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Ring Gear woes

rocketman1988

Well Known Member
Has anyone had issues with breaking teeth on their ring gear?

I am running a Barrett IO-540, 9:1 and EFII. I have a B&C starter.

I do not get and kick back during starts, and it starts right away, every time.

I have spoke with Lycoming, Superior (ring gear), Barrett, and B&C and have no conclusive answers.

I found it funny that Lycoming said "A few broken teeth is normal".

I have checked for the correct pinion, and bendix operation. You can see on the ring gear teeth how far the pinion is engaging, and it is nearly the same as others with the same setup.

A crash engagement is not possible as the VPX disables the start solenoid above 600 rpm.

Please post if you have a similar issue...
 
Bob,

Are you using the BCS206/BC315 starter, how is it wired to the VPX? I.E. a single BFW (big f-at wire) or a BFW and a smaller "starter" wire (18-20ga) wired to the starter solenoid?
 
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Bob,

Are you using the BCS206/BC315 starter, how is it wired to the VPX? I.E. a single BFW (big f-at wire) or a BFW and a smaller "starter" wire (18-20ga) wired to the starter solenoid?

Yes on the starter. It has one BFW from the starter contactor to the starter. The VPX provides power to the contactor coil when you press the button, when it senses about 600 rpm, the VPX disables that pin. I have visual verification of the pin voltage status, and it is working as advertised.
 
I had that happen when I had failed to lubricate the pinion gear for a long time (I didn’t know I was supposed to do that). It was a pretty easy fix though - aside from having to remove the propeller, and then reinstall it. I bought a new gear with the proper number of teeth. Once the starter ring gear/ flywheel was off the airplane, it was easy - whack the ring gear with a chisel - splits open easily. I took the new gear and flywheel to Signature engines here in Cincinnati (KLUK) and they put it together - flywheel in the freezer, ring gear in the oven, and then assemble. I think they charged me about 75 bucks. No problems after that and greasing that pinion gear shaft.
 
I had that happen when I had failed to lubricate the pinion gear for a long time (I didn’t know I was supposed to do that). It was a pretty easy fix though - aside from having to remove the propeller, and then reinstall it. I bought a new gear with the proper number of teeth. Once the starter ring gear/ flywheel was off the airplane, it was easy - whack the ring gear with a chisel - splits open easily. I took the new gear and flywheel to Signature engines here in Cincinnati (KLUK) and they put it together - flywheel in the freezer, ring gear in the oven, and then assemble. I think they charged me about 75 bucks. No problems after that and greasing that pinion gear shaft.

To clarify, you are greasing the pinion shaft, not the gear teeth…

Is Signature engines still there?
 
Has anyone had issues with breaking teeth on their ring gear?

I am running a Barrett IO-540, 9:1 and EFII. I have a B&C starter.

I do not get and kick back during starts, and it starts right away, every time.

I have spoke with Lycoming, Superior (ring gear), Barrett, and B&C and have no conclusive answers.

I found it funny that Lycoming said "A few broken teeth is normal".

I have checked for the correct pinion, and bendix operation. You can see on the ring gear teeth how far the pinion is engaging, and it is nearly the same as others with the same setup.

A crash engagement is not possible as the VPX disables the start solenoid above 600 rpm.

Please post if you have a similar issue...

I would completely go through the ignition system looking for flaws. The biggest cause of broken teeth is ignition systems firing at the wrong time. I just helped a poor aviator that took his 9 to a real hack A&P. He broke 5 teeth trying to start the plane. I took the mag off and brought it to my shop. Turns out the idiot re-assembled the mag with the gears out of phase. Kick backs can also break teeth and the most common cause is the ignition sparking too advanced at cranking RPMs. The EFII should have setting for crank RPM threshold and ignition retard amount at cranking RPM (a threshold too low can cause the EFII to drop the retard). These setting may or may not be exposed to the end user, but if they are wrong kick backs can happen and won't always be observed by the pilot. At higher cranking speeds, you can get reversionary pulses that are strong enough to break teeth but not strong enough to produce a visible effect on prop movement.

sometimes a bad plug or wire creates too much resistance and the spark jumps across the wire to it's neighbor and creates an out of phase spark event, so be sure to check for this also.

It is difficult for a bendix style (NL series) pinion to break gears due to the engagement angles ground into both the ring gear and pinion gear teeth. An exception to that is inadequate spacing. Apparently there are a few different ring gear thicknesses and if you put the wrong one on the wrong flywheel you get a VERY small clearance and this can break teeth. Skytech has a bulletin describing this and how to measure.

Larry
 
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I would completely go through the ignition system looking for flaws. The biggest cause of broken teeth is ignition systems firing at the wrong time. I just helped a poor aviator that took his 9 to a real hack A&P. He broke 5 teeth trying to start the plane. I took the mag off and brought it to my shop. Turns out the idiot re-assembled the mag with the gears out of phase. Kick backs can also break teeth and the most common cause is the ignition sparking too advanced at cranking RPMs. The EFII should have setting for crank RPM threshold and ignition retard amount at cranking RPM. These setting may or may not be exposed to the end user, but if they are wrong kick backs can happen and won't always be observed by the pilot. At higher cranking speeds, you can get reversionary pulses that are strong enough to break teeth but not strong enough to produce a visible effect on prop movement.

sometimes a bad plug or wire creates too much resistance and the spark jumps across the ire to it's neighbor and creates an out of phase spark event, so be sure to check for this also.

It is difficult for a bendix style (NL series) pinion to break gears due to the engagement angles ground into both the ring gear and pinion gear teeth. An exception to that is inadequate spacing. Apparently there are a few different ring gear thicknesses and if you put the wrong one on the wrong flywheel you get a VERY small clearance. Skytech has a bulletin describing this.

Larry


I am checking the ignition timing map. I have a B&C starter. This has happened on two different ring gears…superior and Lycoming.
 
To clarify, you are greasing the pinion shaft, not the gear teeth…

Is Signature engines still there?

Its been a while since I worked on these, but IIRC, the guts of a bendix drive (mostly rollers) SHOULD NOT be greased. They are all hardened steel, so don't wear much, and the grease will dry out and create poor operation. gear teeth should not be greased. Solenoid actuated drives are different and think it is ok to grease the shaft the that the drive slides on, but is not necessary.

A bendix drive can get filled with crude and will not operate properly. They can be disassembled and cleaned. However, this seems very unlikely after a couple hundred hours of time.
 
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I am checking the ignition timing map. I have a B&C starter. This has happened on two different ring gears…superior and Lycoming.

Is the B&C a bendix drive or a solenoid actuated drive? Never seen one. If you have broken teeth on two different ring gears, you definitely have something wrong somewhere and my guess is an issue with ignition. The timing map is not where you want to be. That map is only used once the RPMs have surpassed the cranking RPM threshold. When RPMs are below the cranking RPM threshold, it will either use a fixed timing advance or an offset from the timing map. These are the areas that problems will create broken teeth. If it uses an offset and you raised the lowest advance in the map, that could be an issue. Some people, myself included, will raise the advance at idle levels in order to improve idle performance. If the threshold is too low and starter too powerfull, you could be jumping into the main timing table and the excess advance there causing the broken teeth.
 
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VPX Logic...

When the start button or keyswitch input to the VPX is activated, does the VPX turn on the starter and then keep the starter powered on until the engine hits 400RPM or does it turn off the power as soon as the button/keyswitch is released?
 
To clarify, you are greasing the pinion shaft, not the gear teeth…

Is Signature engines still there?

Guess I shouldn’t have said ‘grease’, rather lubricate, and yes, only on the shaft - nothing on the gear or ring gear teeth. I pull the gear forward with a piece of wood or something that won’t damage the gear and spray something like LPS 1 on the exposed shaft behind the gear. It’s a greaseless lubricant that doesn’t leave a build up. Signature Engines is still there at KLUK (+1 (513) 871-9966).
signatureenginesinc.com
I dropped off my flywheel/ring gear, and picked it up the next day. It was at least three years ago, but the cost was somewhere around $75 as far as I can remember.
 
All of my engine experince must be "abnormal", because I've never broken a tooth. The Lycoming guidance is BS.

If you are not kicking back and the engine starts "first time", then when are you seeing broken teeth? Preflight its good, then normal start, then on postflight the teeth are gone?
 
All of my engine experince must be "abnormal", because I've never broken a tooth. The Lycoming guidance is BS.

If you are not kicking back and the engine starts "first time", then when are you seeing broken teeth? Preflight its good, then normal start, then on postflight the teeth are gone?

You see, the problem with your statement is that you cannot see the ring gear on preflight or post flight unless you remove the cowl, so to answer your question, I don’t know when I am losing the teeth. Could it be during the initial engagement? I’m starting to think so but the weird thing with that theory is where the teeth are missing. If they were being broke during the initial engagement, you would expect to see the broken ones line up with the starter at the initial prop position which could only be in one of three places (I always put one blade vertical on postflight). When I get the airplane back, this is something I plan to check.
 
Wrong Ring Gear??

Have you verified you have the correct ring gear? There are two choices, 122 tooth or 149 tooth. Sounds to me you might have a 122 tooth ring gear with a starter intended for 149 tooth ring gear. Or, the teeth are meshing too deep?
Or is the mesh too shallow?
Something is causing starter torque to be applied with partial tooth engagement. A picture of the failed teeth would be most helpful.
 
You see, the problem with your statement is that you cannot see the ring gear on preflight or post flight unless you remove the cowl, so to answer your question, I don’t know when I am losing the teeth. Could it be during the initial engagement? I’m starting to think so but the weird thing with that theory is where the teeth are missing. If they were being broke during the initial engagement, you would expect to see the broken ones line up with the starter at the initial prop position which could only be in one of three places (I always put one blade vertical on postflight). When I get the airplane back, this is something I plan to check.

Maybe both blades need to be vertical....:D
 
Have you verified you have the correct ring gear? There are two choices, 122 tooth or 149 tooth. Sounds to me you might have a 122 tooth ring gear with a starter intended for 149 tooth ring gear. Or, the teeth are meshing too deep?
Or is the mesh too shallow?
Something is causing starter torque to be applied with partial tooth engagement. A picture of the failed teeth would be most helpful.

Ring gear and pinion have been verified. I have matched pictures of my ring gear with those of a nearly identical engine setup and the engagement marks look very similar. I will try and dig up the pix. I am going to have the starter checked by B&C to verify it is functioning normally.

Just an annoying issue...
 
You see, the problem with your statement is that you cannot see the ring gear on preflight or post flight unless you remove the cowl, so to answer your question, I don’t know when I am losing the teeth. Could it be during the initial engagement? I’m starting to think so but the weird thing with that theory is where the teeth are missing. If they were being broke during the initial engagement, you would expect to see the broken ones line up with the starter at the initial prop position which could only be in one of three places (I always put one blade vertical on postflight). When I get the airplane back, this is something I plan to check.

Pinion engagement issues tend to chip teeth not break them off cleanly. Reversionary pulses or sudden stoppage forces tend to break teeth off cleanly. No pics to view, so can't speculate. If you are good with engine theory, you can determine the angles relative to TDC for each of the broken teeth. This will help to better understand what forces are in play and from what cause.

starters, both solenoid and bendix style, have a pretty good history of not breaking teeth during engagement when clearance is proper maintained. Still believe you have an ignition issue. Engaging the starter with the engine running also typically does not break teeth clean off.
 
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Pinion engagement issues tend to chip teeth not break them off cleanly. Reversionary pulses or sudden stoppage forces tend to break teeth off cleanly. No pics to view, so can't speculate. If you are good with engine theory, you can determine the angles relative to TDC for each of the broken teeth. This will help to better understand what forces are in play and from what cause.

starters, both solenoid and bendix style, have a pretty good history of not breaking teeth during engagement when clearance is proper maintained. Still believe you have an ignition issue. Engaging the starter with the engine running also typically does not break teeth clean off.

It is difficult to believe that it is a timing issue as there are at more than 50 engines running the same system as me that aren’t having problems.

As far as the angles of the broken teeth, that is a project for when I get the airplane back. I also plan on getting the starter checked. It’s currently being painted at Evoke…
 
It is difficult to believe that it is a timing issue as there are at more than 50 engines running the same system as me that aren’t having problems.

As far as the angles of the broken teeth, that is a project for when I get the airplane back. I also plan on getting the starter checked. It’s currently being painted at Evoke…

WHile your normal running timing may be fine, I believe that that issue is with the cranking timing. When you go to computerized ignition, most software separates out a mode for cranking based upon an RPM threshold and treats everything different in this mode (with EFII, most fuel parameters are also very different). Most engines uses much less advance during the cranking phase than they do even at idle revs. Everything may be fine and normal once outside the cranking threshold, but that is no guarantee that all is fine inside the cranking threshold or even that you may be spinning faster than the threshold, putting you out of cranking mode and thereby not running the cranking specified advance. I suggest checking all of the SW parameters.

teeth getting cracked off at a relative position where the crank is about 0-10* BTDC or 110-120* BTDC or 230-240 BTDC (end of compression stroke for each of the three phases), is a good indicator of too much advance during cranking. As I mentioned WHERE the teeth are breaking off can be highly informative in some cases.

Lots of guys have snapped off gear teeth when accidentally starting on a non impulse mag, as it has no retard function like the impulse lag and induces a lot of stress on the teeth.
 
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WHile your normal running timing may be fine, I believe that that issue is with the cranking timing. When you go to computerized ignition, most software separates out a mode for cranking based upon an RPM threshold and treats everything different in this mode (with EFII, most fuel parameters are also very different). Most engines uses much less advance during the cranking phase than they do even at idle revs. Everything may be fine and normal once outside the cranking threshold, but that is no guarantee that all is fine inside the cranking threshold or even that you may be spinning faster than the threshold, putting you out of cranking mode and thereby not running the cranking specified advance. I suggest checking all of the SW parameters.

teeth getting cracked off at a relative position where the crank is about 0-10* BTDC or 110-120* BTDC or 230-240 BTDC (end of compression stroke for each of the three phases), is a good indicator of too much advance during cranking. As I mentioned WHERE the teeth are breaking off can be highly informative in some cases.

Lots of guys have snapped off gear teeth when accidentally starting on a non impulse mag, as it has no retard function like the impulse lag and induces a lot of stress on the teeth.

Yes, I will check those positions when the aircraft returns. Also checking into ignition/timing settings.
 
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