Warbird Information Exchange

I started to find out if the inverted "V" engines of any manufacturer, with all cylinders down would need to have props hand turned or otherwise to clear out any oil that would drain into the cylinders as with the lower radial cylinders. Looking up the Daimler -Benz inverted "V" 603A and 605 , those engines had compression ratios of 7.5-1 on the left bank and 7.3-1 on the right bank. WHAT!!! ??? A reason given by some was the engine rotation and engine oiling. Can anyone give a diffinitive answer if inverted "V" engines needed prop turns, and why the diff. comp. ratios on the Daimler engines? The DB 601A - CR 6.9; and DB 600C- CR 6.8 have equal each bank.

The cylinders on RANGER 440 6 bangers, and I would assume on the 770 V-12 had long skirts that stuck up inside the cylinder block to prevent oil from creeping into the cylinders,and scavenge was through the camshaft housing on the bottom of the engine as I recall.

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Don't make me go get my flying monkeys-

Never saw either 109G (Black 6, Black 2) have the prop hand turned before flight that I can recall. Black 6 was cranked with the flywheel to start of course, never got volunteered for that...

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

@pjpahs: I have no idea if so, but you could try to get info on the Argus 10 C, 410 or 411 engines, all of them inverted "V" ones, though not liquid- but aircooled.

Michael

I've read of the differing compression ratios. The reason given was to compensate for different length and flow of the piping from the supercharger (offset to one side) to the cylinders. With the supercharger running at full speed the effective CR at the cylinders was the same.
Either the induction trunking was changed in later engines, or it was decided that it wasn't enough of an effect to worry about compared to possible variation in compression anyway

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Lest Hero-worship raise it's head and cloud our vision, remember that World War II was fought and won by the same sort of twenty-something punks we wouldn't let our daughters date.

We regularly pulled the A10 engine on the Storch thru before starting...required??? or just habit??? Only once did we pull the plugs to clear it (don't remember if it was locked) and squirted oil on the unlucky pilot that day who was standing about 60' away.

There was a discussion on the Flypast forum last year where it was stated the different compression ratios were because one bank received more oil splash than the other. Sounds feasible and the guy appears to know what he's talking about.

http://forum.keypublishing.com/showpost ... stcount=40

I'm afraid I don't buy the "splash oil" reasoning. If that were the case horizontally opposed engines would be subject to the same issue, and they are not, from any practical point of view.

The poster also questions roller bearings used at the big end - which continued to be used quite successfully in post-war racing applications until modern shell bearings with exotic materials reduced their advantage, and the benefits of direct fuel injection, which, aside from the classic diving Messerschmidt anecdotes, has shown to be advantageous enough that no production automobile (available in the US at least) has been fitted with a carburetor in the last 20 years.*



*and before someone says you can't compare automotive and aircraft engines, I work with a/c recips and if you want to discuss legislated technology stagnation that should be a another thread entirely.

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Lest Hero-worship raise it's head and cloud our vision, remember that World War II was fought and won by the same sort of twenty-something punks we wouldn't let our daughters date.

I'm not sure how you can say horizontally opposed engines would have the same problem. The majority of any excess oil would drain into the crankcase, with an inverted engine the only place it can go is to/through the rings.

The excess oil in an inverted engine is collected in troughs in the crankcase, where it is either routed to the valve gear, rocker cover and through the scavenge pump to the tank, or directly to the scavenge pump to the tank.
If the splash from the crank did collect significantly more on one side of the engine in a way that would affect the compression ratio, then it would also happen in horizontally opposed engines, or upright V's, or even W's no matter how the oil ultimately drained out. For that matter, it would mean that radial engines should have varying CR's from top to bottom, which is a design feature I've certainly never heard of.

Like a radial, more oil may drain through the rings at rest than an upright V engine, but if enough oil is getting through them while running to affect the compression ratio, then you would have serious problems no matter what configuration the engine is in.

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Lest Hero-worship raise it's head and cloud our vision, remember that World War II was fought and won by the same sort of twenty-something punks we wouldn't let our daughters date.

Do the connecting rods of the Benz engines share a crank pin, or is on a master rod and the other a link rod?

If you google daimler benz 605 on wikipedia will show a section view that can be enlarged and would show the piston rods. One is forked over the one that rides on the crank throw . Interesting design of the head to block connection.