Build the perfect water cooled engine

[Readie]

Indeed, you're right. It would've been cool if someone has the good data covering the rigidity of the boxer engine crankcase whole engine.

Further to shortrounds post.
The Porsche flat 6 is as smooth as an Englishman in the Costa de Sol.
The Subaru flat 4 is grunty.
These are both powerfull motors.
Aren't some light aircraft engines flat 6 /4's ?
Cheers
John

 

[Shortround6]

Almost all modern (after the 60's) light aircraft engines are flat fours and sixes. But they are large engines compared to car engines. over 8 litres for 300hp. They are separate cylinder air cooled engines over 90% of the time. and for the most part, the bigger ones are being fitted to aircraft that have side by side seating, width isn't that big a concern. A 100hp Lycoming four has an overall width wider than a Merlin.
Just because an engine works as a Six doesn't mean it will work as a twelve without a little beefing up. with a crankshaft twice as long the twelve with suffer more from torsional vibration, which is not a vibration that a pilot or driver would really feel.

It is perfectly possible to design a flat twelve with enough strength to handle the load the designer wants. It is just that because of the shape of the engine it will be heavier than an equivalent V shape engine. The designer may go for the flat engine anyway because of other considerations that trump the weight difference.

 

[Readie]

Almost all modern (after the 60's) light aircraft engines are flat fours and sixes. But they are large engines compared to car engines. over 8 litres for 300hp. They are separate cylinder air cooled engines over 90% of the time. and for the most part, the bigger ones are being fitted to aircraft that have side by side seating, width isn't that big a concern. A 100hp Lycoming four has an overall width wider than a Merlin.
Just because an engine works as a Six doesn't mean it will work as a twelve without a little beefing up. with a crankshaft twice as long the twelve with suffer more from torsional vibration, which is not a vibration that a pilot or driver would really feel.

It is perfectly possible to design a flat twelve with enough strength to handle the load the designer wants. It is just that because of the shape of the engine it will be heavier than an equivalent V shape engine. The designer may go for the flat engine anyway because of other considerations that trump the weight difference.

On the button SR.
I see what you mean and thanks for thev information update.
cheers
John

 

[tomo pauk]

The propellor shaft was positioned so it was in the centre of area of the engine when looking from the front. When it wa sinstalled in the airframe it gave less frontal area than otherwise, and thus less drag.

The gearbox of the boxer would've been located at almost same position for fighter plane installation, with a cannon behind the prop, then hull fuel tank, then cockpit. Totally a conservative layout, like Yak-9 or something.

 

[wuzak]

I think this picture helps with what I am trying to say....

http://www.gkweb.net/images/machines/engines/merlin/images/0701071210.jpg

Notice that the engine protrudes very little from the line of the spinner. A boxer engine would have a significant amount of the block and heads hanging out from the side of the spinner, be it above or below centreline (for one with a motor cannon), or on centreline (for a coaxial reduction drive).

 

[wuzak]

Her is a front view of the Merlin

http://www.aviationphoto.co.uk/Front view Rolls Royce Merlin engine Hangar 11 Feb 10.jpg

The round cover plate on the centre of the black part of the reduction gear housing cover is where the crankshaft is. The width of a boxer version of the Merlin is twice the distance from its centre to the top of the cam cover. The prop drive would likely be in a similar position, as the reduction ratio would need to be the same (or similar) and the pinion (the smaller gear) probably could not be much smaller. The ratio determines the size of the gear in comparison to the pinion, and the sizes of teh gear and pinion determine the centre distance between them.

 

[Shortround6]

If I may be so bold as to interpret for you, while the placement of the propshaft on the Merlin did not actually reduce the square footage of the frontal area, it did allow for a more symmetrical cowling over the front of the engine which may have made streamlining it easier?

 

[tomo pauk]

Already posted in this thread (the rounded red rectangle shows approximate layout of engine block, in boxer configuration); the variant with coaxial drive would've neatly served in Mosie

 

[Shortround6]

Getting back to the original idea the "ideal" liquid cooled engine is going to be a V-12 (either upright or inverted) or an H-24 (more than likely horizontal) of between 35 and 45 litres displacement. 4 valves per cylinder if poppet valves or sleeve valves. If it is to be used for a variety of roles then it should have the ability to use several supercharger designs or configurations.

Now we get into 'trade-offs':
What is the configuration more likely to cost less per engine,
What is the configuration that will be easiest to service.
What will be the TBO hoped for.
Is there a maximum or minimum desired weight.

 

[Shortround6]

Already posted in this thread (the rounded red rectangle shows approximate layout of engine block, in boxer configuration); the variant with coaxial drive would've neatly served in Mosie

I am still not seeing what this gets you. Unless you can come up with a bunch of very tiny pilots

If you move the propeller down more in line with engine you wind up hitting the ground or using a lot of small blades.

Or having some really strange landing gear.

If you leave the prop where it is you don't gain much in making the frontal area smaller.

Yes you do get room for a cannon but that is a lot of hoop jumping to go through.

A few dimensions for your consideration.

Width of the Merlin ........30in.
Width of the Sabre ........40in.
Width of O-1230............44in.
height of Arsenal 24H..... 59in.
height of Hispano 24Z.....54.5in
Width of Potez 12D.........37.2in
Height of Potez 12D........32.7in

The Lycoming engine was one of the US hyper engines and was good for about 1200hp at 3400rpm from it's 20.2 litres, later doubles into a 24cylinder H engine. used a 120mm stoke.
The Arsenal 24 used Jumo 213 cylinder blocks in an H arrangement and if lair flat a few inches could be trimmed from the height but 165mm stokes don't go with flat engines very well.
Same for the Hispano, a 24 cylinder H engine using Hispano Z cylinder blocks. 170mm stoke, again a few inches could be saved if laid flat.
Potez is air cooled but uses a spur gear to offset the propshaft to the top. It is also a 17.6 liter engine with a 120mm stoke. It used push rods and had the supercharger horizontal underneath the crankcase.
The Sabre used a a 121m stoke and half a one is going to give an 18.4 litre engine with about 1000hp for most of the war.

BTW, the Mossie still has to fit the landing gear behind the engine

 

[wuzak]

The Pennine was 39in wide x 37.5in high - a sleeve valve X24 (air cooled). It's stroke was either 5in/127mm (according to Wiki) or 5.08in/129mm (according to Lyndon Jones/RRHT).

The Merlin 61 was 30.8in wide x 40in high.
Earlier Merlins were slightly different, and 130 series engines were not as tall due to downdraft induction (rather than updraft).

The Griffon was 30.3in wide x 46in high. (Stroke 6.6in/167.6mm)

The Sabre was 40in wide x 46in high. (Stroke 4.75in/121mm)

The Napier Dagger was 22.5in wide x 45.125in tall (Stroke 3.75in/95.25mm).

The DB505 was 30in wide x 41in high. (stroke 160mm/6.3in)

 

[wuzak]

The Rolls-Royce R, which was based on the Buzzard and had the same cylinder dimensions as the Griffon, was 32in wide x 42in high.

 

[Lighthunmust]

Getting back to the original idea the "ideal" liquid cooled engine is going to be a V-12 (either upright or inverted) or an H-24 (more than likely horizontal) of between 35 and 45 litres displacement. 4 valves per cylinder if poppet valves or sleeve valves. If it is to be used for a variety of roles then it should have the ability to use several supercharger designs or configurations.

Now we get into 'trade-offs':
What is the configuration more likely to cost less per engine,
What is the configuration that will be easiest to service.
What will be the TBO hoped for.
Is there a maximum or minimum desired weight.

Please give me a reality check:

The Vee would probably cost less due to simplicity.
The Vee would probably be easiest to service because of easier access to all parts.
A poppet valve engine would be easier to service for minor repair but a sleeve valve engine for major repair.
The time between overhaul would be greater for the poppet valve engine.
I am not sure which configuration would be lighter for the same displacement or power, I assume the Vee.

You know I am never going to get around to finishing the reading of those engine books I bought if you guys keep this up.

 

[davparlr]

An issue of Flight magazine is interesting regarding liquid cooled verses air cooled engines.

fig | fineness ratio | frontal area | 1941 | 0626 | Flight Archive

 

[Trilisser]

Lighthunmust, it would be highly likely that sleeve valves provide much longer TBO as far as valve gear is considered. Harry Ricardo found out in his tests that in high time engines the cylinders of a sleeve valve engine had much less wear. Plus as in the sleeve mechanism there no compnent that is subject to pure reciprocating movement the stress would be lower there as well. E.g. the standard Merlin valve gear is no good for long TBO.

As for servicing, I would say the same.

 

[Shortround6]

Please give me a reality check:

The Vee would probably cost less due to simplicity. A 12 is going to cheaper than a 24
The Vee would probably be easiest to service because of easier access to all parts. A 12 is going to be easier to service than a 24
A poppet valve engine would be easier to service for minor repair but a sleeve valve engine for major repair. This one is debatable, the sleeve valve should make it to major overhaul without any work on the valve train excluding battle damage)
The time between overhaul would be greater for the poppet valve engine. Sleeve valve engines (the radials) wound up with much longer TBOs but that was post war
I am not sure which configuration would be lighter for the same displacement or power, I assume the Vee. the Griffon and the Sabre were about 1 cu in difference in displacement so make a good comparison. With single stage two speed superchargers the Sabre was more powerful, depending on version much more powerful, it could also be 600lbs (31%) heavier.

You know I am never going to get around to finishing the reading of those engine books I bought if you guys keep this up.

Please read, I don't think I can type several hundred pages

 

[tomo pauk]

I am still not seeing what this gets you. Unless you can come up with a bunch of very tiny pilots

If you move the propeller down more in line with engine you wind up hitting the ground or using a lot of small blades.

Or having some really strange landing gear.

If you leave the prop where it is you don't gain much in making the frontal area smaller.
Yes you do get room for a cannon but that is a lot of hoop jumping to go through.

As I've already said, the reduction gear layout remains almost the same. The advantage of boxer vs. V is that intake manifolds are not as tightly mounted, so there is plenty of room for cannon it's ammo above the crankshaft, so not so mach of hoop jumping here

A few dimensions for your consideration.

Width of the Merlin ........30in.
Width of the Sabre ........40in.
Width of O-1230............44in.
height of Arsenal 24H..... 59in.
height of Hispano 24Z.....54.5in
Width of Potez 12D.........37.2in
Height of Potez 12D........32.7in

Since the boxer can be mounted so to lay more or less in line with wings, while being half of the height of a comparable V engine, the drag cost is negligible.

The Lycoming engine was one of the US hyper engines and was good for about 1200hp at 3400rpm from it's 20.2 litres, later doubles into a 24cylinder H engine. used a 120mm stoke.
The Arsenal 24 used Jumo 213 cylinder blocks in an H arrangement and if lair flat a few inches could be trimmed from the height but 165mm stokes don't go with flat engines very well.
Same for the Hispano, a 24 cylinder H engine using Hispano Z cylinder blocks. 170mm stoke, again a few inches could be saved if laid flat.
Potez is air cooled but uses a spur gear to offset the propshaft to the top. It is also a 17.6 liter engine with a 120mm stoke. It used push rods and had the supercharger horizontal underneath the crankcase.
The Sabre used a a 121m stoke and half a one is going to give an 18.4 litre engine with about 1000hp for most of the war.

Thanks

BTW, the Mossie still has to fit the landing gear behind the engine

Of course, will try to draw that too
(edit - attached down; diameter of the wheel is only slightly greater than of the spinner, so we have a net gain drag-wise. Or mr. de Havilland can install the undercarriage akin to P-36/40, or F4U/6F)

(key:
red - boxer
green - prop spinner
pink - cannon barrel for Spit)

 

[Lighthunmust]

Lighthunmust, it would be highly likely that sleeve valves provide much longer TBO as far as valve gear is considered. Harry Ricardo found out in his tests that in high time engines the cylinders of a sleeve valve engine had much less wear. Plus as in the sleeve mechanism there no compnent that is subject to pure reciprocating movement the stress would be lower there as well. E.g. the standard Merlin valve gear is no good for long TBO.

As for servicing, I would say the same.

Please read, I don't think I can type several hundred pages

Thanks for the replies guys. I had a headspace and timing error when I wrote poppet when I meant to write sleeve about longer TBO.

I am trying to stay off this addictive forum for a while so I can get that reading done. So if you don't see me around for a while that is what I am doing.

Thanks again guys.

 

[wuzak]

Daimler Benz DB604 (X24)

Daimler Benz DB606


Uploaded with ImageShack.us

 

[wuzak]

Talking about dimensions, the V-3420 was 56.0 in (1,422 mm) wide x 34.0 in (864 mm) high and 100.0 in (2,540 mm) long.

This makes it slightly wider than the big radials (R-2800, R-3350, R-4360, Centaurus, Hercules), significantly shorter (height wise) and somewhat longer.