplied, details on installing the new capacitors etc. So I feel confident it was installed properly. I don't worry about rust as I fly the plane 2-7 days a week since 2018.
IMG_E2724_do4YJaxgXsBfTUdyWhGLRo.JPG

I read the paperwork I get several times before I do the work. Just like I have to read Dan's posts several times so it all soaks in. Thanks for every ones input it helps.
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The only Lycoming support assy that did not have markings on the front were ancient.

The is a clip on pointer you attach to ring gear at proper degree

to line up with case . You could likely make it.
 
I would get the crank at 25°BTDC (or whatever the spec is for the H2AD engine) and make a mark with a bit of paint on the front of the wheel at the little ding on the starter housing. I wouldn't go center-punching or scribing it. Might be asking for a crack. The stamped marks on the OEM wheels appear to be done with rounded stamps to avoid stress risers.
 
Dan Thomas said:
I would get the crank at 25°BTDC (or whatever the spec is for the H2AD engine) and make a mark with a bit of paint on the front of the wheel at the little ding on the starter housing. I wouldn't go center-punching or scribing it. Might be asking for a crack. The stamped marks on the OEM wheels appear to be done with rounded stamps to avoid stress risers.
Click to expand...
old picture.
IMG_8641(1).JPG

Looks like there is one mark on the front, I don't what is? It is not TDC or 25 BTDC.
IMG_8192.JPG
 
The one at about 10 o'clock-ish?
I see what looks like an old sharpie at approx. 3 o'clock. Also in the 'old picture' ?
 
mondtster said:
I see two marks and both are labeled as to what they are.
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I put the red marker on the face of the support but don't use them to set the timing as I dont feel they are accurate enough?
The only picture shown is the engine fresh out of the engine crate before i marked it up.
 
Gary Ward said:
I put the red marker on the face of the support but don't use them to set the timing as I dont feel they are accurate enough?
The only picture shown is the engine fresh out of the engine crate before i marked it up.
Click to expand...

The bottom photo with no sharpie markings has two marks. One for TDC and the other for 25 before. They are both clearly marked as to what they are. 25 before is at about 10:00 in that photo and TDC is at about 11:00.
 
mondtster said:
The bottom photo with no sharpie markings has two marks. One for TDC and the other for 25 before. They are both clearly marked as to what they are. 25 before is at about 10:00 in that photo and TDC is at about 11:00.
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OK I will look again next time I have the cowl off. This why I posted the pictures because I figured I was missing something.
I flew it last night and am on my to the airport to fly again. I will have the cowl off again next week for an oil change and will look. Thank you for posting.
Those factory marks on the front don't line up with the factory ones on the back that I use to time it. Something is weird.
 
mondtster said:
The bottom photo with no sharpie markings has two marks. One for TDC and the other for 25 before. They are both clearly marked as to what they are. 25 before is at about 10:00 in that photo and TDC is at about 11:00.
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I'm trying to follow along, because his and my plane have very close serial numbers.
-
These markings?

1717709007994.png
 
Gary Ward said:
OK I will look again next time I have the cowl off. This why I posted the pictures because I figured I was missing something.
I flew it last night and am on my to the airport to fly again. I will have the cowl off again next week for an oil change and will look. Thank you for posting.
Those factory marks on the front don't line up with the factory ones on the back that I use to time it. Something is weird.
Click to expand...

Nothing is weird. The ones on the front of the starter ring gear are used in relation with the mark on the starter, not the spine of the crankcase.
 
mondtster said:
Nothing is weird. The ones on the front of the starter ring gear are used in relation with the mark on the starter, not the spine of the crankcase.
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Oh OK Thanks for teaching me something. It is all starting to make sense. I wonder why my AP never mentioned that?
Thank you all helping me understand this more. I had no clue as you can tell. So valuable to get on here and ask. thanks again!
 
Gary Ward said:
Oh OK Thanks for teaching me something. It is all starting to make sense. I wonder why my AP never mentioned that?
Thank you all helping me understand this more. I had no clue as you can tell. So valuable to get on here and ask. thanks again!
Click to expand...

Some guys prefer to use the back of the ring gear and the spine while other guys prefer to use the starter mark and the front of the ring gear. Perhaps your guy favors the first method and didn't think to mention the others because there was no need to employ them on your airplane. In my experience however, a mechanic should be proficient at using either method, as well as finding TDC with a piston stop and going from there because you can't always see the same timing mark set on all aircraft.

I think using the indent on the starter with the marks on the front of the ring gear produces the best results with the least effort.
 
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