Radial engines more favored in Germany, 1935-45?

[don4331]

When the gov't is trying to limit warplane size, its extremely difficult to order large engines... USA was fortunate that the commercial industry was wanting larger planes and with them larger engines. Large twin is more economical to operate than quad engined plane. If industry isn't designing airframes for 2,000hp/2000lb engines why would a engine business commit to developing them?

Aside: Even in '90s, I could get from Canary Wharf (London) to Guyancourt (Paris suburb) faster on tube/train(Chunnel), than my colleague could drive/fly (via Heathrow/de Gaulle - if he got flight via City/Orly, bets were off). It was hard for commercial aviation to compete in Europe during 30s.

R-2800 broke so many crankshafts during development that P&W questioned if high power 18 cylinder was even possible. And even when they got it running they had issues with gallons of oil getting whipped like toffee around the crankshaft limiting power. Does Germany have the resources both human and financial to tackle the problem.

The issue with starting too soon is your 87 octane with pre Rubbra supercharger on derated R/Buzzard/Griffon I needs the nameplate lifted off the engine and everything underneath replaced with clean sheet design for 100 octane with post Hooker supercharger on Griffon IV. Which is what happened with RR's "big block" V-12. Thankfully, for RR only prototype had be build because if they had committed to production tooling Griffon might never have seen light of day.

Vulture starts out with that wonderful idea - just connect 4 Kestrel blocks/cylinder heads on common crankcase. But when the initial testing of single row "X", demonstrates that the master/slave rod(s) need more bearing area, so Vulture needs its own block/cylinder heads, RR should have shutdown the project and re-evaluated if it was the right engine to be focusing on. Especially when Peregrine is on the chopping block, so all parts become unique to the X-24 engine (OK, there might be some parts common to Kestrel and RR was pumping out Kestrels for advanced trainers, etc).

Note: Germany's war is won/lost in the battle with Russia. Does committing to radial engines solve that problem?

 

[Shortround6]

OK, there might be some parts common to Kestrel and RR was pumping out Kestrels for advanced trainers, etc).

I am not sure about this. I could very well be wrong but one story is that they had hundreds (if not well over 1000) Kestrels in stock that were reverbs/rebuilt engines taken out of some of the vast fleet of Hart family aircraft and those are what went into Miles trainers. Limited new parts for maintenance?

 

[tomo pauk]

Note: Germany's war is won/lost in the battle with Russia. Does committing to radial engines solve that problem?

Germany shot themselves in the foot by attacking East without securing a workable peace with the UK, that left them fighting west of France and south of Italy. Starting out against another big opponent, despite having meager access to raw materials and fuel while depending on enemy to drop in the towel when they wanted was the death warrant.

Scenario that discusses the ways for German win, or even not loosing the ww2, starts with fixing their Grand Startegy 1st.

 

[z42]

Germany shot themselves in the foot by attacking East without securing a workable peace with the UK, that left them fighting west of France and south of Italy. Starting out against another big opponent, despite having meager access to raw materials and fuel while depending on enemy to drop in the towel when they wanted was the death warrant.

Scenario that discusses the ways for German win, or even not loosing the ww2, starts with fixing their Grand Startegy 1st.

So what is a workable grand strategy for Germany starting in, say, 1930?

Abandon 'lebensraum' in favor of agricultural mechanization and increased use of synthetic fertilizer, and peacefully develop Germany into an economic powerhouse would be the best bet, but without the need for lebensraum much of the ideological justifications for nazism fade away. No 1000 year Reich.

 

[tomo pauk]

So what is a workable grand strategy for Germany starting in, say, 1930?

Abandon 'lebensraum' in favor of agricultural mechanization and increased use of synthetic fertilizer, and peacefully develop Germany into an economic powerhouse would be the best bet, but without the need for lebensraum much of the ideological justifications for nazism fade away. No 1000 year Reich.

To play the devil's advocate:
The less thinking about the conquest and more focusing on internal German advantages and disadvantages would've been a boon for both Germany and the whole world. However this means than Nazis become Notzis - a very unlike scenario.
So with conquest still happening, Austria, Czechoslovakia and Poland are the likely targets as it was the case historically. Already the pre-1940 historical Greater Germany is a huge powerhouse. Without the Russia to worry, and with UK refusing to 'return to the Continent' until too late, France fails.
War with UK is a given. Okay, so then focus on the UK, while still maintaining the good relations with Stalin.
You need 2 years to force UK to the negotiations table - okay.
Five years - okay.
20 years - okay.
Just don't go East.

 

[z42]

Already the pre-1940 historical Greater Germany is a huge powerhouse. Without the Russia to worry, and with UK refusing to 'return to the Continent' until too late, France fails.
War with UK is a given. Okay, so then focus on the UK, while still maintaining the good relations with Stalin.
You need 2 years to force UK to the negotiations table - okay.
Five years - okay.
20 years - okay.
Just don't go East.

Yes, already before 1940 Germany was an economic powerhouse. However agricultural mechanization was AFAIU far behind the US and UK. Which implies a huge fraction of the workforce tied up in farming. So lots of untapped potential.

As far as 'don't go east' yes good idea in principle, although AFAIU both Germany and the Soviets were planning to renege on the Molotov-Ribbentrop pact. Germany just got there first OTL. So no guarantee that their eastern flank would remain peaceful while they concentrated on the UK.

 

[tomo pauk]

Yes, already before 1940 Germany was an economic powerhouse. However agricultural mechanization was AFAIU far behind the US and UK. Which implies a huge fraction of the workforce tied up in farming. So lots of untapped potential.

Agreed.
Toss in the need to reserve a big % of the available land to grow fodder for horses, and the economical equation is even worse.

As far as 'don't go east' yes good idea in principle, although AFAIU both Germany and the Soviets were planning to renege on the Molotov-Ribbentrop pact. Germany just got there first OTL. So no guarantee that their eastern flank would remain peaceful while they concentrated on the UK.

A two-front war is a guarantee for a loss. If/when Germany declares on the USA, it redoubles their need to secure West and South.
Germany that is not in a huge war along the long frontier from mid 1941 is in a far better shape to respond when USA comes in knocking, even if in mid-1942 Soviets decide to attack.

 

[WARSPITER]

Agreed.
Toss in the need to reserve a big % of the available land to grow fodder for horses, and the economical equation is even worse.

Good point. Prior to the widespread adoption of the internal combustion engine for farming and transport 50% of agricultural land
was required to grow feed for working animals. Add also the labour required to collect manure in cities and towns - New York by the
beginning of the twentieth century was around 2,000 tons of manure per week.

 

[tomo pauk]

Prior to the widespread adoption of the internal combustion engine for farming and transport 50% of agricultural land
was required to grow feed for working animals.

50%?? Wow, totally bonkers.

 

[WARSPITER]

I couldn't see how it would be 50% until I delved a bit. All horses in towns and cities had to be fed and required more than a backyard
in town to do it. Again, New York in 1900 had a horse population of around 100,000. Feed would have been brought in every day at
around 1,000,000 kg required (10kg per working animal). Spread that across a whole country and that is a massive chunk of crop.

People snort about vehicles with engines but they have allowed a massive increase in human feed production without the proportional
increase in farm land required.

 

[Shortround6]

A big problem with working animals is that they have to feed everyday, year round. When worked hard they need more feed than light work or resting. However they may need more feed in cold weather (?). Many countries only get one crop per year (depending on crop) and horses are best feed with a mixture of grains. Even at about 5kg of oats per day you need one bushel per 3 1/2 days or 100 bushels per year and for much of 20th century they averaged around 35 bushels per acre per year so at least 3 acres just for oats for one horse. Now throw in the next preferred grain and add in plain grass/hay for total feed.
Now try to figure horses used for pulling cart or carriage and horses used for heavy haulage (beer wagons seldom used 6-8 horses in history but they did use big horses)
A word of warning. Researching grain production can lead to madness
a lot of countries don't use the same weight per bushel of each type of grain and prices can be either weight or bushel and sometimes change depending on the transaction (grain silo buys by weight but sells by ?????

 

[marathag]

50%?? Wow, totally bonkers.

Numbers I have point to 1/3 or acreage devoted to Fodder, but that's USA, where Farming was done differently than Europe before Steam Traction was popularized after the Civil War.

A big problem with working animals is that they have to feed everyday, year round. When worked hard they need more feed than light work or resting. However they may need more feed in cold weather (?). Many countries only get one crop per year (depending on crop) and horses are best feed with a mixture of grains. Even at about 5kg of oats per day you need one bushel per 3 1/2 days or 100 bushels per year and for much of 20th century they averaged around 35 bushels per acre per year so at least 3 acres just for oats for one horse. Now throw in the next preferred grain and add in plain grass/hay for total feed.

And what goes into an animal, comes out in the form or Manure and Urine. Too much grain in a horse and not enough hay, they will have digestive issues.
It's surprising to people who don't deal with horses, to realize how fragile they really are.
Treat them rough, and they die by the score, shown by the Germans in both World Wars.

The British were just behind the USA in farm productivity, call it 10 years behind.
The Germans were really behind the USA, like a generation behind.

I've got this text I repost from time to time, about the efficiency of Horsedrawn transport to early steam

For efficiency, you're putting in Oats at 8000 BTU/lbs and Hay is similar into these horses. Each one of those needs around 25 pounds of Hay and 20 pounds of Oats when doing work. It's not much less when not working hard, you got to feed them each day, working or not. Then 15-20 gallons of clean water for how much they are working.

That's your Dual 'One HP' engine. On a wagon, 5-7 mph, with an expected working time of 8 hours, a 40 mile trip for 18 Gallons of water and 45 pounds of Fodder for moving 1.5 tons of cargo

A 124 HP Sentinel Steam wagon, using 1890s technology, uses 4.3 gallons of water and 7.4 lb. of Bituminous coal(12,000BTU/lbs) per mile. if the lower energy Lignite is used, a bit more needed.
6 ton payload. Top speed 30mph on surfaced roads. Two Crew, Driver and Fireman

So to move 6 tons of cargo 40 miles, that's 175 Gallons of water, 300 pounds of coal and an hour and 20 minutes of time to get to the destination

The horse drawn wagons to move the same amount of cargo, that's 4 wagon loads, 8 horses. Four or eight Drovers.
144 Gallons of Water, 360 pounds of Fodder, and takes 8 hours.

After the work is done, there's about an hour of maintenance for for the entire day for the steamer, but the feeding and care of the horses is longer. Then the Horses need to rest, 10+ hours a days work for horses, repeated day after day, will slowly kill them.

Steam engines, the limit is crew endurance, not the machine

 

[WARSPITER]

My wife had horses for decades and they definitely can go through some food.

They are fragile if misfed mainly due to their stomach only being about the size of a fist. The wrong stuff and it will block
very quickly. Add in that a horse can't throw up and it gets dangerous very quickly. Sometimes it can go the other way too.
A lady down the road had a problem as her horse got into the shed and tipped over a large tin of molasses.
It managed to down most of it. It wasn't a good idea to stand behind that horse for quite a few hours after that.

The usual feed level for a horse is best calculated by body weight at 1.7% feed - ie 1.7 kg per 100kg of weight. Again, due to
the digestive system this must be done in in smaller amounts during the day. As pointed out already the amount needed
also increases according to workload.

Also wondering with radials vs inline engines, do they have differences in workload amounts at different altitudes / revs or
are they roughly the same ?

 

[Shortround6]

Also wondering with radials vs inline engines, do they have differences in workload amounts at different altitudes / revs or
are they roughly the same

Kind of depends on the superchargers, which depends on the country and fuel availability.
Large displacement engines tended to have less room between peak power and max cruise. However lean cruise was different. again supercharger can make a difference

engine.....................................R-2600 B (B-25)............................Allison V-1710-85 (P-39Q)
Take-off............................1700hp/2600rpm.......................................1200hp/3000rpm
Max low...........................1700/2600/4500ft......................................1420/3000rpm/9000ft war emergency
Max hi..............................1450/2600/12,000.......................................1125/3000rpm/15,500
max cont low.................1500/2400/6700............................................................................................
Max cont..hi...................1350/2400/15,000.........................................1000/2600/14,000
max cruise lo.................1125/2100/6700................................................................................................
max cruise hi.................1012/2100/15,000..........................................750/2280/14,000


Many American radials did NOT get a war emergency rating (R-2800s were excepted with water injection and few others)
The supercharger on the R-2600 used about 1/2 the power in low gear that it used in high gear and that accounts for a lot of the difference in power. The other is the lower temperature and lower pumping losses although in low gear it isn't throttle back all that much.

Also note that for this radial the Max cruise settings were still done at rich settings. Lean required the same RPM but 2in less pressure (1lb boost) but power dropped to 1005hp and 905hp. Saved 25 US gallons an hour at low attitude.
Radials tended to use raw gasoline for cooling

 

[tomo pauk]

Also wondering with radials vs inline engines, do they have differences in workload amounts at different altitudes / revs or
are they roughly the same ?

ind of depends on the superchargers, which depends on the country and fuel availability.

Indeed, a lot depends on a supercharger.
Between the superchargers, and for service engines, Japanese were probably with best 1-stage superchargers during the best part of the war, while Ameircans gotten better with the later R-1820s, and the C series R-2800s. Germans dropped the ball with not pressing on with the BMW 801E (a much more refined S/C than what the 801C and D had; the 801S was too late), while the Americans tended to use too small impellers, and P&W using impellers with straight vanes, that were a step behind what they were using in early 1930s. Bristol engines and BMW 801 used big impellers.
Designers of radials of the day were trying to keep their engines short, that often meant that intake elbow for the S/C ended up being too much squished (see here for example), resulting in greater losses and lower power output for the propeller. Disposal of auxiliary items, like the generators or pumps, also messed up with making the intake elbow being as unrestricted as possible - a thing where V-12s were again in advantage.
See here for a detail of a supercharger for the Bristol Centaurus (probably not the early model), where the air is directly fed to the impeller; the curved inducer vanes are not that discernible, but these can be seen here.
More refined superchargers that P&W used on their C and E series R-2800s were much very worth it, again these were a bit too late, talk 1945 service use.
Americans, OTOH, were the only bunch that made, again for the service use, the 2-stage superchargers, that at the end of the day, meant they can more than compete vs. what Japanese produced, and then some.

Americans were also the only ones that made turbocharged engines to work while producing & using these in tens of thousands, that again paid off handsomely.

If a country has no guaranteed access to the hi-oct fuel, they should be feel doubly pressured to make better S/C for their engines for he ww2.
High-octane fuel is not a replacement for a good S/C, while the lack of hi-oct fuel can be countered by a good deal by keeping the CR low, use of ADI (water-alcohol injection; MW 50 for the Germans), use of intercooler, and not making the engines too small in the 1st place.

 

[Reluctant Poster]

I am not sure about this. I could very well be wrong but one story is that they had hundreds (if not well over 1000) Kestrels in stock that were reverbs/rebuilt engines taken out of some of the vast fleet of Hart family aircraft and those are what went into Miles trainers. Limited new parts for maintenance?

True. From " The Rolls Royce Meteor" " Rolls Royce's wartime manufacturing capacity was concentrated on the Merlin. This meant that they might not be able to get Kestrel engines even if their adaptation was successful. It should be mentioned here that Derby was at that time undertaking a programme of refurbishing old Kestrels into Mk.XXXs for the Miles Trainer, but the supply was finite."

 

[Reluctant Poster]

Want an unpopular take?
Original Ramp Head Merlin was pure trash, whole line should have been dropped for the Griffin, right then in 1936, than upscaling the Kestrel to make the Merlin II in time for 1939

In 1937, the R-2800 first ran, with production types in 1940, so '36 to '39 should be enough

That gets a big V-12 in service for the War. No need to rush for the Vulture or Exe, all that development goes to the Griffon, or to a 2900 class V-12, call that the Griffon Major if that's desired. or a 1800 cubic inch Griffon Junior to take the place of the OTL wartime Merlin

Bristol makes a poppet four valve, two row powerplant from the 1519 cubic inch Mercury to a 2360 cubic inch 14 cylinder and an 3039 cubic inch 18 cylinder, to take the place of the sleeve valved Hercules and Centaurus before WWII starts.

The Aquilia/Taurus line is dropped completely, just too small.

The development effort wasted there is instead made more towards a larger displacement sleeve valve radial to scratch that more sophisticated/tricky itch, while the poppet valve units are in service.

And this is just fixing RR and Bristol

Hindsight is 20-20. Even to this day with all our advanced technology no one has built a successful crystal ball. Your timeline assumes that you know the war doesn't start until 1939. There is a rush to rearm ASAP. No one in their right mind is going to accept a delay of at least a year likely more to get the new monoplane fighters into service. The people making these decisions weren't complete idiots.

 

[marathag]

Hindsight is 20-20. Even to this day with all our advanced technology no one has built a successful crystal ball. Your timeline assumes that you know the war doesn't start until 1939. There is a rush to rearm ASAP. No one in their right mind is going to accept a delay of at least a year likely more to get the new monoplane fighters into service. The people making these decisions weren't complete idiots.

Just going from 1936, and being able to see trends
The trend was for more power, as there was demand for Fighters(and Bombers) to carry a greater load for longer distances, and do it faster, as well.

To get more power, you can:

1 add more engines, with the downside of more drag, weight and complexity

2 add more cylinders, that brings in cooling issues

3 spin at higher RPMs, vibration and durability, piston speed

4 higher compression ratios, fuel octane issues with knock

5 larger cylinders, weight and drag

Supercharging and Turbocharging lets you retain sea level power at higher altitudes when normalizing, but more boost can be added for more power, leading to reliability issues. Needs more octane/water injection/etc

 

[Reluctant Poster]

Just going from 1936, and being able to see trends
The trend was for more power, as there was demand for Fighters(and Bombers) to carry a greater load for longer distances, and do it faster, as well.

To get more power, you can:

1 add more engines, with the downside of more drag, weight and complexity

2 add more cylinders, that brings in cooling issues

3 spin at higher RPMs, vibration and durability, piston speed

4 higher compression ratios, fuel octane issues with knock

5 larger cylinders, weight and drag

Supercharging and Turbocharging lets you retain sea level power at higher altitudes when normalizing, but more boost can be added for more power, leading to reliability issues. Needs more octane/water injection/etc

And what aircraft are you putting them into? I suggest you read this.

The Royal Air Force and Aircraft Design 1923-1939 Air Staff Operational Requirements by Colin Sinnott: Near Fine Hardcover (2001) 1st Edition | Booklover Oxford

ISBN: 9780714651583 - 1st Edition - Hardcover - Frank Cass Publishers, London - 2001 - Condition: Near Fine - Near Fine - Very good condition used 2001 First Edition Hardback with intact Dust Jacket. Published in 2001 by Frank Cass Publishers, London. Author: Colin Sinnott. ISBN: 9780714651583...

www.abebooks.com

1936 is s till largely a biplane world with the monoplane in its infancy, but you're going to skip a generation. This begs the question of what you do with all those Spitfires and Hurricanes with no engines. If war breaks out a year early you fighting with Galdiators

 

[marathag]

And what aircraft are you putting them into? I suggest you read this.

The Royal Air Force and Aircraft Design 1923-1939 Air Staff Operational Requirements by Colin Sinnott: Near Fine Hardcover (2001) 1st Edition | Booklover Oxford

ISBN: 9780714651583 - 1st Edition - Hardcover - Frank Cass Publishers, London - 2001 - Condition: Near Fine - Near Fine - Very good condition used 2001 First Edition Hardback with intact Dust Jacket. Published in 2001 by Frank Cass Publishers, London. Author: Colin Sinnott. ISBN: 9780714651583...

www.abebooks.com

1936 is s till largely a biplane world with the monoplane in its infancy, but you're going to skip a generation. This begs the question of what you do with all those Spitfires and Hurricanes with no engines. If war breaks out a year early you fighting with Galdiators

Similar to this Centaurus powered Tornado, but Hurricane with say, Hercules power

or pretend this is P.24 Monarch in place of Vulture power

1936 was still a biplane fighter world if you weren't Germany, France, Japan, USSR or USA, who had monoplane fighters flying.
Gladiator was a terrible mistake.
1937!