Yeah, Hugh.

Just think of it, if the tube-stock brass sleeves of Magnum engines, would need to be heated, as decribed [link=http://en.wikipedia.org/wiki/Annealing_(metallurgy)]here[/link].
The sleeve would have to be heated to a glow... Can you imagine that in a glow engine, where the metal temperatures seldom exceed 300°F (176°C)..?

Maybe that's the source of the term 'Glow Engine'...

I remember learning that the Chevrolet dealerships were instructed to pour Bon Ami through the carbs of '55 Chevy V-8 engines that blew oil smoke out of the exhaust (smoked) when new. Later on, I saw our local American Motors dealership doing the same thing to 1963, or so, seven main bearing six cylinder inline engines that were slow to break-in the chromed rings that they came with. But that was with completely differently scaled machines, with different fuel lubricity and tolerances.

Fox used to sell Lustrox (might still), which, when mied with castor oil, was used to help break-in some models of their engines. I witnessed two fellows break their Fox engine in and out all in one running session. That convinced me that some things were just worth waiting and working for.

Let me repeat. I AM NOT an engine expert. I do have lots of experience and some chiseled in stone opinions, but don't do as I say. Guiding the layman thusly is the job of the manufacturer, Dar Zeelan and the few MECHANICAL engineers (no, software engineers don't count) that inhabit this forum.


Ed Cregger

Or electrical engineers

I remember the lapping compounds. Unless you knew what you were doing you could easily ruin an engine in a few minutes. Running those mehanite piston engines at the 2 4 break for a gallon or so for break-in would give you a long lasting engine. Now an engine with pinch, I've seen engines fitted so tight you had to preheat the cylinder and head to get them to turn over. Extra lube and a slightly, slightly rich needle is whats called for on those babies to maintain the fit. Enya AAC engines had no pinch but with a plug installed could hardly be turned over slowly the fit was so good. I had a NIB 60xlf-4 gp w/ pipe but sold it, couldn't pass up the offer from a Japanese collector. btw, that little gem sold for over $300.00 in the 80's but the quality was above anything else on the market at the time. I still have a nib rear exhaust 60 xlf-II, same piston and liner, no pump and different carb. A great deal of engineering went into those engines and carburators. Most people will never know the quality of the top Enya engines from days gone by.

How soft do you want it?

You have absolutely no heat treating effect in our engines at the temperatures they operate at. The lowest temp is for tempering which is around 600 degrees F or so. The only exception is some aluminum alloy's age harden at roomtempwhich is complete when you recieve the product, and if notwould happen regardless of running your engine.

You can't make brass harder by heating it.

I never said anything about hardening, I said heat treating. That includes hardening, anealing (make softer), and stress relieving (tempering), Also our engines have several metals that can be heat treated to one degree or another.

HI
the engine break in is the single thing that will determine how long and how well the engine will perform through out its lifeexcluding crashing
the engines metals are polished and seated at this time to each other the better the surfaces are polished the smoother the metals the better the engine will be long term ( polishing is accomplished with extra lubrication on the first few tanks of fuel -and cooling completely between runs)
best to get the needle valves set to keep the engine running very slightly richi use the pinch the fuel line method to be sure i am rich top and bottom-mostly applies to glo engines
get the engine into the air A S APso it breaks in under actual flying conditionslimit your bench run time as these engines are air cooled and do require air over there surfaces to prevent any over heating which cause a lean run which must be avoided as much as is possible through the engines life-aluminum is soft and will warp from high heat
staying with one fuel and prop from day one will keep the head temps of an engine always close to the same temp
building flying and rebuilding for 26 yearsMORE THAN MOSTLESS THAN FEW
BEST REGARDS TONY

You put far too much stock in Wikipedia. See the little thumb nail of the book with a question mark on the page.

This article needs additional citations for verification.

Now read the references...

Are there any references to the word Brass in any of them...


It's funny you should mention it but 300°F (176°C) is where the annealing process begins...300 - 2250°F

You could anneal your brass cylinder liner to 500 degrees but it would be dead soft and probably wouldn't work very well.

Neither did I.

I think you are confusing the recovery temperature (the temperature that the crystals soften deform and relieve stress) with the recrystallization temperature.

http://www.lfa-wire.com/c26000.htm

Aren't they both annealing processes?

Recovery Anneal: (300 - 1000°F)
Annealing process typically applied to cold-worked material to reduce residual stresses and recover ductility in the material. Temperatures used are below those required for recrystallization or new grain formation.

Recrystallization Anneal: (330 - 1450°F)
Annealing process typically applied to cold-worked metal to produce a new grain structure without going through a phase change in the case of ferrous materials.

They way I read it is @300 degrees non-ferrous material begins to become ductile, and can deform under stress. (Piston being forced into the bore at the top of the stroke)
It takes a little more for ferrous material.

I've always wondered what goes away first, the piston or the liner... I guess I'd have to accurately measure the parts, ruin them and measure again....

If you fully anneal your liner, its junk.

I don't know where you got your temperature of 300 degrees. Brass keeps its hardness to about 500 degrees and must be above 600 degrees to anneal. 300 degrees is when the grain crystalizes, the recovery temp is the higher temp the metal must reach before annealing can begin.

http://www.pmpco.com/annealing/annealing.html

http://www.riheattreating.com/heat-t...ecialties.html

http://www.tristateflame.com/annealing.htm

If you want to fully anneal the liner to a dead soft condition heat it to 600 degrees.

"How soft do you want it"...


Here's the chart you posted.

MECHANICAL PROPERTIES
70-30 BRASS, C26000

For Round, Half Round and Square Wire
DESIGNATION TENSILE STRENGTH YIELD STRENGTH â€*
.5% EXTENSION
NOMINAL
STD FORMER KSI* MPa** KSI* MPa**
Annealed (A) 48-54 â€*â€* 330-372 â€*â€* 16-23 110-158
H00 Eighth Hard 50-55 345-450 46 317
H01 Quarter Hard (1/4H) 62-77 425-530 57 393
HO2 Half Hard (1/2H) 79-94 545-650 65 448
HO3 Three Quarters Hard (3/4H) 92-107 635-740 70 482
HO4 Hard 102-117 700-810 70 482
H06 Extra Hard (XH) 115-129 790-890 70 482
H08 Spring 120 min 830 min 70 482

Maybe you should fly them,a fourstroke going by makes my sunday

The objective of break-in, in an ABC/ABN/AAC/ABL model engine, is to mutually mate the piston to the sleeve (and to a degree, the con-rod the the crank-pin and to the wrist-pin).

It is not intended to heat-treat any of the parts, or to aneal them (make them mallable, ductile).


This whole discussion has 'flown off the handle' several pages ago.


We're discussing metallurgy; instead of debating the OP's original question.
Let's get this thread back on-track.

As was explained to me, by a respectable engine manufacturer, the ABC fit is at its best when it leaves the factory. The only "break-in" required is for parts other than the piston/liner combo. But I know that no one will agree with what I'm repeating. How do those stupid engine manufacturers continue to stay in business year after year? (smile)


Ed Cregger

Ed,


Let's split what you wrote into two...

Quote:

ORIGINAL: NM2K

As was explained to me, by a respectable engine manufacturer, the ABC fit is at its best when it leaves the factory. The only ''break-in'' required is for parts other than the piston/liner combo. But I know that no one will agree with what I'm repeating.

I would say this manufacturer is clearly wrong...
If this was so, the engine's performance would be top-notch 'out of the box' and it would steadily deteriorate, as time is accumulated by the engine.

But this is not so. ABC engines perform better as time is accumulated on them.
I can tell you from my own experience with MVVS, that their engines gain 400-600 RPM on top with the same prop, by the time they run 6-10 hours.
From there on and until 3-400 hours, they perform the same.

If 'best fit' can be described by optimum sealing and highest output, then they were not at their 'best fit' when new.

Quote:

ORIGINAL:

...How do those stupid engine manufacturers continue to stay in business year after year? (smile)

Some of them stay in business because of us users, who are willing to shal out these outrageous sums to buy engines; and then proceed to 'follow the manual'.
If it doesn't last, many just buy a new one, of the same type and brand...

Some don't continue to stay in business... Webra rings a bell?

Is there a problem discussing metallurgy?

The parts inside the engine are made of metal. ABC/ABN/AAC/ABL ....................

Do you not believe that metal reacts to heat?

Quote:

ORIGINAL: Broken Wings

Is there a problem discussing metallurgy?

The parts inside the engine are made of metal. ABC/ABN/AAC/ABL ....................

Do you not believe that metal reacts to heat?

BW,


No problem at all discussing metallurgy... Except it is not what the OP asked.

Metals do react to heat.
But not the metals that our ABC engines are constructed from; and not at the temperatures they reach inside a running glow engine.

In tapered-bore engines, it is only possible for the piston to be work-hardened slightly.
No metal transfer takes place.


In Meehanite-steel engines, other processes do take place... Minute shards of steel from the sleeve embed themselves in the cast-iron piston's surface; and make it into a hone, which eats away from the sleeve, as the iron piston grows and stabilizes in size.

But the great majority of current engines are not like that any more. It is an overwhelming minority, after nearly all current engines are either taper-bored, or ringed.


I am sure Brian Hampton (downunder) can elaborate on this issue.

This is not intended for any one person, but to the group as a whole; let's be sure to keep the discussion friendly. Drifting off topic too far is a judgement call that I don't want to have to be asked to decide on.

I don't know for sure if they still use the same materials, but some of the Super Tigre and K&B pistons could be heat treated or normalized (or whatever term you feel is best ) in an ordinary kitchen oven...
Check out the Control Line Speed forums...there are some guys over there who could give us all some lessons on "Materials and Processes"...I'm not gonna drop any names here.

You can "grow" a piston by placing it in an oven at a certain temp for a specific amount of time. (I'm talking about some of the X 40 and 6.5 K&B pistons ) The pistions are then lapped to fit the ABC sleeves.

Agreed, the average "sport" flyer has no need to do this...basically they just wanna fly...but there is, IMO, no need to squelch a good thread. A discussion of model engine metalurgy is very interesting...again IMO.

I find metallurgy to be an amazing subject...

Maybe Bob Brassel of Jet Engineering will chime in as well.

Webra made good but expensive engines. My 91p is very strong and doesn't need to scream or use nitro to make it's power.

I could but instead of making it seem like I'm an expert I'll simply refer to [link=http://www3.bc.sympatico.ca/dieselcombat/about_diesels.htm]this[/link] page which is where I learned the metallurgical reasons for the time honoured method for running in that type of piston/liner.

In addition, some worn out iron pistons have been forced to grow slightly by heating them in an oven to quite high temperatures and letting them cool very slowly. It doesn't always work but this could possibly be because of the type of cast iron used.