Burned down units
 

Here is my fine example,

I had a horrific burndown lean run on 10% nitro and 20% Castor ,

she went black could not stop as its a controline model , but amazingly it still runs OK and richens up well and holds its tune right through

Its 10x6 prop it rips , it sat for years in the shed and the bearings dont scream , I cant belive it

Please show your burned down, well used , well crashed working motors, in a close up with details <br type="_moz" />

RE: Burned down units
 

Ha!:) could you hop over to the saito forum and ask them for theirs,they just love that..:)

RE: Burned down units
 

That's the reason I liked the Fox 35 stunt and OS MAX 35S for stunt as they wouldn't run away on a lean mixture like you are talking about.

RE: Burned down units
 

I have a couple of Enyas , same condition too ,black , but seem strangely perfect in the acual fit , of the shaft and the piston , its the plain bearing ones

I would love to run them , will try and get a snap of them<br type="_moz" />

RE: Burned down units
 

Thank goodness for the high temp protection of castor oil... Ross

RE: Burned down units
 

A little Dawn Power Dissolver and it will look like new. http://www.rcuniverse.com/forum/js/f...wink_smile.gif

RE: Burned down units
 

I still have an OS 32sx and tuned pipe spinning a black M.A. 10X4 mounted on a PBF (Pizza Box Flier, a two foot square piece of Coroplast). That thing kept my son occupied for hours and hours. He loop it through the tall grass and if it got hung up, he'd just try to power it free most of the time. The poor engine was draped with grass & dirt. Every once and a while I'd pick the carb clear,and comb the fins clear to reveal a goopy black engine then hand it back to the kid. "Here, go have fun".

RE: Burned down units
 

You where lucky.
Can't be that bad of a lean run if everything works/runs OK.
Your engine looks more like the typical burnt castor embedded clump... due to sprayback or what ever.
Engines like I remember for the castor induced 1970's.
Thank goodness for synthetic I say.http://www.rcuniverse.com/forum/js/f.../msn/49_49.gif

Good to hear it'll still run for more years.
Enjoy.

RE: Burned down units
 

Pardon my ignorance; but how exactly does one get a runaway lean run? I have no experience with airplanes, much less control line models. I know they aren't a throttled engine but how do they just "go lean" and what's meant by a "runaway"? The engine in the first post looks terrible but I know looks can be very much deceiving.

I've also seen some folks refer to CL models running on the 4-2-4 break. Does that mean they're sent out for a run in a 4-stroke rich and clearing out into a 2-stroke scream and bouncing between the two? Why are they ran like this? I'm just trying to understand. (I've been a rc car guy for 14 years and am just now trying to get into planes..)

RE: Burned down units
 

I thiunk he means that the engine went too lean on him in the air, but not enough to stall and stop, and having no throttle, he couldn't chop the throttle to land. So all he could do was hang on until the engine finally stopped for whatever reason. You can get the effect with a RC plane where you have no throttle, but you set the needle valve a little too close to lean, and flew the plane like that. Thus as the fuel tank emptied, it went lean and all you could do was keep flying until the engine quit, for good or bad.


The 4-2-4 break is where in level flight the 2 stroke engine runs a little on the rich side thus having a 4 cycling effect. Then when you nose the plane up, like for doing a loop, the engine suddenly goes more lean and breaks into a nice 2 cycle run and you get more power for the climb into the loop. Then as soon as you levle out again the engine slows back down into its more rich running 4 cycling phase. The better engines do this change almost instantly. Some other engines were terrible at it and had a slow transition from the 4 to 2 cycle break.
So you sort of had a 2 speed throttle effect on the control line engine like that with s 4-2-4 break.

I think the 4-2-4 break worked best on the crossflow scavenged engines (they had a baffle on the piston and no Schnuerle porting). I have seen some modern custom made CL engines and the builder/designer opted for a cross flow scavenged design as well. You also do not run muffler pressure to the fuel tank, as that tends to spoil it and then the engine runs only in a 2 2 cycle mode. The venerable Fox .35 stunt on a CL plane when it was running and flying displayed a really good example of the 4-2-4 break effect. If I run across a video clip of it, I'll post it here.

RE: Burned down units
 

Earl, thanks for explaining that. I won feel as stupid reading these posts now. I don't have a lot of personal interest in CL, but I like reading about what over folks like to do and post about.

Veteran flyers like you and many others have a wealth of knowledge I'm fortunate to be able to learn from. Kudos.

p.s. If you do find a video clip, do post it. I'd love to see it. Thanks!

RE: Burned down units
 

A 'runaway' is best described as a run that gets away from where it is intended.

(In a control line context this can be serious because of the fixed throttle. Once set on the ground with a maximum load you predict what the in air setting will be - this is your 'intention.'}

But what can happen is a vicious escalating heat cycle takes place, the engine unloads in the air thus creating this recurring sequence of events - the engine draws more fue/air into it, this in turn creates more heat and power, which in turn unloads the engine further until a point is reached where the amount of extra drag can not be overcome and this becomes your now missile like cruising speed with no way to shut it off.

So setting a richer setting on the ground (this is where the 'lean' meaning comes from) can prevent this upward spiral from occuring in the first place as it cools the engine more, or more accurately 'prevents' excess heat from entering into a runaway syndrome.

Other methods of keeping the heat down also work such as reducing friction caused by castor varnishing (something that Imight suspect with the engine in question), making sure that enough oil is present, air flow, prop size and most importantly for control line use, engine design.

But a runaway can also be caused by a partial fuel blockadge or extreme tail wind.

Does that help?

RE: Burned down units
 

Earl has described the 4-2-4 quite well and it should be understood that all 2 strokes, when running with a rich enough mixture, will run in what's called a 4 stroking mode in that it consistently only fires every second rev. What's not known for a certainty is how it does this but there's a very neat and logical explanation involving scavenging which also explains why, when 4 stroking, the engine develops quite a bit more than just the half power you might expect. Actually they only lose about 30% of the power that a rich 2 stroke gives which is why there's only a small change in revs.

A "runaway" can be caused by a couple of things. The first, and most common, is trying to run an engine that's designed to give high power at high revs at the low revs (~9000) usually used for CL stunt. The high power (meaning RC engines) develop peak torque somewhere in the 12,000 rev area so if it unloads a little which allows more revs it produces more torque (climbing up the torque curve slope) which allows for more revs yet again giving even more torque and hallelujah you have an uncontrolled runaway :). The usual fix if an RC type engine is to be used is to fit a low pitch prop and let it rev. A dedicated CL stunt engine will be designed to give max torque at the ~9000 rev mark or lower so that any increase in revs will give less torque so tends to keep a very constant speed.

Another thing that can cause a "runaway" is insufficient cooling either by airflow or too little oil. The ability of a rich mixture to fire is, amongst other things, quite dependent on the temperature of the mixture so if the engine gets hotter then the mixture gets hotter and fires more easily leading to going from a 4 stroke to a continuous 2 stroke that can't go back to a 4 stroke unless the engine can cool down. I had this problem once with an ST G51 which would break into a screaming 2 stroke at the slightest provocation and take at least 2 laps of level flight to get back into a 4 stroke. I tried everything trying to cure it but nothing worked, even flying without the cowl in case airflow was the problem. One day, after about a month of fiddling and ready to give up, I ran out of my usual 80/20 all castor fuel but by chance had some 75/25 all castor with me so I figured one more flight and go home. The engine run was a dream and ran the entire flight in a solid 4 stroke. This had me baffled until one day the penny dropped. The G51 was exceptionally economical on fuel useage (for those into CL stunt it only needed a bit less than 3 ounces for a 6 minute flight) which meant that oil flow through the engine was much less than it needed putting it on the raggedy edge of overheating.

RE: Burned down units
 

Brian,
          I think that Brett Buck did a pressure sensor test on a Super Tigre years ago concerning four stroking and found out it was poorly named.

If my memory serves me well the engine never gets into a misfire at all but simply loads up every second stroke more than usual and the loaded stroke actually produced more torque but less speed than the normal stroke - hence the lower fatter tone when in 'four stroke' mode.

Must go and find that test and reread it .. again!

Cheers.

RE: Burned down units
 

It all makes perfect sense now. Thanks for the explanations, guys. This 'rookie' learned something today. One of these days, I will get a plane in the air.

Is there a more inert chemical that can be used to remove the castor gunk off the outside of an engine besides the caustic stuff like Dawn P.D.? I have some gunk accumulating on one of my K&B's and my TT 46 and I don't want it to get any more gunky.

RE: Burned down units
 

You can boil your engine in anti freeze, I have used "Prestones" brand with good success and its been deemed safe.

Or use acetone and a plastic scourer for things like gummed up pistons.

RE: Burned down units
 

Ok you can hear the engine on the CL plane in this video with the 4-2-4 break on it.
I sorta like that Pilot seat. it looks like it works pretty well. http://www.thepilotseat.com/


[youtube]http://www.youtube.com/watch?v=lZk-ANUsXUI&amp;feature=player_embedded#![/youtube]

RE: Burned down units
 

I've read about that on several occasions though I don't have a pot or crockpot to use to heat the stuff up. I suppose it has to be warm or hot to work?

RE: Burned down units
 

I am totally impressed with how well Dawn Power Dissolver works on the glow engines.
But it is possible to find a engine with too much zinc or copper in the aluminum alloy, so you want to test it on something small first to be sure the aluminum doesn't get stained on you.
I bought mine at Wal Mart here in the USA. I am sure other countries probably have something similar.
http://www.dawn-dish.com/en_US/dawn-power-dissolver.do

RE: Burned down units
 

I have never used a crock pot before but simply an old tin can (I think the last one was used for baked beans).

Disassemble the engine, place the 'needed' parts in the tin can and cover with antifreeze, then place on an old barbeque that is well outdoors because of the fumes.
Bring to a rolling boil for 15 minutes and remove parts, air cool naturally and rinse with water.

I say 'needed' parts because some times stripping the varnish off a piston and liner is undesirable if its old and seals well enough that way.

RE: Burned down units
 

I did that to an OS 61, and it came out black as your mum's army boots.

RE: Burned down units
 

Earl - that video was great, thanks for locating and posting it. Very neat phenomena. Neat idea for the pilot chair, also.

Recycled Flyer: I might try the grill trick, though my concerned areas are on the crankcase and cylinder head on my TT. The piston is a pain to get off the crankpin for whatever reason and the prop hub is even worse to get off. I will have to experiment a little without tearing the engine down. (it's not that bad yet, but I'm a clean freak so I want to keep it from turning black like the engine in post #1. It's just light brown right now).

Think automotive brake cleaner will cut the castor crud?

RE: Burned down units
 

Um, did you use Prestones? Never had an issue with that brand.

And (really don't know how to take this one), my mother never wore army boots, ever.

RE: Burned down units
 

That engine looks like many of my old Fox Stunt .35's after about ten flights or so.  Those things spit a lot of fuel and the castor stains the engine.

RE: Burned down units
 

I have a couple of old plain bearing Enyas that look the same , class engine,,,

will make up a muffler and fly them


Im working on a plane that can take a TT39 , OS 40 FP , enya 29 , Enya 35 and Enya 35X,,,,,, to kind of see, which feels nice on the end of 60 ft lines