Yes Dar, I understand that Bob Brassel knows how to break-in a Jett engine as he knows what the cylinder sleeve in a Jett engine is made of. There are over a dozen different types of Brass and they all have different physical properties. Isn’t brass an alloy? A mixture? A little of this, a little of that?

That is why he states;


In general, a procedure outline by an engine manufacturer should be followed as written.

Other engine manufacturers have their noted procedures. The procedures depend a lot on MATERIALS.
Jett uses special alloy aluminum for all pistons, and all sleeves "He knows what it is"

You assume that you know what the cylinder is made of in the Magnum engine. Can you tell us what type of brass the Magnum cylinder is made of?

Again,
Something of note. 'Taper bore' engines and AAC/ABC engines can be different. Some have a 'fixed' taper that does not change or changes unevenly. A well designed AAC/ABC engine has a taper and piston/sleeve fit that DOES change. Both the piston and sleeve change with temperature. THE MATERIALS THAT MAKE UP THE CYLINDER CAN BE DIFFERENT


I would venture to guess that the "Jett" cylinder and the "Magnum Sanye" cylinders are entirely different in composition. Wouldn’t you?

BW,


The alloys used by manufacturers to make an ABC P+L set differ very little amongst themselves.

The difference is so small, in fact, that the a procedure correctly outlined, by one manufacturer, can closely be followed for engines made by another manufacturer.


The differences in the materials; which are practically the same, may be in cleanliness and purity; not in actual material choice.
I.e. brass is brass, whatever alloy is used. Only some of these alloys are suitable for cylinder sleeves and those used by all engine manufacturers differ so very little that one procedure is suitable for all of them. Especially when some of the break-in processes are written by the company's PR dept..

The same goes for the high-silicon aluminium used in the piston and chromium just is (there are few that still do it - I am not sure what process is used).
All use the same plating process.

The same goes for other coatings (AAC/ABN)...


The procedure outlined for the Magnum ABC engines, was apparently written for ringed engines...




Differences between the manufacturers instructions stem more from ignorance, disregard and 'foreign interests'; than from an actual choice of materials.

Brass is Brass?...... You can NOT be serious....

Architectural Alloy Brass
ASTM B121 Brass
ASTM B134 Brass
ASTM B135 Brass
ASTM B16 Brass
ASTM B21 Brass
ASTM B36 Brass
ASTM B453 Brass
ASTM B455 Brass
ASTM B70 Brass
ASTM Specification Brass
Brass Alloy 260
Brass Alloy 353
Brass Alloy 360
Brass Alloy 385
Brass Alloy 464
Brass Alloy 485
Brass Alloys
Cartridge Brass
Engravers' Brass
Free-Cutting Brass
Free-Machining Brass
Leaded Brass
Naval Brass
Perforated Brass
Polished Brass

Why don't you just use the term "Metal"......

Your ABC engine is made of metal...

Here are a few linear expansion numbers for different alloys; [link=http://www.engineeringtoolbox.com/thermal-expansion-metals-d_859.html]Thermal expansion[/link]

Quote:

ORIGINAL: Broken Wings

Brass is Brass?...... You can NOT be serious....

BW,


If you had just bothered to read a bit further down the same line, in your quote of my post...

I have not edited that... I can't...

"I.e. brass is brass, whatever alloy is used. Only some of these alloys are suitable for cylinder sleeves; and those used by all engine manufacturers differ so very little that one procedure is suitable for all of them."

Is someone here being overly knit-picky???[>:]

Knit-Picky...?

Are you saying that you don't have a clue as to what alloy is used to make up the cylinder sleeves in a taper-bore engine for which this thread is about?


Bob Brassel stated:

Jett uses special alloy aluminum for all pistons, and all sleeves

I would venture to guess that Dub Jett ordered a mill run in order to get the metal(s) with the material properties that he needed in order to make Jett Engines.

You have to have some clue as to what you're going to make something out of when you order material.

"Hello, ACME METALS... Yea, I need 50 1" bars of brass......

(Of course, what kind of brass would you like?)

"Well, Brass is Brass and I just need to manufacture a bunch of cylinders for some ABC model airplane engines"

(Oh, OK.... Will you be making an engine that has a taper piston and brass sleeve that changes with temperature or a fixed taper engine that uses a brass liner? You know, some types of brass, when overheated, tend to "bell mouth" and can loose taper...... )

"Lets not get "knit-picky" I want the yellow kind"

NOOOO Problem, 50 1" bars of the yellow kind brass will be delivered to your door


There is some good and bad information out there about break in proceedures for ABC type engines...... some info is a mixture of both. In general, a proceedure outline by an engine manufacturer should be followed as written. (They KNOW what kind of material they made the engine out of)

Other engine manufacturers have their noted proceedures. The proceedures depend a lot on materials.

Are you SURE that YOUR break-in instructions are correct for ALL taper bore model airplane engines?

BW, Dar and Downunder are rather respected here. What they are suggesting/recommending as the "proper" break-in procedure IS the generally accepted method for the majority of common tapered-bore engines. It has been tried and proven by many people and even more engines.
I personally have used it or something similar with great results.

It is, of course, your right to disagree. The level and manner of your disagreement is being monitored by moderators and thousands of other readers.

Good luck to all

I'm not saying its wrong. What I'm trying to point out is that different manufacturers in different parts of the world use different materials. To assume that ALL materials used by various manufacturers are the same is irresponsible. As Mr. Brassel points out, We (Jett Engineering) make our engines "this way" using special materials. Some other manufacturer may use something else so you should follow their instructions or procedures.

If you DON'T KNOW what its made of, how can you assume to know what's best?

I'm not an enginner but I work very closely with several engineers in the manufacture of Weapons Systems for our Armed Forces. When they (Engineers) specify a Material/Process or Tollerance there is a reason for doing so.

They have "Done the Math"...

If I was to assume that they didn't know what they were talking about and said to myself, "Screw it," I'm going to make this bolt carrier for this high powered snipper rifle out of 12L14 because it cuts so much easier then this AERMET 100....It's all metal, what difference will it make" Someone could get hurt or killed.

Its dangerous to disregard any manufactures instructions for any product. Even toy model airplane engines.

If you want to question the manual, Call the number in the manual or send an email and have them clarify the instructions or process. They made the product that your about to use.

BW,


You seem to be grossly over-rating the amount of engineering involved in the design of model engines...
...You are going even further than that, with the amount of engineering that you think is in break-in procedures outlined in most model engine manuals...

The leading criterion when writing the break-in instruction, should be 'ease of understanding and following, by a layman'.
Oh, I nearly forgot; it must also get the job done to a reasonable degree...


No model engine 'break-in' procedure, is designed to be performed by an engineer, with accurate measuring instruments...

...It is designed for a layman to perform.


The editors of engine manuals are by and large, NOT engineers. They may ask the engineers, if the method they included in the manual would critically damage the engine... NOT if it will achieve optimum results...
They, or the PR dept. have an overwhelming propensity to leave things as they were - even if some engines underwent a drastic change in design, or several different types of engines, are covered by just one manual...


How else would you explain the procedure for the Magnum .91 ABC engine; outlined in [link={akamaiimageforum}/upfiles/29710/Hf97502.pdf]its manual[/link]; so closely resembling that of a ringed-piston, steel-sleeve engine?
And how else can you explain [link=http://manuals.hobbico.com/osm/50sx-40-46-61-91fx-manual.pdf]the OS .40-.91 manual[/link], containing just one procedure; to cover both ringed and ABN/ABL engines?


Do you truly think the OS engineers devised a 'special design' for their ABN/ABL engines; that would get 'optimal break-in results', when it is done in the method for ringed engines?
This, just so they could have a single, 'uniform' method in the manual?

Do you suppose the Sanye engineers, have designed their .91 ABC engine, so it will get the optimal results, using the ringed engine break-in technique?


I think I would not be over-rating your judgment, by saying you are way too smart to think so...



The technique outlined in the beginning of this thread, would get very good results with ALL tapered-bore engines; regardless of the exact 'high-silicon aluminium', aluminium and brass alloys used for the piston and the sleeve, by their various manufacturers; or the exact tapers and tolerances that they use...

...Which is much more than I can say for the flawed, 'legacy' methods, as detailed in the above two manuals and in many others not listed here...

I'm not sure that's true as the break-in proceedure in the beginning of this thread was written by a layman....
You have said it yourself.

Quote:

I intuitively comprehend complex situations, for which most engineers would need to make intricate mathematical calculations to understand... And my Tel-Aviv University Bachelor's degree is in ... economics.
I was always too lazy for high mathematics of engineering studies, but got A+ in these subjects in economics.

End Quote:

Once again, If you don't know what it made of, how can you assume to know what's best? I'm not saying your wrong. I just want to know that your correct.

How do I know for sure that I should disregard the instructions that came with my engine?

BW, give up. Dar would have the CL guys never four stroking their ABC stunt engines, at least during break in. Never mind that they are designed for this.

Simple. Buy two same tapered bore engines, Break-in one of them with method "a) from manual" and the other one with method "b) this thread". Then compare performance. You can then extrapolate and apply the good method to other tapered bore engines.
Things are changing however. Some engine manufacturers (including OS engines) have now updated their manuals with a procedure which looks similar to the one at the beginning of this thread.

I have reviewed several of the newer models for OS, they are still recommending breakin at a four stroke for there ABN engines.

http://manuals.hobbico.com/osm/55ax-manual.pdf

As far as OS is concerned, It's apparently a mix of 2-stroke mode and 4-stroke mode. This is already a big step from their old manuals.

I'm not sure it's quite that simple (for one thing, no two engines are ever identical) because everyone seems to think that pinch is the be all and end all of the condition of the engine. In my infamous experiment where I flogged a new ABC slobbering rich for 45 minutes the pinch didn't change from what it was straight out of the box. A further 20 minutes of running closer to what's suggested in post #1 and the pinch had all but disappeared. My conclusion from this was that very rich running does nothing whatsoever as far as running in the piston/liner although the rod was running in very nicely.

Note that these are only my conclusions from my hands on experiment with my own engine and, although I know for myself what procedure to use in future (which I've since done several times), I'll leave it up to the individual to decide for themselves how they want to go about it. Hmmmm...this suggests a new thread on a somewhat related topic .

Yes, BW.


I am a very experienced layman and one who understands processes better than most. At least many others think I do...
...Yes, these processes include what happens between the moment an engine is started and the point at which it attains operating temperature

I obviously did not use my degree in economics to write this thread, but instead compiled the experience and knowledge, conveyed by those revered by many as *real* engine experts...
In fact, I had written this also in the beginning of the thread (or the original thread written about a year earlier).

The people whom I am talking about are; for example, the late George Aldrich, Harry Higgley, Peter Chinn and others; all quite distinguished and experienced with engines, who wrote engine columns, reviews and tests in the model aviation magazines.


And my own vast experience has just strengthened by belief in the method I complied.
I have confidence in it because it works very well, even though it is not something one takes to bank.

I have sensibly explained those parts of the break-in procedure in some manuals, which I find nonsensical; and why.
And that, you can take to the bank.

You forgot to mention Bob Brassell of Jett Engineering... http://www.rcuniverse.com/forum/m_1890371/tm.htm

I would explain it this way. The person the specified the material(s) necessary to manufacture the engine “KNOWS” what its made of and what the Physical and Mechanical properties of the material are. “Brass is NOT Brass” It can reach a Rockwell Hardness of 95 on the “B” scale. That’s some pretty hard BRASS.

“I believe” that the brass cylinders in THESE engines start out as tubing, NOT solid bar stock that some other engine manufactures may use. Brass tubing has the mechanical and physical properties that allow it to be drawn on mandrel. I also believe that the taper is formed using a burnishing tool that forms the taper and creates the surface finish at the same time. Roller burnishing moves the material on its surface and creates a “Rind” like a watermelon. The surface on the “inside” in the case of a cylinder is much harder as it has been “Work Hardened” . You can experience this process buy bending a paper clip. The first bend, bends easy, keep bending it and it will work harden and break.

ALL the Engineers that I know take great pride in their work. I have a real hard time believing that an Engineer would allow the PR department to write the instruction manual for the engine that they just designed “INCORRECTLY”……

When Bob Brassell wrote:

There is some good and bad information out there about break in procedures for ABC type engines...... some info is a mixture of both. In general, a procedure outline by an engine manufacturer should be followed as written.

Other engine manufacturers have their noted procedures. The procedures depend a lot on materials. Jett uses special alloy aluminum for all pistons, and all sleeves are TRUE chrome plated. For a Jett, that first minute of being rich does no damage to the piston or sleeve. It is no different than starting a Jett or any other ABC engine when cold and at idle. The procedure outlined in the instructions and on the web site is very tried and true. Always follow it with a Jett engine, and the engine will run flawlessly.

Something of note. 'Taper bore' engines and AAC/ABC engines can be different. Some have a 'fixed' taper that does not change or changes unevenly. A well-designed AAC/ABC engine has a taper and piston/sleeve fit that DOES change. Both the piston and sleeve change with temperature. When the engine is cold (at start) there is an interference that you can feel and hear turning over the engine... with a Jett, the audible 'squeak' is a good thing to hear! As soon as the engine starts (for sport engines, at idle) the engine begins to warm up, creating the appropriate fit between piston and sleeve. As you take the engine to full power and it reaches operating temperature, the fit becomes optimal, and you will hear the engine rpm increase to its full potential. If anything, you want it on the 'tight' side.

Perhaps if Mr. Le fou had followed the instructions in his manual he would not have had to buy a replacement piston and cylinder for his new engine…

You can do what you want…I’m just saying. “Everything is not as it appears”.

BW,


I (and several others here) do not think Le Fou needs to replace the sleeve in his engine...
Only Le Fou, after reading this thread (and probably Dub Jett's break-in procedure...) thought that a problem exists, because the pinch at TDC was not as tight as he thought it should be, after break-in...

If any engine manufacturer(s) actually thought following the technique outlined in this thread, could actually compromise the well-being of their tapered-bore engines, he/they would have 'chimed-in' and written something to indicate this...

None have and also, even OS did not go into the Q&A of their US rep and 'removed' the 'harmful info' that contradicts their manual...


So far, it seems, the only person of the over 22,000 who have seen this thread, who actually thinks following it may be harmful to engines; is you!
You seem to also be the only one who assumes the manufacturer's PR people, actually know what they are talking about...


While many engineers do take pride in their work, it is not engineers who write most manuals.
If they did, the manuals would not have contained WRONG break-in instructions.

I don't think a tedious and elaborate process is used to produce any sleeve, of any manufacturer...
It is probably machined bar-stock, before getting its plating/coating and final machining.


Current sleeves are cross-hatch finished to the final taper (not wrought, stretched, Etc.)... I have seen previous generation MVVS sleeves, that have hand-polished sleeves and a pretty tight TDC pinch!
No costly alloy is used for sleeves either... As it is they already cost nearly their weight in gold...

Quote:

ORIGINAL: Sport_Pilot

Quote:

Some engine manufacturers (including OS engines) have now updated their manuals with a procedure which looks similar to the one at the beginning of this thread.

I have reviewed several of the newer models for OS, they are still recommending breakin at a four stroke for there ABN engines.

http://manuals.hobbico.com/osm/55ax-manual.pdf

Hugh,


The procedure from OS I was referring to, is [link=http://osengines.com/faq/product-faq.html#q2]this one[/link].
The manuals are still written by not-so-enlightened PR people...

Break-in? I thought the whole point of an ABC engine was to allow the user to abuse it mercilessly with rpm, nitro, tuned pipes, and lean mixtures with out causing damage that would occur with any other type. Sport engines are so loose these days that no consideration to tuning is needed.

Once again, You don't Know if he needs a sleeve in his engine. He seems to think so...

Machining a sleeve from bar stock "IS" the tedious and elaborate process. If you were to make a sleeve for an engine would you leave the majority of the material in the
"chip pan" by using solid bar-stock (which is "priced" by the weight $$$) or buy "tube stock" with a "hole" already there? (You're going to make a bazillion of them when you go into production...)

Why take the time to machine all that material away only to make scrap metal out of it?

They have........You just fail to read and understand what was written.

There is some good and bad information out there about break in proceedures for ABC type engines...... some info is a mixture of both. In general, a proceedure outline by an engine manufacturer should be followed as written.

Other engine manufacturers have their noted proceedures. The proceedures depend a lot on materials.


Perhaps we could ask "Magnum Engines" to post the "Why We Want It done This Way".

Then you could explain to them why they have their heads up their [sm=confused.gif]

Todd Nicholson

Global Services
18480 Bandilier Circle
Fountain Valley, CA 92708

EMail: [email protected]

BW,


I don't actually know, how the base brass is received by any engine manufacturer...
I guess the best one to ask would be Dub Jett.

Even in his case, it could be possible; the AAC is received in one form and the ABC in another, before it is machined to fit, prior to assembly.

Quote:

There is some good and bad information out there about break in procedures for ABC type engines...... some info is a mixture of both. In general, a procedure outline by an engine manufacturer should be followed as written.

Other engine manufacturers have their noted procedures. The procedures depend a lot on materials.

If the information contained is both good and bad, why would anyone in sound mind follow the bad parts, as well as the good?
Is there anything good to be gained from following any bad info; for the sole reason it is there with some good info?

You're not getting married to the manufacturer... you CAN select to do only what's good and ignore all the bad!

Ah hahahahah.....! "the information contained" ? Would that be in this "Taper-Bore break-in thread" or "in the procedure outlined by the engine manufacturer"?

It's been fun

BW,


Some good and some bad info - meaning a break-in description telling you to start the break-in running at a rich, four-cycle... then continuing at a rich two-cycle setting...

"...start running at a rich, four-cycle..." = Bad info. Don't follow that part!

"...continuing at a rich two-cycle setting..." = Good info. Do follow that part.


This would mean "a mixture of both good and bad information", as stated by Bob Brassell...


The source of this thread does not contain any bad info... just some of the opposition.

I think I'll go with the Engineer....

http://www.rcuniverse.com/forum/m_9808339/tm.htm