Ford 300 Inline Six

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a41capt

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Terry, this is exactly as I expected it! Truly fantastic work, an exquisite running representation of a fine engine. I only hope that some day I can come close to your level of craftsmanship.

Thank you for sharing!
John W
 

CFLBob

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In addition to congratulating you for presenting a work of art, I want to thank you for the journey. I don't remember exactly when I first came across this build but have been following it for most of the time and have learned lots. To me, that's what it's all about.


Bob
 

kvom

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Can't imagine what the next project will be. Terry has really hit all the main themes for IC engines.
 

ddmckee54

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OOOHHH, OOOHH, I know... The Chrysler turbine? Or doesn't that count as IC?

Or maybe German aircraft engine, he built a Merlin. Gotta keep the Yin and Yang balanced dontchaknow.

Or what about that 30 cylinder monster Chrysler built for the Sherman?
 

KennyMcCormick315

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That thing sounds pretty damn good! Though the idle is definitely up; real thing ticks over at just 500rpm or so. Makes me wonder if it's just scaling of physics laws that makes it so excruciatingly hard to get these small engines to idle as slow as their namesakes in full scale. Thermal camera shows nice and even heating which says all six pots are hitting; the MkI earball confirms that much.

Maybe CR is up? Cam grind? That thing does seem to have the kinda growl I hear from actual 300s with comp 264s in them. Not a bad thing by any stretch!
 
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Kenny, you are right about the laws of physics, scale and speed. Designing a model engine, you can work to the SAME piston max speed (to do with rings rubbing bores) as a full sized engines, but at 1/10th scale the engine is running 10 x faster. See what I mean?
Also, to get the SAME pressures and combustion flame speed in the combustion chamber... which affects idle running. Cam timing, ignition timing, flywheel mass, etc. all have an influence, and some modellers tweak the "tune" of the engine to slow them down. But that moves away from "exact" scaling...
But there are dozens of factors, some linear, some square and some cube - that screw-up scale engines working exactly like full sized ones. e.g. the 100th of the power, but 1/10th of the friction for a 1/10th scale engine: Yes, the laws of physics apply, but also the laws of mathematics (squares, cubes, etc.).
But I agree it is a fantastic model!
K2
 

KennyMcCormick315

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Kenny, you are right about the laws of physics, scale and speed. Designing a model engine, you can work to the SAME piston max speed (to do with rings rubbing bores) as a full sized engines, but at 1/10th scale the engine is running 10 x faster. See what I mean?
Also, to get the SAME pressures and combustion flame speed in the combustion chamber... which affects idle running. Cam timing, ignition timing, flywheel mass, etc. all have an influence, and some modellers tweak the "tune" of the engine to slow them down. But that moves away from "exact" scaling...
But there are dozens of factors, some linear, some square and some cube - that screw-up scale engines working exactly like full sized ones. e.g. the 100th of the power, but 1/10th of the friction for a 1/10th scale engine: Yes, the laws of physics apply, but also the laws of mathematics (squares, cubes, etc.).
But I agree it is a fantastic model!
K2
yeah I imagine getting it to idle at 500-600RPM would require an insanely oversized and out-of-scale flywheel that would never fit inside that bellhousing. Either that or it would have to be made out of something like tungsten or depleted uranium.

I can also see that in my commercially made RC engines. My Fox 049 FAI has had an airbleed carb fitted to it and I can get that tiny little bugger to idle at about 4500-5500. My Super Tiger G3250 will tick over at 1800RPM all day long. My Saito 125GK is more content to lope over at ~2200RPM than my FS26 Surpass is. Physics just does not like small engines running slowly. Can also see timing playing its role; my OS 25AX will idle along happily at 2750RPM while my Kyosho KE-25 won't even think about anything lower than 5 grand or so despite both engines being single cylinder 2-stroke glow mills of the same displacement; the Kyosho unit is much MUCH more aggressively timed.
 

stevehuckss396

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Another trick to get a lower idle is to cut your cam with good amount of duration and overlap. Most of the model engine plans I look at (except mine) have 220 to 240 degrees duration I made my v8 280 duration resulting in 60 degrees overlap.

What many people forget is the valves don't start to lift until all the valve lash is out of the valve train. Long story short, not enough duration and excessive valve lash can choke off an engine. Too much and it will start to lope like a hotrod.

That sweet spot is probably different for every engine. In a multi-cylinder engine imo there can be more almost every time. In the event that you "over cammed" and don't like the sound just add lash and you can reduce duration and overlap.

Worked for me. I get alot of positive comments on how low my engine idles. Didn't want it to sound like a 2 stroke. Mission accomplished.
 
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I worked with a guy who did a Doctorate and PhD on mass-elastic systems. He improved the tuning of the valve train on some Cummins engines (his sponsor for his thesis) before the job he had alongside me. He explained to me that most "time delay" between cams and valves is not clearances, but elasticity in the valve train (mostly push-rod systems). That is why so many engines now have "direct" action of "cams on valves". Much better for valve timing control, especially with variable valve timing. And on models with push-rods, as the stiffness of systems relies on a cube of dimensions, like volume, and mass of parts, there is a curious symmetry of how the mass -elastic characteristics of valve trains actually scale effectively. Otherwise they would not work.
Interesting how you have tuned the overlap to tune the idle performance. (If I understand correctly?).
Well done on a superb model.
K2
 
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What many people forget is the valves don't start to lift until all the valve lash is out of the valve train.
At the risk af adding mud:

That's why you have relief round the heel of the cam, and ramps to take up the valve clearance by the time you get to the start of the flank.

If you rely on increased clearance to reduce the duration, somewere in the valve train there will be an impact when the cam takes up the slack, instead of smoothly acceleratng it from rest. So you will definitely get (a minute amount of) elastic deflection as the train tries to come up to the speed of the cam.

Low idle speed sure, but I want minimum mechanical noise too.
 
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Hi Charles, to try and clarify the "mud" of mass-elastic systems: I was referring to the natural elasticity within the components after the slack has been eliminated. Tension members stretch a tiny amount, Rockers & pins bend (Loaded like a beam), push-rods in compression compress (all-be-it another tiny amount) - All of which is significant in push-rod engines (and my 6m long push-rods in HV circuit breakers). - And possibly in model engines with fine piano wire push-rods? Unless you have had to study this and re-design systems according to the effects of the system elasticity, you are probably not aware that this is something high speed engines have "suffered" from, for generations. (Race car enthusiasts cope with it usually without appreciating what they are doing).
An Horologist friend used his smallest gauge piano wire on his push-rods on a model, and they buckled at high engine speed - when the acceleration force applied by the cam to operate the valve increased. (The forces go up as the inverse of the t-squared bit of acceleration! - so as event time comes down, forces rise dramatically!). So he used the next size of wire: Mass increased as the square of the wire diameter (F = Ma stuff), but the stiffness of the "rod" increased as the cube of the diameter = so "simply Much better" - and demonstrated mathematically.
My point (Badly made?) was that the total real "lash" in a pushrod valve train comprises 2 elements: Clearance AND elasticity of the valve train. AT high revs, the elasticity (Or stiffness if you prefer) becomes more significant, usually appreciated just as valve bounce occurs. But that is another dynamic issue we don't need to discuss here.
Ultimately, we are all discussing the "ether" when we should simply appreciate a beautifully made model.
(Controller: please delete this post if inappropriate to the subject).
K2
 
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Yes. And springs "delay" outputs relative to input motion. They also store energy that is released later as kinetic energy. Hence the study university study of mass-elastic systems for Cummins diesels that my Doctor colleague modelled on the computer.
Enough Mud.
K2
 

stevehuckss396

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If this discussion is interesting and everyone still would like to continue with it I suggest a new thread be created on the topic. We have already infringed upon this build thread enough and gone way off topic. Please reserve all further discussion in this thread to the 300 build Edit

Thank you.
 
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