Flywheel Ring

[OkieAviator]

Looking for some info on what could cause chipping on the inside of the fly wheel ring.

Lycombing 360
Lycombing X-drive SRZ-9021 Starter

Some history on it is about 2 months ago a buddy and I were leaving Austin and the plane wouldn't start. You would engage the starter and all you would get is a loud click. This had happened before but usually would start on the second time, I thought it was a loose wire or something and was deferring to next annual. However my buddy's hobby is racing high performance trucks in the sand. So his comment was 'that's not a loose wire, could be a solenoid or the starter'.

So we popped the top out there in 100 degree heat on the ramp. He immediately recognized the issue. We discovered that the bendix (I think that's what it's called) of the starter was slamming against the fly wheel and not engaging. The work around was turn the prop horizontal where it was a bit more free moving. Again was going to defer 'fixing' it until annual, however this weekend flying back it started doing it again even in the horizontal position which leads me to think that there's additional chipping occurring.

Now sort of a chicken and the egg question... what caused these notches to begin with? Lack of lubricant on the starter gear? The gear not disengaging the flywheel properly or just a worn down 40 year old fly wheel ring? Some other item?

Before involving the A&P I use I wanted to at least have some idea on how to prevent this from happening to a new part. Also is it typical to just replace the ring or replace the entire assembly? Last time we fixed a fly wheel on one of my buddy's trucks we sent it off and had a new ring pressed on.

Thanks in advance

 

[Norman]

Bendix drive on starter is not properly engaging. When you replace it, turn the ring gear over so good teeth can be engaged. It can be replaced by heating it a bit. It should fall off and when you put it back on be sure it's on a FLAT surface.

 

[wsuffa]

If you replace it, give some thought to a lightweight starter like Skytech. I did on mine and never looked back.

 

[Dan Thomas]

Some mechanics oil that starter bendix, which causes it to gather dust and sludge up and start sticking and doing that to the ring gear. Lycoming will tell you that the ONLY lube that goes on that drive is dry silicone spray. But to get the old crud off, the starter has to come off and come apart and get cleaned.

The Skytech is the better bet. They have a proper solenoid in them that does the engaging of the drive gear instead of relying on an inertial affair like the old starters, and they don't need lubing.

That ring gear is normally removed by cutting through it to relieve the tension. A good one has bevelled teeth, and turning it over defeats that. The new ring is warmed in an oven and the flywheel is chilled in the freezer, and it drops together nicely.

 

[Thomas Dietrich]

I replaced the Skytec on an O-360 3 times within 1000 hrs. Now switched to the Hartzell for more than 1200 hrs without ANY problem.

 

[Soldier64]

I replaced the Skytec on an O-360 3 times within 1000 hrs. Now switched to the Hartzell for more than 1200 hrs without ANY problem.

Can't go against what your experience has been, but my SkyTech has been awesome for me the last 300 hours and all my flight training.

 

[Graueradler]

I've used dry ice to chill the center part when replacing the ring. No need for any heat on the ring.

 

[Timbeck2]

Looks like your prop is in the same exact position every time you start it too.

 

[bnt83]

What the new gear cost? $1200?

 

[OkieAviator]

Some mechanics oil that starter bendix, which causes it to gather dust and sludge up and start sticking and doing that to the ring gear. Lycoming will tell you that the ONLY lube that goes on that drive is dry silicone spray. But to get the old crud off, the starter has to come off and come apart and get cleaned.

The Skytech is the better bet. They have a proper solenoid in them that does the engaging of the drive gear instead of relying on an inertial affair like the old starters, and they don't need lubing.

That ring gear is normally removed by cutting through it to relieve the tension. A good one has bevelled teeth, and turning it over defeats that. The new ring is warmed in an oven and the flywheel is chilled in the freezer, and it drops together nicely.

I'll double check, I don't think anything was put on it. I'm concerned that I'll replace the gear and it will eat away the ring gear again. I'm going to check around to see if there's a shop at one of these local airports that can test the starter, make sure the assembly isn't warped and dynamically balance the prop.

Looks like your prop is in the same exact position every time you start it too.

The prop stops exactly up and down.. one A&P said it should stop more at a 45 degree angle, another said up and down is how you want it.

What the new gear cost? $1200?

The ring part I think is a few hundred, if you buy the entire assembly it's more like $900.

 

[BigBadLou]

Can't go against what your experience has been, but my SkyTech has been awesome for me the last 300 hours and all my flight training.

I've seen people swear by SkyTec, I've seen people cuss it out. It seems there are two distinct groups. I have seen both ends of the spectrum: a sh*tty SkyTec and a decent SkyTec starter.
I wonder whether it has to do with some change in manufacturing process where they might have started using inferior Chinese c*ap parts etc. Just pure guess and speculation on my part.

 

[Timbeck2]

My prop stopped exactly up and down as well, that is until it was installed correctly. Now it stops at 2 and 8 o'clock. Different engines, different prop but that is my experience. However, my comment was in relation to the wear on your ring gear. It looks as if your starter engages the ring gear at the same point every time which is why it is worn and chipped at that place. Nothing else would do that short of something getting caught in it.

The maintenance manual should state that when the engine is at top dead center on the number one cylinder, the prop should be at ___ and ___ o'clock.

 

[Dan Thomas]

Reclocking the propeller won't change the position of the ring gear. The flywheel has one larger bolt hole that fits over the one larger nut in the crankshaft flange, and that's where it stays no matter where the propeller is set. It has to be that way to get the timing marks lined up right.

That ring gear will suffer in the same two places because that's where the engine wants to rest. It's a place where one cylinder is coming up on compression and another is going down on power. Pulling the mixture or killing the mags results in roughly equal pressures in compression upstroke and power downstroke, and the engine will bounce to a stop between two of those. A four-banger has two possible ring gear wear spots, an six has three.

 

[Tom-D]

Bendix drive on starter is not properly engaging. When you replace it, turn the ring gear over so good teeth can be engaged. It can be replaced by heating it a bit. It should fall off and when you put it back on be sure it's on a FLAT surface.

How can it engage when all he gets is a "CLICK"

 

[Tom-D]

Reclocking the propeller won't change the position of the ring gear. The flywheel has one larger bolt hole that fits over the one larger nut in the crankshaft flange, and that's where it stays no matter where the propeller is set. It has to be that way to get the timing marks lined up right.

That ring gear will suffer in the same two places because that's where the engine wants to rest. It's a place where one cylinder is coming up on compression and another is going down on power. Pulling the mixture or killing the mags results in roughly equal pressures in compression upstroke and power downstroke, and the engine will bounce to a stop between two of those. A four-banger has two possible ring gear wear spots, an six has three.

That ring gear doesn't look bad enough to cause this problem. If the gear was the problem he will get a gear grinding sound, not a Click.
He has a starter solenoid problem.

 

[Tom-D]

As always ------ RTFQ.

A good one has bevelled teeth, and turning it over defeats that.

yeah that, !!! Only mechanics that don't have a clew will try to turn it over. and for the folks that don't know, the engine timing marks are on the fly wheel not the ring gear. and the fly wheel only goes on the crank flange 1 position.

 

[OkieAviator]

That ring gear doesn't look bad enough to cause this problem. If the gear was the problem he will get a gear grinding sound, not a Click.
He has a starter solenoid problem.

The 'click' is the bendix slamming against the ring gear, i assume causing all the dents on the ring gear. Correct me if I'm wrong but the starter gear won't engage unless the bendix is fully extended correct?

 

[Dan Thomas]

The 'click' is the bendix slamming against the ring gear, i assume causing all the dents on the ring gear. Correct me if I'm wrong but the starter gear won't engage unless the bendix is fully extended correct?

No, that starter will spin even if the gear doesn't engage and it will chew up the ring gear exactly as in the first picture. Some automobile starters had huge switch contacts in them that would make sure that the gear was fully engaged before the starter was energized, but this one isn't like that. Those old auto starters used a solenoid to pull the gear in, or, as Ford did, one of the field coils had a moveable core that did the work. The Lycoming (Prestolite) starter uses an inertial setup where the drive gear assembly (which includes the ratchet assembly and engagement lock) weighs quite a bit and it's on spiralled splines. The starter begins turning very abruptly and the inertia of the drive gear makes the splines fling it out into the flywheel gear. It's those spiralled splines that get gummed up and can grind the teeth.

Just a "click" when attempting to start means the starter contactor (some call it a solenoid) is trying to work, but its contacts might be burned or the starter is shot and not responding. It's a different problem from the torn-up teeth. Sounds like the airplane needs some money spent on it.

 

[Tom-D]

The 'click' is the bendix slamming against the ring gear, i assume causing all the dents on the ring gear. Correct me if I'm wrong but the starter gear won't engage unless the bendix is fully extended correct?

The spinning starter motor is what causes the bendix to engage the ring gear, no spin, no engage.

 

[Norman]

As usual, Tom is clueless.

 

[Tom-D]

As usual, Tom is clueless.

Wrong again

https://en.wikipedia.org/wiki/Bendix_drive

The Bendix system places the starter drive pinion on a helical drive spring. When the starter motor begins turning, the inertia of the drive pinion assembly causes it to wind the spring forcing the length of the spring to change and engage with the ring gear. When the engine starts, backdrive from the ring gear causes the drive pinion to exceed the rotative speed of the starter, at which point the drive pinion is forced back and out of mesh with the ring gear.

 

[Soldier64]

I've seen people swear by SkyTec, I've seen people cuss it out. It seems there are two distinct groups. I have seen both ends of the spectrum: a sh*tty SkyTec and a decent SkyTec starter.
I wonder whether it has to do with some change in manufacturing process where they might have started using inferior Chinese c*ap parts etc. Just pure guess and speculation on my part.

I'm not sure, but mine is a recent purchase. I really can't complain about the SkyTec and the people I know with them all have good things to say. Of course my local sample size is small for statistical relevance.

 

[mondtster]

There are two different ring gear tooth counts, does the starter and the ring gear match?

I'll be honest and say that I've never held the two up to each other before or tried mixing and matching. It may be impossible to have a mismatch, but something worth looking into.

 

[Graueradler]

The prop stops exactly up and down.. one A&P said it should stop more at a 45 degree angle, another said up and down is how you want it.

Some Piper model/engine/prop combinations are supposed to be one way, some the other. Google prop clocking for your model Cherokee (or check prop installation in the maintenance manual for your plane) and see what you find. What ever way you decide it should be, put it that way before dynamic balancing.

Sample:
PIPER AIRCRAFT
PA - 2 8 - 1 8 1
AIRPLANE MAINTENANCE MANUAL

C. INSTALLATION OF PROPELLER
1. Archer II (Refer to Figure 61-2)
a. Ensure magneto switch is OFF.
b. Place generator or alternator drive belt in groove of starter ring gear and position starter gear on
flange of crankshaft. Verify stamped “O” on gear is aligned with “O” on crankshaft flange.
c. Install propeller spinner back plate or bulkhead on starter ring gear.
d. Rotate crank shaft until top center (TC) mark on starter gear and crank case parting flange (or
index mark on starter housing) are aligned.
e. Install propeller with tips pointing at two and eight o’clock position.
f . Install and tighten each propeller bolt, with washer, finger tight. Use a torque wrench for final
t i g h te ning and tighten in sequence so all bolts are pulled down evenly. Tighten one-half inch bolts
to a torque of 720 to 780 inch-pounds (60 to 65 foot-pounds).
g. Check propeller blade track. (Refer to paragraph D)
h. Safety propeller mounting bolts with MS20995-C41 wire.
i. Install spinner and tighten cap bolts to a torque of 35 to 40 inch-pounds.
j. Adjust alternator drive belt per Checking Alternator Belt Tension, chapter 24.
—NOTE—
If propeller - engine combination feels rough on initial run-up or
flight, propeller may be rotated 180 degrees from initial
i n s t a l l ation.

 

[Dan Thomas]

Wrong again

https://en.wikipedia.org/wiki/Bendix_drive

The Bendix system places the starter drive pinion on a helical drive spring. When the starter motor begins turning, the inertia of the drive pinion assembly causes it to wind the spring forcing the length of the spring to change and engage with the ring gear. When the engine starts, backdrive from the ring gear causes the drive pinion to exceed the rotative speed of the starter, at which point the drive pinion is forced back and out of mesh with the ring gear.

The Lyc's Prestolite doesn't use that spring. It's a different setup. Just bump the starter on one, and see how it engages and stays that way because the centrifugal lock keeps it there until the engine starts and spins the gear fast enough to disengage the locks, the spiral splines pull the drive back, and a very light spring keeps it back. That light spring is also know to break and let the starter gear rub on the running ring gear.

 

[Tom-D]

The Lyc's Prestolite doesn't use that spring. It's a different setup. Just bump the starter on one, and see how it engages and stays that way because the centrifugal lock keeps it there until the engine starts and spins the gear fast enough to disengage the locks, the spiral splines pull the drive back, and a very light spring keeps it back. That light spring is also know to break and let the starter gear rub on the running ring gear.

Minor difference, still uses the spiral shaft, and the starter must spin it up to cause the gear to move forward and engage the ring gear. Like I said, "no spin no engagement". When you only hear the click, you won't get any rotation of the motor to spin the bendix.
Had he said he heard the motor spin, I'd say he has a bendix problem.
Had he heard the ring-a dinging, of the two gears trying to engage I'd say he has a ring gear or bendix problem.
But all he hears, is a click, I'd say he has a solenoid not hooking the starter to the battery., or possibly bad brushes in the starter motor.
A voltage drop test across the solenoid is my first trouble shooting test.
Next would be a high amperage test at the starter motor, If that proves the solenoid good, yet no rotation of the motor, it's the starter.

 

[OkieAviator]

Minor difference, still uses the spiral shaft, and the starter must spin it up to cause the gear to move forward and engage the ring gear. Like I said, "no spin no engagement". When you only hear the click, you won't get any rotation of the motor to spin the bendix.
Had he said he heard the motor spin, I'd say he has a bendix problem.
Had he heard the ring-a dinging, of the two gears trying to engage I'd say he has a ring gear or bendix problem.
But all he hears, is a click, I'd say he has a solenoid not hooking the starter to the battery., or possibly bad brushes in the starter motor.
A voltage drop test across the solenoid is my first trouble shooting test.
Next would be a high amperage test at the starter motor, If that proves the solenoid good, yet no rotation of the motor, it's the starter.

I'm so confused now... The click I hear I swear is the starter bendix slamming into the ring gear. What I read on the starter is it won't spin unless it's fully engaged, if it was spinning then I would hear a grinding. The starter gets warm after a few attempts, and the click isn't really a solenoid sound, more of a mechanical hammer sound.

I'm going to talk to the A&P today and see if it's something he feels he can troubleshoot and correct or if I need to go to one of the FBO shops. Sounds like the only equipment you need is an oven and a freezer to replace the ring... although I would like the prop balanced after messing with all that stuff.

 

[Tom-D]

What happens when yo move the prop a little and try again?
You may have a bad connection in the electrical circuit, where by the starter motor isn't getting the amperage it needs to spin the prop.

 

[OkieAviator]

What happens when yo move the prop a little and try again?
You may have a bad connection in the electrical circuit, where by the starter motor isn't getting the amperage it needs to spin the prop.

That's the work around... originally it was working 100% when I would put the prop horizontal... now it doesn't, almost as if it's grinded down the teeth on that side now... so the last two times it's done it I would get in and out turning the prop a few degrees until the starter would engage. Also something else I've noticed is sometimes the starter will lag a bit and turn a bit slow (Even on battery just off the tender and first start). Since it's the first 180 conversion 172 I've ever flown I assumed it was a higher compression engine or something like that.

 

[OkieAviator]

A&Ps prognosis, cracked starter housing....

Can't tell you what caused it, wear and tear, improper install, faulty part... who knows but it was put on less than 3 years ago and has maybe 250 hours on it. I have the logbook entry but looking for the original receipt to see if I get get a warranty replacement (36 months / 1000 hours). This crack shifted the starter enough to tear up the ring gear causing the starter issues I mentioned.

 

[BigBadLou]

Yikes! That will ruin your day for sure.
How fresh is the crack and how far back does it extend?

 

[Dan Thomas]

A&Ps prognosis, cracked starter housing....

Can't tell you what caused it, wear and tear, improper install, faulty part... who knows but it was put on less than 3 years ago and has maybe 250 hours on it. I have the logbook entry but looking for the original receipt to see if I get get a warranty replacement (36 months / 1000 hours). This crack shifted the starter enough to tear up the ring gear causing the starter issues I mentioned.

Looks to me like the front dowel was too large or a bit out of position, or maybe the hole in the crankcase had some crud in it, so that the dowel couldn't go in far enough and the nuts pulled the casting corners up and broke them.