Best tank engines of WWII (1 Viewer)

[Reluctant Poster]

Great link, thanks!

They did some solid research.

I would also add the Allied carriers torpedoed while traveling at higher speeds. Courageous, Eagle, Wasp, Saratoga (twice). There were also plenty of cruisers and destroyers torpedoed while steaming at faster speeds as well.

 

[EwenS]

I would also add the Allied carriers torpedoed while traveling at higher speeds. Courageous, Eagle, Wasp, Saratoga (twice). There were also plenty of cruisers and destroyers torpedoed while steaming at faster speeds as well.

Eagle was travelling at only 13 knots when torpedoed. That was also the speed of the Pedestal convoy that day.

Wasp was travelling at 16 knots when torpedoed on 15th Sept 1942, per the official USN report into her loss.

Saratoga, when torpedoed on 11th Jan 1942, was travelling at 15 knots per the official damage report. Can't immediately find details of the second incident.

By the way, I'm not denying other vessels were torpedoed at higher speeds. Just not the examples you quote.

Edit :- Courageous was travelling at 18 knots to recover her aircraft when torpedoed.

Edit 2 - Ark Royal was steaming at 19 knots to land on her aircraft when torpedoed in Nov 1941.

 

[SaparotRob]

As long as we're chucking torpedoes around, I want to give a shout out to Mogami. I know what got hit weren't really maneuvering but I love the story.
Carry on.

 

[yosimitesam]

You have deliberately or otherwise misapplied the graph. Here is the section you took it from:

View attachment 873120

The key sentence is : "an analysis of the effect of merchant vessel speed on the safety of independent ships". You have ignored the benefits of convoys which had a lower loss rate than independently routed ships even ones as fast as the Victories. The cut off speed was 15 knots with ships below that speed required to travel in convoy. Obviously they were areas of the oceans were conveys were not a regular feature but by the tine the Victory ships appeared in mid 1944 the convoy system was well established.

View attachment 873121

Ships in convey were in fact safer than even fast independent ships. As a consequence fast troopships with speed of 15 knots or greater and oil tankers with minimum speed of 14.5 knots were conveyed in their own fast convoys. From the same page as the graph:

View attachment 873128
Clearly stating the most successful measure was escorted convoys.

The 15 knot limit was established in by the British early in the war as compromise between the loss rates verses the much faster turnaround time of independently routed ships. It proved to be a good number but in no way does it mean that fast independently routed ships were invulnerable. Interestingly the Cabinet ordered a reduction in minimum speed for 15 to 13 knots with unfortunate results. After some moths the 15 knot limit was reinstated.
From Roskill The War At Sea 1939 - 1945 Volume 1 : the Defensive:

View attachment 873129

The real reason that no Victory ships were sunk by U Boats is simply opportunity . By the time Victory ship appeared the U boat war had changed dramatically due to the Normandy invasion. Atlantic shipping was no longer under serious threat. At the time of D Day there only 31 Victories had been delivered and they were on the west coast of the US. Only 104 of them were delivered in 1944 along with 112 Haskell Class Attack Transports. The vast majority of these Victories stayed in the Pacific although some did serve as troopships in the Atlantic. There was virtually no opportunity for a U-boat to actually encounter a Victory in the open ocean.

The radically different nature of the U-boat war after D-Day is discussed in a different chapter of the same document you reference
HyperWar: Antisubmarine Warfare in World War II [Chapter 7]
The entire document is well worth a read.

My post was only to assert that the faster the merchant ship the lower the probability that a successful attack by a U-boat, simply due to the speeds of the attacker and target being about the same or if the target is faster than the submarine (on the surface or submerged.) To attack with torpedoes the sub must get the target within a certain number of degrees either side of 90 degrees of the beam (the optimal). This almost always required an "approach" to get into that position. (Sometimes luck would put the approaching target to pass through an optimal or near-optimal position. This is what usually happens when warships traveling at speeds >= 15 knots are successfully torpedoed.) If the submarine does not have a speed advantage of a least 4-5 knots, the probability that the sub can get into that position drops dramatically. Whether the ship is alone or in convoy, the faster Victory ships would present a much greater problem to U-boats due to their surface speeds being nearly the same or greater than the U-boat's surface speed.

Of course you are correct that the U-boats were "on the back foot" by the time the Victory ships appeared in numbers and their overall successes against convoys, in general, was nearly completely over.

 

[GrauGeist]

However, even Victory ships were not immune to U-Boats:
Ship types hit by U-boats during WWII - Fighting the U-boats - uboat.net

 

[EwenS]

However, even Victory ships were not immune to U-Boats:
Ship types hit by U-boats during WWII - Fighting the U-boats - uboat.net

And this is where the confusion begins.

The built in the USA for Britain "Ocean" type, the Canadian built "Fort" and "Park" ships and the US built "Liberty" all shared a common ancestry that can be traced back to designs by the firm of Joseph L Thomson & Sons of North Sands, Sunderland in Britain in the late 1930s through into WW2. All were ships capable of roughly 11 knots.

The Canadian built ships, generally referred to in Canadian sources as the "North SandsType", break down into several groups:-
Fort ships - coal fired with 3 Scotch boilers. 198 built.
Park ships - as above but ordered by the Canadian Govt owned Park Steamship Co Ltd. 114 built.
Victory ships - same design but oil powered with 2 water-tube boilers (essentially the same power plant as a US built "Liberty").
Canadian ships - a Victory type as above but which reverted to 3 Scotch boilers that were capable of running on either coal or oil.which

Confusingly, the latter two types were also given "Fort" & "Park" names. There were detail design differences between each group because of the different machinery types fitted. More confusingly still is the use of the term "Canadian Victory" or sometimes just "Victory" type in relation to those ships.

It is these ships that the Uboat.net article refers to as having been sunk in WW2 with their speed limitation being noted.

The above designs however have nothing to do with the US built VC2-S-AP2 (6,500shp turbine) / AP3 (8,500shp turbine) 15-17 knot "Victory" merchant ships or the Haskell class VC2-S-AP5 APA Amphibious Transports built on the same hull, or the single diesel powered VC2-M-AP4 which were capable of speeds ranging from 15 to 18 knots depending on the machinery fitted. As I noted previously these were the successors to the fast 14-17 knot C1/C2/C3 pre war US Maritime Commission designs that continued to be built through the early war years alongside the "Liberty" design.

As far as I can see only three US VC2 merchant "Victory" type were lost in WW2. These were the Logan Victory & Hobbs Victory lost to kamikaze attack at Okinawa on 6th April while offloading ammunition for the troops ashore. Both burned and exploded for a day before any ship could get near enough to sink them with gunfire. Canada Victory was lost in similar circumstances on 27th April, but sank much more quickly due to the nature of the damage she suffered. The effect of the loss of these ships was that the troops ashore suffered shortages of certain types of ammunition, particularly 81mm mortar rounds.

 

[yosimitesam]

You have deliberately or otherwise misapplied the graph. Here is the section you took it from:

View attachment 873120

The key sentence is : "an analysis of the effect of merchant vessel speed on the safety of independent ships". You have ignored the benefits of convoys which had a lower loss rate than independently routed ships even ones as fast as the Victories. The cut off speed was 15 knots with ships below that speed required to travel in convoy. Obviously they were areas of the oceans were conveys were not a regular feature but by the tine the Victory ships appeared in mid 1944 the convoy system was well established.

View attachment 873121

Ships in convey were in fact safer than even fast independent ships. As a consequence fast troopships with speed of 15 knots or greater and oil tankers with minimum speed of 14.5 knots were conveyed in their own fast convoys. From the same page as the graph:

View attachment 873128
Clearly stating the most successful measure was escorted convoys.

The 15 knot limit was established in by the British early in the war as compromise between the loss rates verses the much faster turnaround time of independently routed ships. It proved to be a good number but in no way does it mean that fast independently routed ships were invulnerable. Interestingly the Cabinet ordered a reduction in minimum speed for 15 to 13 knots with unfortunate results. After some moths the 15 knot limit was reinstated.
From Roskill The War At Sea 1939 - 1945 Volume 1 : the Defensive:

View attachment 873129

The real reason that no Victory ships were sunk by U Boats is simply opportunity . By the time Victory ship appeared the U boat war had changed dramatically due to the Normandy invasion. Atlantic shipping was no longer under serious threat. At the time of D Day there only 31 Victories had been delivered and they were on the west coast of the US. Only 104 of them were delivered in 1944 along with 112 Haskell Class Attack Transports. The vast majority of these Victories stayed in the Pacific although some did serve as troopships in the Atlantic. There was virtually no opportunity for a U-boat to actually encounter a Victory in the open ocean.

The radically different nature of the U-boat war after D-Day is discussed in a different chapter of the same document you reference
HyperWar: Antisubmarine Warfare in World War II [Chapter 7]
The entire document is well worth a read.

This sub-thread needs to fade away but I wanted to "go on the record" to show in a simple diagram the point I was trying to get across. (Please excuse the "chicken-scratch" handwriting of mine in the labels on the diagram, but I had hand surgery five days ago and still have bandages on my writing hand.)

This diagram has a target (T) that is a Victory ship traveling at 18kts. The submarine (S) can make 17kts at best. (Typical for a VIIC doing long runs.). The sub is running on the surface. This one-knot advantage has the following effect: If the sub spots the target (moving to the right) at a point on the perpendicular of the target's track, or further to the right on that track, the sub will never be able to approach the target to get into a firing position, unless the target passes very close to the sub. This is the simple geometry of the problem. Unless the target's track passes within a short distance to the sub's present position, it cannot get into a reasonable firing position. This is because the sub has to track and approach the target on a hypotenuse of the right triangle (the longest "side") formed by the target's track, the perpendicular line to the target's track, and the sub's direct track (hypotenuse). Since the sub's track will always be longer that the target's track, the sub will never be able to "catch up" to the point he can attack at a reasonable range and angle. If the target has an even larger advantage (e.g. warship running at 20kts) the hopelessness of the situation is apparent. (This is why reminiscent books of WWII submariners and ships logs, etc. are replete with situations where the sub "could not approach target and get into firing position.") Running down the hypotenuse means that the sub's velocity vector has a component in the direction of the target track as well as a "forward" component to get ahead of (or equal to) the target's position. The target's vector, on the other hand, is a straight line down his chosen track.

There are 3 scenarios in the diagram based on the perpendicular distance to the target when spotted: 12nm, 8nm, 4nm. (The horizon for the top of cargo ship from a sub's coning tower is about 12-13nm in daylight, by my calculation, although this varies greatly depending on sea state, mist, fog, etc.) The position of the target is the tic-mark on the target track with the time and travel distance along his own track. The semi-circle is a 3000-yard "firing envelope" for the target (about 1.5nm). I chose this number simply because the examples in the US submarine torpedo firing manual rarely list any distance beyond this. The little "dot" in the semi-circle is half this distance perpendicular to the target, or about 1500yds. This is where the sub captain will "aim" his vector or, rather, where I draw his vector aiming here. This would be his "ideal" firing position, if the sub can reach this. The sub's position at this time is the tic mark at the end of its vector line.

Note that the longer the perpendicular distance to the target's track the greater the sub will eventually lag behind the firing range semi-circle. Conversely, the shorter the perpendicular distance to the target's track when spotted the more likely the sub will get into a firing position within the semi-circle. In the 4nm case, the sub can just get to the edge of the semi-circle (3000yds from target). At shorter distances than 4nm it will have an even better chance to "shoot." (This is because the distance to the track is smaller and, thus, the hypotenuse's length is closer to the target track's length.)

The diagram was made with meticulous attention to scale accuracy. (Note the smudges where I was off by 1 or 2mm and had to re-draw.) Looking at the big picture, imagine a submarine in the center of a big circle whose radius encompasses the sub's ability to spot a target at any direction. The actual angle that the target is approaching is immaterial, as the diagram is circularly symmetric and you just have to draw a line from the sub perpendicular to the target track and rotate the diagram sheet and you have the equivalent problem. The above arguments mean this: If the target has a speed advantage over the submarine, then the right two quadrants (right semi-circle of the big circle) are off limits as to the possibility of approaching the target to get into a good firing position. The greater the target speed advantage the closer its track must be to the sub position in order to get even a chance at a torpedo shot. The German's understood this fact well and is why they worried that, eventually, the majority of convoys might be all 17-18 knot Victory ships which would significantly reduce their success rate at tracking and attacking a convoy due to simple geometry. In this case their subs would have to spot the target in the "left" half semi-circle of the maximum spotting whole circle. Due to the vastness of the ocean and the randomness of finding convoys, this could not always be guaranteed and would probably not be the case in about 50% of the time, due vagaries of navigation and the state of the sea. They would always be unable to get in front of the target (convoy) if first spotted in the right semi-circle. In some cases this would apply as well to targets spotted well into the left spotting semi-circle, if the speed of the targets are much more than 1 knot greater than the sub's maximum speed and their track is perpendicularly far enough away from the sub.

 

[z42]

Looking at the big picture, imagine a submarine in the center of a big circle whose radius encompasses the sub's ability to spot a target at any direction. The actual angle that the target is approaching is immaterial, as the diagram is circularly symmetric and you just have to draw a line from the sub perpendicular to the target track and rotate the diagram sheet and you have the equivalent problem. The above arguments mean this: If the target has a speed advantage over the submarine, then the right two quadrants (right semi-circle of the big circle) are off limits as to the possibility of approaching the target to get into a good firing position. The greater the target speed advantage the closer its track must be to the sub position in order to get even a chance at a torpedo shot.

Yes, simple geometry really. Additionally one might add, that during the day spotting is easier but then the submarine must dive before it is spotted by the freighter, lest the freighter just turns and speeds away. And underwater the submarine is a lot slower, making the situation rather hopeless unless the submarine has managed to get into a position where the freighter track passes quite closely before diving. At night the submarine can remain on the surface, but then spotting distance is a lot shorter.

 

[Elvis]

Other people answered about the steam engines.
In the electric engines, that are siblings to the electric magnets, the highest torque is indeed at zero RPM (so is the current needed to provide that torque). If the engine is prevented from turning - we, future electricians, did that in high school - the current the engine consumes rises sharply, and so is the torque. That, maximal current required was referred as the 'current of the short circuit' back in the day, and I guess today, too. We were doing the experiments and measuring on the AC motors.
Obviously, the electric engine that is on and cannot turn will start burning, due to the great current flowing - short circuits are no fun.

When the engine starts to turn, then it makes the power and torque.

Exactly. If its running at zero rpm, then its not turning, thus is produces nothing.
You still haven't explained how an engine, electric or otherwise, can produce maximum torque at zero rpm.
Current draw does not equal torque. It only equals melted electrical parts if they're not stout enough to withstand the current draw.

 

[tomo pauk]

(snip)

I will bid you a good day.

 

[z42]

Exactly. If its running at zero rpm, then its not turning, thus is produces nothing.
You still haven't explained how an engine, electric or otherwise, can produce maximum torque at zero rpm.
Current draw does not equal torque. It only equals melted electrical parts if they're not stout enough to withstand the current draw.

If we look up the definition of torque, e.g. from wikipedia ( Torque - Wikipedia ), we have the torque tau = r x F (where tau, r, and F are vectors, and "x" is the vector cross product), or colloquially torque is a force applied on a lever arm producing a twisting force around the center of rotation. No rotation is necessary.

Power, in contrast, is work per unit of time. And as long as nothing is moving, no work is being done.

Combining these two, it's easy to see we can have a situation with non-zero torque applied but no movement and hence no work is being done and thus no power is produced either.

So for a steam engine, you can have steam pressure on the cylinders producing torque, but if the pressure is not enough to overcome whatever is preventing the engine from moving, no movement. Similarly for an electric motor, a non-zero magnetic force between the stator and rotor can exist thus producing torque, but not enough to actually cause the motor to rotate. Only the cooling etc. is preventing maximum torque from being produced at a standstill for a prolonged period of time. But for a short period of time, the motor can produce maximum torque at standstill.

 

[Elvis]

A steam piston engine generates force on the piston by the action of the pressurized steam being allowed to flow into the cylinder, the push force on the piston and conrod is converted into rotational turning torque by the crankshaft. If the resistance to the crankshaft is too large, the piston will stop, say at half travel, even though the full steam pressure is still applied to the piston. In this condition the maximum torque is being applied to the stopped crankshaft, but no work is being done.

I wonder if we're not defining "maximum torque" differently.
You state when resistance to the crankshaft is too great for the steam pressure to overcome, maximum torque is being applied to the stopped crankshaft.
I'm defining "maximum torque" as the work the engine produces, not the pressure the steam applies to the piston.
So, if the engine doesn't produce enough power to overcome the resistance of the work that needs to be done, it stalls, even though maximum pressure is being applied to the piston.
The torque, or the work the engine produces, is then zero, because it has stopped moving. Thus, maximum torque @ zero rpm is either an incorrect statement, or I'm defining torque differently than you guys are.
"Pressure". "Torque".
This may be where the confusion lies.

 

[swampyankee]

I wonder if we're not defining "maximum torque" differently.
You state when resistance to the crankshaft is too great for the steam pressure to overcome, maximum torque is being applied to the stopped crankshaft.
I'm defining "maximum torque" as the work the engine produces, not the pressure the steam applies to the piston.
So, if the engine doesn't produce enough power to overcome the resistance of the work that needs to be done, it stalls, even though maximum pressure is being applied to the piston.
The torque, or the work the engine produces, is then zero, because it has stopped moving. Thus, maximum torque @ zero rpm is either an incorrect statement, or I'm defining torque differently than you guys are.
"Pressure". "Torque".
This may be where the confusion lies.

There is exactly one way to define torque. See, for example, 21A: Vectors - The Cross Product & Torque

Automobile fans abuse a lot of physics terminology in ways that make a journalist calling a destroyer a battleship pale in comparison.

Electric motors, steam engines, steam turbines, and gas turbines using free power turbines can all produce torque at zero rpm. They are producing no power because at 0 rpm, they do no work. They can produce this torque while Otto or Diesel piston engines cannot because these can't complete a combustion cycle unless the piston can move

 

[Reluctant Poster]

When I torque a bolt to 80 lb ft on my cars wheel it does not move. I can however change the setting on my torque wrench to 100 lb ft and it does move. Force of any sort is not a guarantee of motion.

 

[Reluctant Poster]

Yes, simple geometry really. Additionally one might add, that during the day spotting is easier but then the submarine must dive before it is spotted by the freighter, lest the freighter just turns and speeds away. And underwater the submarine is a lot slower, making the situation rather hopeless unless the submarine has managed to get into a position where the freighter track passes quite closely before diving. At night the submarine can remain on the surface, but then spotting distance is a lot shorter.

A surfaced submarine is difficult to spot for a trained navy crew let alone a merchant navy crew. Most merchant ships never saw the submarine that sank them. A ship revels itself with its smoke before you can actually see it. The submarine has to plot an interception course not engage in a stern chase. There are plenty of stories of life boats being passed by ships not spotting them even when firing flares or signaling with mirrors in broad daylight.

 

[yosimitesam]

A surfaced submarine is difficult to spot for a trained navy crew let alone a merchant navy crew. Most merchant ships never saw the submarine that sank them. A ship revels itself with its smoke before you can actually see it. The submarine has to plot an interception course not engage in a stern chase. There are plenty of stories of life boats being passed by ships not spotting them even when firing flares or signaling with mirrors in broad daylight.

Absolutely true. That's why microwave radar on escorts was a "game changer". Even the first 271 model could "spot" a surfaced submarine at 3 miles (2.6 nm or about 5,300 yds), which is beyond the usual shooting range at which you have a reasonable chance of a hit. Even with "slow" convoys (8-9 knots) it was easy for the sub to get ahead and in front of the convoy but it would usually be spotted on radar during it's approach before getting into realistic firing range, forcing it to use submerged tactics. The 271 could even pick up a periscope at 900yds at night. At night, the Germans had to resort to the usual end-arounds on the surface but had to submerge for attack (just like in daylight) which meant the sub captain had to be very skillful due to his quarry now being as fast or slightly faster than he was. Then, when air cover was enlarged the subs could not even end-around on the surface in daylight, if spotted by an aircraft. The night had become much less "dark" for subs and the daylight much more dangerous. (Note for non-US readers: "End-around" is an American football play strategy and the term was used by US submariners.)

 

[Admiral Beez]

Why wasn't the Allison V-1710 used in a tank instead of the repurposed aero radials? The V-1710 would allow lower hull decks.

 

[GrauGeist]

Why wasn't the Allison V-1710 used in a tank instead of the repurposed aero radials? The V-1710 would allow lower hull decks.

The Allison was in great demand and couldn't be diverted to power AFVs.

And the radial engines used, were not aircraft rated (meaning not intended to be used in aircraft).

 

[Shortround6]

It was also timing.
A lot of engineering for the M4 Medium is from the M3 Medium which is from the M2 Medium which was derived from the T5 series of experimental tanks.
In 1937-39 when the work on the T5 and M2 medium was being done the Allison was still a very experimental engine and was over-powered in any case.
A 350-400hp engine was all that needed or even wanted. A clutch and transmission that would stand up to a higher-powered engine would be larger, heavier and more expensive. Wright engine used was the R-975 Whirlwind, not the larger Cyclone and the Allison would have much more torque even if not supercharged and fitted with a small carburetor.
The small R-975 wound up in demand for trainer aircraft and the search for substitute engines began.

 

[z42]

The Allison was in great demand and couldn't be diverted to power AFVs.

And the radial engines used, were not aircraft rated (meaning not intended to be used in aircraft).

Well, presumably, had they decided to use the Allison as a tank engine they would have produced a non-aviation-rated variant, just like the radial engines used, or the Meteor etc.