A What-If on Liquid v. Air cooled/Radial v. Vee v. inline.

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steffen19k
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A What-If on Liquid v. Air cooled/Radial v. Vee v. inline.

Postby steffen19k » Wed Jun 20, 2012 2:27 am

So I was thinking.

There were a LOT of engines available for both Tank and Aircraft manufacturers in WW2. Some of them were cool, and some of them were absolutely horrible.

My question is IF

You were to design a WW2 vehicle (small to medium aircraft, medium to large land vehicle, boats of up to 80 or 100 feet, etc.)

which type of engine would you choose? For the sake of simplicity, the engine types to choose from are strictly radial, In-line, and Vee.

would the cooling system be air or liquid based?

Are there any other design features you would incorporate, like Overhead Cam, 2-stroke, etc...

The design I like best will recieve a shiny gold "thumbs up" smiley face from me in lieu of a real prize, since I'm lazy like that.

Past that, my only rule is HAVE FUN. Feel free to put down everyone else's design, trump your own up, whatever.
Last edited by steffen19k on Wed Jun 20, 2012 2:44 am, edited 1 time in total.
Here is everything I know about war: Someone wins, Someone loses, and nothing is ever the same again. Here is everything I know about life: The only certainties are death and taxes.
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steffen19k
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Re: A What-If on Liquid v. Air cooled/Radial v. Vee v. inlin

Postby steffen19k » Wed Jun 20, 2012 2:39 am

Here's my Entry. :D

120* V engine,
6 cylinder
Common Rail Diesel injection
12 Liters or 720 CID.
9 inch stroke, 4 inch bore. 14:1 Compression Ratio.

Air cooled.

2-stroke

Turbocharged

Welded Crankcase w/ Dry Sump lubrication system.
Disk Crank. 120* crankpin separation.
Air Scavenging intake. Rotary Valve exhaust.

Electric Generator/Starter.

1000 RPM Idle, 2500 RPM Max Output
Here is everything I know about war: Someone wins, Someone loses, and nothing is ever the same again. Here is everything I know about life: The only certainties are death and taxes.
The enemy of freedom are those who proclaim only they can uphold it.

paul.mercer
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Re: A What-If on Liquid v. Air cooled/Radial v. Vee v. inlin

Postby paul.mercer » Wed Jun 20, 2012 7:08 pm

Gentlemen,
On this theme, which was the best aircraft engine in WW2 the in line or the radial and what were their merits (or otherwise)

steffen19k
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Re: A What-If on Liquid v. Air cooled/Radial v. Vee v. inlin

Postby steffen19k » Thu Jun 21, 2012 3:50 am

paul.mercer wrote:Gentlemen,
On this theme, which was the best aircraft engine in WW2 the in line or the radial and what were their merits (or otherwise)


Hi Paul. Good question. According to what Data I have available, Radial Engines were the preferred aircraft engine, although the preference is usually subjective to the situation at hand.

To make this somewhat easier, I broke it down into two parts. Vee vs. Radial and Liquid vs. Air Cooled. My reasoning is that you can have aircooled Vee engines or liquid cooled radials. I've seen cases of one, and firmly believe its possible for the other.


The Benefits of Radial Engines:
Smoother running. (At least in concept.)
More cylinders for a given displacement.
High Torque at lower RPM.
Fewer Main Journals and a shorter crankshaft length.
Often easier to maintain.

Disadvantages of Radial Engines:
Harder to Manufacture because they Require more machined parts vs. cast or forged.
Weigh more.
Problems with fuel/air delivery.

Benefits of Vee Engines:
Easier to manufacture, because they can make use of large castings or forgings for the engine block with minimal machining.
Better air/fuel delivery
Smaller and easier to fit into unusual or awkward spaces.

Disadvantages:
Multiple Main Journals/longer crankshaft.
More prone to Harmonic Imbalance.
Harder to maintain.



Advantages of Liquid Cooling:
Higher Thermodynamic Efficiency.

Disadvantages of Liquid Cooling:
Prone to coolant loss and subsequent engine failure.
Radiators and plumbing can be hard to fit.


Advantages of Aircooled:
Lighter, fewer parts.
Will operate longer in overheat condition before engine failure

Disadvantages:
Require more regular maintenance.
Hard to maintain adequate airflow.

Anyone else who has better information regarding this subject is more than welcome to speak up.
Here is everything I know about war: Someone wins, Someone loses, and nothing is ever the same again. Here is everything I know about life: The only certainties are death and taxes.
The enemy of freedom are those who proclaim only they can uphold it.

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Dave Saxton
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Re: A What-If on Liquid v. Air cooled/Radial v. Vee v. inlin

Postby Dave Saxton » Sun Jun 24, 2012 3:35 pm

The main advantage of liquid cooled engines in aircraft was better aerodynamics. Air cooled radial engines required a large flat cross sectional area at the front of the cowling which was terrible from an aerodynamic point of view. Thus Kurt Tank tried to over come this problem with the nose cone/prop spinner and cooling fan design on the FW190.

The problem of radiators making for dirty areodynamics, was one of they great design achievements of the P-51. The belly scoop of the P-51 was at least areodynamically nuetral. Any drag it created was off set by the small amount of thrust that came out of the back. The secret of the P-51 was its aerodynamics. It was so areodynamically clean -even into the transonic speed ranges. This would not have been possible with a radial engine.

Liquid cooled piston engines at this level of sophistication took many years to develop. For example, The Allison V1710 began development in the early 1930s and by Pearl Harbor was still under developed by comparison to the Merlin, or the Daimler Benz inverted V12's, or even the Hispano inline engines. The RR engines such as the Merlin and Griffon were developed on the foundation of RR's series of air racing engines dating back into the 1920s. New inline engine designs by Ford and Chrysler began during the war remained unready by the end of the war, and by then they had been eclipsed by jet engine technology. Chrysler was trying to design a X16 for the P-47 that would have allowed better aerodynamics (yet the basic P-47 airframe was already up against its transonic limitations).

Radial engines had been the mainstay of aircraft engines for decades and could be built to higher levels of power output, with greater levels of reliability, easier and sooner. Yet BMW's 800 series radial engine remained very problematic until 1942 when it began development during the 1930s.
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marcelo_malara
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Re: A What-If on Liquid v. Air cooled/Radial v. Vee v. inlin

Postby marcelo_malara » Mon Jun 25, 2012 12:57 am

There are two more things. Liquid cooling better preservates the engine, as que cylinder is cooled more even than a radial engine cylinder, which has hot spots that are difficult to deal with. The radial has an additional requirement in the machining of the cooling fins, which are machined from a solid ingot.

Regards

steffen19k
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Re: A What-If on Liquid v. Air cooled/Radial v. Vee v. inlin

Postby steffen19k » Tue Jun 26, 2012 6:36 am

Ok, back on task...

My original reason for this post was to see what sort of engine you would design, if you were responsible for engine development in WW2. I posted my idea, and that is the rough format for your entries. Just so long as you get the basics.

And note this is not about an engine that develops horsepower. This is just about what features you would use in your engine, keeping it to an approximate WW2 standard of parts. Anything from 1939 - 1946 goes, with the exception of turbines.
Here is everything I know about war: Someone wins, Someone loses, and nothing is ever the same again. Here is everything I know about life: The only certainties are death and taxes.
The enemy of freedom are those who proclaim only they can uphold it.


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