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#1
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IO 360 G (1500Hrs. since new, 1977)
Question guy's. My 77 337 G's front engine is the original just into the 1500 hrs running great (knock on wood) however it has not been trouble free either. (2) alternator failures, the shaft both times sheared where it exits the alternator body. I am not sure if it isn't something I induced. Have one of them fancy gauges that tell all, which alternator is or is not doing any work. I would shut down the one that was working to make the one not working work. Maybe not the thing to do. The last one that failed was replaced was a new one. A closer look at the last one to fail looked as thou the machineing was not radius', just a machined turning and then stoped, that is where it sheared. I don't do that any more and have the (2) alternators balanced closely. the first one to fail or stop any out put was a disaster. The drive gear on the alternator to the cam gear damaged the cam gear. needless to say what had to be done. My suggestion here would be to land as soon as a sutable field is available to see if the shaft is still in tact. One can reach in on the non turbo's and check the fan and see if it is still connected or if it has sheared. Back to the engine. It is using about one qt. the first 10 hrs. then increases slightly to (8) and then to (7) then changed at about (30) hrs. Oil analyses are fine. Think I should just press on???? Its (25) years old and I have had it about (11) years. Guy Paris....
Last edited by Guy Paris : 08-17-02 at 02:16 PM. 
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#2
08-11-02, 11:58 PM
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Guy, very interesting.
I have experienced 2 alternator shaft failures on the rear engine of my T337G. Failure was in exactly the same position you describe. Really looks like a manufacturing fault - no radius at point in shaft where the diameter changes. I could possibly count a third failure too - of the Lord Coupler...probably it failed first and saved the shaft...I changed to the Continental Coupler at that point. All 3 failures have been within the last 600 hours. My theory is that the Lord coupler allows some 'flex', and it is this which weakens the rubber compound - leading to the regular failure of the Lord coupler we're familiar with. In this case it seems the lesser of two evils - at least you don't have to remove the engine - the Lord coupler doesn't snap the shaft sending bits of steel shaft through the engine! The feedback I've been getting suggests that the IO360 has an inherent vibration which manifests itself here...any ideas? Anyone else had similar problems? I know Blair Howe had problems with the vac pump drive. Regards, Damon
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#3
08-12-02, 01:41 PM
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Re drive couplings and shaft.
Problem is an inherent design problem with the shaft. It is not perfectly aligned which causes problems. Niagra air parts has developed a new fix for the problem and are working on the STC as we speak. Saw the new design last thursday. They also have new oil coolers at 50% of the price of new ones which makes overhauls less attractive. They also have a new lightweight replacement starter for the 360s which will cut 18 lbs off and improve reliability. The bendix spring on the old starter couplers gave lots of problems. Fyi Bob
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#4
08-13-02, 05:29 PM
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Well... Yes and No......
I thought we went over this issue with the alternator stuff written in great depts before... but, as to the two couplers... the cont one is much better... why because it doesn't have the rubber potting problem that is caused by the heat and oil impregnations...
also the alignment problems is not as great as one would think.. Bob... as the gear is held by the bearings on the alternator thru the shaft and a bushing that controls movement... and while I agree its kinda a flakeie design... their are millions of cont engines out their from 0-200s on that are using them... and they have a good life expectancy... No rather because your breaking the shaft... something else is happening... which can range from the cam gear and its bearing in the case being worn out... to the alternator its self and the instanious power loading... and these range from the bearing in the alternator.. the reason we say change them ever 500 hours... to the gear motor in the plane spiking it when you flip the gear handle... it is this spike that will demand that the alternator go from a low current setting to a high one suddenly.. and requiring more hp in a instant... which puts a larger load on the coupler and invertenly on the gear... Also engine RPM... plays a part.. after all if your crusing along.. the alternator mass is real happy at what ever RPM its spinning at... but, if you go to a lower RPM.. and demand the same power thru the shaft... it gets to vibrating by the gear tooth messhings and not... Now as to the issue again of the larger alternators... 65 amp... the engine was never designed for it... the gear is at its max when you put it in.. and that includes the shaft from the alternator.. unless they change their dia and design ... they will have quite a large loading on the little shaft... and with the gear hanging almost 3 inches off the nose of the alternator... think of the stress that the little gear is putting on the shaft... when your demanding all that power... kinda wants to make the cam gear force the alternator gear out of mesh.. reason for the gear vibration and groan... Another thing we have found is that the shiming and locking nut on the end of the shaft... is incorrect... in other words some bozo... cranked it down until it bound up the whole mess... when in fact he didn't put the gear assembly on the shaft correctly and check its seating... the gear is supposed to have some play in it... (rotary) If it doesn't then something is binding and yes you can snap the shaft off...because the coupler can't do its job of dampning the vibrations... and load spikes... Most mechanics don't even know that their is a overhaul manual... that specs out the tolarances for assembly of the drives... actually cessna sells it.. yep it a charging system manual.. even covers the regulators and the changes that took place... and shows the design of the highly reguarded 400 series... which we have covered before... you don't need it.. never will and its a bandade for the real problem that is happening... Oh and one last thing to check... is contenuity... of the connections... ya we found one that the output post/stud was lose on... because again some bozo over tightened (actually the owner did it himself and was real proud that he found it lose and thus cranked it down with his little wrench)... and cracked the plastic insulator... it was bouncing around and this caused a lot of problems in the system that one would not think the stud was.... and yes he changed the regulators thinking that everyone else knew what was right for him... besides the regulator change... and the new overhauled alternator... it was a cool 3 grand... and the system was finally back where it should have been.... smile... so before you leap into ... lousy design... you might want to go check the connections... 90%of what we find... it connections that have gone bad.. not the mechanical equipment... And a few simple rules... replace alternator bearings and have it overhauled every 500 hrs.. for the high flyers.. more often... Use a battery in line with your voltmeter to check connections... that way you can see the IR drop... otherwise the connection could look good... and really be bad when the current demand flows... Don't jump to conclusions.. early.. on... their is nothing wrong with one altenator taking the load... as you need more.. it will bring the other one on line to suplement the output demand... and actually the offset will keep them from doing something else that will break shafts and shear couplers... called alternator bounce... where they oscilate back and forth with the output... that is not good... resulting in both of them tripping off line eventually.... so for you all who want the alternator balanced... beware of the alternator bounce/osclation... it can damage your engine/drives and alternators... but, as we mentioned before... the fact that their is a differance in the cable IR drop/lengths... this hasn't been as much of a problem as one would think...as cessna engineers lucked out on the position of the engines... etc... smile... What ever happened to the articles that were written on this subject... does anyone have a copy of them that they could repost... I see that their were only two people who want to have a siminar on the alternators and charging system.. so I guess we won't schedule anything for it... must not be a topic of interest... Hmmmmm AC in a plane has no place... except in the wet hot state of florida.... I kept hearing the words... we should give it back to the indians... but, they probably took the money and ran to the north... thinking the settlers were stupid and would want their money back onece they lived their a while... why... we fond that just lifting your glass to drink water you swett...more than you drink.... smile... GMAs
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#5
08-13-02, 08:52 PM
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SAC
See, I'd love to come to the meeting in Sacramanta, except I can't spell it, and it doesn't have a beach. Now, if you held the charging seminar at Treasure Cay, I bet a bunch of folks would show up. Great Beach, too. So, lets make that part of the seminar at Treasure Cay in the Spring.
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#6
08-13-02, 11:14 PM
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GMAs,
Something you said in your last post really hit me. "kinda wants to make the cam gear force the alternator gear out of mesh.. reason for the gear vibration and groan..." ahhh this makes some sense. I've looked at the shaft after failure, and it is not a 'torsional' failure, rather a fatigue crack starting at the point where the diameter of the shaft steps down as it leaves the alternator. I couldn't figure how the shaft was snapping in this way if it were being loaded normally - the failure wasn't consistent with the forces. However, as you say, the higher torsional load pushes the alternator drive gear further out from the accessory drive...now that makes sense, the bending of the shaft will cause the fatigue and failure I've seen. As to alternator life - I'm more than happy to overhaul at the 500 hour life...I'd just like to get that long without having to remove it from the engine again! The last two failures have been within 250 hours! Now, thinking about the loads being demanded, I don't know how well the alternators are sharing the load (or whether they're fighting), so I'd better install the IE volt/ammeter to see what's going on here. I don't have the flickering lights syndrome - well not anymore anyway - replaced most of the compontents on the front firewall some time ago and no trouble since...however, I do cycle the gear frequently (my normal stage length is less than 20 minutes between airports) - and I agree with you that it is a very high instantaneous current demand. What can I do to soften the blow to the alternators? How about huge capacitors on the gear circuit? Damon
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#7
08-15-02, 08:37 PM
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Ahhhh... well you already have a big capacator....
Its called the battery... it probably is the biggest one on the plane... but, how to soften the blow.. from the gear pump... well hmmmmmm I would say give it more time between cycles... however that wouldn't really be quite practicle...
However... the two alternators are preforming.. if they are putting out... but, rather its the gear pump motor that is dragging more current out of them causing them to have to respond with more output in current... I would check the gear pump motor for a higher than normal current pull... you may find your problem their... As to the rest the cont engine drive coupler is probably the best one around... if installed correctly... the rubber dampners in the cup will usually take any surge pulses in power out a little.. after all they are miniture version of the mag couplers... and they snap along at anything below 800 rpm... so the alternator is just a scaled down version of that... It would be hard to say if your alternator drive shaft is bad or not out of the box... most are not made anymore... so we only have the ones that were made by ford or autolight... another thing I would do is go look closely at the oil pump drive gear... with a good inspection mirror... and see how those gears are doing too... if the cam bearing in the back is out of limits.. you will see that gear also wearing funny... actually it only runs on half a tooth... smile... leaving only about 1/8 inch to drive the oil pump... but, we have seen that for years... it is the meshing of the gears that you want to check... and to do that if you can't see the wear pattern is to take some persion blue.. grease or some other indicator.. and coat the gear... then pull the engine thru a couple of times and you can see the wear pattern as the bluing will be gone where the gears make contact... and if the gears are not seating correctly.. on the high side.. miminal tooth contact.. then you need to find out why the cam gear is not runing right or the accessory case is not aligned right... as the oil pump and alternator both are relieing ont the alignment of the accessory case to keep the gears in mesh... We have seen accessory cases repaired that did not meet the alignment specs... and thus had to replace them with others... this could be your problem too... so do the gear check and see... then get back to us... with the report... GMAs
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#8
08-16-02, 09:43 PM
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True enough, the battery is one heck of a filter! I sure wouldn't want to cope with what it puts up with!
Will have a look at the gear motor for current draw, good advice. What should it be when in good health? This last alternator drive shaft failure spread some metal about, and since we didn't have much left to run, we've decided to pull the engine and replace...but I'll have the guys check the accessory gear on the engine currently being built to go into the rear, as you suggest. I'll also have them take a look at the engine we've removed to see if there's any evidence of a problem there. Thanks, Damon
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#10
08-17-02, 03:50 PM
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What !!!!!
Hey give us a call back when you get to 1700 hrs on the engine... till then just enjoy... it should be able to make it that far... smile... If its got the NON VAR crank... wear it out.. because your not going to be able to use it again except for a mail box stand.... smile... Same with the cyc's.. en all... only thing you will be keeping is the cam the gears...the cases... and the accessories... the rest are just so many scrap parts... GMAs...
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#11
08-17-02, 09:56 PM
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I agree with Gmas, with the proviso that there is no metal in the filter (or rather, no abnormal amount of metal). If it is not "making metal", and the compressions are reasonable using Continental's test procedures, my number would be 1800 hours. Seneca engines (very similar to ours) have had their TBO increased to 1800 hours. I ran my last one to 1650, it was still going strong.
My 2 cents, worth what you paid for it. Kevin
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#12
08-20-02, 12:15 PM
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non - turbo
The front engine on our plane was 250 past TBO when we bought it, and it was just starting to make metal, but we replaced it at that time, as part of the acquisition.
I will take exception to what GMAs said, about wearing it out. They will want the engine to be in one piece when you go to get another, so you don't want to run it until it completely fails. Also, it is more economical to purchase the Factory ReMan engine than having yours overhauled. Even if you had a VAR crank, you're looking at <$2K difference between overhaul and ReMan. Obviously, if you have a non-VAR crank, the cost is substantially more. So, a question.  If they get an engine in with a non-VAR crank, is it likely (possible) that they will use that crank in another engine? I was talking to a person with Lycoming powered plane, this AM. He was telling me that the crank in those are being replaced in the engines that are 300HP or greater, his, but the same crankshaft part number is found in the 260 HP engines. In theory, they could take that crankshaft out of his engine, and use it in a rebuild of a 260 HP engine. Also, he expects to be down somewhere between 1 - 10 months.
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#13
08-21-02, 09:55 PM
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GMAS,
In a previous post in this thread, you mentioned an overhaul manual that the alternator drive couplings should be assembled with reference to. Do you have the name of the manual handy? I'd like to ensure that the coupler is assembled the way Cessna intended...just to cover all the bases I can! Thanks, Damon
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#14
08-23-02, 04:47 PM
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Yep we do.... smile
its the alternator charging System service/parts manual D5107-13
and it can be gotten from your local cessna dealer... or parts person... but, it is for the alternator and regulators...and goes into detail on overhaul of such... the actual assembley of the cont drive is located in the engine overhaul manual under alternator assembly sub groups... where it says to install nut and tighten to 175 inch pounds torque. If necessary, the nut may be tightened further to align the cotter pin hole with the nut slots, but do not exceed 200 inch lbs, install cotter pin 12... the engine overhaul manual is avab.. from sac sky ranch or TCM for your particular engine... the other manual that should be also gotten is the parts manual.. again for your engine... both can be gotten on microfilm and I think now on CD for the computer... this ones part no.. that I grabbed off the rack is Part no X30594A... and they have superseasions.... which changes the number slightly but, you should be able to find the new one by the old no... they can cross ref it... and if you go to the TCM site.. they usually have the new torque values that you can print out...as a SB or SID... actually its SB-96-7 (just checked it out on their site...) these are the latest and greatest.. and in their you will by thread size find the alternator nut... torque also... but, we suggest that everyone have not only the service manual.. illistrated parts manual but, also the engine overhaul manual and parts manual... or a copy... smile... but, we find it cheeper to buy direct... its much nicer as well as legal... smile... hope this helps...GMAs
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#15
08-25-02, 11:13 PM
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Very good of you!
Thanks
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