Inverted V engine vs. V engine

Readie · Jul 6, 2011

Kryten said:
I'm still not fully comprehending the reasoning to invert the engine, as it does seem to produce more issues than an upright installation, and offers little if any realistic advantage?

Join the club, neither do I and I have to say that I'm not been convinced by the points on this thread.
Cheers
John

Mustang nut · Jul 6, 2011

Readie said:
Join the club, neither do I and I have to say that I'm not been convinced by the points on this thread.
Cheers
John

I think this thread has thrown up some interesting stuff both types have plusses and minuses. Personally I think in the 1920s and 30s designers had less of a fixed idea about what was the "right way up" then going down whichever road they chose they had to find solutions to the problems they threw up.

P-40K-5 · Jul 6, 2011

advantages were two main ones:

lower center of gravity, and increased pilot foward visability due to having the engine inverted.

Shortround6 · Jul 6, 2011

The center of gravity is dubious and the better view was theoretical. While it should give a better view than an upright engine in the SAME air-frame (check Spanish 109s with Merlins) the location and size of the cockpit in relation to the engine may have more to do with the view than which way the V went.

P-40K-5 · Jul 6, 2011

oh lordy lordy. the DB605 sits much more below the C/L of the a/c, as compared to say, oh, a P-40.
while I agree with the Pilots visibility, perhaps a better reason to invert the engine would be for the machine guns placement
and the cannon. does that make more sense?

Readie · Jul 6, 2011

P-40K-5 said:
oh lordy lordy. the DB605 sits much more below the C/L of the a/c, as compared to say, oh, a P-40.
while I agree with the Pilots visibility, perhaps a better reason to invert the engine would be for the machine guns placement
and the cannon. does that make more sense?

That would be one option. but, if the cannons/machine guns fit in the wings why place them around the engine?
Unless, the wing space was needed for fuel tanks?
DB preferred inversion, RR preferred conventional. Both produced powerful engines, so may be they were both right....
Cheers
John

P-40K-5 · Jul 6, 2011

the more weight you keep off the wings, the better I would think, no? (" dutch roll" is that what I'm thinking of?) I know that when cannons where placed on the wings,
the overall performace suffered. same with the struts being attached to the fuse rather then the wing.

fastmongrel · Jul 6, 2011

The heaviest part of an engine is the crank and crankcase. I dont think it would make a massive difference in centre of gravity whether it was upright inverted or on its side. If you look at drawings of a DB and a RR engine there isnt much difference in height if you flip them over its a matter of a few inches, nothing raising the cockpit the same wouldnt cure.

P-40-K5 I am still interested where you think the authors of Tartles quoted piece made mistakes I am not an expert but would like to read further.

gjs238 · Jul 6, 2011

The Merlin powered Spanish Bf-109 is interesting.
Anyone have details?
Performance changes?

Kryten · Jul 6, 2011

Shortround6 said:
The center of gravity is dubious and the better view was theoretical. While it should give a better view than an upright engine in the SAME air-frame (check Spanish 109s with Merlins) the location and size of the cockpit in relation to the engine may have more to do with the view than which way the V went.

Yes it does actually, every design has compromises so inverting the engine to allow the placement of weaponry would be a passible trade off if that was required when your looking to keep rotational masses down in the wings, we have to bear in mind however the Me109 in its original guises was put into service with wing mounted weapons?

P-40K-5 · Jul 6, 2011

fastmongrel said:
The heaviest part of an engine is the crank and crankcase. I dont think it would make a massive difference in centre of gravity whether it was upright inverted or on its side. If you look at drawings of a DB and a RR engine there isnt much difference in height if you flip them over its a matter of a few inches, nothing raising the cockpit the same wouldnt cure.

P-40-K5 I am still interested where you think the authors of Tartles quoted piece made mistakes I am not an expert but would like to read further.

I'm no expert either, not by a long shot. but I covered the mistakes in post #108. I appologise if it wasn't thorough, what specifically?
I wouldn't be to sure about most of the wieght being in the crank and lower crankcase, remember the crankshaft did not have counter-
weights.

Kryten said:
Yes it does actually, every design has compromises so inverting the engine to allow the placement of weaponry would be a passible trade off if that was required when your looking to keep rotational masses down in the wings, we have to bear in mind however the Me109 in its original guises was put into service with wing mounted weapons?

nicely put!

tyrodtom · Jul 6, 2011

I've never had a V12 on a engine stand, but i've had plenty of V8's on one.
While the crank and rods may be the heaviest components in the engine, they can't compensate for all the weight of the complicated metalwork in the head ( valves, springs, cams, passages,) and the fact that in a V engine there are TWO of them. Any V engine put on a rotating engine stand wants to go pan up, if you leave it free to rotate.

Readie · Jul 6, 2011

tyrodtom said:
I've never had a V12 on a engine stand, but i've had plenty of V8's on one.
While the crank and rods may be the heaviest components in the engine, they can't compensate for all the weight of the complicated metalwork in the head ( valves, springs, cams, passages,) and the fact that in a V engine there are TWO of them. Any V engine put on a rotating engine stand wants to go pan up, if you leave it free to rotate.

The oil has to drain out somehow JOKE...

I assume you mean cast iron USA V8's? Very heavy.

If RR thought inversion would be better then they would have gone down that route.

Cheers
John

P-40K-5 · Jul 6, 2011

ALL aluminum USA V-8's do the same thing, wanna roll onto there back.
well at least my Chevy 6.0L LS series engine does anyways. most 'V' style
engines are very top heavy.

Readie · Jul 6, 2011

P-40K-5 said:
ALL aluminum USA V-8's do the same thing, wanna roll onto there back.
well at least my Chevy 6.0L LS series engine does anyways. most 'V' style
engines are very top heavy.

Fair comment. I have most experience with in line 4's.

tyrodtom · Jul 6, 2011

I've not read a convincing arguement for either arrangement.

Just saying the upright V is the best because RR did it that way, and their side won the war, doesn't have a lot of meat in it.

There's advantages and disadvantages to either orentation.

DB and Jumo went inverted because that was a requirement from their air ministry, ( from a previous poster ). Who knows what they would have come out with without that restriction ? Be seeing as how most civilian engines of that era were inverted, or partly inverted in the case of radials, DB wasn't exactly breaking new ground.

The only major disadvantage I can see to a inverted V is more oil lose through the ring seal, into the combustion chamber, but it would partly compensate for that through less oil leakage through the valve stems.

P-40K-5 · Jul 6, 2011

tyrodtom said:
I've not read a convincing arguement for either arrangement.

The only major disadvantage I can see to a inverted V is more oil lose through the ring seal, into the combustion chamber, but it would partly compensate for that through less oil leakage through the valve stems.

in the pic below you can see the 5 ring setup, 3 compression 1 oil ring relativley close together, with 1 more oil ring way down on the skirt.
it somewhat remedeed that problem. although it did wear the cylinder bores somewhat faster then normal.

fastmongrel · Jul 6, 2011

Those knife and fork rods and roller bearings look like a complicated job to make and assemble. Was the forked rod a single forging or is it 2 slim seperate rods mounted side by side.

Shortround6 · Jul 6, 2011

The forked rods were almost always a single forging.

When mounting an auto engine on a stand is the pivot point near the crankshaft or is it near the camshaft on a cam in block engine?

While the aircraft's center of gravity doesn't have to be on the propeller center line I am not sure that the center of gravity of the engines is going to be that different. The Upright engines had the crankshaft offset a number of inches down in relation to the propeller.

Here is a picture of a V-12 Hispano without cylinder blocks showing the 20mm cannon. There is an awful lot of engine below the center-line of the propeller and if you flipped it there would be an awful lot of engine over the center line. Please note that the entire supercharger is below the cylinder blocks.

http://www.quarry.nildram.co.uk/img319.jpg

Now maybe the German engines were able to mount the gun (centerline of the prop) a bit closer to the crankshaft but there is still going to be a lot of engine above that centerline.

P-40K-5 · Jul 6, 2011

Hello,

you are correct that the CofG does not run along the C/L of the propeller hub. it is several inches higher on a Bf109 for instance.

interesting on the name for the Rods, I always called them std. I-Beams. sorry for the confussion.
pivot point on my stand anyways is at the camshaft. many years of working with "V" style engines
I can safely say they are top heavy for the most part.

Inverted V engine vs. V engine

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