Recycled Flyer

Iknow that its been two months since the last reply and this thread threatens to go to 15 pages in length but Ifeel that I must add something here.

I have a third hand MVVS 49 that Dar ran in originally and this engine is in no way any like new but the compression and pinch it displays after all these years must be felt to be believed - suffice to say that it now runs as a diesel just fine. No greater test can be performed to determine whether or not the piston liner seal is successful or not than to change a ten year old glow engine over to diesel!

Now the only previous experience that Ihave had in the model engine world really involves old school PAW's and Iwas initially taught the run rich and cool proceedure with a big prop up front, so I was indoctrinated from the start. That was the way to do a break in regardess fo the engine type.

But recently I was challenged on this by two very experienced engine builders and they both say to drop the prop size, don't run it rich beyond the run setting and use plenty of oil at first.

The smaller prop unloads the big end (and it's here that the most 'wear' or material removal will take place) and allows the engine to spin out so that it can effectively heat cycle the piston/liner.

I am going to stick to the run fast method for run in now and simply up the oil content for that period.

Cheers.

w8ye

My Feedback: (16)

It is your engine.

You may be crossing the Ring vs ABC type procedures

tonywayne

Wow can’t believe I just read that whole thread. A lot of good info thanks to everyone who shared their knowledge. I will definitely try Dars procedure on my next engine. The oldest engine I own is a 46fx of about 10 years with at least 50 hours on it and its still running strong, I just followed the manual during break in. I also have other brand engines I ran in using an os technique and so far they have given good service. If there is better technique that could result in longer/ better performance I’m sure down for it.

Broken Wings

My Feedback: (20)

I like the "Downunder" method... or the one described by Novarossi ... http://www.novarossi.it/files/manuals/uk-general.pdf

All Brass is NOT Brass.....

DarZeelon

Quote:

ORIGINAL: Broken Wings

I like the ''Downunder'' method... or one one described by Novarossi ... http://www.novarossi.it/files/manuals/uk-general.pdf

All Brass is NOT Brass.....

BW,


I began this thread with ample reasoning, explaining WHY the break-in should be done as described.
I also wrote about possible consequences of doing a cold, wet, very rich break-in, when the engine is of the tapered-bore design.

Brian Hampton (downunder) justifies his method of running the engine rich, in his own experience that the possible mishaps I described never happened to any of his engines...
Perhaps he's right about his engines, but I wrote I treat any such engine, as if it is the tightest racing engine; and so I also recommend that others do.

Brian never gave any other reason, of a technical, chemical, or physical reason to justify his choice; just that it has been working for him to his own satisfaction.
I say that he's probably never met his nemesis - yet.


The method stated by Novarossi does not state the engine must be run rich! Not even in one word.
It just states it must be run slow... Does this suggest they think their engine should be idled (or run just off it) for 30 minutes and that break-in is achieved by that? Strange. Truly strange...


So, in order to overcome your 'schizophrenia' (preferring two polarly different methods - Dr. Jackel and Mr Hyde); try stating the reasons you prefer *them*...

The other way is for you to understand and accept what I wrote in post #1.


For all practical purposes, all brass alloys used for glow engine cylinder sleeves, are the same... And the engines they are parts of should be treated the same.


This is the most highly rated thread in this sub-forum, with over 31,000 views - I believe there are good reasons for this.

Broken Wings

My Feedback: (20)

Unless you know what materials were used to manufacture the liner your just guessing. All BRASS is NOT Equal. I find it astonishing that you can't comprehend that fact.

DarZeelon

BW,


I called you no names. I just stated that you liking both Brian's method and Novarossi's, is like holding the bat at both ends, at the same time...
You cannot hit the baseball that way; can you?

I believe Novarossi, who make very good engines, don't think their engine needs a break-in of any kind; because what they tell you to do hardly has any effect.
They just want you to 'go through the motions', so as not to state their above view.
They don't ask you to richen the mixture - just to close the throttle - the surest way to get RPM down...

Of course there are different brass alloy...
But the physical properties of those used by different engine manufacturers for their sleeves (and the high-silicon aluminium piston), are similar enough not to necessitate a different break-in procedure.

My method works very well for all tapered-bore engines, no matter which manufacturer produces them.

The thread's rating is not 'my belief'... Just click the 'Rating' title a the top of the 'Glow Engines' table and this thread appears at the very top, just below 'Bill Robison's Saito notes' 'sticky' thread.

DarZeelon

BW,


I called you no names. I just stated that you liking both Brian's method and Novarossi's, is like holding the bat at both ends, at the same time...
You cannot effectively hit the baseball that way; can you?

I believe Novarossi, who make very good engines, don't think their engine needs a break-in of any kind; because what they tell you to do hardly has any effect.
They just want you to 'go through the motions', so as not to state their above view.
They don't ask you to richen the mixture - just to close the throttle - the surest way to get RPM down...

Of course there are different brass alloys...
But the physical properties of those used by different engine manufacturers for their sleeves (and the high-silicon aluminium piston), are similar enough not to necessitate a different break-in procedure.

My method works very well for all tapered-bore engines, no matter which manufacturer produces them.

The thread's rating is not 'my belief'... Just click the 'Rating' title a the top of the 'Glow Engines' table and this thread appears at the very top, just below 'Bill Robison's Saito notes' 'sticky' thread.

Broken Wings

My Feedback: (20)

I'll take schizophrenia over narcissism...

downunder

*sigh*...here we go again.
OK, if you need me to spell out technical reasons I'll give you two (but surely with your intuitive knowledge you'd know this).

First there's the hydrodynamic pressure built up by the oil film as it tries to be squeezed out from between the piston and liner in the pinch area. This pressure (which can be extremely high) both compresses the piston crown and expands the liner keeping them apart (and I'm talking a stone cold engine here).

Second, an engine gets a lot of its cooling internally by the evaporation of fuel in the crankcase, An engine running rich has more fuel in the crankcase so more available for evaporative cooling (latent heat as you should know). The piston interior is in direct contact with this cold air plus there's more raw fuel that can collect inside the piston to evaporate and give it extra cooling. The top of the liner can only be cooled mainly by convection to the air by whatever heat path is available to it.

As for my nemisis, I thought I'd finally met it in one particular engine. You talk about tight racing engines, well this one was beyond tight because it was almost impossible to turn through the pinch. Let's just say it was so scarey tight I was very worried about the rod. Once started (finally!) it burbled away quite happily at as rich a mixture as it would handle without cutting out. When the fuel ran out it went to near max revs then stopped instantly with the piston jammed up in the pinch. After close on an hour of running it finally stopped jamming in the pinch. Now this was an engine with a cast iron piston and steel liner so you may (rightly) ask the relevance of this. Well there's no differential expansion so that enormous pinch should have always been there...except it wasn't once it started. That basically was a proof of hydrodynamic pressure even with a much more rigid iron piston. It also made a fallacy of the myth that a rod can get torn to pieces with the piston of a cold ABC type engine having to be pulled back out of the pinch area.

DarZeelon

BW,


How did you quote my post, without the word 'effectively' preceding the clause 'hit the baseball'???

A bunt is hardly an effective way to hit.


I have no way of giving you schizophrenia... Even if you prefer it.
And no, I don't love myself...


Brian,


Hydrodynamic pressure is what works between two rapidly spinning/moving parts; such as a sliding main bearing of an engine.
The piston, when reaching TDC is dwelling and for a moment comes to a dead-stop in the sleeve's pinch.

Hydro-static pressure does not have the same effect and it hardly can be a part of an explanation.


The engine that you discuss in your letter does not have a tapered-bore, i.e. the sleeve is parallel.
The piston is more effectively cooled from below by the fresh mixture, than is the sleeve.
This creates some play which allows the engine to continue running.


The engines that had their rods let-go after a rich break-in, were K&B pylon racing engines, written about by George Aldrich, if I recall correctly.
Maybe that con-rod was particularly frail...

I never had a con-rod go south in any engine I ran either... But I do it my way.

Broken Wings

My Feedback: (20)

Check post 339....

DarZeelon

Brian,


Hydrodynamic pressure is what works between two rapidly spinning/moving parts; such as a sliding main bearing of an engine.
The piston, when reaching TDC is dwelling and for a moment comes to a dead-stop in the sleeve's pinch.

Hydro-static pressure does not have the same effect and it hardly can be a part of an explanation.


The engine that you discuss in your letter does not have a tapered-bore, i.e. the sleeve is parallel.
The piston is more effectively cooled from below by the fresh mixture, than is the sleeve.
This creates some play which allows the engine to continue running.
In this engine, hydrodynamic pressure does apply.


The engines that had their rods 'let-go' after accumulating fatigue-stress from a bubbering rich break-in, were K&B pylon racing engines, written about by the late George Aldrich, if I recall correctly.
Maybe that con-rod was particularly frail...

I never had a con-rod go south in any engine I ran either... But I do it my way.

378

My Feedback: (4)

...My two cents from the land of glow cars agrees somewhat with the OP. We run ours at a highly rich mixture though, as rich as we can get away with without using the glow ignitor, and use other methods to ensure it warms up. Wrapping the cooling head in aluminum foil or an old sock is a common trick, forces the engine to warm up despite the richness. We also don't jam ours WOT right out of the box, that's a pretty good way to destroy the rod in an engine spinning upwards of 35,000RPM. I've broken in two. Did the first one blubbery rich without wrapping the head, never really got it warmed up. It lost pinch at two gallons, though it still ran okay. Down on power. Second engine, an OS to be specific, I broke in a bit leaner, though still rich enough to puke smoke out. Got that one warmed up, it's still got enough pinch to pick the car up by the pull starter after three gallons.

A good breakin for us car nuts involves fueling it up, setting it at a rich 2-cycle as they just die when you hit the brakes if it's four cycling, and then we throw the car on the ground and start doing figure eights to build the temps in the engine and wear in the chassis as well. Warm it up, run about 90% of the tank through, shut it off without running it dry, set it to BDC, let it cool, repeat four or five more times, and then we tune for power and let it rip.

I suppose it's also worth noting that a typical oil content for us ground pounders is...oooh, 12%? Tops? Some guys run as little as 6-8%. And that oil is usually 75% synthetic if not full, we don't like castor because it makes a royal mess on the wheels and makes dirt stick to everything it touches and turns it into this strange clay-like substance called 'nitro mud'. I run what's considered 'excessive' oil content, 16-18%, in my cars, which is in the low to average range for aircraft. But, figuring that our engines last just fine despite spinning twice the RPM of comprably sized A/C engines, running half the oil content, and living in the dirt their entire lives, all while being broken in on this stuff, I do disagree with the "Add oil until you hit 25% oil content" part. It's not necessary and just makes a mess, there's more than enough oil flowing through on a rich 2-cycle setting to flush out any debris.

downunder

Sorry Dar, you lost me there. What engine are you referring to?

DarZeelon

I am the OP (original poster)...

Your method is hardly the same as the one I prescribe for airplane engines.


It does share the "getting the engine to proper working temperature" ASAP. But we do it in different ways.
I subscribe adding oil (castor) to a total of 25% to cater for the increased lubrication needs, while you run a very rich mixture, which in a plane engine will cause the engine to run too cool for its own good.

This thread addresses mostly airplane engines.
Owners of engines intended not to spin a prop, might not find it very useful.


But even those car guys in another thread stated the blubbering rich method results in their engines lasting 3-4 gallons, while the two-stroke rich method got their engines past 11-12 gallons.

378

My Feedback: (4)

That's why I said "Somewhat agrees with"


We can't really run ours at a four stroking mixture because there's nothing to keep it running when we hit the brakes. Our engines drop to idle, the clutch disengages, and we're left with a rather light flywheel to keep it turning. This is fine when it's two stroking, but if it's four stroking they absolutely love to flame out, and that isn't helped at all by the rather tight pinch our engines tend to get(ABC is standard, ABN is rare, and 25,000RPM is considered a lazy engine). We more or less have to run ours on a rich two-cycle if we want it to stay running at all.


As for blubbery rich killing engines, I will agree with that on the condition that nothing is done to force the engine to heat up through other means. If the head is wrapped sufficiently then it doesn't matter how rich you run the thing. All that oil pulling heat out will suddenly become the only way the engine can cool itself, so it will still warm up properly. The first engine I broke in was done that way, piss rich and nothing around the cylinder, and when the crankshaft broke(Unrelated, it snapped just past the drive washer) at two and a half gallons I noticed the sleeve had absolutely no pinch left. I could get about half of the wrist pin above the top of the sleeve before it stuck in the cylinder. The engine still ran well, despite losing the flywheel I still had to manually shut it down as it continued to idle, but it was clearly quite worn out. I broke my new engine in using a heat cycle method with the carb set rich but not blubbery rich and it's hit the same age, but as I mentioned it's still got enough pinch to pick the car up by the pull starter.

DarZeelon

378,


Regarding oil carrying away heat in glow engines... Well, some heat is carried away by the oil, but it is much, much less than you think.

I don't have the exact numbers for oils, which aren't supposed to evaporate, but it is methanol that does most of the engine's cooling, through its own evaporation.
Methanol has a very high latent heat of evaporation.

378

My Feedback: (4)

...and then it burns in the combustion chamber creating the very heat you're trying to remove from the engine.

DarZeelon

Of-course, 378.

But it still is the major contributor to cooling...
Oil does very little.

In any internal combustion engine, the fuel's main job is to burn and to provide power.

The engine's job is to make power from the fuel. Heat is just a useless product that is necessary to remove, both by airflow on the cylinder fins and by the latent heat of evaporation of the fuel's components.
The oil? Its job is lubrication.

378

My Feedback: (4)

The oil does a significant amount of cooling. I mentioned how little oil us car guys run in our engines, right? I've run a 12% oil blend through my engine before. It ran considerably hotter than it does on the 18% oil blend I'm using now. I also noticed muuuch less mess on the 12%, as it was a pure synthetic while the stuff I have now is about 25% castor or so, the balance synthetic.


The oil in every engine carries with it a considerable amount of heat, that goes for the engine in my NTC3, the one in my NexSTAR, or the engine in my F150. Oil has four jobs in any engine, cooling is one of them.

See:

http://en.wikipedia.org/wiki/Motor_oil

http://members.themotoroilevaluator....dex.php?id=151

DarZeelon

378,


I will not argue with you for the sake of arguing, regarding the oil's contribution to carrying away heat in glow engines.
Oil flows through a .46-.61 glow engine, at a rate of about 5 cc per minute. It is expelled from the engine (running at 12,000 RPM), about 5 milliseconds after it enters it.
The droplets undergo induction through the carburettor; flow through the crankshaft; sub-piston compression; flow through the bypasses; normal compression and expulsion through the exhaust.
They are exposed to combustion and are neither supposed to burn, nor to evaporate.

Oil can really do very little, as far as carrying away heat; even though the popular myth does say such things.
Oil does much more to reduce heat, by reducing friction between the engine's parts.

Brian Hampton (downunder), who is also a participant in this discussion; and who compiled [link=http://www.flyhi.org.il/fuel.htm]this table[/link] about fuel components, may be able to add more to this specific issue.

Quote:

ORIGINAL: downunder

As for my nemisis, I thought I'd finally met it in one particular engine. You talk about tight racing engines, well this one was beyond tight because it was almost impossible to turn through the pinch. Let's just say it was so scarey tight I was very worried about the rod. Once started (finally!) it burbled away quite happily at as rich a mixture as it would handle without cutting out. When the fuel ran out it went to near max revs then stopped instantly with the piston jammed up in the pinch. After close on an hour of running it finally stopped jamming in the pinch. Now this was an engine with a cast iron piston and steel liner so you may (rightly) ask the relevance of this. Well there's no differential expansion so that enormous pinch should have always been there...except it wasn't once it started. That basically was a proof of hydrodynamic pressure even with a much more rigid iron piston. It also made a fallacy of the myth that a rod can get torn to pieces with the piston of a cold ABC type engine having to be pulled back out of the pinch area.

Brian,


It is this engine you wrote about that has a parallel sleeve and can benefit from the oil's hydrodynamic pressure for its protection.


EDIT: Spelling.

Mr Cox

I actually agree that on an ABC engine there is no need to run in a four stroke mode, a rich two stroke on a small prop is fine. But there are so many odd statements in this thread that it is unbelievable...

Take this one just as an example:

Have you ever tried to turn over a brand new ABC engine with and without a glowplug installed? The difference in pinch at the top is substantial, in fact turning a high performance engine over without a glow plug installed is not recommended at all.

DarZeelon

Quote:

ORIGINAL: Mr Cox

I actually agree that on an ABC engine there is no need to run in a four stroke mode, a rich two stroke on a small prop is fine. But there are so many odd statements in this thread that it is unbelievable...

Take this one just as an example:

Quote:

ORIGINAL: DarZeelon
It is this engine you wrote about that has a parallel sleeve and can benefit from the oil's hydrodynamic pressure for its protection.

Have you ever tried to turn over a brand new ABC engine with and without a glowplug installed? The difference in pinch at the top is substantial, in fact turning a high performance engine over without a glow plug installed is not recommended at all.

Mr Cox,


When you reply in a thread, it is advisable to first read through the posts to fully understand what is being discussed.

In post #337 Brian mentioned, toward the end of it, an engine with an iron piston running in a steel sleeve.


This is what the sentence you quoted relates to and it is definitely not a tapered-bore engine.

378

My Feedback: (4)

so I suppose the side of the piston in contact with the sleeve is cooled by magical fairy dust? And what about the bearing surfaces in each end of the rod? The crankshaft in a bushed engine?

Not every drop of oil goes flying out the exhaust port the moment after it comes through the carb. If it did we'd have to run more oil than fuel less we get excessive wear. Quite a bit of it hangs around, picks up heat and debris, lubes moving parts and flushes that heat out of the engine.


Also, synthetic oils are supposed to burn. That's why fuels using synthetic oil only often market as 'low mess' or 'low slime', the oil burns in the combustion chamber instead of getting spat out the exhaust and onto the model, and it's why it's increasingly hard to obtain castor-only oil blends. I'm fine with them, a little castor helps sure but it also makes a huge mess.