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Posts: 13460
Joined: 3/20/2002 From: San Bernardino County,
CA, USA Status: online
Did anyone notice any similarities in what the author of the diesel tutorial said, and what I said ? We are both talking about rubbing cast iron and steel together in small aero-model engines. ______________________________________________________ _____________________________________________________
The rules for Vintage diesel combat require the use of a non-schnuerle .15 cu. In. diesel motor (plain bearing or stock PAW .15 BR) having a cast iron piston running in a steel sleeve. We call this a ferrous piston/cylinder set-up, since both cast iron and steel are ferrous metals. _________________________________________________ Me: For all practical purposes, lets assume that the engines we talk about have plain steel cylinders, and cast iron rings. __________________________________________________ 2) Start the engine and run it slightly rich and a touch under compressed (smoky and missing slightly ) for 4 minutes or so. _________________________________________________ Me: Shouldn't you warm up the engine for a minute (like you would any other motor) then bring up the rpm's and let the parts expand to their normal running clearances....which BTW, the manufacturer has gone to great lengths to assure are correct.....then adjust the carb so the engine is running correctly....and not over heating ? __________________________________________________________ (3) Keeping the engine running, adjust the compression and needle valve for fastest speed (leaned right out). __________________________________________________ Me: OK, I only warmed my engine up for one minute. ___________________________________________________
The purpose of this is to get the piston as hot as possible to help it to grow to its stable dimension as discussed above. ___________________________________________ Me: Yes, I discussed it above as well. ________________________________________ (4) Allow the engine to air-cool slowly but completely before restarting _____________________________________________ Me: Two five minute runs, with a cool down in between....and the engine is ready for business. ____________________________________________________________
Run it like this for one minute maximum, then stop the engine .
5) Repeat this process a minimum of 8 times or until the motor feels nice and smooth throughout the stroke when turned over slowly. At this point, the motor can be flown. _________________________________________________ Me: OK, he says 8 minutes....I said 10 minutes, and he's talking about racing engines. _________________________________________________End _________________________________________________
I didn't see anywhere where the author said to run the engine sloppy rich for hours and hours, gallon after gallon. As a matter of fact, the procedure for breaking in those cast iron pistons has undergone the same myths as all the other engines on the Internet. After these silly stories are repeated enough times, the become Internet fact....when in fact they have no basis in truth whatsoever.
Which brings us back to the pretense:
"ringed engines take a very long time to break-in".
False. The cast iron ring and the steel cylinder liner begin the surface mating operation instantly....and satisfactory bedding-in and normal compression is attained in a very short time....10 minutes in my estimation, if the engine is allowed to attain normal operating temperatures.
If the engine is run too cool, or run way too rich....it will take considerably longer to break-in.
FBD.
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An engineer says.... "That won''t work". A mechanic says..."Oh yeah, watch this". "Old Age, and Treachery will overcome youth and skill". Revver Bro #4.
Posts: 7096
Joined: 4/9/2003 From: Rosh-Ha'Ayin, ISRAEL Status: offline
Dave,
Diesel model engines are very different from glow engines.
1. Their fuel typically contains much more lubricant; 25-30% Castor oil.
2. Their main combustible component (kerosene) also has lubricant properties.
3. When set too rich, a Diesel model engine will not 'four-cycle' as a glow engine would, and will not run cooler. The sheer volume of the fuel will actually make it over-compressed and may even cause it to overheat.
4. When set too lean, a Diesel will never pre-ignite, or detonate, as a glow engine would. It will just mis-fire and will do it more, the leaner it is set.
5. Diesel model engines run significantly cooler than glow engines, so the MVVS .61 ABC Diesel comes with a glow head for break-in, that is replaced by the Diesel head, once you're done with this stage. Otherwise, the colder Diesel running temperatures would inhibit a correct ABC break-in.
6. Despite the structural similarities of most smaller Diesels, to some ferrite glow engines (ring and piston) and due to the above facts, the recommended break-in technique for these Diesels has no practical bearing in this discussion.
< Message edited by DarZeelon -- 7/23/2005 9:15:40 AM >
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Dar Zeelon - ISRAEL - ddzeelon@gmail.com MVVS - Jett - Nelson - Bolly - Mejzlik
Posts: 7727
Joined: 1/21/2002 From: Acworth,
GA, USA Status: offline
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quote:
Rest assured....there is no oil in the gasoline out here in Calif. That would cause a high hydrocarbon reading that would be through the roof, and would displease the EPA to no end.
There is small amounts of oil in all gasoline, it is actually not a very refined distillate. When I say refined I don't mean octane, which has nothing to do with the refining process. I mean it has a wide range of thin or thick distillates, from a light oil to thin distillates. Only paint thinners and aircraft fuel is highly refined. Oil will not necessarily have a higher hydrocarbon reading, as oil is a longer molecule chain, it does not necessarily contain more hydrogen or carbon.
quote:
A normal two cycle engine will run forever on 5% mineral oil in the gas (or methanol) at 20:1 ratio. This ratio can be extended to 32:1, 40:1, 50:1, and even higher....all the way to 100:1.
Many manufactures of the cheap weed whackers will not allow a ratio of more than 50:1.
quote:
The finish left on a new cylinder wall by the manufacturers hones, and the face of the cast iron ring....which is usually ribbed, are designed for one thing....that is rapid and sure break-in. The initial seating of these parts, enough to insure a satisfactory amount of compression take place in seconds....not minutes or hours.
Because the tolerance of rings and cylinders vary, the ring will be slightly oval shaped when in place, most of the break in is to allow the ring to mate into the cylinder and get rid of the gaped at two sides of the oval shaped ring. The exception is when the ring is honed to fit each cylinder as is done on many racing engines, especially drag engines, which may only get a few minutes of idling and a pumped throttle for a break in. Break in on a car can take thousands of miles, but initial ring seating takes minutes not seconds.
Posts: 13460
Joined: 3/20/2002 From: San Bernardino County,
CA, USA Status: online
Sport Pilot....
...I worked as a precision engine rebuilder full time for 15 years. I also did all the cylinder boring, honing and ring fitting in production and racing engines of all types....mostly two cycles. I don't know where you get your information, but I know one thing for sure....
....if your rings are fitting "oval shaped" on the cylinder wall....tell the man you want your money back.
Flyboy Dave.
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An engineer says.... "That won''t work". A mechanic says..."Oh yeah, watch this". "Old Age, and Treachery will overcome youth and skill". Revver Bro #4.
Posts: 7727
Joined: 1/21/2002 From: Acworth,
GA, USA Status: offline
quote:
ORIGINAL: Flyboy Dave
Sport Pilot....
...I worked as a precision engine rebuilder full time for 15 years. I also did all the cylinder boring, honing and ring fitting in production and racing engines of all types....mostly two cycles. I don't know where you get your information, but I know one thing for sure....
....if your rings are fitting "oval shaped" on the cylinder wall....tell the man you want your money back.
Flyboy Dave.
Take a ring out of the box and compare it to a circle. It may or may not be round, now pinch it till the gap is closed and compare it again. Many rings will be very close to a circle, some were closer to a circle out of the box. Now don't tell me it is a perfect circle for all ring gaps, cause it is impossible. You may not be able to tell the differance with your naked eye, but it is not the same.
Posts: 13460
Joined: 3/20/2002 From: San Bernardino County,
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Rings are checked visually by pushing the ring into the cylinder, then pushing it in a bit more with the piston crown, which will align the ring perpendicular to the bore and straight. If you can see light between the ring and the cylinder wall, the ring is not round, and should be replaced with a round ring.
That's the way it is....like I said., I bored-out cylinders and fitted rings every day for 15 years.
There is no such thing that I know of what you said...."honing the ring". The ring either fits, or it doesn't.
FBD.
_____________________________
An engineer says.... "That won''t work". A mechanic says..."Oh yeah, watch this". "Old Age, and Treachery will overcome youth and skill". Revver Bro #4.
Posts: 7727
Joined: 1/21/2002 From: Acworth,
GA, USA Status: offline
quote:
If you can see light between the ring and the cylinder wall, the ring is not round, and should be replaced with a round ring.
The fact that you can not see lignt does not make it perfectly round! You cannot see this with your naked eye! In fact most rings will be touching the wall all the way around, but with varing pressure.
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Joined: 10/18/2003 From: Paducah,
KY, USA Status: offline
Welp Might as well jump in with my experience..
I've broken in and run a couple Ringed engines and have 1 employed and one temporaril without a plane. I took my sweet time breaking in both engines... Neither really rich.. But I tuned them for good transition and at the same time plenty of smoke..4 gallons through my ST 1.40 and it gained power and RPM every run still with the smoke trail...Then I leaned her out to peak and backed off the RPM's (500 to be exact)...
It now has more than 14 gallons through it and it starts 1 or second flip EVERY time, holds a tune great... Capable of turning an 18X6 at about 9,500 RPM Leaned out and easily tunrs 9,100 with a good smoke trail..
Probably the best running engine at our field with the least amount of fuss and gobs of power.
If you try to break in a ringed engine in 10 minutes then your engine will not last and will not hold a tune... Will not be reliable..
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Joined: 3/20/2002 From: San Bernardino County,
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The initial break-in on a ringed engine that places place very rapidly, doesn't mean that additional bedding-in doesn't take place in flight. Initial break-in starts the very second the engine fires up. Some Guys prefer to finish the bedding in of the engine while flying it. Others may prefer to spend a couple hours or even longer on the bench, infuriating their "favorite neighbors".
I contend that a lot of this time at the bench is wasted time, and wasted fuel. Running the ringed engine sloppy rich is actually hindering the break-in process, not helping it. How many times have you read where a Guy spent a couple gallons of fuel on the bench, before the engine started acting right, or would idle properly ?
I contend also, that once the engine leaves the protective custody of the engine stand and enters the real world....that time will have very little if anything at all to do with the longevity of that particular engine. Now the engine is going to be subjected to all kinds of awful things. Heat, vibration, accidental lean conditions that get the engine hotter than a pistol. The treatment the operator gives the engine in the plane, as well as the fuel, oil, prop, muffler, cowling, ect.....not to mention the careful tuning of the engine has all to do with how long the engine will last....not what happened in the garage a few weeks ago.
The manner in which the engine is operated might have something to do with it as well. An engine that is blasted back and forth in dives, full throttle, screaming for every last RPM might not last as long as an engine that never really got much over 2/3 throttle in it's life. One might go 10-20 hours, the other might go 100-200.
I've had pretty good luck with the ringed motors, running them since '69. I get about 15 years out of a ringed engine....if it stays in one piece.
This OS is a good example of a "once every 15 years ring-job".
FBD.
_____________________________
An engineer says.... "That won''t work". A mechanic says..."Oh yeah, watch this". "Old Age, and Treachery will overcome youth and skill". Revver Bro #4.
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Joined: 10/18/2003 From: Paducah,
KY, USA Status: offline
"I contend that a lot of this time at the bench is wasted time, and wasted fuel. Running the ringed engine sloppy rich is actually hindering the break-in process, not helping it."
Did I ever say I took my sweet time on the bench?? I ran about 5 tanks through it on the bench for around an hour... To get her tuned in and idleing properly.. Checking the engines vital signs ETC. Then I threw her on the plane for the rest of the time! I just made sure to take it easy on them keep a good smoke trail.. Didnt fly it hard.. No Highspeed flying, no hovering etcetc.
Since yor compare to GAS two strokes.. (Motorcycles) How do alot of guys break in there gas plane engines? On the plane, slightly rich, takin it easy!
Posts: 694
Joined: 4/9/2004 From: Cape TownN/A, SOUTH AFRICA Status: offline
Nope they fly them, the guys who no things about rc gas engines say that altough the rings will bed in after some time running its a waste of time running them on a bench, unless of coarse there is a problem with the engine.
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