Eight alternators in 24 months!

Trogdor

Trogdor

Pre-takeoff checklist
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Trogdor
1979ish 182 O-470 about 1000 before TBO. G3X+GTN650+GFC500 modern Garmin panel.

The problem: Every 25-30 hours, the alternator fails. Every single time. We have replaced the pulley, starter bearings, pulley assembly, two different kinds of belts, three voltage regulators, new battery, dynamically balanced the prop and yet, the alternator still fails. Two of the eight we know failed due to vibration. The last one we have just sent back to Hartzell for eval.

We took the engine into Columbia and asked them to look at the crankshaft counterweights and they said they were fine (but AFAIK didn’t caliper bushings or actually measure the weights). They also claimed that if we DID have a vibration issue it would “obvious” - I have doubts about that to be honest. I think any kind of small vibration can create harmonics and cause the rectifier to scrape.

We confirmed with Continental that our O-470 is NOT part of their SB about operating below 2.3k due to a known vibration issue with some of their motors.

Does anyone have any recommendations or have heard of O-470 eating alternators for lunch every few hours? What else have we not thought of?
 
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Is the mount right?

www.pilotsofamerica.com

Alternator Mounting Problem

Noticed my alternator (ES-4011) has a fair amount of movement in the lower bracket attach point contributing to excess vibration and wear. I pulled the unit and examined all of the mounting hardware and discovered several problems as shown. Trying to find an assembly drawing but Hartzell tech...
www.pilotsofamerica.com www.pilotsofamerica.com
 
Trogdor said:
Every 25-30 hours, the alternator fails.
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Do you know for certain what the failure mode is? Electrical? Mechanical? ??

Have you performed an in-depth check of the electrical system wiring for serviceability?

Have you done an engine spectrum vibration check? (It requires a 2nd accelerometer and specific equipment to check)

Eight in a row does seem to point to an aircraft problem.
 
Wrapped in the bundle of wires around the switches is an 'Over Voltage Sensor'...
Snapshot_20160502_69-20160502-121615.JPG

This aged unit can cause all sort of issues including alternators falling apart. Some parts just don't age well and this is one of them. :confused:
 
Klaus M said:
Wrapped in the bundle of wires around the switches is an 'Over Voltage Sensor'...
Snapshot_20160502_69-20160502-121615.JPG

This aged unit can cause all sort of issues including alternators falling apart. Some parts just don't age well and this is one of them. :confused:
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It won't cause the alternator to fall apart. It just shuts off the regulator, thereby shutting off the alternator's field.
 
Do you have the EIS option in your G3X? Or another engine monitor with logging? Maybe there are some clues in the data logs.
 
With this many failures, somebody must have done the forensics. Bearings, diodes or stator checked? Slip rings? Failed due to vibration is an awfully broad brush.
 
IF vibration is the main culprit, chances are your alternator/mount combination is resonating, amplifying whatever broadband vibrations the engine is generating (which, by themselves, might not be a problem).

Get one of these, figure out a way to attach it to the alternator, fly around and log the data.

SparkFun OpenLog Artemis - DEV-16832 - SparkFun Electronics

The SparkFun OpenLog Artemis is an open source data logger that comes pre-programmed to automatically log IMU, GPS, serial data, and more.
www.sparkfun.com www.sparkfun.com
 
Are you able to download long-term electrical data from the G3X? If it’s a chronic electrical problem that gets worse over the 30 hours of each of the 8 alternators then you might be able to see that on a data trend graph for each one, assuming the Garmin unit records that many hours. It still might be a longer term mechanical root cause, but you might be able to note a killing event.
 
I’d you have enough vibration to kill stuff every 30 hours, you should have lots of problems like cracked on metal bits like heat shields etc.
 
Dan Thomas said:
It won't cause the alternator to fall apart. It just shuts off the regulator, thereby shutting off the alternator's field.
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@Dan Thomas, You sir are absolutely so correct... That is exactly what I told the avionics guy who had me replace the 50 year old Over Voltage Sensor the first time. Since then every time the Cessna Over Voltage Sensor has been replaced the alternators quit failing and falling apart. Don't know what to tell you but, who cares? Hey, as long as the electrical system works.

I'm aware of several pulleys falling off, all the safety wired through bolts pull out, the rotating shaft break and other internal components coming loose. Both the Ford and the Plane Power alternators.
 
AV8R_87 said:
IF vibration is the main culprit, chances are your alternator/mount combination is resonating, amplifying whatever broadband vibrations the engine is generating (which, by themselves, might not be a problem).

Get one of these, figure out a way to attach it to the alternator, fly around and log the data.

SparkFun OpenLog Artemis - DEV-16832 - SparkFun Electronics

The SparkFun OpenLog Artemis is an open source data logger that comes pre-programmed to automatically log IMU, GPS, serial data, and more.
www.sparkfun.com www.sparkfun.com
Click to expand...
This is what I suspect is going on.

All the above has been already combed over by several folks. There is nothing abnormal in the G3X logs in terms of voltage spikes and things of that ilk.

We know vibration killed two maybe three alternators (what was damaged in the alternator itslef I don't know but maybe can ask).

My thinking is some kind of harmonic resonance shaking it. Everything on the electric side is new. Literally.
 
AV8R_87 said:
IF vibration is the main culprit, chances are your alternator/mount combination is resonating, amplifying whatever broadband vibrations the engine is generating (which, by themselves, might not be a problem).

Get one of these, figure out a way to attach it to the alternator, fly around and log the data.

SparkFun OpenLog Artemis - DEV-16832 - SparkFun Electronics

The SparkFun OpenLog Artemis is an open source data logger that comes pre-programmed to automatically log IMU, GPS, serial data, and more.
www.sparkfun.com www.sparkfun.com
Click to expand...
IMU over time is what you are getting at? Also, how would I know what is abnormal by looking at it? i.e. I don’t have a reference.
 
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Every time an electrical load hits your system there is a mechanical force generated when your alternator responds to this. I had a situation where my anti-collision light (still using incandescent lamps) was placing a sudden load on my alternators every few seconds. I was surprised at the damage done by the cumulative mechanical stress on the alternator mounting hardware over time. I am replacing the light with LEDs. You might want to consider this condition.
 
Rob58 said:
Every time an electrical load hits your system there is a mechanical force generated when your alternator responds to this. I had a situation where my anti-collision light (still using incandescent lamps) was placing a sudden load on my alternators every few seconds. I was surprised at the damage done by the cumulative mechanical stress on the alternator mounting hardware over time. I am replacing the light with LEDs. You might want to consider this condition.
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Wouldn’t that spike be seen in the G3X logs? Also I‘m pretty sure most lights are LEDs except NAV.
 
My guess is there may well be a problem in the torsional vibration control system. Have there been signs of wear on the belt drive (I assume this is that version of O-470)? At least I would be very suspicious of the actual crankshaft damper bushing and drive pins dimensions.

I wonder if the torsional vibration could be monitored on the alternator voltage (or even current) output? Never tried this and I would have to look more deeply into the physical nature of the whole torsional system - which may very well be beyond me. The possibilities of an incorrect assembly in the crankshaft damper system should be considered too.

Torsional vibration is very subtle. You can't generally hear it though I could point it out and demonstrate it to others in our 172M since it had no damper system. Otherwise it takes a lot of equipment to monitor it properly. Simple linear accelerometer(s) can't detect it. But 8 failures suggest something is very wrong here. FWIW - you are probably dealing with a frequency of about 200 Hz in the presence of a LOT of noise.

Most of this is based on my industrial experience with torsional vibration testing systems for the auto industry. It's spooky stuff.
 
nrpetersen said:
My guess is there may well be a problem in the torsional vibration control system. Have there been signs of wear on the belt drive (I assume this is that version of O-470)? At least I would be very suspicious of the actual crankshaft damper bushing and drive pins dimensions.

I wonder if the torsional vibration could be monitored on the alternator voltage (or even current) output? Never tried this and I would have to look more deeply into the physical nature of the whole torsional system - which may very well be beyond me. The possibilities of an incorrect assembly in the crankshaft damper system should be considered too.

Torsional vibration is very subtle. You can't generally hear it though I could point it out and demonstrate it to others in our 172M since it had no damper system. Otherwise it takes a lot of equipment to monitor it properly. Simple linear accelerometer(s) can't detect it. But 8 failures suggest something is very wrong here. FWIW - you are probably dealing with a frequency of about 200 Hz in the presence of a LOT of noise.

Most of this is based on my industrial experience with torsional vibration testing systems for the auto industry. It's spooky stuff.
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Someone suggested planting an IMU sensor on the alternator itself which I’m all for, but then what? What am I looking for exactly? i.e. if the alternator is getting shaken to death, by what? I would assume the rotating rectifier has some play so it won’t take too much vibration to get it to scrape, right?
 
I all of my rambling above on torsional vibration assume that all of the failures have been on the alternator rotors. If the failures are on the stator or the rest of the stationary mechanical support system, linear accelerometers would be a valid diagnostic tool. You certainly have thrown enough parts on this problem....!-
 
182 P,Q, and R are plentiful. Compare your parts to others if you think it’s something mechanical.

Another question - does operating these alternators below 2300 rpm stress them out from a load supporting standpoint? I wouldn’t think so, but you’ve added more electron-needy stuff to your bird than was available in 1979 (I realize you’ve replaced everything to account for it).
 
Klaus M said:
I'm aware of several pulleys falling off, all the safety wired through bolts pull out, the rotating shaft break and other internal components coming loose. Both the Ford and the Plane Power alternators.
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First, read my post, #8, in this thread already pointed out by George C:
https://www.pilotsofamerica.com/community/threads/alternator-mounting-problem.145235/

If the mounting hardware is not as per the IPC, you WILL have alternator failures. One cannot mix the hardware. The fully-cushioned stuff already had a habit of throwing the belt, and mixing the stuff up with the rigid hardware just makes things ten times worse.

Failures of though bolts, rotor shafts, and pulleys are a result of overtightening the belt. It won't matter whether its a Ford or a Plane Power alternator. They all cannot tolerate excessive side-loading on that shaft or the pulley or the mounting hardware. Some mechanics seem to think that there's a lot of horsepower being transmitted through that belt; it's baloney. A 60-amp alternator at 14 volts is generating 840 watts. Even if the alternator was only 60% efficient, it's consuming 1400 watts of mechanical power, or a bit less than two HP. Cessna has this to say in their R182/TR182 manuals:

1710094800261.png

That's one way. 12 pounds is VERY little deflection pressure. The 58 to 72 pounds of belt tension is impossible to measure without a belt tensiometer. So the better and more accurate way is this one:

1710095518433.png

Now, 7 to 9 foot-pounds or torque on the pulley nut as the belt starts slipping is a lot lower than most mechanics will tighten the belt by "feel." Even the 11 to 13 ft-lb isn't much. So they're being way overtightened, and the shaft and bearings and mounting hardware hate that.

Sometimes the tightening of the alternator mounting bolt after belt tensioning is forgotten. That's a recipe for a wrecked alternator, too.

I never had any alternator fall apart or lose its pulley or anything else like that in my time maintaining the flight school airplanes. Maybe 35,000 hours of flight, no problems. The only thing was to make sure those brushes were inspected every 500 hours as per the service manuals; they do wear out much faster in the airplane than in a car, because that alternator is operating near its redline all the time in flight, while the car's alternator is a long way from redline even while cruising. In both cars and airplanes the alternator drive is designed for the alternator to reach its 10,000 RPM redline at engine redline. We cruise at around 90% of redline in the airplane, maybe 30% of engine redline in the car. Big difference.

These alternators can handle the vibration. They last a long time if they are inspected properly and the mounting stuff is checked at annual or 100-hour. The OP's eight failed alternators are a symptom of either an incompetent rebuilder, or incompetent installation.
 
Rob58 said:
Every time an electrical load hits your system there is a mechanical force generated when your alternator responds to this. I had a situation where my anti-collision light (still using incandescent lamps) was placing a sudden load on my alternators every few seconds. I was surprised at the damage done by the cumulative mechanical stress on the alternator mounting hardware over time. I am replacing the light with LEDs. You might want to consider this condition.
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I would bet that your airplane is missing the ballast resistor in the anticollision light circuit. It's there to keep the current flow fairly constant. The powerpack switches between it and the bulb. A 10-amp (or so) load. Without the resistor, yes, you have constant current and load fluctuations. The circuit should look like this. Check your Viking manual:

1710096439851.png

#9 is that ballast resistor. It might be busted, missing, wire disconnected, or its ground connection is bad.
 
I am absolutely positive @Dan Thomas it was not incompetent installation - at least not all eight of them. We have at least two A&Ps with over 40 years of experience (each) who installed it. I’m not buying it. We had the belt and pulley and mounting hardware combed over by both two A&Ps and an engine shop. Columbia did identify a problem with the mounting hardware which was addressed - still failed.

Bus spikes I’m pretty sure should be logged by the G3X’s logging facility which has been combed over. There is nothing out of the ordinary AFAIK in those logs. But I am certain that two (maybe three) we do know that have come back from the manufacturer with a post mortem said that the most likely cause was vibration (unfortunately, I’m not sure what the exact damage was since I don’t have the report).
 
455 Bravo Uniform said:
182 P,Q, and R are plentiful. Compare your parts to others if you think it’s something mechanical.

Another question - does operating these alternators below 2300 rpm stress them out from a load supporting standpoint? I wouldn’t think so, but you’ve added more electron-needy stuff to your bird than was available in 1979 (I realize you’ve replaced everything to account for it).
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Ah, progress. I have thought of this. I operate at 22 squared and around 11 gps in cruise at most altitudes (CHTS say way below 400 in this config). I am wondering if manifold under 2300 is in fact the culprit. I just don’t know how to quantify it (read smoking gun) and because it is a club plane it is difficult to mandate a regime that should absolutely be pilot’s discretion.
 
nrpetersen said:
I all of my rambling above on torsional vibration assume that all of the failures have been on the alternator rotors. If the failures are on the stator or the rest of the stationary mechanical support system, linear accelerometers would be a valid diagnostic tool. You certainly have thrown enough parts on this problem....!-
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If it is the rotating rectifier, how can that be diagnosed?
 
There is no rotating rectifier. All that stuff is on or near the stator. A key is look at the detailed nature of the failure of each alternator. It is not hard to do. I'm surprised it hasn't been flagged earlier - just to say "vibration". Of what? What broke in each case?
 
nrpetersen said:
There is no rotating rectifier. All that stuff is on or near the stator. A key is look at the detailed nature of the failure of each alternator. It is not hard to do. I'm surprised it hasn't been flagged earlier - just to say "vibration". Of what? What broke in each case?
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I just asked. Caps.
 
If the alternators are coming without the pulley on them, is the mechanic using an impact wrench to tighten the pulley nut? That tears the shaft splines out of the rotor. Failure is the result. There is most likely some common factor in most of those eight failed units. Vibration alone cannot do so much damage. I used the same alternators on one engine after another in the flight school airplanes, with nothing more than brush and bearing checks. Some of my alternators had five or six thousand hours on them.

Low power settings don't do it, either. The alternators in cars are running much slower than they do in the airplanes, like I said. The typical alternator will also produce its full rated output at runup RPM, sometimes even less. The regulator does the job of varying the field current to get the voltage at 13.8V or so, and that voltage will want to vary according to the current drawn on the alternator. When you load it up with radios and lights and beacons and flaps and stuff, the regulator just keeps feeding the field more current to get more amps out of the alternator. The voltage output will also rise and fall with RPM changing up and down, and the regulator fixes that, too. In the flight school we did extensive slow flight, and the alternators did not suffer.

In post #21 I said this, and I still think it's the problem, as is so often is with old Continental installations:

Dan Thomas said:
If the mounting hardware is not as per the IPC, you WILL have alternator failures. One cannot mix the hardware. The fully-cushioned stuff already had a habit of throwing the belt, and mixing the stuff up with the rigid hardware just makes things ten times worse.
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I want to see a picture of all the mounting hardware on this installation, including the bracket on the engine. All apart, laid out on the bench.
 
Dan your information is very valuable and completely logical. Hope the OP can solve his problem. I'm going to follow your advice on the ballast resistor. I will also follow the installation instructions from the 182 manual since I do not have, and cannot obtain, the details of the installation instructions from the STC holder on my Commander 90A ES-4011 alternator upgrade. I had not really considered the 100-140 in-lbs torque on the bottom bolt, but it makes sense to eliminate the play (and resulting wear) to the alternator case. Much appreciated advice!
 
Dan Thomas said:
If the alternators are coming without the pulley on them, is the mechanic using an impact wrench to tighten the pulley nut? That tears the shaft splines out of the rotor. Failure is the result. There is most likely some common factor in most of those eight failed units. Vibration alone cannot do so much damage. I used the same alternators on one engine after another in the flight school airplanes, with nothing more than brush and bearing checks. Some of my alternators had five or six thousand hours on them.

Low power settings don't do it, either. The alternators in cars are running much slower than they do in the airplanes, like I said. The typical alternator will also produce its full rated output at runup RPM, sometimes even less. The regulator does the job of varying the field current to get the voltage at 13.8V or so, and that voltage will want to vary according to the current drawn on the alternator. When you load it up with radios and lights and beacons and flaps and stuff, the regulator just keeps feeding the field more current to get more amps out of the alternator. The voltage output will also rise and fall with RPM changing up and down, and the regulator fixes that, too. In the flight school we did extensive slow flight, and the alternators did not suffer.

In post #21 I said this, and I still think it's the problem, as is so often is with old Continental installations:



I want to see a picture of all the mounting hardware on this installation, including the bracket on the engine. All apart, laid out on the bench.
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@Dan Thomas how would the mounting hardware break the caps? And what happens when the capacitor breaks? I thought that was for noise and isn’t required (but apparently it is).

Apparently when it failed both the cap and bushing were loose.
 
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Trogdor said:
@Dan Thomas how would the mounting hardware break the caps? And what happens when the capacitor breaks? I thought that was for noise and isn’t required (but apparently it is).

Apparently when it failed both the cap and bushing were loose.
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If the bushing (which is really a Torrington needle bearing) was loose, that is usually a result of too much belt tension.

What "caps" were failing? Is that the alternator housing castings? Is this a Motorola=type alternator with two mounting lugs, one on each casting? Or is it a Ford, with one long lug on the front casting? Pictures of the alternator, damage and mountings would help a lot.

The capacitor is across the field brushes to stop back-EMF getting into the system via the regulator. If it was loose, the rotor had to have chewed up the brush holder, and that would be because of the rear bearing failure.
 
Dan Thomas said:
If the bushing (which is really a Torrington needle bearing) was loose, that is usually a result of too much belt tension.

What "caps" were failing? Is that the alternator housing castings? Is this a Motorola=type alternator with two mounting lugs, one on each casting? Or is it a Ford, with one long lug on the front casting? Pictures of the alternator, damage and mountings would help a lot.

The capacitor is across the field brushes to stop back-EMF getting into the system via the regulator. If it was loose, the rotor had to have chewed up the brush holder, and that would be because of the rear bearing failure.
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Ford style
 
Trogdor said:
IMU over time is what you are getting at? Also, how would I know what is abnormal by looking at it? i.e. I don’t have a reference.
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If you have some harmonic resonance, it will be at specific RPMs and such, with lower levels in-between. So look for high vibration peaks well above the noise floor.
 
Dan Thomas said:
If the bushing (which is really a Torrington needle bearing) was loose, that is usually a result of too much belt tension.

What "caps" were failing? Is that the alternator housing castings? Is this a Motorola=type alternator with two mounting lugs, one on each casting? Or is it a Ford, with one long lug on the front casting? Pictures of the alternator, damage and mountings would help a lot.

The capacitor is across the field brushes to stop back-EMF getting into the system via the regulator. If it was loose, the rotor had to have chewed up the brush holder, and that would be because of the rear bearing failure.
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Btw, that is correct. The rear bearing was "loose" hence vibration.
 
Trogdor said:
@Dan Thomas how would the mounting hardware break the caps?
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Should have addressed this earlier. The wrong hardware lets the alternator rattle around on its lower mounting bolt, pounding out the bore and cracking that long lug. The shock of that pounding could easily break the castings, maybe even Brinell the bearings. Once again, see this thread:
https://www.pilotsofamerica.com/community/threads/alternator-mounting-problem.145235/

I found damage much worse than that on a 185. The alternator was trashed. All the hardware was a cobbled-together mix of junk. The owner wanted a Plane Power alternator, and by the time we sourced all the right mounting stuff and mounted that alternator and the new regulator and modified the wiring as necessary, the cost was pretty high.

There is NO substitute for doing the work right the first time. If it's not, it gets real expensive later on.
 
Dan Thomas said:
Should have addressed this earlier. The wrong hardware lets the alternator rattle around on its lower mounting bolt, pounding out the bore and cracking that long lug. The shock of that pounding could easily break the castings, maybe even Brinell the bearings. Once again, see this thread:
https://www.pilotsofamerica.com/community/threads/alternator-mounting-problem.145235/

I found damage much worse than that on a 185. The alternator was trashed. All the hardware was a cobbled-together mix of junk. The owner wanted a Plane Power alternator, and by the time we sourced all the right mounting stuff and mounted that alternator and the new regulator and modified the wiring as necessary, the cost was pretty high.

There is NO substitute for doing the work right the first time. If it's not, it gets real expensive later on.
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Definitely. Don't think it's the mounting hardware though. It has been looked at.
 
Have YOU looked at it? Could you post a photo?
 
Domenick said:
Have YOU looked at it? Could you post a photo?
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I can't. The borked alternator went back and so now we have a new one. What picture would you exactly like? We are also now investigating cooling but my suspicion is a bearing wouldn't go but rather the diodes would be shot first...
 
How often do you wash down the engine? Do you take any precautions to keep the water, or solvent out of the alternator?
 
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