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Hey wuzak,
Do you know why the Eagle XVI was not proceeded with? That engine sounds kind of promising.
Problem here is like this...the British scrap the SMLE and go for the P14 rifle instead. How changed is history? Answer is zero.
There are some physical limits to V-12s that start getting into diminishing returns.
The Griffon was 36% larger than the Merlin but ran at 92% of the speed (rounding up) If you make the cylinders even larger your run into cooling problems, (less wall area for the volume) and if the stroke is longer you need to limit the rpm/piston speed assuming constant oil, piston ring, bearing technology. And flame travel unless you go to three spark plugs per cylinder.
This is why most designers shift to 16 or 24 cylinder engines if possible.
The Russian AM-35 engine used in the Mig-3 was a 2847 cu in engine but it ran at 2050 rpm. The later low altitude engines AM-38 ran at 2350rpm to get 1700hp. But the Russian were willing, A, to accept a rather low altitude for the power and B, accept a truly dismal engine life compared to western engines. Even so the engine ran at 2929 fpm piston speed for the 2350rpm version (on the short stroke pistons) compared to the Merlin's 3000fpm and the Griffon's 3025fpm.
An H16 engine might've been interesting for the airforces of the day - not as long, complicated and expensive as the 24 cylinder engines, with short & stiff crankshafts to better withstand stress, and with not too big cylinders so they can
Not sure what were the "short stroke pistons" there. The similarly big DB 603 run at 2700 rpm.
Big engines can offer a 'cushion' with regard to the fuel available - not everyone was sure that their fuel octane/performance rating will go up. Thus we have the AM-38 making much better power than the smaller VK-105 engines of the day and on the Soviet fuel available. Or the DB 603 making better power than DB 601/605 under the same conditions.
Fairy Monarch was a H24, the Prince was a H16
Fairey Monarch - Wikipedia
Devoid of the problems of complex crankshafts and Conrod forks as well as sleeve valves.
Not sure what were the "short stroke pistons" there. The similarly big DB 603 run at 2700 rpm.
Big engines can offer a 'cushion' with regard to the fuel available - not everyone was sure that their fuel octane/performance rating will go up. Thus we have the AM-38 making much better power than the smaller VK-105 engines of the day and on the Soviet fuel available. Or the DB 603 making better power than DB 601/605 under the same conditions.
Hispano 12Y was 2200 cu in compared to the Griffons 2240 cu in but the 12Y-45 weighed 1135lbs compared to the Griffon II (single stage/two speed) 1790lbs.
All this talk of engine development makes me ponder what would have changed if, for example, RR had pursued their early X16-cylinder engines wuzak mentioned up-thread. If RR had started development in the early-1930s, they should have at least found out the problems involved and worked out solutions, before they started on the Vulture. When the demand came along in the mid- to late-1930s I think that would have had a major effect on the practicality of large displacement powerful engines. How would a successful X16 design have affected the Kestrel/Merlin/Griffon path? Food for another thread maybe.
The AM-35/38 had different length stokes due to the articulated connecting rods. One bank of cylinders had over 6mm more stroke than the other. I gave the piston speed for the "short" stroke.
Big engines can offer a cushion, they also weigh more. AM-35 went over 1800lbs, the AM-38 was over 1900lbs the VK-105 went under 1300lbs for the early versions.
DB603 went over 2000lbs.
The bigger engines do have a better power to weight ratio, just not quite as good as a quick glance looks.
And in some cases it is two big engines or 3-4 small engines.
It is possible to make a big, light engine. It just won't stand up to high power or high rpm.
The BMW VI engine that the AM-35 is supposed to trace it's linage to was slightly larger (longer stroke on the articulated pistons) but only weighed 1124lbs.
of course it only ran at 1700rpm (for one minute) and gave 750hp at sea level (no supercharger)
Hispano 12Y was 2200 cu in compared to the Griffons 2240 cu in but the 12Y-45 weighed 1135lbs compared to the Griffon II (single stage/two speed) 1790lbs.
View attachment 618752
RR Condor of 1918-1930
327 made
2137 cu in
1380lbs
MK III gave 670hp at 1900 rpm, no supercharger and absolute crap fuel.
Most of the European/British engine makers had a large engine (or more than one) in their history.
What they learned or didn't learn may have varied and technology was constantly evolving. the Aluminum alloys of the mid 30s were not the alloys of the mid 20s, they stopped using castor oil as an engine lubricate, heat treatment changed and so on.
One large engine could at times replace two smaller ones, and sometimes to great advantage.
But sometimes an engine was a dead end, perhaps too complicated or it took long to develop and bring to market and had been passed by.
Probably simpler than 18cyl radial engines.
Them's Fighting Words!!!
V12s were very simple engine when looked at many competing designs, like H16, let alone X24, H24 or W24 engines. Probably simpler than 18cyl radial engines.
the physical layout is certainly simpler. It is the details that get complicated on many engines.
Lots of pictures of the Condor.
Rolls-Royce Condor IA, V-12 Engine | National Air and Space Museum
Take notice of picture 5.
4 valve head. but is a good one?
Like Bristol RR seems to be putting one intake and one exhaust valve on each side of the head? unless the head was semi spherical instead of pent roof?
size/shape of exhaust ports? intakes any better?
a longer description of the engine and changes made is here.
all-aero
The Condor used the older bore to stroke ratio rather than the bigger bore but shorter stroke (but still under square) ratio on the Kestrel, Merlin and Griffon.
size of valves needed to breath on a 1900rpm engine are different than the ones needed on a 2750-3000rpm engine.
Details like harmonic vibration, cylinder cooling (a 16 cylinder of the same displacement as a 12 is easier to cool) intake tract design and other things can complicate the "simple" V-12 to where a 16 or 24 cylinder engine looks attractive. Of course some designers under estimated the problems of the 16 and 24 cylinder engines
18 cylinder radials looked simple, just stick two 9 cylinder radials together, what could go wrong
Seems to me that intake valves were towards the inside, and exhaust valves were towards the outside on the Condor.
With V12 engines, there is a good deal of 'institutional knowledge' within companies for people to compare stuff by late 1920s/early 1930s. V12s were also used on luxury cars. Knowledge about 16, 18 let alone about 24 cylinders was small to non-existent; greater number cylinders and/or banks will tend to drive price and complexity of engine upwards very fast. Granted, there is a practical ceiling for engine displacement vs. weight/complexity/price, my point was that a working big V12 was too good of an opportunity (if the opportunity actually existed - eg. does not apply for Japan or USA in the 1930s/40s) to pass.
So in reality Britain could have waited till 1935 to order prototypes of a new fighter, this is about 1 year latter than the spitfire. Assuming progress was as fast as the defiant Britain would have the new fighter in service in late 1939.