Greatest/Best Tank - Mobility

[The Exorcist]

BT, I don't know how you can fault a tank than can go as fast as most cars back then.

Excellent (36) BT-5/7, PzKpfw 38(t), T-34, IS-2, M3 Medium, M4 Medium

Good (24) Crusader, Cromwell, Churchill, PzKpfw III, Panther,

OK (12) Valentine, Somua S-35, Char B-1 bis, PzKpfw IV, Tiger II, M 13-40/14-41/15-42, Type 97 Chi-Ha, KV-1

Poor (0)Matilda II, Tiger I,

[panther3485]

Thanks Exorcist. All recorded.

I gave the BT-5/7 the full 40 points for you, as this was your 'primary' vote.

[broderickwells]

I've just come across a lovely comment in Glantz & House's When Titans Clashed that the Soviets quite liked the M4 medium apart from its mobility - the narrow tracks meant it sucked in the mud.

[smallvillekalel]

I've just come across a lovely comment in Glantz & House's When Titans Clashed that the Soviets quite liked the M4 medium apart from its mobility - the narrow tracks meant it sucked in the mud.

That's predictable. The soviets excelled at mud and snow performance out of neccessity. I've also noticed that they seem to like a ground contact pressure of 11.2 psi. Armor additions and other factors change this during its lifetime, but it seems to be an important factor in their tanks as all I've seen have started out the same, BT-7, T-34, KV-1, and IS-2 all had the same 11.2 psi at initial production.

[JBark]

This was not an easy category for me as so many of the tanks that might possibly take high marks had periods of bad performance or aspects of their performance which made them questionable. Bad flotation (M4) or horrendous shifting/bad transmission (T-34) or low power/overheating (Churchill) or bad final drive (guess) all had to be factored. Which problem had the least negative impact overall? I went with the T-34. Despite mechanical difficulties with the transmission and resulting problems it had to deal with teremendously different and difficult terrains and came away with as reputation of superb mobility.

Excellent-Bt-5/7, M4, M3, Churchill, Cromwell


Good-Tiger I, Px38T, PzIII, PzIV


OK-Panther, Char B-1, Somua, Crusader, KV-1, Matilda II,M-13, Type 97, IS-2, Valentine

Poor- Tiger II

[panther3485]

This was not an easy category for me as so many of the tanks that might possibly take high marks had periods of bad performance or aspects of their performance which made them questionable. Bad flotation (M4) or horrendous shifting/bad transmission (T-34) or low power/overheating (Churchill) or bad final drive (guess) all had to be factored. Which problem had the least negative impact overall? I went with the T-34. Despite mechanical difficulties with the transmission and resulting problems it had to deal with teremendously different and difficult terrains and came away with as reputation of superb mobility.

Excellent-Bt-5/7, M4, M3, Churchill, Cromwell


Good-Tiger I, Px38T, PzIII, PzIV


OK-Panther, Char B-1, Somua, Crusader, KV-1, Matilda II,M-13, Type 97, IS-2, Valentine

Poor- Tiger II

Thanks, John. All registered.

[Nick the Noodle]

Nice to see the Churchill doing well in this category

That commitment of the 8th Armored Division (General Devine) in quest of a breakthrough south of the Lippe was no solution to Simpson's problem was demonstrated early on 28 March. Although the fatigued infantrymen of the 30th Division had fought through the night of the 26th and the day of the 27th to open a route for the armor, they failed to do more than dent the positions of the enemy's 116th Panzer Division. Dense forest and poor roads, when combined with determined resistance from German tanks and antiaircraft guns, prevented the armor from gaining more than three miles. When the fighting died down with the coming of night on 28 March, the Germans still held Dorsten. Prospects of a breakout faded.

It was a different story north of the Lippe. There, in fulfillment of the promise foreseen by General Ridgway, paratroopers of the 17th Airborne Division's 513th Parachute Infantry in midafternoon of 28 March mounted Churchill tanks of the British 6th Guards Armoured Brigade. With scarcely a pause, they raced seventeen miles beyond Dorsten. As the commander of the enemy's XLVII Panzer Corps, General Luettwitz, was quick to note, the spectacular advance outflanked the positions of his corps, including those of the 116th Panzer Division.

It's not often you hear of Churchills racing .

Source.

[panther3485]

It's not often you hear of Churchills racing .

I guess they could always race each other.

[DogDodger]

Well, racing may be relative. Mud wasn't that friendly to any tank, even Churchill. Fletcher relates that "[b]y mid-June 1942 142 RAC had formed a composite squadron of its Shermans while its Churchills were kept out of action. This may have something to do with mud. For example 51st RTR had reported roads so bad during that month that none of their tanks could be moved and a plan to send the Shermans up first had to be abandoned. But there were reports of mud causing serious damage to the Churchills. It was heavy, glutinous stuff which worked its way into the tracks and then got carried around beneath the track guards. Often bits of wood or lumps of rock would get caught in it, and there are instances on record of the mud scraper, just ahead of the drive sprocket, being torn off. The foreign objects, lodged in the mud, could literally rip segments of the tracks [sic] guards off or at least bulge them to the point where they jammed up against the turret ring." The track guards were reportedly often removed because of this issue.

Fletcher also details how the British 1st Armoured Division staged a trial between the Churchill and Sherman in December 1943 during which the tanks would "climb a scrub covered slope of average gradient, traverse the side of a hill which was cut up by small wadis and then tackle a very steep hill." The tankers reported that while Churchill could tackle difficult terrain slightly faster, the test was a draw: "There was no obstacle which the Churchill surmounted that proved impossible to the Sherman on the day of the trial." The trial was repeated after a rainstorm, and again the results between the tanks were similar: "Neither the Churchill nor the Sherman managed to get more than one third of the way along the course and both broke tracks when mud got into the drive sprockets and under the tracks." The Sherman reportedly got stuck and towed out of its mire by the Churchill, but the Churchill's final drive broke when driving on the wet plowed ground. Flecther states that driver skill would be more of a factor in mobility than the two tanks themselves.

Overall, mobility is a very complicated topic, as requirements for high speeds or the ability to cross rough or soft ground are often at odds with each other. Nominal ground pressure, or the tank's weight divided by the area of its tracks, doesn't really accurately portray how a vehicle will endure soft soils. Mean maximal pressure, or the pressure under each road wheel, is a better predictor since it is these maximum pressures that will distort soils. The pressure under the road wheels can be decreased by having wider tracks, giving these tracks a longer pitch, and giving the tank more road wheels. The VVSS M4 Sherman had an MMP of 252 kN/square meter, while HVSS reduced this to 205. At zero penetration, Churchill Mk.IV's MMP was 217, Matilda II's 252, Panther's 157, Tiger Ausf.B's 190, T-34-76's 174, BT-5/7's 175/240, and Cromwell IV's 368. The nominal ground pressures don't always closely correlate, and this difference accounts for some counterintuitive performance reports (e.g., Matilda's adequate performance in the Pacific or Panther's better performance in soft ground than the M4 despite having similar nominal ground pressures).

For high speed travel on rough ground, low springs rates are necessary to absorb irregularities in the ground. Necessarily, large amounts of wheel deflection are desirable to allow theese soft springs to work. In practice we can see that the faster tanks had larger amounts of wheel travel (e.g., T-34 had 240 mm total and Cromwell had 416), and slower tanks less (Churchill's road wheels had 127 mm of travel).

Steering is interesting, and the vehicles above used many disparate methods. The Pz.Kpfw.III and IV used epicyclic clutch-brake steering and the BTs and T-34 used "regular" clutch-brake steering. The US tanks used regerative steering with their controlled differentials, but these could not make as sharp of turns as many vehicles since the inside track could not be locked or reversed. Pz.Kfpfw.38(t) used a geared steering system, and IS-2 used a similar system. Panther used a geared system that could also be used as a clutch-brake system in tighter turns. Char B used a double-differential system with an hydrostatic pump and motor that allowed for infinitely variable steering. S-35 used a less complex double-differential. Churchill used a triple-differential system that allowed for one turn radius per gear, and the Tigers used a similar system that allowed for two radii per gear. The multi-differential systems of S-35, Churchill, Cromwell, Panther, and Tiger allowed pivot turns with the tracks spinning in opposite directions.

So with those thoughts out there, my votes are as follows:

Top: T-34

Excellent: Churchill, M4, BT-5/7
Good: Char B, S-35, Panther, Pz.Kpfw.III, Pz.Kpfw.IV, M3, Tiger I, Comwell, Pz.Kpfw.38(t)
OK: Matilda II, IS-2, KV-1, M-13/40, Type 97
Poor: Crusader, Tiger II

Overall, I think I'll vote the T-34 as the best in this category. Its low MMP allowed it to cross soft soils, and its relatively large wheel travel allowed it to cross rough terrain at decent speed. It had the best of both worlds, so to speak. Churchill still has a reputation for climbing and being good over rough terrain, but its suspension design wouldn't tolerate high speeds without transferring undue forces to the crew. Later versions were also reliable. M4 could at times match the Churchill's off-road performance, was reliable thanks to being based on proven components, and HVSS dramatically lowered its MMP. The BT tanks had low MMPs due in part to their long-pitched tracks, and their suspension allowed for high-speed travel as well.

Panther had a complex but great suspension design, but it suffered from reliability problem relating to its final drives that could affect its maneuverability.

Crusader was let down by the reliability part of this category. Tiger II also suffered here as well as in fuel consumption (860 L of fuel yields a road range of 170 km).

[panther3485]

"Well, racing may be relative. "

Absolutely. When my brother and I were kids, we'd get a few mates together for snail racing. The toughest part of the whole thing was getting the snails to go consistently in one direction. And we found all sorts of ways to cheat; or to declare our favourite snail the winner even if it didn't cross the line. The magic of childhood. Good fun.

Top: T-34

Excellent: Churchill, M4, BT-5/7
Good: Char B, S-35, Panther, Pz.Kpfw.III, Pz.Kpfw.IV, M3, Tiger I, Comwell, Pz.Kpfw.38(t)
OK: Matilda II, IS-2, KV-1, M-13/40, Type 97
Poor: Crusader, Tiger II

Valentine?

"Churchill still has a reputation for climbing and being good over rough terrain, but its suspension design wouldn't tolerate high speeds without transferring undue forces to the crew."

But the tank was not capable of high speeds; so, not an issue, surely?

[Nick the Noodle]

Well, racing may be relative. Mud wasn't that friendly to any tank, even Churchill. Fletcher relates that "[b]y mid-June 1942 142 RAC had formed a composite squadron of its Shermans while its Churchills were kept out of action. This may have something to do with mud. For example 51st RTR had reported roads so bad during that month that none of their tanks could be moved and a plan to send the Shermans up first had to be abandoned. But there were reports of mud causing serious damage to the Churchills. It was heavy, glutinous stuff which worked its way into the tracks and then got carried around beneath the track guards. Often bits of wood or lumps of rock would get caught in it, and there are instances on record of the mud scraper, just ahead of the drive sprocket, being torn off. The foreign objects, lodged in the mud, could literally rip segments of the tracks [sic] guards off or at least bulge them to the point where they jammed up against the turret ring." The track guards were reportedly often removed because of this issue.

Fletcher also details how the British 1st Armoured Division staged a trial between the Churchill and Sherman in December 1943 during which the tanks would "climb a scrub covered slope of average gradient, traverse the side of a hill which was cut up by small wadis and then tackle a very steep hill." The tankers reported that while Churchill could tackle difficult terrain slightly faster, the test was a draw: "There was no obstacle which the Churchill surmounted that proved impossible to the Sherman on the day of the trial." The trial was repeated after a rainstorm, and again the results between the tanks were similar: "Neither the Churchill nor the Sherman managed to get more than one third of the way along the course and both broke tracks when mud got into the drive sprockets and under the tracks." The Sherman reportedly got stuck and towed out of its mire by the Churchill, but the Churchill's final drive broke when driving on the wet plowed ground. Flecther states that driver skill would be more of a factor in mobility than the two tanks themselves.

Concerning the report re driving in mud, I spoke to David Fletcher about that when I visited the Tank Museum. Of course, the driver in the Sherman could have been better also.

What we do know from White's report here is that Stuarts could move when the Shermans could not, and from Beale's book, Tank Tracks, Churchills could move when the Stuarts could not. Therefore, the order of mobility in mud is probably the Churchill, Stuart and then the Sherman in this case.

This is not to say Churchills could cross any mud. In the Scots Guards by David Erskine (p402) many Churchills were lost in the mud due to the fact they were deliberately deployed where the enemy did not think tanks could operate. However, the fact that tanks were now positioned in an area no significant enemy AT weapons were stationed proved decisive. This is why the Churchill enjoys significant tactical mobility in very many situations.

That the Sherman enjoys operational mobility over the Churchill is not in doubt. It was easier to maintain and lighter, and until the VI model, the M4 enjoyed a deserved repuation for superior reliability over the A22. However, the Churchill was known for being able to move under its own steam for hundreds of miles, and enjoyed better reliability, in the 5th Guards tank army, than either the T-34 or T-70 on the long march to Prokhorovka.

While KV's had been withdrawn from T34 units by 1943, Churchills were added to the 5th Guards Tank Corps under Kravchenko. This corps made a surprise advance across the Desna using an underwater bridge, and were instrumental in defending a bridgehead across the Dnieper. Of the 75 T34's and 15 Churchills that started the crossing and drive across the following marsh (22nd Sept 43 iirc), losses were 15+ T34's but 0 Churchills (source).

On paper the Churchill does not appear anything special. Given its apparant low BHP and thus road speed, it appears inferior to even average tanks of WW2. Actual usuage appears to paint another picture.

Overall, mobility is a very complicated topic, as requirements for high speeds or the ability to cross rough or soft ground are often at odds with each other.

Indeed.

Nominal ground pressure, or the tank's weight divided by the area of its tracks, doesn't really accurately portray how a vehicle will endure soft soils. Mean maximal pressure, or the pressure under each road wheel, is a better predictor since it is these maximum pressures that will distort soils. The pressure under the road wheels can be decreased by having wider tracks, giving these tracks a longer pitch, and giving the tank more road wheels. The VVSS M4 Sherman had an MMP of 252 kN/square meter, while HVSS reduced this to 205. At zero penetration, Churchill Mk.IV's MMP was 217, Matilda II's 252, Panther's 157, Tiger Ausf.B's 190, T-34-76's 174, BT-5/7's 175/240, and Cromwell IV's 368. The nominal ground pressures don't always closely correlate, and this difference accounts for some counterintuitive performance reports (e.g., Matilda's adequate performance in the Pacific or Panther's better performance in soft ground than the M4 despite having similar nominal ground pressures).

For high speed travel on rough ground, low springs rates are necessary to absorb irregularities in the ground. Necessarily, large amounts of wheel deflection are desirable to allow theese soft springs to work. In practice we can see that the faster tanks had larger amounts of wheel travel (e.g., T-34 had 240 mm total and Cromwell had 416), and slower tanks less (Churchill's road wheels had 127 mm of travel).

Steering is interesting, and the vehicles above used many disparate methods. The Pz.Kpfw.III and IV used epicyclic clutch-brake steering and the BTs and T-34 used "regular" clutch-brake steering. The US tanks used regerative steering with their controlled differentials, but these could not make as sharp of turns as many vehicles since the inside track could not be locked or reversed. Pz.Kfpfw.38(t) used a geared steering system, and IS-2 used a similar system. Panther used a geared system that could also be used as a clutch-brake system in tighter turns. Char B used a double-differential system with an hydrostatic pump and motor that allowed for infinitely variable steering. S-35 used a less complex double-differential. Churchill used a triple-differential system that allowed for one turn radius per gear, and the Tigers used a similar system that allowed for two radii per gear. The multi-differential systems of S-35, Churchill, Cromwell, Panther, and Tiger allowed pivot turns with the tracks spinning in opposite directions.

So with those thoughts out there, my votes are as follows:

Top: T-34

Excellent: Churchill, M4, BT-5/7
Good: Char B, S-35, Panther, Pz.Kpfw.III, Pz.Kpfw.IV, M3, Tiger I, Comwell, Pz.Kpfw.38(t)
OK: Matilda II, IS-2, KV-1, M-13/40, Type 97
Poor: Crusader, Tiger II

Overall, I think I'll vote the T-34 as the best in this category. Its low MMP allowed it to cross soft soils, and its relatively large wheel travel allowed it to cross rough terrain at decent speed. It had the best of both worlds, so to speak. Churchill still has a reputation for climbing and being good over rough terrain, but its suspension design wouldn't tolerate high speeds without transferring undue forces to the crew. Later versions were also reliable. M4 could at times match the Churchill's off-road performance, was reliable thanks to being based on proven components, and HVSS dramatically lowered its MMP. The BT tanks had low MMPs due in part to their long-pitched tracks, and their suspension allowed for high-speed travel as well.

Panther had a complex but great suspension design, but it suffered from reliability problem relating to its final drives that could affect its maneuverability.

Crusader was let down by the reliability part of this category. Tiger II also suffered here as well as in fuel consumption (860 L of fuel yields a road range of 170 km).

Some nice info there.

[DogDodger]

Absolutely. When my brother and I were kids, we'd get a few mates together for snail racing. The toughest part of the whole thing was getting the snails to go consistently in one direction. And we found all sorts of ways to cheat; or to declare our favourite snail the winner even if it didn't cross the line. The magic of childhood. Good fun.

Outline the track with salt, perhaps?

Valentine?

Ugh, thought I counted them. OK, please. It wasn't called "slow-motion" suspension for nothing.

But the tank was not capable of high speeds; so, not an issue, surely?

The intent was never for the infantry tank to be quick, but Churchill's suspension design was one physical factor its the lack of speed I'd say?

Concerning the report re driving in mud, I spoke to David Fletcher about that when I visited the Tank Museum. Of course, the driver in the Sherman could have been better also.

Well what did he say? Having first-hand access to experts is jealousy-inducing. We'll make it to Bovington at some point!

What we do know from White's report here is that Stuarts could move when the Shermans could not, and from Beale's book, Tank Tracks, Churchills could move when the Stuarts could not. Therefore, the order of mobility in mud is probably the Churchill, Stuart and then the Sherman in this case.

Perhaps generally. However, turretless Stuarts were put through the same trial Fletcher mentioned: in the dry they failed at the same point as the medium tanks, and in the wet failed at the first ditch.

This is not to say Churchills could cross any mud.

No, of course not. But it apparently did have issues in certain heavy muds due to certain design decisions.

Some nice info there.

Thanks.

[JBark]

Absolutely. When my brother and I were kids, we'd get a few mates together for snail racing. The toughest part of the whole thing was getting the snails to go consistently in one direction. And we found all sorts of ways to cheat; or to declare our favourite snail the winner even if it didn't cross the line. The magic of childhood. Good fun.

I would have thought the toughest part was finding a snail that could carry even a small boy?

[panther3485]

"Ugh, thought I counted them. OK, please. It wasn't called "slow-motion" suspension for nothing."

Erm, .... yes, ... and ... precisely where do you want the Valentine ranked?

" ... The intent was never for the infantry tank to be quick, but Churchill's suspension design was one physical factor its the lack of speed I'd say?"

I would not have thought so. Just that the fact the Churchill was a slow tank already for other reasons; so such a suspension design was not, and could not become, a factor that would limit its speed. A bit like tyres rated for 150mph max, on a car that is only physically capable of 120mph anyway.

But if somebody would like to educate me by producing information or evidence to the contrary, I'll happily entertain that. Always grateful for education.

[Nick the Noodle]

Perhaps generally. However, turretless Stuarts were put through the same trial Fletcher mentioned: in the dry they failed at the same point as the medium tanks, and in the wet failed at the first ditch.

Tests are enlightening. However, actual usuage paints another picture. In some ways its a bit like armour penetration data, whereby one gun can theoretically penetrate a tank at a certain distance. However, we know from combat reports that there are many instances, for a variety of reasons, where the ammunition does not perform as expected.

No, of course not. But it apparently did have issues in certain heavy muds due to certain design decisions.

As did all tanks . However, the Churchill was specifically designed for the tactical role, just as the Sherman was designed for exploitation, pursuit and other deep penetrating strikes. The reason I prefer the Churchill over the Sherman is simply that the former role was far more common, especially 44/5.

Well what did he say? Having first-hand access to experts is jealousy-inducing. We'll make it to Bovington at some point!

The 'problem' with David Fletcher is that his first love is WW1 armour. He is also bored with WW2 German armour, and knows next to nothing on Soviet armour. The latter is because he only uses primary sources, and feels he does not have enough time to learn Russian. He is also smart enough not to be drawn into any comparrison of tanks.

The next time we meet, hopefully I'll buy him lunch at a pub and use booze to loosen his tongue. Then I'll just listen and perhaps take notes .