Why Luftwaffe and Kreigsmarine diesels but petrol Wehrmacht?

[Admiral Beez]

Why was Germany designing and making diesel engines for aircraft and surface warships when the Wehrmacht could have better used diesels for its tanks, AFVs and trucks? It just seems an odd direction to focus on.

There's some info here.

How the Wehrmacht's Diesel Stalled

A blog about World War II era archive documents, primarily dealing with armoured warfare.

www.tankarchives.ca

 

[ThomasP]

For ships, diesel has a large advantage over steam powered reciprocating or turbine engines in terms of range per ton, and it has a huge advantage over gasoline in terms of flammability and vapor explosion issues. The greater weight of diesel engines will not usually have a particularly large effect on ship design - while the steam turbine/boilers/reduction gearing will generally weigh significantly less per HP than the diesel - the diesel engine arrangement will normally take up significantly less hull volume.

For land vehicle use, a gasoline engine of similar power will weigh less and take up less volume. The range advantage of diesel will generally not make up for the weight and size difference, particularly if combined with the greater availability of gasoline. Additionally, the ability to use foreign fuel types encountered when invading other countries was probably a valid concern in the WWII period. I may be wrong, but I do not think diesel was readily available in the same volumes as gasoline in most of the European countries on Hitler's hit list.

I realize that diesel is more easily processed than gasoline, but most countries in WWII ran on gasoline in their civil automotive markets.

As far as an aircraft fuel is concerned I do not think that diesel is pertinent in this case as there were only a few diesel powered German aircraft operated to any degree in WWII - the Ju 86 and various flying boats. For the flying boats it made a certain amount of sense as they were likely to be based near and operating in close concert to naval forces. Diesel was generally used for ship's emergency generators and ship's boats, as well as many harbour vessels. Supply was not as much of a problem in normal circumstances. If it is pertinent then the weight of the diesel engine per HP output is the deciding factor. Only larger aircraft where weight was not as much of a factor would allow diesel engines to be used effectively.

I do not know how much of a problem the German supply chain had keeping diesel powered land vehicles supplied during the war, but there were only a few that saw any significant amount of service - I think they were all heavy movers or earth movers of various types.

 

[WARSPITER]

The use of petrol engines in tanks stemmed from an early requirement to save weight with higher revving engines
which allowed lighter drive components such as transmissions. By doing things that way tanks could be made which
were lighter but still had plenty of power while being able to cross bridges.

Maybach produced the HL100 engine which developed 300hp at 3000 rpm. This fitted the requirement and lead to the
HL120 which was used in the Panzer III and IV. Gearboxes and other drive components were made to fit the engine. These
type of plug ins became the standard driveline throughout the war, giving Maybach a virtual monopoly.

Diesel tank engines were developed and tested throughout the war with plans to replace the Maybach petrol types, especially
the 230 series (Tiger / Panther) which had definite problems. Petrol engines and been standardised due to a 1940 report
stating that synthetic diesel would be hard to produce. In 1942 the Army was informed synthetic diesel was easier to produce
then petrol. This caused a change of mind as to engines but the usual infighting occurred. Projects to change to diesel
were chopped and changed or deliberately hamstrung.

Meanwhile, Germany produced around 150,000 diesel powered trucks with a fair proportion of synthetic diesel to power them.

 

[marathag]

Why was Germany designing and making diesel engines for aircraft and surface warships when the Wehrmacht could have better used diesels for its tanks, AFVs and trucks? It just seems an odd direction to focus on.

Don't forget that Wiemar Germany licensed the 2862 cubic inch BMW VI to the USSR, and they used that as a inspiration for most of their following V12 efforts, in the air, and on the ground in the form of the V-2 diesel. The USSR took the crank and connecting rod setup of the BMW, and the head and block design from the 2197 cubic inch Hispano 12Y

Main problem in Nazi Germany was political, Maybach had things locked in. They wanted to make high rpm motors of moderate displacement, than lower speed diesels. Daimler-Benz got to make due with Navy contracts

Tanks run on Torque, not HP, so the Germans needed to have a lot more gearing to keep the motor near its peak torque output.

 

[MIflyer]

In a given barrel of crude oil, considerably more gasoline will be produced than diesel, kerosene, Jet-A, etc. The reason the USAF went to JP-4, a mixture of gasoline and kerosene, instead of 100% kerosene JP-1 was because using just the kerosene would create a problem with what to do with the "left over" gasoline. Prior to around 1900, after the useful kerosene (heating, light, and cooking), tars, and petroleum distillates used in paints and lubricants had been extracted, the left over gasoline, which was too volitile and dangerous to be used for fuel, was usually just dumped into the nearest river.

 

[marathag]

In a given barrel of crude oil, considerably more gasoline will be produced than diesel, kerosene, Jet-A, etc. The reason the USAF went to JP-4, a mixture of gasoline and kerosene, instead of 100% kerosene JP-1 was because using just the kerosene would create a problem with what to do with the "left over" gasoline. Prior to around 1900, after the useful kerosene (heating, light, and cooking), tars, and petroleum distillates used in paints and lubricants had been extracted, the left over gasoline, which was too volitile and dangerous to be used for fuel, was usually just dumped into the nearest river.

That all started to change in the late 1910s, when 'Straight Run' processing was superseded by more advanced processes besides just heating up crude with a distillation tower

Doing 1910-20s style distillation, You get from 10-25% Gasoline per barrel of Crude, depending on how sweet or sour the base Oil is. Octane rating typically under 60.

Thermal cracking (Dubbs Process) became widespread in 1931 after patent disputes were settled and shared between US Oil Companies. Earlier Thermal cracking methods were expensive and dangerous, but gave 70 Octane

Dubbs Process gave about 40% Gasoline per unit, even with sour grades, but Octane ratings were in the 70-80 range.

Economical catalytic cracking started in 1938 with the Houdry Process by Sun Oil Company, giving about twice the gasoline output than the earlier thermal cracking, and improved by the new moving-bed catalyst process in 1943, replacing the batch process for refilling the reactor. This also allowed economical production of 100 octane AvGas.

Before WWI, Gasoline consumption matched, and then exceeded Kerosene consumption

 

[Shortround6]

There was a considerable push for aircraft diesels in the 1930s.
It had several advantages, at least in theory, over gasoline.
One was less danger in a crash. While this may have been true burns in the crash were heavily out numbered by the crash injuries.
The German flying boats (and some of the airliners) used diesels because the combined weight of the engines and fuel for longer ranges was less than for gas engines. 1930s gasoline engines not being particularly economic with fuel and late 20s, early 30s gas engines (mainly 9 cylinder radials) not being all that much lighter than the diesel engines. spending 300-500lb per engine for around a 25% savings in fuel might have been considered a good trade. Gasoline engines increased power faster than the Diesels did which allowed for increased size of the aircraft and the balance remained with the gasoline engines. Trying to build 1200hp aircraft diesels for a diesel DC-3 wasn't going to work well in 1939-41.
Cold weather operations of diesels was also not easy. Gasoline is still useable as you approach 40 degrees below zero. Diesel gets harder to pump. Cold air also means the engines get hard to start.

Problems also include vibration. Peak cylinder pressure is higher than spark ignition, which means heavier construction.

The greater weight of diesel engines will not usually have a particularly large effect on ship design - while the steam turbine/boilers/reduction gearing will generally weigh significantly less per HP than the diesel - the diesel engine arrangement will normally take up significantly less hull volume.

The key here is normally. A low/medium speeds the diesel shows a significant advantage. For high speed it flips. When you need double the power to go just a few knots faster you have double the size of the engine rooms. Diesels do not scale well and they do (or did) not take to overloading well. A high power steam plant can be fairly compact, it will be inefficient in fuel burn (and smoky and may require more maintenance.)

A problem for the Germans is when do you convert your gasoline based motor transport system to diesel? Granted rail was still well over 90% coal and river traffic was also mostly coal. But light/medium trucks? And you need to start converting in the mid 1930s (if not earlier) without disrupting production too much.

Tanks have a lot of their own requirements. Weight of the engine/s is almost insignificant. A extra 100-200kg in the engine out of 10ton tank or more? What is significant is the size of the engine that you have to enclose in the armored envelope. Weight of the armor could be more than the weight of the larger diesel engine. While torque is important to tanks, the amount of torque transmitted in a given gear is also important. A gear or shaft transmitting 1000ft/lbs of torque at 500rpm needs to larger and heavier than a gear or shaft transmitting 500ft/lbs of torque at 1000rpm. Germans used more smaller gears. Maybe they did chose wrong.

A lot of the German light/medium trucks used basically car engines.
the famous Opel Blitz trucks first used a 3.5 liter flat head 6 cylinder engine that was produced on machinery GM had shipped to Germany in early 1930s from a defunct Buick model.
In 1937 they used a 6 cylinder overhead valve engine also used by the Opel Admiral car.

maybe a small 4/6 cylinder diesel would have been a better military vehicle, But how many would have been made/sold to the public during the 1930s?
I don't thinly you are going to get a 1 to 1 replacement rate on the gasoline vehicles. What is the trade off between better fuel economy and few vehicles (lift capacity).

 

[Admiral Beez]

Tanks have a lot of their own requirements. Weight of the engine/s is almost insignificant. A extra 100-200kg in the engine out of 10ton tank or more? What is significant is the size of the engine that you have to enclose in the armored envelope. Weight of the armor could be more than the weight of the larger diesel engine. While torque is important to tanks, the amount of torque transmitted in a given gear is also important.

I can't help but wonder how the Tiger II or Panther might have improved its mobility if its Maybach HL230 (690 hp @ 3,000 rpm and 1364 lb⋅ft at 2,100 rpm) petrol engine was replaced by a diesel of greater power. Though, to be fair to Maybach and the Germans, IIRC the HL230 was the most powerful mass produced tank engine of the war, petrol or otherwise.

Just for fun, let's stick in the postwar M60 tank's diesel Continental AV1790 with its 750 hp and stump-pulling 1,750 lb⋅ft.

 

[Shortround6]

alhough, to be fair to Maybach and the Germans, IIRC the HL230 was the most powerful mass produced tank engine of the war, petrol or otherwise.

Maybe, are you measuring HP or torque?
British Meteor was between 550-650hp inmost versions/
Using German naming system it was 270 engine,
It also gave about 1450ft/lbs of torque.
Engine in the T-34 was a real stump puller. It was also a 38.8 liter engine.

The HL230 started as the HL210, the Jumo 210 was 19.7 liters. A RR Kestrel was 21.2 liters.
Now with no supercharger and no reduction gear/prop shaft the HL 230 was short.

Using a converted aircraft engine might mean it would not fit or you need a larger engine compartment?

 

[Admiral Beez]

Maybe, are you measuring HP or torque?

I was thinking HP, but you're right to point out torque as it's the more useful measure for getting a stationary tank moving. I remember the first passenger vehicle I drove with stick shift was an Opel Zafira minivan in Germany in about 2013, and the torque from its diesel was forgiving when as a newbie I was lugging in a too high a gear.

The Tiger II is so tall and wide I'd expect nearly any engine to fit, though the Sherman is slightly taller, so its radial air cooled engines might not work in a Tiger II. I wonder what mods the Israelis would have done to the Tiger II or Panther if they'd been granted some postwar. The French didn't think much of their Panthers, but the Israelis might do better with their mods.

Outside of the USSR, who else fielded diesel tanks in WW2? Wasn't the USMC diesel-powered in the PTO? Why? And the Italians and Japanese?

 

[EwenS]

Nearly 11,000 diesel powered M4A2 Shermans were produced with just over 5,000 going to Britain under Lend Lease and another 4,000+ to the USSR. After spring 1944, production was maintained solely for the USSR. Only 493 went to the USMC for use in the Pacific, but by April 1945 even they were receiving petrol engined M4A3 versions as the M4A2 losses piled up. There were also 4,993 diesel powered M10 tank destroyers as well as some M3 Stuart light tanks and M3 Lee/Grant medium tanks.

 

[marathag]

More Engine info, and the transmission they were bolted to

Bedford Flat 12 1296 cubic inches max 350hp@2000
4 speed forward
Torque 960 ft lbs@800-1600 rpm

M4A1
Continental R975 radial 973 cubic inches governed max rpm 2400 400 hp@2,400 rpm
5 speed forward, 5th overdrive
Net Torque 940 ft lbs@1700rpmh

M4A2
GM twin 6 inline Diesel 850 cubic inches 375hp@2,100 rpm 410hp at 2900rpm, max rpm
5 speed forward, 5th overdrive
Net Torque 1000 ft lbs@1400rpm

Ford GAA 1100 cubic inches max rpm 2600
5 speed 5 speed forward, 5th overdrive
Net Torque 950 ft lbs@2200rpm

M6
Wright G200 1832 cubic inch radial 825hp max rpm 2300
Max torque 1850 ft lbs@2300rpm Electric Drive or 5 speed with Torque Converter

M26
Ford GAF V8 1100 cubic inches max rpm 2600
Torque Converter, 3 speeds forward
Net Torque 950 ft lbs@2200rpm

T29E3
Ford GAC V12 1649 cubic inches max rpm 2800
Torque Converter, 3 speeds forward
Max torque 1560@1600

T-34
V-2 V12 500HP@1800 for 2368 cu. inches
Five speed, 5th overdrive
Net Torque 1600 lbs/ft torque

Panzer IV
Maybach HL 120TRM V12 265hp@2600rpm 300hp at higher, but again reliability
Five speeds forward
Tiger I
Maybach HL230 1457 cubic inches max 3000 rpm(2600 rec) 700HP Torque 1,364 ft. lbs@2100
8 speeds forward

Maybach HL210 1302 cubic inches max 3000 rpm Aluminum, almost 800 pounds lighter than HL230 650bhp at 3000rpm, but for reliability ran at 2600.

 

[WARSPITER]

Tiger II and Panther were actually both slightly taller than the Sherman and decidedly "fatter" - width and weight.
The problem with the extra weight was that the original requirements for earlier tanks carried through to the heavier
vehicles resulting in driveline components being less robust than needed.

Daimler Benz had developed the 17.5 litre MB 809 which gave 360HP at 2400 RPM (1939). Permission was given for this
seperate to the ordnance directorate which was firmly attached to petrol Maybach engines only.

The engine was first trialled in February 1940 and fitted to a tank chassis in March of the same year. The designation
was VK 20.01(D) - D for diesel. By winter 1941 the project was dropped as specification VK 30.01 was introduced.
This was for a thirty ton tank.

The vehicles using the 20ton spec were produced until the end of the war using the Maybach HL 120 which was a
mistake as the 809 diesel was lighter, better on fuel, and had more power.

Daimler Benz then came up with the MB 507 and variants which started at 700HP (507), 800HP 507C, and the MB517
which was a supercharged 507 and could output 1200HP. Although these engines would have been far better than
the Maybach petrol types for heavier vehicles the army showed little interest.

Ironically, the DB diesel was fitted in a prototype Maus to provide enough power to move the ridiculous thing.

Also, in 1942 a group of companies were asked to look at development of eight ? diesel engine types from 30 to 1200HP
with three standard cylinder sizes for ease of mass production. Tatra ended up having an air cooled diesel which was to become
the main engine for tanks from late 1945 and on. This didn't eventuate as the war drew to a close before the rationalised
E series tanks could go into production.

 

[Shortround6]

The French didn't think much of their Panthers, but the Israelis might do better with their mods.

The Israelis weren't changing the engines in their M4s until about 1959 (prototypes) and that required a fair amount of work. Sometimes involving buying scrap M4A3 hulls and sending the hulks to Israel where the new engines were fitted (the M4A3 had space for the radiators, the radial engine hulls did not) new suspensions were fitted, new/modified turrets and a lot of bits and pieces like interior fittings, control levers, and all the little stuff was taken out of the old radial engine tanks. Production of the conversions didn't start until 1960.

Amazing what you can do with 12-15 years newer engines, guns, fire-controls, etc.
The Cummings diesel had 460hp instead of the 375hp of the old twin 6 diesel set up.

Different countries used diesels for different reasons. Japanese and Italians used them in part due the combat theaters being hundreds (Japanese well over 1000 miles) from the home bases, fuel shipment was harder than even the Germans faced. Neither country had a very extensive truck/automobile industry so tooling up for small diesels wasn't going to be that much more difficult. Very little tooling/factory space at idle while tooling up for new engines.

Engine technology was not static even for diesels. What they could do in 1944-45 was not what they could do in 1934-35. A lot of these schemes that Germany (or brand X) should have done such and such in the mid-30s because they had an experimental engine in 1943-44 that would have allowed XXXXXXXXXXXXXXX. kind of misses the point. Germans could not build enough trucks of any sort in 1938-42. Focusing on Diesels trucks might have eased the fuel supply a little bit (10-20%?) but more costly trucks and fewer of them would have hurt the German supply effort in General. Kreigsmarine tried to be too tricky (a problem with a lot of German weapons) and just because you can make MTB Diesels doesn't mean you can make Destroyer or Cruiser diesels. A ships/boats got larger the engines got heavier, to make them more reliable. Battleship steam power plants were a lot heavier per horsepower than Destroyer steam powerplants. They expected the battleships to last longer and they expected the battleships to need fewer repairs/refits in 12-20 years than destroyers. Germans tried to be too tricky and German steam power plants were unreliable. The U-boat Diesels were pretty good, but they weren't trying to push the U-boat diesels all that hard. Replacing U-boat diesels means using cutting torches on the pressure hull, replacing the diesels and then welding the pressure hull back up. Not something that was to be done in routine maintenance.

 

[EwenS]

There is some information here about the diesels intended to power the never built German H class battleships, buried in amongst talk of armour layouts.

NavWeaps Forums-Building Contract for Battleship H (1939)

This building contract can be found on the Deutsche Digitale Bibliothek. As usual no details of cemented armor are given (in that it was delivered to

www.tapatalk.com

 

[marathag]

but more costly trucks and fewer of them would have hurt the German supply effort in General

Standards would have helped, even if as minor as the Canadian Military Pattern for the GM and Fords in the Great White North

German manufacturers making Trucks and cars for the Heer

Adler
AEG
Afa
Audi
Bergmann
Bergmann-Metallurgique
Bleichert
BMW
Borgward
Brennabor
Breuer
Büssing-NAG
Daimler-Benz
Demag
Deuliewag
Deutz
DKW
Esslingen
Famo
FAUN
Ford
Framo
Freund
Fuchs
Goliath
Hagedorn
Hamor
Hanomag
Hanno
Henschel
Horch
Kaelble
Klöckner-Deutz
Kramer
Kraus-Maffei
Krupp
Lanz
MAN
Manderbach
Maschinenbau Lüneburg
Mercedes-Benz
MIAG
Neander
Normag
NSU
O&K
Opel
Ostner
Phänomen
Primus
Renger
Sachsenberg
Saurer
Schlüter
Stoewer
Talbot
Tempo
Trippel
VW
Vögele
Vomag
Wanderer
Zettelmeyer
Ziel-Abegg
Zündapp

These Austrian

Austro-FIAT
Austro-Daimler
Fross-Büssing
Gräf & Stift
ÖAF
Perl
Saurer
Steyr-Puch

These Czechoslovakian trucks
Jawa
Praga
Skoda
Tatra
Walter

By 1942, they pretty much decided on two dozen types to focus on

 

[WARSPITER]

The Kreigsmarine could have done with one of these then ? 25,480 litre diesel. Get yours today.

 

[Snautzer01]

Standards would have helped, even if as minor as the Canadian Military Pattern for the GM and Fords in the Great White North

German manufacturers making Trucks and cars for the Heer

Adler
AEG
Afa
Audi
Bergmann
Bergmann-Metallurgique
Bleichert
BMW
Borgward
Brennabor
Breuer
Büssing-NAG
Daimler-Benz
Demag
Deuliewag
Deutz
DKW
Esslingen
Famo
FAUN
Ford
Framo
Freund
Fuchs
Goliath
Hagedorn
Hamor
Hanomag
Hanno
Henschel
Horch
Kaelble
Klöckner-Deutz
Kramer
Kraus-Maffei
Krupp
Lanz
MAN
Manderbach
Maschinenbau Lüneburg
Mercedes-Benz
MIAG
Neander
Normag
NSU
O&K
Opel
Ostner
Phänomen
Primus
Renger
Sachsenberg
Saurer
Schlüter
Stoewer
Talbot
Tempo
Trippel
VW
Vögele
Vomag
Wanderer
Zettelmeyer
Ziel-Abegg
Zündapp

These Austrian

Austro-FIAT
Austro-Daimler
Fross-Büssing
Gräf & Stift
ÖAF
Perl
Saurer
Steyr-Puch

These Czechoslovakian trucks
Jawa
Praga
Skoda
Tatra
Walter

By 1942, they pretty much decided on two dozen types to focus on

Dint forget the Frech

 

[Thumpalumpacus]

I can't help but wonder how the Tiger II or Panther might have improved its mobility if its Maybach HL230 (690 hp @ 3,000 rpm and 1364 lb⋅ft at 2,100 rpm) petrol engine was replaced by a diesel of greater power. Though, to be fair to Maybach and the Germans, IIRC the HL230 was the most powerful mass produced tank engine of the war, petrol or otherwise.

Just for fun, let's stick in the postwar M60 tank's diesel Continental AV1790 with its 750 hp and stump-pulling 1,750 lb⋅ft.

Diesels are heavier, which will only exacerbate the problems with transmission breakdowns, which were a significant part of their problems.

 

[Thumpalumpacus]

View attachment 778923
The Kreigsmarine could have done with one of these then ? 25,480 litre diesel. Get yours today.

I bet Ford offers that as an option for one of its compensation machi -- er, big trucks.