My OS 91 HZ after 10 flights ....

[Otatiaro]

No comment ... http://otatiaro552.free.fr/IMG_6850.JPG

Regards,
Thomas Legrand.

[Kjones3181]

what u think happened

[Otatiaro]

No idea ... I mailed the french distributor of OS Engine to try to activate the garantee (not sure of the word ;-) ).

But no real hope ... that's 200€ of spare parts.

[J-S-Q]

Here's mine after less than 20 flights with the needles set richer than the manual suggests for just running in (2.25 turns):

[PhnX]

Here's another one, not mine but a friend's. Engine just quit in the middle of the flight (was its 10th flight or so). We even tried to restart the engine but you know, there was a lack of "compression" . Well, i thought a hole in the piston is the best upgrade you can do for your engine.

[aneill75]

And all these engines were all running perfectly before the damage???? Temps were within reason?? Probably still kind of cool - just coming off of break in period?? Sounds and looks like they were run much too lean. Probably had GOBS of power, though.

Either way, it still sucks that they're toasted.......

HC

[3DBEAM]

you only have to see how dry the piston crowns are on both engines , i would be checking both the fuel / oil mix plus the carby settings as this is lean my boys.

[J-S-Q]

Well you would presume that it was obviously run lean but I checked absolutely everything I could think of. I knew something wasn't right because I had to have the needles so far out to keep it cool (2.25 turns).

The muffler was bolted on tightly with extra long bolts and 'Aero Lock' nuts.
I tested the whole fuel tank/plumbing system submerged under water and there were no leaks.
The cylinder head bolts were all tight.
The plug was brand new and well tightened.
I had disassembled and cleaned/checked the carb.
The clunk line was brand new, in perfect condition and with an OS bubbleless clunk.
I was using Wildcat 3DLV 30% purchased recently and with the correct shim.
I had used an IR temp gun a couple of flights prior to this and it was well under 100C -probably something like 80C, taken on the cylinder wall where it meets the head.

I just don't know what I did wrong but I'd welcome any advice as I'd hate to repeat this expensive experience! (this is my first 90 but have run 50's with no problems). When this happened I was running on a throttle curve of 0,45,90 and was advised by some guys at my club that the headspeed was sounding too high and that I should bring the curve down. The backplate was fairly warm but I wouldn't say too hot. I brought the curve down to 0,37.5,75 and then it blew.

[HeliBenj]

Originally Posted by Otatiaro

No comment ... http://otatiaro552.free.fr/IMG_6850.JPG

Regards,
Thomas Legrand.

Salut Thomas,

Bearing retaining cage broke and ball went into the chamber? I can't see another explaination for this kind of damage. How was the bearing before failure?

[davidz58]

This is scary.

I am currently running my 91HZ (about 8 to 9 tanks now) at about 1.3 turns on the high, and 1.5 on the mid, I get about 90degrees celcius measured at the bottom where heat sink meats head. Running on 15% nitro. This is basically normal flying with some WOT pitch pumps... no 3d.

Everything else seems good, sound, smoke, transition....power (given its 15%)

At anywhere more than 1.5 turns on the main and mid needle, the engine gets absolutly no power at all for me. outside temp about 22 to 25 degrees.

[outhouse]

Both engines above were a result of a typical lean run. no mystery there.


needle settings are only 1 cause of many that can cause a lean run.

jsq by the time you land the engine temps often drop sharply

needle settings at 2.25 indicate you have some other issue causing yours to lean out to run with the needle that far out. possibly carb related its juts s guess at this point but that needle setting is plain wrong. your buddies said to turn it down because it was overspeeding due to a lean condition. I can run a 91 at 100 flat all day slightly rich and it wont overspeed enough to cause damage.

i can break mine in at 1.5 its so rich. needle setting vary but not that much

[Otatiaro]

Originally Posted by Benoah

Salut Thomas,

Bearing retaining cage broke and ball went into the chamber? I can't see another explaination for this kind of damage. How was the bearing before failure?

Hello,

Nop ... both bearings are still in perfect condition.

Scientific France did not even bother to reply to my mails ...

Regards.

[outhouse]

Originally Posted by Otatiaro

Hello,

Nop ... both bearings are still in perfect condition.

Scientific France did not even bother to reply to my mails ...

Regards.

they generaly wont warranty a lean run anyway

the metal dings in the head are from the piston and ring breaking apart in flight

[J-S-Q]

Originally Posted by outhouse

Both engines above were a result of a typical lean run. no mystery there.


needle settings are only 1 cause of many that can cause a lean run.

jsq by the time you land the engine temps often drop sharply

needle settings at 2.25 indicate you have some other issue causing yours to lean out to run with the needle that far out. possibly carb related its juts s guess at this point but that needle setting is plain wrong. your buddies said to turn it down because it was overspeeding due to a lean condition. I can run a 91 at 100 flat all day slightly rich and it wont overspeed enough to cause damage.

i can break mine in at 1.5 its so rich. needle setting vary but not that much

I realised that something was obviously wrong but the frustrating thing is that I haven't managed to find the cause of it so I don't feel I've learnt a great deal from such an expensive mistake.

I checked absolutely everything I could think of. I disassembled/cleaned the carb, new fuel lines, new clunk line, check head and muffler bolts, carb fully seated etc etc. I don't know what else I could have done -that's the frustrating thing about it. The only thing I didn't change was the OS Bubbleless clunk which might possibly be at fault here -it had been lying on the shelf for 6 months (having come out of another heli) although I did clean it very thoroughly with alcohol and then fuel before use.

Anyway, yesterday I started running in a brand new 91HZ-R in the same heli (minus the bubbleless clunk) with the same fuel and it's running great -very cool at the recommended run-in settings.

[outhouse]

Originally Posted by J-S-Q

I realised that something was obviously wrong but the frustrating thing is that I haven't managed to find the cause of it so I don't feel I've learnt a great deal from such an expensive mistake.

I checked absolutely everything I could think of. I disassembled/cleaned the carb, new fuel lines, new clunk line, check head and muffler bolts, carb fully seated etc etc. I don't know what else I could have done -that's the frustrating thing about it. The only thing I didn't change was the OS Bubbleless clunk which might possibly be at fault here -it had been lying on the shelf for 6 months (having come out of another heli) although I did clean it very thoroughly with alcohol and then fuel before use.

Anyway, yesterday I started running in a brand new 91HZ-R in the same heli (minus the bubbleless clunk) with the same fuel and it's running great -very cool at the recommended run-in settings.

if the clunk was restricting flow it very well could have caused it.

Hope you have better luck with this one

[Otatiaro]

Hello,

Originally Posted by outhouse

they generaly wont warranty a lean run anyway

the metal dings in the head are from the piston and ring breaking apart in flight

Thanks a lot for those so smart replies ...
You KNOW it's a lean run, so tell me where does the lean condition come from, "no mystery" for you as you said.

You think it's my first nitro engine ?
You think this is normal that the distributor does not even reply to the mails ?
You know my needles settings, my engine and fuel line installation ?
You know the manufacturer's tolerances on parts milling ?

MY feeling is that you don't know anything, but just enjoy the "i told you" effect.


Regards.

[J-S-Q]

Originally Posted by outhouse

if the clunk was restricting flow it very well could have caused it.

Hope you have better luck with this one

Well that's the only real suspect at the moment. I tried blowing water through it from my mouth and it does seem to have slightly more resistance than I would expect but hard to say if it's normal or not.

[PhnX]

My example is also not definitely a lean run . I do not tune engines to their temps as this means nothing but I always tune the engine to give best smoke it can at all rpms. That engine was just about its correct tuning and was not lean, owner only hovered\forward flight with the heli and did not load the engine at all. Also the HS was not more than 1800 .


I tune many engines each day and see people tune their engines to death with their holy temp guns where they can actually somehow measure how much oil the engine is getting. In this case problem was not predetonation or tuning.

[outhouse]

Originally Posted by PhnX

My example is also not definitely a lean run . I do not tune engines to their temps as this means nothing but I always tune the engine to give best smoke it can at all rpms. That engine was just about its correct tuning and was not lean, owner only hovered\forward flight with the heli and did not load the engine at all. Also the HS was not more than 1800 .


I tune many engines each day and see people tune their engines to death with their holy temp guns where they can actually somehow measure how much oil the engine is getting. In this case problem was not predetonation or tuning.

if you dont tune by temp its no wonder your engine is blown. temps are everything.

doesnt matter how you fly or what headspeed if its lean it will blow. you cooked it hard plain and simple. Its %100 definatly a lean run.

[outhouse]

Originally Posted by Otatiaro

Hello,



Thanks a lot for those so smart replies ...
You KNOW it's a lean run, so tell me where does the lean condition come from, "no mystery" for you as you said.

You think it's my first nitro engine ?
You think this is normal that the distributor does not even reply to the mails ?
You know my needles settings, my engine and fuel line installation ?
You know the manufacturer's tolerances on parts milling ?

MY feeling is that you don't know anything, but just enjoy the "i told you" effect.


Regards.

well your missing the obvious, your cylinder is scorched and the side of the piston fried from lack of lubrication and heat as your piston expanded under this lean condition. it then dissintigrated itself.

i never stated it was your first nitro engine and nver ment you any dissrespect

and i think it sucks they dont reply to your emails . im just saying if they did they will say user error. OS warranty isnt the greatest and ive seen there track record and little shops dont look at it as there problem.

i dont need to know the parts size and milling lol or any of your other installation or needle settings. none of that matters i see the evidence. your motor got to hot and fried and a few other people stated you all had a lean condition.

its not about " i told you so" this is after the fact. You posted here and im not sure why with "no comment" maybe your trying to trash OS i dont know and dont care. Maybe you wanted a pity party.

you need to figure out why yours went lean and fix said problem or youll fry your new cylinder and piston/ring if you dont recognize the problem youll do it again.

its not all about needle settings and who knows how you broke your engine in or what tuning method your using. I know if your using %30 nitro and have 1 stock head shim theres a fine fine line between rich and toast your motor lean.