Why were V engines 12 cylinders?
- Thread starter Admiral Beez
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From V12 engine - Wikipedia
Balance and smoothness
Each bank of a V12 engine essentially functions as a straight-six engine, which by itself has perfect primary and secondary engine balance. By using the correct V-angle, a V12 engine can therefore have perfect balance. The even firing order for a four-stroke V12 engine has an interval of 60 degrees, therefore a V12 engine can be perfectly balanced if a V-angle of 60 degrees, 120 degrees or 180 degrees is used. Many V12 engines use a V-angle of 60 degrees between the two banks of cylinders.[1] V12 engines with other V-angles have been produced, sometimes using split crankpins to reduce the unbalanced vibrations. The drawback of a V12 engine is the extra cost, complexity and friction losses compared with engines containing fewer cylinders.
At any given time, three of the cylinders in a V12 engine are in their power stroke, which increases the smoothness of the power delivery by eliminating gaps between power pulses.
A V12 engine with a 180 degree V-angle is often called a flat-twelve engine (or a 'boxer twelve'). However, this terminology is incorrect for the majority of 180-degree V12 engines, since they use shared crankpins and are therefore not configured as flat engines.[2]
Theoretically, the rotating parts of a V12 racing engine could be lighter than a crossplane V8 engine of similar displacement, due to the V12 engine not requiring counterweights on the crankshaft or as much inertial mass for the flywheel. In addition, the exhaust system of a V12 engine is much simpler than would be required for a crossplane V8 engine to achieve pulsed exhaust gas tuning. However, use of V12 engines in motor racing is uncommon in the 21st century.
Balance and smoothness
Each bank of a V12 engine essentially functions as a straight-six engine, which by itself has perfect primary and secondary engine balance. By using the correct V-angle, a V12 engine can therefore have perfect balance. The even firing order for a four-stroke V12 engine has an interval of 60 degrees, therefore a V12 engine can be perfectly balanced if a V-angle of 60 degrees, 120 degrees or 180 degrees is used. Many V12 engines use a V-angle of 60 degrees between the two banks of cylinders.[1] V12 engines with other V-angles have been produced, sometimes using split crankpins to reduce the unbalanced vibrations. The drawback of a V12 engine is the extra cost, complexity and friction losses compared with engines containing fewer cylinders.
At any given time, three of the cylinders in a V12 engine are in their power stroke, which increases the smoothness of the power delivery by eliminating gaps between power pulses.
A V12 engine with a 180 degree V-angle is often called a flat-twelve engine (or a 'boxer twelve'). However, this terminology is incorrect for the majority of 180-degree V12 engines, since they use shared crankpins and are therefore not configured as flat engines.[2]
Theoretically, the rotating parts of a V12 racing engine could be lighter than a crossplane V8 engine of similar displacement, due to the V12 engine not requiring counterweights on the crankshaft or as much inertial mass for the flywheel. In addition, the exhaust system of a V12 engine is much simpler than would be required for a crossplane V8 engine to achieve pulsed exhaust gas tuning. However, use of V12 engines in motor racing is uncommon in the 21st century.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
That's the clearest technical explanation I've read in years. Thanks!!!
Shortround6
Major General
There are/were several physical limits to cylinder size and to get the required power they usually needed 12 cylinders. The Mikulin AM-35 series used about the biggest liquid cooled cylinders in a liquid cooled engine. If you had tried a V-8 using the same size cylinders you would have had an 1880 cu in engine which fits in with the others but some of those physical limits meant it didn't run much over 2000rpm which would rather limit it's power compared to the 1650-2300 cu in V-12s that ran at 2400-3000rpm.
A V-8 of the same displacement is shorter and lighter than a V-12. However the bigger cylinders tend to limit rpm and breathing (although supercharging helps overcome that)
V-16s are longer and heavier and run into torsional vibration problems, the longer a crankshaft is the greater the tendency to twist and untwist as the engine runs. This is totally different than the pistons going up and down in balance or other forms of vibration. Most V-16s that were designed for aircraft (or racing cars) were actually set up as two V-8s (in regards to the crankshaft anyway) including the example you linked to. the reduction gear to the propeller drive was in the middle of the engine and the propshaft ran through the the inside of the V of one of the 8 cylinder sections.
These are generalities and exceptions may be found.
The Hispano engines were developed from V-8 engines, in fact some of the bore spacing, valve arrangements (size and spacing) on the early Hispano V-12s were the same as the V-8s so they could use some of the same tooling even if the V angle changed.
The V-12 gave the most power with the fewest problems while keeping the weight and frontal area the lowest. The old Napier Lion engine
was a W-12 and shows the another side of the compromise. Short, stiff, crankshaft and crankcase for lightness, but larger frontal area.
wuzak
Captain
There was the DB 609 - a V-16. Same stroke as the DB 603, but larger bore, 61.8L capacity.
The DB 603 was already a log engine, so the DB 609 was huge.
http://www.enginehistory.org/Piston/Daimler-Benz/ged0111.jpg
Opportunity lost - DB 16 cyl
And the Chrysler IV-2220 - essentially arranged as two V8s with the power take-off in the middle.
And FIAT A.38, A.40, and A.44 Aircraft Engines
Rolls-Royce were asked to develop an engine in the same class as the Curtiss D-12, but better and more powerful. Rolls-Royce came up with two engines - the F and the Eagle XVI.
The F would be developed into the Kestrel (and scaled 6/5 to become the H/Buzzard/R).
The Eagle XVI was an X-16 unsupercharged engine (as was the F). It was slightly smaller in capacity (19.8L vs 21.2L). The Eagle XVI had no relationship to the earlier Eagle series.
The Eagle XVI was not built into an airworthy engine, the airframe manufacturers and the government preferring the size and shape of the Kestrel. Royce preferred the Eagle XVI.
One wonders what would have happened had the Eagle XVI been chosen ahead of the F - whether the Merlin would have been developed as an X engine.
Note that the Eagle XVI used fork and blade rods, like the Kestrel, Merlin and Griffon, and not the master and slave rods of the Vulture. This meant that two banks were set back from the other two.
The DB 603 was already a log engine, so the DB 609 was huge.
http://www.enginehistory.org/Piston/Daimler-Benz/ged0111.jpg
Opportunity lost - DB 16 cyl
And the Chrysler IV-2220 - essentially arranged as two V8s with the power take-off in the middle.
And FIAT A.38, A.40, and A.44 Aircraft Engines
Rolls-Royce were asked to develop an engine in the same class as the Curtiss D-12, but better and more powerful. Rolls-Royce came up with two engines - the F and the Eagle XVI.
The F would be developed into the Kestrel (and scaled 6/5 to become the H/Buzzard/R).
The Eagle XVI was an X-16 unsupercharged engine (as was the F). It was slightly smaller in capacity (19.8L vs 21.2L). The Eagle XVI had no relationship to the earlier Eagle series.
The Eagle XVI was not built into an airworthy engine, the airframe manufacturers and the government preferring the size and shape of the Kestrel. Royce preferred the Eagle XVI.
One wonders what would have happened had the Eagle XVI been chosen ahead of the F - whether the Merlin would have been developed as an X engine.
Note that the Eagle XVI used fork and blade rods, like the Kestrel, Merlin and Griffon, and not the master and slave rods of the Vulture. This meant that two banks were set back from the other two.
pinehilljoe
Senior Airman
- 673
- May 1, 2016
good summary, also the same reason 6 cylinders in cars are smoother than straight 4's.
MIflyer
1st Lieutenant
RR used the Merlin engine as a basis for a V-12 tank engine. Ford was given drawings of the Merlin and asked if they wished to produce it, and declined - but then came out with a V-12 engine of similar design and then actually produced a similar V-8 engine for use in tanks.
I guess the main reason that V1-2's were used was to provide higher horsepower. Smaller air cooled engines, including inverted V's, radial and flat horizontally opposed engines were availble for the lower power ranges and it was pointless to compete in that area.
I guess the main reason that V1-2's were used was to provide higher horsepower. Smaller air cooled engines, including inverted V's, radial and flat horizontally opposed engines were availble for the lower power ranges and it was pointless to compete in that area.
- Thread starter
- #8
Admiral Beez
Captain
So did RR, the Meteorite - their V-8 also included a diesel variant.
wuzak
Captain
Ford was approached to build the Merlin under licence because Ford UK already were starting that process. Henry Ford was willing to build the Merlin - but only for use by US forces.
Since that defeated the purpose of having the Merlin built in the US, Rolls-Royce went elsewhere and ended up with Packard.
In the end, they both should have been building Merlins in the US.
The US could have put them to good use.
- Thread starter
- #11
Admiral Beez
Captain
Ford does have a habit of making strange business decisions. This is not a Mustang, for instance.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
You could have come up with better proof of strange Ford decisions. I'm thinking the 1958 model year. Anyone?
swampyankee
Chief Master Sergeant
- 3,954
- Jun 25, 2013
A quibble: fork and blade rods don't require offset between the cylinder banks; plain rods would. Each type has its pros and cons. One of the cons of plain rods is they force an offset between banks. Fork-and-blade rods require a bearing surface between the big ends. Articulated rods, if the geometry isn't done right, will result in different strokes for the two cylinder banks. I suspect they're also the heaviest of the three types.
soaringtractor
Banned
- 33
- May 8, 2014
Because actually all V12 engines are really just two six cylinder engines attached to the same crank !!! The six cylinder is one of the most balanced of all engine designs !!! The most correctly balanced design with any capacity....smoothness and compact design !!!
soaringtractor
Banned
- 33
- May 8, 2014
Henry Ford REFUSED to build the Merlin for the Brits, would only build for US use !!!! WHY RR had to go elsewhere....to Packard, as Chrysler had already refused to build the merlin.... a fact that does NOT seem to be well known......info from "PACKARD as an aero Engine builder, Packard Merlin , by Robert J Neil....
soaringtractor
Banned
- 33
- May 8, 2014
What else would/could have used the merlin ???? The first order of 3,000 merlins for the USA had no plane to put them in !!!! They used them in 1311 P40 F&L's but the V1650-1 single stage engine made no difference in the performance of the P40. Actually the Allison performed better in all aspects of fighter service only giving some slight gain in altitude do to the 2nd SPEED on the supercharger of the early merlin, Maybe the P38 could have used the merlin....BUT only IF it were the LATER 60 series 2 stage supercharged version...........the turbocharged Allison out performed the 20 series single stage merlin !!!
They did have a plane to put the Merlins, apart the P-40 - the P-51.
The P-40F was faster by 20-30 mph above 18000 ft than P-40E or K. Despite the multiple question marks and explanation marks.
Early turbocharged V-1710s (1941-42) were barely better than V-1650-1, wile being heavier (due to turbo and intercooler), requireing bigger & heavier prop, and required more levers to operate. Times 2, since there were 2 engines on P-38.
wuzak
Captain
Each pair of banks had a fork and blade rod set up in the Eagle XVI.
So there was an offset between (IIRC) the upper and lower banks).
Articulated rods will always have different strokes than the master rod, except for one where the cylinder is directly opposed to the master cylinder.
- Thread starter
- #19
Admiral Beez
Captain
- Thread starter
- #20
Admiral Beez
Captain
Plus the Hurricanes (1940-43) and later Lancasters and Mosquitos produced in Canada.
