Best tank engines of WWII (5 Viewers)

[Shortround6]

The Merlin's non-aviation siblings went into more than just tanks, including powering Royal Navy torpedo boats.

There is just enough truth to this to prevent it being call 100% false. Somewhere around 8 to 20(?) boats got Merlins. Records are hazy, some boats may have been repowered.
More boats were built with Isotta-Fraschini engines than with Merlins.

Interestingly, the USN's PT Boats were powered by Packard V-12 engines, which presumably is another lost opportunity for Allison

Not really, the USN was not that dumb. MTB engines have a different duty cycle than aircraft engines. the continuous power rating for a MTB engine was 10 hour or more, later 24 hours? not 1 hour like early WW II engines. Max power was either 30 minutes or 1 hour. The Packard marine engines were 2540cu in (41.6 liters) and could run at higher power than either Merlin or Allison for the desired times. A 5 minute WEP rating was useless to a MTB.

Rolls Royce also developed the V-8 Meteorite in both diesel and petrol versions for transporter trucks. It seems to me that Allison's V-12 could have found more applications beyond aircraft.

The UK truck market was small, too small to support purpose built truck engines of the size wanted by the customers.
That was not the case in the US. The US had several companies making large (for 1940-46) truck engines like the 210hp Hercules DFXE used in thousands of M-19 tank transporters and 240hp 1,090 cu in (17.9 L) 6-cylinder Hall-Scott used in the M-25/26 tank transporters. Mack and Waukesha also made large 6 cylinder truck engines, like over 800 cubic in engines with high torque. The Allison was too expensive for what it offered. Aluminum construction was not needed. 4 valves per cylinder was not needed. The Ability to run for hundreds of hours with minimal attention was.

 

[swampyankee]

The Merlin's non-aviation siblings went into more than just tanks, including powering Royal Navy torpedo boats. Interestingly, the USN's PT Boats were powered by Packard V-12 engines, which presumably is another lost opportunity for Allison. Rolls Royce also developed the V-8 Meteorite in both diesel and petrol versions for transporter trucks. It seems to me that Allison's V-12 could have found more applications beyond aircraft.

I think one of the first 8 USN PT boats -- PT-8 -- had two Allison engines, but these were not V-1650s.

 

[Engineman]

I think one of the first 8 USN PT boats -- PT-8 -- had two Allison engines, but these were not V-1650s.

No, and not R-R V-1710's either!

Eng

 

[WARSPITER]

The Meteor engine was also chosen for the Helmover radio guided torpedo to be dropped from a Lancaster and guided to target
by a Mosquito.

 

[GrauGeist]

The Packard 3M amd 4M engines were close in power output to the V-1710, so it would not have made.much sense to burden Allison, who's production was already struggling to keep up with demand.

The U.S. had the luxury of having a range of engine options available for their equipment, which allowed for uninterrupted production output.

Just imagine if the Germans decided that they wanted DB601s for their tanks instead of Maybach's HL120TRM. As it was, many German projects were cancelled because of demand for the DB6xx was so great.

In the case of the Allison, which aircraft would have been cancelled if the V-1710 was to be used in aircraft, tanks and boats?

 

[swampyankee]

The Packard 3M amd 4M engines were close in power output to the V-1710, so it would not have made.much sense to burden Allison, who's production was already struggling to keep up with demand.

The U.S. had the luxury of having a range of engine options available for their equipment, which allowed for uninterrupted production output.

Just imagine if the Germans decided that they wanted DB601s for their tanks instead of Maybach's HL120TRM. As it was, many German projects were cancelled because of demand for the DB6xx was so great.

In the case of the Allison, which aircraft would have been cancelled if the V-1710 was to be used in aircraft, tanks and boats?

Leaving aside tanks, there were about a thousand boats PT boats and SC wooden subchasers -- which could use the Allison engine (the SC did not use Packard V-12 engines, but GM diesels ) That would be about 1500 P-38s or a total of about 3000 P-39, P-40, early P-51, and P-63s.

If the Packard designed V-12 isn't produced, the Allison could be produced in its stead, so the long-term effect could be a wash.

One question not asked: would GM want their airplane engine division to go into ground vehicle and marine engines in competition with their Electro-Motive division?

 

[ThomasP]

Scott Paine/BPB (British Power Boat) felt the Power Merlin (sometimes referred to as 'Sea Merlin') was a viable boat engine in their modified form - both reliable and durable. I have never been able to find a detailed spec covering all the differences between the Power Merlin and the regular aircraft versions, but they were getting a reliable rating of 1000 HP continuous with 1100 HP for sprint. The engine used a supercharger almost identical to the pre-war aircraft engine type, with the same 6.313:1 S/C ratio of the Merlin VIII, but with a relocated carburettor and thus without the restriction of the designed for aircraft air intake problems, along with seawater-to-coolant system heat rejection. This allowed the Power Merlin to be run at high power for significantly longer periods than the early-war aircraft variants, while using 87 grade fuel.

Unfortunately for Scott Paine/BPB the war interrupted their plans, and - partly due to the fact that they were still relying on RR for most of the parts for the engine - the MoD ordered a cut of the program and for BPB/Scott Paine to redirect their efforts during the War. The access to US built boat engines such as Packard and Hall-Scott put the final nails in the Power Merlin coffin.

 

[Elvis]

The Packard 3M amd 4M engines were close in power output to the V-1710, so it would not have made.much sense to burden Allison, who's production was already struggling to keep up with demand.

The U.S. had the luxury of having a range of engine options available for their equipment, which allowed for uninterrupted production output.

Just imagine if the Germans decided that they wanted DB601s for their tanks instead of Maybach's HL120TRM. As it was, many German projects were cancelled because of demand for the DB6xx was so great.

In the case of the Allison, which aircraft would have been cancelled if the V-1710 was to be used in aircraft, tanks and boats?

To add to this, the Packard engines were about 50% larger in displacement, over the Allison, and as we all know...there's no replacement for displacement.
So the smaller Allison engine would've had to have been in a higher state of tune to achieve the same power level.
That adds additional stress to any engine, which can cut into its reliability...and as the Unlimited Hydroplane guys found out in the 1960's and 1970's, the Allison's couldn't take the stress of putting out more and more power, like the heavier built Merlin, or (in this case) the Packard, would have.
Remember, the Allison's original design parameter was as a dirigible engine, so it's meant to run more like a generator motor...run the engine at its peak torque rpm and hold it there for hours on end.

 

[Admiral Beez]

The Meteor engine was also chosen for the Helmover radio guided torpedo to be dropped from a Lancaster and guided to target by a Mosquito.

Imagine flying a Lancaster, low and slow towards IJNS Yamato to drop the Helmover torpedo.

 

[Shortround6]

Operator's Manuals - Downloadable

Downloadable Operator's Manuals (PDF format) for the 85, 63, 42, and 18foot swamp glider. Several manuals include parts manuals with exploded views. Manuals are instructions to operate systems.

uscrashboats.org

This has the Engineers op manual for the Packard engines and there is a table showing power ratings using different fuels and models of the engine, operating limits and manifold pressures used.

 

[Admiral Beez]

As to transmissions and power, the the HL 210 / 230 / 245 are all examples of pushing the limits. Although much larger in capacity with a lot of horsepower they were far more fragile and prone to overheating than the 120. This was also due to the weight they were pushing which in the end was too much.

Would the HL 230 have been fine for the 70 ton Tiger II if mated to a better transmission and drive train? Was improved cooling possible? What was the primary point of failure?

It would have been interesting to see what the Israelis would have done with a fleet of Panthers or Tiger I/II. Scrap the lot is most likely, but what engine and transmission would have been available in the 1950s to make the German cats run better?

 

[Elan Vital]

Would the HL 230 have been fine for the 70 ton Tiger II if mated to a better transmission and drive train? Was improved cooling possible? What was the primary point of failure?

It would have been interesting to see what the Israelis would have done with a fleet of Panthers or Tiger I/II. Scrap the lot is most likely, but what engine and transmission would have been available in the 1950s to make the German cats run better?

The transmission wasn't a particularly problematic item on the Tiger II. The suspension was conducive to low rolling resistance compared to other types, so it wasn't forcing the engine to push harder than with another suspension. Perhaps the gearing could have been set to favor lower top speeds but fewer gear changes and make the engine work less often in demanding conditions, but it was not uncommon to see such gearing at that power to weight ratio. Of course, a low power-to-weight ratio is undesirable if you want maximum engine reliability.

The main points of failure on the HL230 were the head gaskets, seals, pumps, fuel lines and the lubricant. Some of these issues came from the relatively recent development of the HL230 as a wartime product (so design faults), others came from Germany's shortage of certain materials (lubricant and seals). Cooling was an issue initially. The HL 234 introduced many durability improvements on top of increasing power, which would have been conducive to increased durability.

From Jentz' and Doyle's Germany's Tiger Tanks, from VK 45.02 to Tiger II:

 

[GrauGeist]

Would the HL 230 have been fine for the 70 ton Tiger II if mated to a better transmission and drive train? Was improved cooling possible? What was the primary point of failure?

It would have been interesting to see what the Israelis would have done with a fleet of Panthers or Tiger I/II. Scrap the lot is most likely, but what engine and transmission would have been available in the 1950s to make the German cats run better?

Dr. Porsche originally wanted to power his heavy tanks with a diesel-electric system.

If he had more time to work it out, I imagine that would have been a huge leap in their heavy tank's reliability.

 

[Admiral Beez]

Dr. Porsche originally wanted to power his heavy tanks with a diesel-electric system. If he had more time to work it out, I imagine that would have been a huge leap in their heavy tank's reliability.

That seems like napkinwaffe as far as tanks go. How much time does Dr. Porsche need? Ninety years on, has anyone worked out diesel-electric power for tanks? It seems like a dead end while forced induction direct-drive diesels went onto power pretty much every tank until the advent of gas turbines. Dr. Porsche backed the wrong horse.

 

[GrauGeist]

I disagree - DE propulsion has been a tried and proven means of power not only for subs, ships and trains, but busses, heavy equipment (like quarry vehicles) and is the intended Powerplant for a Swedish AFV that's currently being developed by BAE.

Electric motors can produce impressive torque when compared to internal combustion engines. Dr. Porsche was headed in the right direction, as his design/theory became commonplace by the late 40's/early 50's when DE locomotives replaced steam.

 

[Shortround6]

French Saint Chamond SPG WW I.
The Vehicle to the left was the power car/cart. 120hp gasoline engine and the electric generator and electric motor/s to drive the tracks.
There was a 50 meter cable to gun carriage with electric motors driving the tracks for cross country work, 2 meter tow bar for roadwork the power cable shorter.
Electric drive was not new or novel. Getting it to be lighter than mechanical drive was the problem.
Diesel electric and gas electric locomotives were standard catalog items in the late 20s and early 30s for industrial and short railroads (low speed) but when you need 20-80 tons just for traction light weight was not desired.
Now maybe in a "what if" Germany abandons the U-Boat strategy and devotes it's copper resources to electric tank transmissions

Porsche used electric drive in these things.

 

[Admiral Beez]

I disagree - DE propulsion has been a tried and proven means of power

SPGs, tank destroyers and IFVs have given it a go, and yet we have never seen a series production conventional rotating turret tank thus powered? Perhaps it's not that DE is bad for tanks, but that direct-drive diesels are better, cheaper or lighter?

Was there a forced injection, liquid-cooled direct-drive diesel in development in Germany that could have powered the big cats? Porsche's own Sla 16 (Type 203) diesel was (initially) air cooled and intended for the DE system, but perhaps it could have been modified. This site suggests that the Soviets had a good look.

 

[z42]

SPGs, tank destroyers and IFVs have given it a go, and yet we have never seen a series production conventional rotating turret tank thus powered? Perhaps it's not that DE is bad for tanks, but that direct-drive diesels are better, cheaper or lighter?

I don't think there's any deep insights to be had from SPG's, tank destroyers, and IFV's having used electric drives and not tanks with rotating turrets, other than historical accident.

Also, to nitpick I wouldn't call it direct drive since there clearly was clutches and gearboxes involved. Direct drive you might find in low power aircraft engines (without reduction gearing), or low speed two-stroke marine diesels.

But yes, I think it boils down to mechanical transmissions being better, in terms of being cheaper and lighter at least. And for Germany, as S Shortround6 mentioned, copper was a critical resource in wartime Germany and heavy electrical equipment needed lots of it. Also consider that modern electric drivetrains are, if not dependent on, at least greatly enhanced by power electronics like thyristor/GTO/IGBT's to drive them; Obviously not an option in the WWII time frame.

One can perhaps also compare with warships. Americans, in particular, had an early love affair with electrical drives, as seen e.g. in the Lexington class battlecruisers (later converted to carriers). But once the Washington naval treaty with its displacement limits came into effect, this line of development seems to have died out in favor of the lighter and more compact mechanical reduction gearing for the turbines (there were some destroyer escorts and other minor combatants being built with electric drives, IIRC more due to gear-cutting for large reduction gearings being a bottleneck item rather than any inherent superiority).

Was there a forced injection, liquid-cooled direct-drive diesel in development in Germany that could have powered the big cats? Porsche's own Sla 16 (Type 203) diesel was (initially) air cooled and intended for the DE system, but perhaps it could have been modified. This site suggests that the Soviets had a good look.

There were the DB809 and MB507 diesels, per How the Wehrmacht's Diesel Stalled and Mercedes-Benz 500 Series Diesel Marine Engines , though neither was supercharged. There was the MB517 which was a supercharged version of the 507.

The 809 is perhaps the big missed opportunity for getting diesel powered tanks, 507 is too little too late.

The Sla16 perhaps epitomizes the German penchant for overengineering. Just do a liquid cooled V-12 and call it a day.

 

[Shortround6]

SPGs, tank destroyers and IFVs have given it a go, and yet we have never seen a series production conventional rotating turret tank thus powered? Perhaps it's not that DE is bad for tanks, but that direct-drive diesels are better, cheaper or lighter?

There is big problem with comparing even 1970s/80 tank drive lines to 1935-45 tank drive lines. Everybody's drive lines got better, a lot better.
Tanks have some major problems. Unless you use a real simple system (Bren carrier) the transmission is part of the steering gear. Once you decide that you just can't declutch the inner track and use a brake on the inner track, but you want to apply more power to the outer track at the same time the transmission and steering gear assembly can weigh as much or more than engine.
At certain points in time, depending on steel alloys involved, heat treatment and so on, the size weight of a transmission to handle a certain amount of power changed. So did the size/weight of electric generators and electric drive motors. Electric drive promised to replace not only the clutch and transmission but the steering gear. Even on a T-34 the steering gear involved a clutch on drive to each track and a large brake on the shaft to each track. On many tanks these clutches and brakes wore out in under 1000 miles.
Many tanks shifted to double differential and even triple differential steering systems and hydraulic torque converters on the main drive instead of clutches.
Over 40 years (or more) the electric drive often caught up to mechanical drives but then the mechanical drives made improvements. And at times changing over to a new drive system meant you cannot use any of the old parts in the warehouse
A number of tanks used transmission systems they shouldn't have but at times that was all the country's industrial base could offer.
Electric drive offers a lot of benefits. Delivering those benefits is hard and depends on raw materials and industrial base.

 

[Elan Vital]

Electric transmissions were a big thing at a time when tank designers were looking for improved steering efficiency and reduced driver effort for ever heavier tanks, while improved mechanical, hydraulic or hydromechanical alternatives were young and were not proven. In the end, the latter solutions prevailed as they were lighter, more efficient, better thermally and were easier to handle and build than electric systems, while offering much the same qualities.

1930's France is a notable example of research in all directions, especially with the fortification assault tank and 20 tonne - Char G1 programs. They contemplated the following options:
- conventional mechanical gearbox and clutch/brake steering (FCM 36 and FCM 20-tonne tank): simple, light and compact, suitable for a light tank like the FCM 36 but rejected on the 20-tonne tank as being too conservative and risky

- conventional mechanical gearbox and Cleveland/Cletrac controlled differential (Renault R35, D1, D2 and G1, Hotchkiss H35/39, initial Lorraine 20-tonne tank option): basically the baseline, worked and was moderately light, but had only one efficient turning radius and was noisy, loud and inefficient (especially problematic for front-drive tanks where the differential is next to the crew, which is why it was moved to the rear on the Renault G1 and AMX-38 which had a backup Cletrac solution).

- double-differential mechanical steering system: SOMUA S35/40 and SOMUA 20-tonne tank, ARL fortification assault tanks (mechanical solution): entirely mechanical, yet convenient steering systems. The ARL gearbox was also of the preselecting/somewhat automatic type with servo-assistance, reducing driver effort.

- Wilson and COTAL preselector gearboxes and steering systems with hydraulic and electromagnetic clutches respectively: Fouga 20-tonne/G1 tanks, R35 and Hotchkiss testbeds, Lorraine 20-tonne/G1, AMX-38 with twin Wilson units and geared steering: easy to drive, efficient steering method if Wilson and COTAL steering units are used. COTAL was successfully used on the ARL 75mm SPG.

- Naeder hydrostatic steering system (Char B): a very effective steering system which is however somewhat bulky and reduces efficiency, could be prone to oil leaks. A precursor to postwar hydrostatic steering clutches. The B1 Ter used a different mechanical gearbox

- Robin van Roggen automatic transmission: AMX-38 and 40: promising automatic option, to be upscaled for 45-tonne tanks if possible

- Gebus electric transmission: ARL 45-tonne heavy tank and Baudet-Donon-Roussel 20-tonne/G1 tank: a 2-speed electric transmission, works fine but can be over 3 tonnes heavier than mechanical options. There were also AMX/ARL/FCM electric transmissions designed by Alsthom for fortification assault tanks.

- Poniatowski electric transmission: SEAM/Poniatowski 20-tonne/G1 tank, ARL fortification assault tank, B1 Ter testbed: 4 electric motors integrated with the sprockets (no idlers), a promising lightweight electric system (possibly 20%/1-tonne heavier than mechanical options), but was yet to be proven in 1939/40.

- Kegresse Autoserve transmission (SOMUA S40 option): another type of automatic hydromechanical system

Electric transmissions were the baseline for 45-tonne/fortification assault tank projects, although the ARL studied mechanical solutions.