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Slipping ring gear

C

chuckh1197

Member
Had a problem with starting IO-320 the other day and I assumed it was a starter problem as prop would only move a little , maybe 30-60 degrees but starter was spinning. Turns out my mechanic says it is something he has never seen in his entire time. The ring gear is slipping on the flywheel. Have to get a new flywheel and ring gear I guess. Any other ideas? Also have Lightspeed ignition so I guess it needs to have sensor activators attached. 122 tooth with a lamar starter.

Anyone have one for sale.
 
How did it happen

Have no idea. Just went to start it and it wouldnt start. As I said mechanic ant Reno Flying Service , who works on lots of planes says he has never seen this before. Says that it cant be fixed as it is a press fit and flywheel or gear has probably worn.
 
I installed a new ring gear on my flywheel (I think it is referred to as a "carrier") for my O-360 when I overhauled it. Cut through the old one with a cutoff wheel in a die grinder. Carrier in the freezer and new ring gear in the oven. Dropped right into place. It's more likely the carrier is worn so try and get another. If the one you get has a bad ring gear or the wrong tooth count it's easily replaced.
 
Why can't it be repaired? Drill holes parallel to the mating surfaces and bolt it together? It would not be able to slip. Drastic fix, just a thought.
 
Second case

I now have this issue also. I thought it was the starter, it was making a squealing noise, finally got some help and was able to watch it operate and could see it spin on the gear support. I'm going to try "Stud and bearing mount", a Locktite product and see if it holds. Other thoughts I have are to have the support surface knurled. I doubt it's financially feasible to have a machine shop repair it.
Other thoughts are appreciated, I doubt the previous suggestion to bolt it would work.
Tim Andres
 
You have nothing to lose, Don't think the gear is heat treated. Why not try bringing the ring gear up to a dull red heat and let it cool to see if it will "heat shrink" enough to tighten up and have enough friction to withstand the starter motor torque.
 
chuckh1197 said:
Have no idea. Just went to start it and it wouldnt start. As I said mechanic ant Reno Flying Service , who works on lots of planes says he has never seen this before. Says that it cant be fixed as it is a press fit and flywheel or gear has probably worn.
Click to expand...

The ring gear is not a "press fit" and if that is the way it was installed, that could possibly be the cause of the problem. Doing it that way may have shaved metal from the flywheel. RVSXER (Mike Hilger) has the procedure right.

Joe
 
chuckh1197 said:
Have no idea. Just went to start it and it wouldnt start. As I said mechanic ant Reno Flying Service , who works on lots of planes says he has never seen this before. Says that it cant be fixed as it is a press fit and flywheel or gear has probably worn.
Click to expand...

It is actually referred to as an interference fit, requiring either pressing or heating/cooling for assembly. The latter is used in this case. Either the gear assembly dimension has grown (wear, stretching or crack)or the flywheel dimension has shrunk or both. My $ is on failure of the gear assembly (crack). I would cut off the the gear assembly and mic the flywheel assembly. If it is in spec and without cracks, just put on a new gear assembly.

Larry
 
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tim2542 said:
I now have this issue also. I thought it was the starter, it was making a squealing noise, finally got some help and was able to watch it operate and could see it spin on the gear support. I'm going to try "Stud and bearing mount", a Locktite product and see if it holds. Other thoughts I have are to have the support surface knurled. I doubt it's financially feasible to have a machine shop repair it.
Other thoughts are appreciated, I doubt the previous suggestion to bolt it would work.
Tim Andres
Click to expand...

I would proceed cautiously with this approach. The interference fit is a proven, reliable method of retention. There is a reason that it is no longer tight (something has failed or the original parts were not machined to spec) and you need to figure that out. It is quite unlikely this problem can be solved with adhesive. I am not an Engineer, so couldn't tell you what the interference fit is, but not likely greater than .020" (smaller parts are usually .003 - .005, depending upon the material(. I don't see how you could have it knurled with that little tolerence. While Knurling can work with steel, not sure that applies to aluminum. Also, it would also greatly reduce the contact area between the parts, reducing the holding strength.

Larry
 
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lr172 said:
I would proceed cautiously with this approach. The interference fit is a proven, reliable method of retention. There is a reason that it is no longer tight (something has failed or the original parts were not machined to spec) and you need to figure that out. It is quite unlikely this problem can be solved with adhesive. I am not an Engineer, so couldn't tell you what the interference fit is, but not likely greater than .020" (smaller parts are usually .003 - .005, depending upon the material(. I don't see how you could have it knurled with that little tolerence. While Knurling can work with steel, not sure that applies to aluminum. Also, it would also greatly reduce the contact area between the parts, reducing the holding strength.

Larry
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Thanks all. I did reinstall it today using permatex sleeve retainer. From its spec sheet it's designed for just this type of issue and is suppose to be good for 3000 psi shear, there is roughly 16" of area, so that multiplies up to a impressive figure. I don't have micrometers near this large to measure, but it is still an interference fit and required heating per Lyc's instructions to install.
I agree with Larry, it probably won't work, but for $7 Ill give it a shot.
I have it indexed and if it moves any at all I replace it. In fact Im shopping for one now, if anyone knows of a 12/14 pitch (149 tooth 0-360) 9-3/4" pulley, 1/2" prop bolt support please advise!
My luck I just sold one a few months ago.
Tim
 
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