Best tank engines of WWII

So far we have several of the best tank engines mentioned.

Soviet V-2 diesel - T-34 and many more.

US GM 6046 diesel as used in Sherman M4A2 and M4A2 based M10.
US Ford GAA as used from M4A3 and M4A3 based M10.

UK Meteor - Cromwell, Comet, Centurion.

I would add the German HL120 - Panzer III and IV plus derivatives (Stug III in particular).

WARSPITER said:

I would add the German HL120 - Panzer III and IV plus derivatives (Stug III in particular).

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It was good, best maybe another story.
It didn't seem do any wrong, but it didn't seem to anything great.
An 11.86liter engine running at 3000rpm is not bad, but it is a little on the low end in the power needed for a tank.
Germans used fancy transmissions to make up for the low power. The Liberty engine used in the British tanks made a lot more torque even if not a lot more power. British tanks could get away with a 4 speed gear box because of the torque. Which was the better solution?

If you are in a Panzer III the HL120 is definitely acceptable. This was a well balanced and engineered tank.

The Panzer IV became less acceptable as it put on a lot more weight over time.

The HL120 was a good engine considering the types it was put in.

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.

The Liberty engine is somewhat maligned but that is due mostly to the tanks it went in which were not exactly
state of the art.

Best solution ? Probably an engine with more torque at lower revs than the vehicle it goes in needs thus taking
the strain off and helping with reliability. Gearboxes - best type is one with decent strength that is made to be
easy to use.

This is why I would put the HL120 in the best category - not the best but one of. The larger 200 series no.

Juha3 said:

In fact they were. During the war the British first tried to alleviate the problem by easing the railway clearance criteria, but restrictions were there. In the end it was decided to ignore the railway loading gauge restriction but due to the long development times, Centurion was the first British tank to fully benefit from it. The proliferation of tank transporters made that possible.

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I don't understand which tanks were "hamstrung"? If the Centurion was the first to break the restriction (as is commonly said e.g. Wiki and the post I originally replied to) then everything up to the Comet is restricted, and I would hardly call the Comet "hamstrung". If it's the 9'0 mentioned here then Crusader, Churchill & Cromwell were all breaking it. (Incidentally the Sherman would fit inside it!)

"Hamstrung" also implies that they wanted to build wider tanks earlier and only the railway gauge was stopping them - I haven't seen any evidence of this?

Just on width we have Valentine 2.63m, Matilda II 2.59m, Cruiser I-IV 2.54m. So none of them are right on the line of 2.67m (8'9) given in Technology of Tanks and here (9'0 = 2.74m). Only Valentine is even close.

More discussion here. A 2896mm (9'6) loading gauge is mentioned which corresponds to - North Staffordshire! I'm still confused.

The British rail system was originally designed to carry lighter weights than were later required. The clearance gauge was
the main problem with platforms etc being only a certain distance from the tracks.

Many bridges were not made to carry a lot of weight at one go so had to be avoided with heavier equipment.

The Northern lines could carry widths up to 9' 6" (2.92 metres). Southern and Western lines had a maximum of 9' 3" (2.83 metres)
but many connection and branch lines couldn't even reach that amount. For wider equipment this meant only certain lines could
be used with only certain port facilities having cranes big enough to load heavier equipment.

It was a practical problem that had to be taken into account and is somewhat confusing.

The other factor that made it less of a problem was that earlier tanks didn't need to be too wide as they were using 2 to 6lber guns.

As has been noted in another post tank transporters were getting better at carrying larger weights and a new trailer was designed
especially for the Centurion as first tests had shown it to be a very good design. The transporters also had to be sent by particular
routes due to road constraints.

WARSPITER said:

Best solution ? Probably an engine with more torque at lower revs than the vehicle it goes in needs thus taking
the strain off and helping with reliability. Gearboxes - best type is one with decent strength that is made to be
easy to use.

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A lot of very good points.
The Soviet tank engine was a very good engine with a very bad transmission. Hard to use which often meant the drivers didn't use all 4 of the gears, which meant the top speed and range never matched the book figures.
British used several different transmissions which got better as time went on.
US used two different types of transmissions and the end of the war automatics got mixed reviews. Much easier to use, more complicated/expensive/harder to repair and sometimes didn't match what a good driver could do with a manual in slow rough terrain. Bad drivers could wreck the gear box and clutch much faster with the manual transmissions.
Shermans used a 5 speed for 24-26mph.

Things get even more complicated when you start figuring in the steering gear. Trying to use the same steering gear on a KV tank that was used on a Bren carrier does not work so well. having your KV tank turn the opposite way you intended when going down hill makes for an exciting ride even if not being shot at.

Most of the MK III and MK IV tanks used 6 speed transmissions which does require a lot shifting (even leaving aside #1 once the tank is moving and #6 unless really moving fast on good road).
Most German tanks used small engines for what they were asking them to do. The Ford engine in the Sherman was18 liters. Almost 1/2 way between the engine in the MK IV and the Panther/Tiger. It didn't rev as well but torque is more closely related to displacement.

The T-34 was better earlier on but quality went down when the inevitable demand for higher production was made.

The T-34 clutch system was a problem as the discs didn't fare well under load and it wasn't long before it was hard
to disengage the gearbox to make a gear change. A better box and clutch were introduced in late 1943. Other
problems were addressed in order to continue production at a reasonable pace, a situation mirrored by the Panther.

The Panzer III was fine for it's engine size and was well sorted by the start of the war.

The Sherman had the advantage of high production numbers without many reliability problems at all. Engines, gearbox
and steering just worked and the fit of parts was excellent making repairs easy.

The Cromwell also rated highly in the reliability stakes so after D-day the US and British mediums may not have had the
best armour or firepower but could be relied on to be where they were needed.

A quote from a restorer many years (US I think) later was something like - I would rather have been in a Panzer III guarding
a crossroads than in one of fifty Tigers broken down several miles away.

The engines, transmission and steering gear have to work together for best performance.
The Soviet diesel seems to have good but the transmission and steering were varying degrees of crap.
The T-34s were just under the border line for weight for the system and the KVs and JS were just a bit over. the standardized drive line was good for production but not so good for actual use.
The Russians used clutch and brake steering which is about as crude as it gets and while it works ok in light vehicles it gets more problematic the heavier a vehicle gets.
There are a number of systems that take the power from the inside track and add it to the outer track while turning, this is not only bit more economical (not a big deal with a tank) but makes for smoother turns and less ground shearing and/or changes in the loads being transmitted by the tracks.

With clutch and brake (and depending on system) to turn gently the inside brake lever is used to burn up energy in the brake and slow the inside track, no extra power is given to the outside track. to turn sharper the steering clutch on the inside is used to burn up more power (slipping the clutch) while using the brake. Some systems use a differential but basically turning involves slowing the inside track and slowing the vehicle as the friction devices suck up the power. Feathering the clutch and brake does work but the vehicle does slow while truing and the intermittent power application can break traction with the ground. Doing this with a Bren carrier is one thing, doing with a T-34 is another and doing it with a JS-2 is another thing entirely.
As I hinted at earlier, this works when on the level or going up hill, When going down hill (or slowing using trailing throttle) when the intended inside track is declutched the track, under gravity, actually speeds up and the vehicle turns in the opposite direction unless the Driver is speeding up as the vehicle goes down hill. Hopefully the hill is short and the driver experienced. Out-of-control 45 ton tank coming downhill at even 10mph is rather frightening

Clutches wear out along with the steering brakes. Some Matilda's in NA wore out their steering clutches in 600 miles depending on terrain. Another reason for road or rail transport.

I started this discussion thinking I knew 2 things:

1. the British railway loading gauge was narrower than other countries and this was a potential constraint on the width of their tanks
2. the Centurion was the first time they broke that constraint

Actually cross checking the numbers indicates that the standard loading gauge of 9'0 was too small not only for the Centurion but many previous tanks. And there seemed to be no "magic number" that tanks were stuck at - they kept getting wider and wider.

WARSPITER said:

The other factor that made it less of a problem was that earlier tanks didn't need to be too wide as they were using 2 to 6lber guns.

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Given the British started the war with mostly Vickers light tanks, even the 2-pdr was a big upgrade. And the Cruisers I-IV were well within even the prewar loading gauge. So I'm not seeing a binding constraint there. (Maybe if they have to fit on a certain size wagon that's built to comfortably fit the gauge?)

From Crusader onwards there seems to be a gradual process of accepting widths outside the original loading gauge (only doing certain routes or 1-way traffic?) until the Centurion got so big they just gave up (maybe would still fit on the Great Western?).

I'm still curious as to how much the loading gauge really acted as a binding constraint during the design process of the later cruisers and Churchill. Was it a case of the tanks getting bigger without much consideration of loading gauge and the railways then figuring out various expedients, or was it sort of a moving target that still cramped designs even it it wasn't a hard limit "OK, we can let you have a couple more inches (Crusader) ... OK now you want a three-man turret and a 6-pdr gun (Cromwell), we can live with that if we only do 1-way traffic on XYZ lines ... OK now you want to take a hit from an 88mm and penetrate a Tiger - we give up!" Ultimately an unknowable counterfactual I guess.

Couple more links with interesting info but no definitive answers:
Tanks by Rail - Landships WW1 Forum
Design a better wagon for British Tanks

Edit: I skimmed my old AFV Profiles for Cromwell, Churchill and Crusader and width doesn't come up - they don't go into great detail into the design process admittedly. But then there's that book quoted in Wiki saying "The British railway loading gauge required that the width should not exceed 10 ft 8 in (3.25 m) and the optimum width was 10 ft 3 in (3.12 m),[15]" So ?

I guess I feel British tanks were already "hamstrung" by so many other issues - lack of money in the crucial mid 30s, requirement to run on 65 octane pool petrol, delay in getting the 6-pdr into production after Dunkirk, doctrine splitting cruiser and infantry tanks - how much more damage could an obviously elastic limit on width do?

Final thoughts:

• The only time width comes up in Wiki is Centurion (been over that) and Covenanter (flat 12 leaving no room for radiators).
• Even if you read the original War Office specifications, you don't know the process that produced them or how easily they could have been changed (unless someone took particularly revealing meeting notes!).

Edit: since this is an aircraft forum, thinking of all the (especially British!) specifications that were written after the fact or heavily modified around promising designs.

There were a lot of steering systems tried, some were good but complex. Some were complex and unreliable. Some
were in between.

As noted, the clutch brake system was simple but took power away. Heavier vehicles required some grunt to use
and were hard on components.

Twin drive systems had two engines, one for each track. Hard to keep synchronised as well which made it difficult to
keep the vehicle pointed in the right direction, especially at lower speeds on varying surfaces.

Double transmission systems are more complex but allow power to be geared to each track for speed changes. First used
by the Soviets on the JS series and are still used on T-72 / T-90 with later types having more gears for multiple radius.
Again, complex and can break down if not used correctly.

Double differential - Tiger A used this system where each diff is independent and can slow or speed up according to
the turn. It leaves the tank running straight when not applied and is fully regenerative - no power lost when turning.
Turn radius is limited by the gear selected.

Maybach Double Differential - Only used for the Panther and was simpler than full double differential. It did not speed
the outside tracking was not regenerative but it was cheaper. Still complex to manufacture and could be troublesome
for gear stress.

Triple differential - as used in the Chuchill, Comet and through to the Chieftan (different variations). Two track differentials
with a seperate braked differential for steering. No steering clutches required with continuously variable steering speed.
This gave the type much better cross country / climbing ability as power was direct to the tracks at all stages with no slippage.

Track warping. Bogies were moved left or right to slightly twist the track in the direction of movement. More turn brought
the brakes in as well. Bren carrier used this type. Again, larger types - not a great idea.

Electric transmission. Saint Chamon tank used this in WWI as did the Elefant in WWII. Reliability is a problem as there is
stress on the electric transmissions - the electric motors were basically the diff and steering system. Not such a problem
on diesel electric trains as the tracks provide the steering. Also, a lot of weight added as two large electric motors and
one large ICE are needed. The Saint Chamond weighed around 23 tons all up and five of that was the motors.

Eventually, hydrodynamic transmissions - hydraulic as in automatic types took over as advances were made in that area
with nearly all larger Western style tanks using it.

Best of the lot ? Steam. Yeah, I laughed too. Each side is run by steam pressure which is infinitely variable simply by
changing the pressure on each side. Problem - needs a big steam boiler to constantly provide the pressure.

Again - World War II production abilities were not as sophisticated as they are today so many ideas and implementations
were fragile, very heavy, or complex to service. Trade offs were made for the numbers required but the effect on vehicle
performance (hard to do well if something keeps breaking) in many cases offset the larger number able to be built.

hobbes154 said:

I guess I feel British tanks were already "hamstrung" by so many other issues - lack of money in the crucial mid 30s, requirement to run on 65 octane pool petrol, delay in getting the 6-pdr into production after Dunkirk, doctrine splitting cruiser and infantry tanks - how much more damage could an obviously elastic limit on width do?

Final thoughts:

• The only time width comes up in Wiki is Centurion (been over that) and Covenanter (flat 12 leaving no room for radiators).
• Even if you read the original War Office specifications, you don't know the process that produced them or how easily they could have been changed (unless someone took particularly revealing meeting notes!).

Edit: since this is an aircraft forum, thinking of all the (especially British!) specifications that were written after the fact or heavily modified around promising designs.

Click to expand...

For a good overall history of British designed / built tanks in WW2 see this title:-

If you want a detailed dive into the development of some individual British tanks P M Knight has written a series of detailed technical histories on individual tanks. A bit dry, but follows the twists and turns of each model from initial committees through to service.

A13 Mk.I & II Cruiser Tanks

A13 Cruiser Mk.V Covenanter

A15 Cruiser Mk.VI Crusader



A30 Challenger

A34 Comet

A43 Black Prince

hobbes154 said:

I guess I feel British tanks were already "hamstrung" by so many other issues - lack of money in the crucial mid 30s, requirement to run on 65 octane pool petrol, delay in getting the 6-pdr into production after Dunkirk, doctrine splitting cruiser and infantry tanks - how much more damage could an obviously elastic limit on width do?

Click to expand...

All else being equal, higher octane petrol would of course have been better. But considering that production infrastructure for high octane was quite limited in the run-up to the war (e.g. it was only with the advent of US supplies that they dared to switch the RAF to 100 octane aviation petrol?). So a higher octane petrol for tanks would likely have meant a reduction in supply of aviation petrol, so the choice seems clear. And also considering the extra logistical challenge of supplying two kinds of petrol to ground forces. Finally, a big engine running with less load is likely to be more reliable than a smaller highly tuned engine that would require higher octane petrol. I think this has been mentioned as one of the factors why the Meteor was as reliable as it was; without the supercharger and producing less than half the power of the aviation engine it was derived from, the load on the engine was much lower than what it was designed for.

As for the doctrine, yes, but to an extent the doctrine was also a result of how weak the pre-war tanks were. A 2-pdr gun was adequate for punching through pre-war tanks, whereas for shooting at infrantry and other unarmored targets you probably wanted something around 75mm. It was only later on when tanks got thicker armor it made sense to have something like the QF 75mm as a universal tank gun (although armor penetration was a bit weak). Similarly with the available engines, only with the Meteor they got enough power that they could make a heavy cruiser tank (Comet) that then evolved into the universal tank or MBT.

For an alternative what-if scenario I guess if they had started the Meteor project in, say, 1937, they could have had something like the Cromwell with a medium velocity 75mm in the NA campaign.

Final thoughts:

• The only time width comes up in Wiki is Centurion (been over that) and Covenanter (flat 12 leaving no room for radiators).
• Even if you read the original War Office specifications, you don't know the process that produced them or how easily they could have been changed (unless someone took particularly revealing meeting notes!).

Click to expand...

As has been mentioned in this thread, the loading gauge is sort-of the dimensions that are guaranteed to work across the entire network, and there might well be parts of the network that can take substantially wider cargo. So it's not a binary choice, some kind of 'oversize' load is clearly possible, but obviously the more oversize it is the more problems there are going to be.

Centurion seems to be the point where they completely gave up on the idea of rail transport and relied on road trailers instead?

Centurion was a logical step to take considering the need for bigger and better. Taking away the Christie suspension
also helped give more internal room without having to make the hull even wider.

Two pounders were fitted to cruiser and Infantry tanks used with the BEF and as noted before, the tanks didn't need to be all that wide.

The Cromwell timeline stretched out due to changes with the engine (Meteor instead of Liberty) and other problems setting
up manufacture. It was intended that the Cromwell would be entering service in 1942 but this didn't happen. As a result the
Crusader was up gunned to the six pounder.

WARSPITER said:

Electric transmission. Saint Chamon tank used this in WWI as did the Elefant in WWII. Reliability is a problem as there is
stress on the electric transmissions - the electric motors were basically the diff and steering system. Not such a problem
on diesel electric trains as the tracks provide the steering. Also, a lot of weight added as two large electric motors and
one large ICE are needed. The Saint Chamond weighed around 23 tons all up and five of that was the motors.

Click to expand...

Testing of the T1E1 Heavy Tank with electric drive did impress, being easy to drive, variable speed and turning radius, plus neutral steer, aka spin in place.

So this lead to the Medium Tank T23. Electric Drive powered bu Ford GAA, in place of the Wright Radial in the T1 series.
Electric drive added around 4 tons to the weight, but was 5 mph faster.

What moved the US from adopting Electric Drive, was lack of trained mechanics, and lack of schools for training new ones in quantities needed, not lack of performance or durability.

The US and France(except CharB1) used another type of steering Differential, the Cletrac.

This dated from the Cleveland Tractor Company, and the agricultural crawlers they started building during WWI.

They were one of the first to use a regenerative controlled differential, where no power is lost in turning, unlike the Clutch and Brake setup


Downside was that a turn was at a fixed radius, but given the reliability and ease of manufacture, was acceptable tradeoff.

The other problem with the T23 was uneven weight distribution which required a change to torsion bar suspension
to try to lower ground pressure problems. The other factor was the army not seeing a point to interruption of the
Sherman production for what was essentially still a medium tank with an untried transmission system.

Shortround6 said:

The Soviet diesel seems to have good but the transmission and steering were varying degrees of crap.

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The transmission of the IS was quite reliable. The mobility of the IS was rather satisfying. Technologically, Soviet transmissions were not advanced, however a certain (sufficient) level of reliability was achieved during the war.

Shortround6 said:

The T-34s were just under the border line for weight for the system and the KVs and JS were just a bit over.

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The improved KV-13 (future IS-1 - the first with this abbreviation, weight ~40t) was faster than the T-34.

Shortround6 said:

The Russians used clutch and brake steering which is about as crude as it gets and while it works ok in light vehicles it gets more problematic the heavier a vehicle gets.

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Indeed this problem was specific mainly to the T-34 with extremely sophisticated and unreliable design of the main friction device. The problem was solved partially in 1943 by introduction of a 5-speed gearbox. Clutching on IS was easier - there was no direct correlation with the weight of the vehicle.

Shortround6 said:

Doing this with a Bren carrier is one thing, doing with a T-34 is another and doing it with a JS-2 is another thing entirely.

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All earlier IS models had a planetary two-step traversing gear which significantly improves turning characteristics. The T-54 with syncromech and planetary traversing gears was tested in July-November, 1945.

WARSPITER said:

The other problem with the T23 was uneven weight distribution which required a change to torsion bar suspension
to try to lower ground pressure problems. The other factor was the army not seeing a point to interruption of the
Sherman production for what was essentially still a medium tank with an untried transmission system.

Click to expand...

In 1943, around four factories did not have their Sherman contracts renewed, so would be no interruption of production, and the newly built Burlington Tank Arsenal in the Quad Cities, ended making maybe two dozen tanks M7 Light/Medium tanks.

The US had a surplus of production facilities, no loss of M4A2, M4A3 and M4A1 planned production. Have Pacific Car and Foundry, for example, build enough to combat test in one theater, like the MTO, where lack of Sherman maneuverability had been noted by 5thArmy

One flavor of the T23 with HVSS(before the torsion bar tests) had a ground pressure of 11.8 psi with the 20" wide T80 track

The M4A3 with VVSS had 14.3 psi ground pressure with the 16.5" T48 track

marathag said:

In 1943, around four factories did not have their Sherman contracts renewed, so would be no interruption of production, and the newly built Burlington Tank Arsenal in the Quad Cities, ended making maybe two dozen tanks M7 Light/Medium tanks.

The US had a surplus of production facilities, no loss of M4A2, M4A3 and M4A1 planned production. Have Pacific Car and Foundry, for example, build enough to combat test in one theater, like the MTO, where lack of Sherman maneuverability had been noted by 5thArmy

One flavor of the T23 with HVSS(before the torsion bar tests) had a ground pressure of 11.8 psi with the 20" wide T80 track

The M4A3 with VVSS had 14.3 psi ground pressure with the 16.5" T48 track

Click to expand...

But the facilities freed up did not simply sit idle.

Lima Locomotive finished M4A1 production in Sept 1943. It was then switched to producing M32 Retriever conversion kits and Sherman wading trunks, through to Oct 1944 for use by Presed Steel Car, which had a contract to convert Sherman's to M32s which it began in Dec 1943.. Baldwin & Federal also got in on that act from late 1944.

There was also the Sherman manufacturing programme to consider - taking early production vehicles used for training Stateside during 1942/3 and updating them 1943-45 for reissue.

The army also didn't want two different types the same vehicle doing the same job.

This turned out to be a correct decision. The T23 cast turret for the 76mm gun was used as the basis for 76mm
gunned Shermans as the original turret was unsatisfactory.

Work with the T-23 evolved into the T-25 and T-26 which became the Pershing. This was then upgraded to become
the Patton.