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912 gearbox problems??

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johngilpin

Joined: 23 Mar 2011
Posts: 93
Location: 004

Posted: Thu Feb 21, 2013 12:31 am Post subject: 912 gearbox problems??

Gday,



We're told that we should have the gearbox inspected at 600hrs especially if we've run much 100LL.

I haven't known anyone to really do that, and know of many engines well over 1000hrs, and haven't ever heard of any actual failures anywhere.....  Anyone have real life experience??

 



JG

  [quote][b]

jim.kulbeth(at)insightbb.
Guest

Posted: Thu Feb 21, 2013 4:13 am Post subject: 912 gearbox problems??

I have a friend in South Carolina with a 912UL with 1400 hours and it has exhibited  no problems of any kind. Here in US we use a high RPM motor cycle oil. He plans to go to 2000 hrs, unless oil analysis starts to change. 



Best regards,

Jimmy



On Feb 21, 2013, at 3:30, JC Gilpin <j.gilpin(at)bigpond.com (j.gilpin(at)bigpond.com)> wrote:

[quote]Gday,



We're told that we should have the gearbox inspected at 600hrs especially if we've run much 100LL.

I haven't known anyone to really do that, and know of many engines well over 1000hrs, and haven't ever heard of any actual failures anywhere.....  Anyone have real life experience??

 



JG

   	  Quote: 	
		  

	


[b]

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Thu Feb 21, 2013 5:04 am Post subject: 912 gearbox problems??

Why would the type of fuel used have any affect on the gear box?  Does the fuel go through or into the gear box?



Thought the engine had 2000 Hour TBO?

Barry



 On Thu, Feb 21, 2013 at 3:30 AM, JC Gilpin <j.gilpin(at)bigpond.com (j.gilpin(at)bigpond.com)> wrote:

[quote] Gday,



We're told that we should have the gearbox inspected at 600hrs especially if we've run much 100LL.

I haven't known anyone to really do that, and know of many engines well over 1000hrs, and haven't ever heard of any actual failures anywhere.....  Anyone have real life experience??

  



JG

   	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	
[b]

BruceOviatt

Joined: 13 Feb 2011
Posts: 3

Posted: Thu Feb 21, 2013 5:34 am Post subject: 912 gearbox problems??

I just had an inspection and  spalling of the gears was found.   So the rebuild and new gears cost  $1000.

  

 The possible cause was not  using oil with gear additive. THe LEAF tech recommended Amsoil motorcycle  oil.

  

 Kitfox III

 Rotax 912ul 600 hours.  

  

  

 [quote]   ---

peteohms

Joined: 31 Oct 2007
Posts: 224
Location: Leander, TX

Posted: Thu Feb 21, 2013 6:07 am Post subject: 912 gearbox problems??

I did my 600 hr while attending Rotax Service and Maintenance school.  I have an older 912.  Had to replace some obsolete parts.  Glad I did.

Pete



On Feb 21, 2013, at 2:30 AM, JC Gilpin <j.gilpin(at)bigpond.com (j.gilpin(at)bigpond.com)> wrote:

[quote]Gday,



We're told that we should have the gearbox inspected at 600hrs especially if we've run much 100LL.

I haven't known anyone to really do that, and know of many engines well over 1000hrs, and haven't ever heard of any actual failures anywhere.....  Anyone have real life experience??

 



JG

   	  Quote: 	
		  

	


[b]

_________________
Pete
Leander, TX
Kitfox III, 912ul, Grove

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Feb 21, 2013 6:11 am Post subject: Re: 912 gearbox problems??

Here's why Guys,



The gearbox inspection is at 600 hrs. for 100LL users and or 1500 hr. TBO engines and 1000 hrs. for the 2000 hr. TBO engine with the use of 91 OCT unleaded fuel. If the 2000 hr. engine uses 100LL then it is also in the 600 hr. range.



If you have a 912UL without a slipper clutch not quite as important, but if you have a 912ULS then it is. If you use more than 30% 100LL and especially if you use it all the time the lead paste accumulates in the slipper clutch. [u]At about 800 hrs. your clutch is pretty much useless.[/u] Will you notice it in the cockpit, no, but if you have a prop strike it sends all the shock to the engine. So now instead of a gearbox protecting your engine you now just twisted your pressed together crankshaft and your going to spend about $10K- $12K to get it fixed. You can not split the clutch at home. It takes a special jig and 540 ft/lbs to separate it and there are only 4 places in the country that can do it. The lead paste will be so bad it takes lots of solvent and scrubbing to remove it and make the clutch useful again. Now if you live in a humid climate 100LL mixed with moisture will cause acid and that will erode the gear splines and pit them. As you get up in the higher hours the gearbox Bellville washers loose their tension and your slipper clutch torque drops off so the gearbox should be re-shimmed. Poor shim tension and eroded gear sets cause vibration and kickback situations that are transmitted right to the rest of the engine.

The 912UL should be inspected too, but it gets checked more for the washers, bearings and gear erosion.

For these guys that never maint. their engine ignorance is bliss and  there are tons of stories out there where guys engines fail and they say they just don't understand why. Just because you haven't heard of one doesn't mean they don't happen all around the world everyday. The idea is to stay in the air safely, spend a little now with less down time verses joining the ranks of the crashed, expensive and excessive down times and do it with a little preventative maint. 

The other issue that causes gearbox decline is the wrong oil or a poor ZDDP (zinc phosphate) ladened oil. You absolutely should use a good motorcycle oil. Some are better than others, but these have special additives for use in an engine that uses its engine oil in the gearbox. The ZDDP is a sacrificial coating that helps protect the gears and parts from rubbing metal to metal. Car oils do not have this as it will mess up the catalytic converter. Amsoil motorcycle oil has 1400ppm of ZDDP and Aero Shell Sport Plus 4 has about 1800PPM. Both are good oils. Up to a point the more ZDDP the better. Never use a straight weight oil as that will be an engine killer and do not use a straight mineral based oil like Pensoil or one of the others. You should be using a good semi or full synthetic motorcycle oil. Don't use a full synthetic oil with 100LL as it does not suspend the lead and it will fall out every where in the engine and gearbox. The semi synthetic will suspend the lead and help carry it out with the oil drain. You should also be using a lead scavenger like Decalin if you use 100LL fuel.

Here is an oil article:



http://ctflier.com/index.php?/blog/3/entry-16-oils-a-fluid-discussion/



Hec they change the oil once a year, plugs every 3-4 years and wrote 3 lines in their logbook for an inspection once a year, but never read the maint. manual to what or how things should have been inspected and then it was Rotax's fault when they have to spend $1K-$10K to get their engine fixed.

you can't see or feel problems just by staring at the outside of the gearbox. It needs to be opened up.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Last edited by Roger Lee on Thu Feb 21, 2013 6:27 am; edited 1 time in total

pjeffers(at)talktalk.net
Guest

Posted: Thu Feb 21, 2013 6:18 am Post subject: 912 gearbox problems??

Very simplistically the same oil that lubricates your pistons and bearings also lubricates the gearbox.  The oil on and around the cylinder walls comes in contact with, amongst other things, the lead in leaded fuel should you be using low lead.  The lead remains in the oil and deposits on all surfaces that it comes into contact with.  Gear boxes don’t much like lead.  

Some of the later engines have an ultimate life of 2000 hrs.  Other older ones can be limited to 1200 or 1500 hrs.  All are subject to recommended 600hr gearbox inspections.  Engines run on Low Lead show substantial lead build up in the gearboxes.  

   

Pete Jeffers  

         

  

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of FLYaDIVE

 Sent: 21 February 2013 13:04

 To: rotaxengines-list(at)matronics.com

 Subject: Re: RotaxEngines-List: 912 gearbox problems??  

  

   

Why would the type of fuel used have any affect on the gear box?  Does the fuel go through or into the gear box?    

   

    

Thought the engine had 2000 Hour TBO?  

    

   

    

Barry    

On Thu, Feb 21, 2013 at 3:30 AM, JC Gilpin <j.gilpin(at)bigpond.com (j.gilpin(at)bigpond.com)> wrote:  

Gday,    

   

    

We're told that we should have the gearbox inspected at 600hrs especially if we've run much 100LL.  

    

   

    

I haven't known anyone to really do that, and know of many engines well over 1000hrs, and haven't ever heard of any actual failures anywhere.....  Anyone have real life experience??  

    

   

    

JG  

   	  Quote: 	
		    ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-Listtp://forums.matronics.com_blank">http://www.matronics.com/contribution 	


  

   

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       [quote][b]

BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Thu Feb 21, 2013 6:42 am Post subject: 912 gearbox problems??

Very interesting - - - So that would mean:

1 - You are getting Blow-By on the rings and putting burnt or partially burnt fuel and the byproduct of lead into the engine oil.

That would be either a poor design or bad cylinder & rings.

 2 - Even if you were getting fuel into the engine oil, the fuel would only evaporate quickly.  Adding fuel to engine oil is an old trick in extreme cold to thin the oil.

So I can't see that being a problem for the gears.  Other issues YES.  I don't want blow-by.

 3 - Still, if you were getting burnt fuel - - Lead, into your fuel your oil filter would or should remove the lead.  It wouldn't it be the same type of lead you see on spark plugs?

4 - If you are getting lead and everything else with the engine is good.  The problem is you are running too rich.  Lean more - Use a hotter plug - Use a hotter spark.

 5 - The chemical Tetraethyl lead in liquid form does nothing physical to steel.  In burn form it is conductive and abrasive.  But, again how would it, in that form get to the gears?

 



Barry

  

On Thu, Feb 21, 2013 at 9:17 AM, Peter Jeffers <pjeffers(at)talktalk.net (pjeffers(at)talktalk.net)> wrote:

[quote]                

Very simplistically the same oil that lubricates your pistons and bearings also lubricates the gearbox.  The oil on and around the cylinder walls comes in contact with, amongst other things, the lead in leaded fuel should you be using low lead.  The lead remains in the oil and deposits on all surfaces that it comes into contact with.  Gear boxes don’t much like lead.  

Some of the later engines have an ultimate life of 2000 hrs.  Other older ones can be limited to 1200 or 1500 hrs.  All are subject to recommended 600hr gearbox inspections.  Engines run on Low Lead show substantial lead build up in the gearboxes.  

   

Pete Jeffers  

         

  

From: owner-rotaxengines-list-server(at)matronics.com (owner-rotaxengines-list-server(at)matronics.com) [mailto:owner-rotaxengines-list-server(at)matronics.com (owner-rotaxengines-list-server(at)matronics.com)] On Behalf Of FLYaDIVE

 Sent: 21 February 2013 13:04

 To: rotaxengines-list(at)matronics.com (rotaxengines-list(at)matronics.com)

 Subject: Re: RotaxEngines-List: 912 gearbox problems??  

  

   

Why would the type of fuel used have any affect on the gear box?  Does the fuel go through or into the gear box?    

   

    

Thought the engine had 2000 Hour TBO?  

    

   

  

  

Barry    

On Thu, Feb 21, 2013 at 3:30 AM, JC Gilpin <j.gilpin(at)bigpond.com (j.gilpin(at)bigpond.com)> wrote:  

Gday,    

   

    

We're told that we should have the gearbox inspected at 600hrs especially if we've run much 100LL.  

    

   

    

I haven't known anyone to really do that, and know of many engines well over 1000hrs, and haven't ever heard of any actual failures anywhere....  Anyone have real life experience??  

    

   

    

JG  

   	  Quote: 	
		    ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-Listtp://forums.matronics.com_blank">http://www.matronics.com/contribution  	


  

   

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[b]

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Feb 21, 2013 7:18 am Post subject: Re: 912 gearbox problems??

Hi Barry,



The Tetraethyl lead mixed with moisture is what causes erosion from and acid formation. Yes the rings have some blow-by. You see this when you do differential compression checks and sometimes pass the valves too. If you do a compression test on the Rotax you will hear air coming through the oil tank. No cylinder is perfectly air tight or you would have a differential leak down during the test. The oil is returned to the oil tank with crankcase pressure and there has to be a means for that pressure to get there. The oil filter will not remove the lead as it is too small and it continues to circulate. When you drain the oil you can see the grey lead and if you remove the oil tank and open it up you can wipe the lead paste in the bottom out. By using a semi synthetic oil you keep the lead in suspension. Oil and fuel leaks may not combine because of more than one cyl. ring, but that really depends on the ring condition. The lead build up on the plugs is just burnt lead that adhered to the plug. You will get lead build up on the valve, it infiltrates the valve guides, drops out in the gearbox and crankcase, coats the top of the pistons. There is nothing good about 100LL to your engine. Running lean or rich won't stem leading. Lead is lead and it gets burnt on or falls out of solution. The lead in the suspended oil gets into everything. I have seen 1000-1500 hr. engines that have used nothing but 100LL and what a mess. The lead causes just as many issues in air cooled Continental's and Lycoming's. It has just been a fact of life and an evil they had to live with all these years.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

mortweaver(at)sbcglobal.n
Guest

Posted: Thu Feb 21, 2013 9:52 am Post subject: 912 gearbox problems??

How much or little does the use of fuel additives like Decaline/TCP help with use of leaded fuel?  

Dave Weaver N912GR



Sent from my iPhone



On Feb 21, 2013, at 10:18 AM, "Roger Lee" <ssadiver1(at)yahoo.com> wrote:



 	  Quote: 	
		   

 

 Hi Barry,

 

 The Tetraethyl lead mixed with moisture is what causes erosion from and acid formation. Yes the rings have some blow-by. You see this when you do differential compression checks and sometimes pass the valves too. If you do a compression test on the Rotax you will hear air coming through the oil tank. No cylinder is perfectly air tight or you would have a differential leak down during the test. The oil is returned to the oil tank with crankcase pressure and there has to be a means for that pressure to get there. The oil filter will not remove the lead as it is too small and it continues to circulate. When you drain the oil you can see the grey lead and if you remove the oil tank and open it up you can wipe the lead paste in the bottom out. By using a semi synthetic oil you keep the lead in suspension. Oil and fuel leaks may not combine because of more than one cyl. ring, but that really depends on the ring condition. The lead build up on the plugs is just burnt lead that adhe!

 red to the plug. You will get lead build up on the valve, it infiltrates the valve guides, drops out in the gearbox and crankcase, coats the top of the pistons. There is nothing good about 100LL to your engine. Running lean or rich won't stem leading. Lead is lead and it gets burnt on or falls out of solution. The lead in the suspended oil gets into everything. I have seen 1000-1500 hr. engines that have used nothing but 100LL and what a mess. The lead causes just as many issues in air cooled Continental's and Lycoming's. It has just been a fact of life and an evil they had to live with all these years.

 

 --------

 Roger Lee

 Tucson, Az.

 Light Sport Repairman - Maintenance Rated

 Rotax Repair Center - Heavy Maint. Rated

 Home 520-574-1080  TRY HOME FIRST

 Cell 520-349-7056

 

 

 

 

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 http://forums.matronics.com/viewtopic.php?p=394750#394750

pestar

Joined: 11 Apr 2007
Posts: 61
Location: Auckland, New Zealand

Posted: Thu Feb 21, 2013 11:37 am Post subject: Re: 912 gearbox problems??

This is a question directed to Roger.  What is Rotax's position on the use of Decalin.  I live in New Zealand but when I was in the USA purchased a couple of bottles of the product from Aircraft Spruce and when using 100LL use it.  In NZ there is little experience of the product and  no knowledge of Rotax's position.



Cheers Peter

_________________
Peter Armstrong
Auckland, New Zealand
DynAero MCR-4S (Do not shoot me Smile

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Feb 21, 2013 2:31 pm Post subject: Re: 912 gearbox problems??

Hi Guys,



Decalin and TCP are both lead scavengers. They help keep the lead soft so more of it blows out the exhaust and doesn't stick to your engine surfaces. It isn't a cure all, but definitely helps. Decalin is not near as harsh as TCP to your painted surfaces and is okay to keep in the cockpit if need be. Most of the pilots I know have all switched over to Decalin from TCP. Rotax's position is its okay, but have not tested it like they haveTCP because it has been around longer and more available around different aaa of the world. I use and have used Decalin for years when I travel and can't get 91 oct.

Other wise I only use 91 oct. and our fuel does have 10% ethanol.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Last edited by Roger Lee on Tue Feb 26, 2013 8:06 am; edited 1 time in total

johngilpin

Joined: 23 Mar 2011
Posts: 93
Location: 004

Posted: Fri Feb 22, 2013 12:48 am Post subject: 912 gearbox problems??

So the lead causes the clutch to lock up rather than slip easier. 

 If a torque check on the friction clutch is right on spec, does that mean  that any lead that might be present isnâ€™t really a problem??

  

 JG

   [quote][b]

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Fri Feb 22, 2013 5:59 am Post subject: Re: 912 gearbox problems??

Roger is spot on regarding lead buildup in the gearbox slipper clutch. A couple years ago, I did a gearbox inspection on the Diamond Katana which I am now part owner. The type certificated Rotax engines, in this case 912-F3, all use the slipper clutch in the gearbox, even the 80 hp ones like in the Katana. Before I bought into the airplane it had been flown exclusively on 100LL for its 1000+ hours at the time of its first gearbox inspection (yes, way overdue). 



The gearbox was in fine shape except for the slipper clutch which I sent to Lockwood Aviation for cleaning and inspection. They told me they had never seen a clutch so badly gummed up with lead as this one was. It has been back in service now for more than a year and we did the auto-fuel SB to allow us to fly the Katana with E10 of 87 octane (80 hp engine). 



I burn 87 AKI E10 during most of the year when flying regularly but when winter comes I fill the tank with 100LL and end up using less than one full tank of 100LL/yr because the winter wx here does not allow much flying. Because this is a type certificated engine/airplane, fuel additives like Decalin or Stabil are not permitted. If Stabil were permitted I'd keep auto-fuel in the tank all year, with Stabil added for winter, and use 100LL only when traveling where auto-fuel is not available. I use 100LL in the winter, when it is rarely flown, because it does not deteriorate quickly like auto-fuel does. But I do use Formula Shell semi-synthetic oil which is on Rotax's list of approved oils.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Fri Feb 22, 2013 12:49 pm Post subject: Re: 912 gearbox problems??

Lead will not lube anything in our engine and it will gum up the slipper clutch and leave deposits all over. When you do a friction torque test on the gearbox it has nothing to do with the clutch itself. It is only testing the amount of pressure the Bellville washers are exerting on the dog gear set through its 30 degree arc and 15 degrees if you have an older engine or gear set. Typically the higher the test numbers the better. Average is usually 440-485 in/lbs.

If you can stay away from 100LL as much as possible you are way ahead of the extra maint. cost and time involved. The other problem is most owners don't maint. their engine enough or read the manual so by the time lead is a real problem it has done its damage. 100LL users must change oil more often (25 hrs) and they have shorter maint. time schedules for other components compared to 91 Oct. users.



100LL is a costly fuel in more ways than one.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Gtblu

Joined: 18 Jul 2006
Posts: 37
Location: Australia

Posted: Tue Feb 26, 2013 4:18 am Post subject: Re: 912 gearbox problems??

Hi Guys,

My Rotax 912 uls oil changes every 50 hours max, and plugs, little 100 avgas mostly premium unleaded, 1074 hours suddenly vibrates at 3000 revs. 



gearbox cogs replaced... all good! 



Don't know what would have happened if I hadn't replaced the gears, but the point is a "stitch in time". It's all very well to not follow a maintenance schedule and think its OK, or even to follow meticulously a schedule and think its all OK, but the truth is, ignore the everyday signs of your engine at your own peril. If it sounds wrong, go looking, if it behaves differently, go looking, if it leaks oil , go looking. If the gauges show a change.., if your fuel consumption increases.. etc etc.



And you still may miss something of course, but the name of the game is keeping the odds in your favour. 



The way we jump into cars now without even a cursory glance under the hood isn't good training for a pilot! 



cheers



Gt

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