Greatest/Best Tank - Mobility

[DogDodger]

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

Like I said (with poor wording in retrospect...): OK, please.

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.

I'm not necessarily talking about top speed, but speed over rough terrain. Churchill's rhomboid shape and numerous rollers gave it the shape and low MMP necessary to climb out of craters/ditches and cross soft ground, but it would be tough to cross rough terrain as fast as a tank with a more supple suspension. Suspensions are designed to minimize the forces created by the vehicle driving over uneven terrain, and therefore--even if a tank's top road speed is low--suspensions have a direct impact on the cross-country speed, as a tank's cross-country speed is generally limited by the crew's tolerance to these forces and the risk of injury that they impart.

As an example, the US staged a race between the T25E1, T26E1, M4A3E8, and M4A3 VVSS in Aberdeen's Churchville cross-country area. The T25E1 and T26E1 both ran on torsion bars. All tanks had the same engine, however: the GAF of the T25/26 was essentially the GAA of the M4A3 redesigned to present a lower height, but power output was the same. The T25E1 and T26E1 were the heaviest vehicles in the competition, and as was shown in Korea, the relatively low power-to-weight ratio of the M26 compared to the M4A3(76)W HVSS yielded poorer performance in climbing the steep mountains of that country. Steering was controlled differentials for all the vehicles.

So the stage was set. All tanks had the same engine power output, and steering, but the heavier tanks were running on torsion bars instead of the volute spring suspensions of the lighter and intuitively more nimble Shermans. The results, however, had the torsion bar tanks in first place by a healthy margin: M4A3 finished in 30:40, the M4A3E8 in 28:35, the heavy T26E1 in 26 minutes, and the T25E1 in 23 minutes.

Looking at a comparison of British tanks, Cromwell had bump suspension travel of 226 mm and rebound of 190 mm, yielding 416 mm total. Churchill had bump travel of 3" (76 mm) and rebound of 2" (51 mm) on its bottom suspension bogies. Churchill's springs would necessarily be stiffer than those of Cromwell or else Churchill would be bottoming out on its bump stops constantly. With these stiffer springs, Churchill would be imparting higher bounce forces to its crew over a given terrain, and these forces would limit the vehicle's speed through rough terrain. Churchill could cross ditches or soft ground better than Cromwell due to its shape and lower MMP, but Cromwell should be able to cross hard, broken ground faster.

As did all tanks .

Yes. That's all I was trying to say. Tanks with a lower number of wheels or thinner tracks or whatnot would stand a chance of bellying, but Churchill also had considerations.

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 .

I wish you the best of luck with that. Wish I could tag along.

[Nick the Noodle]

Like I said (with poor wording in retrospect...): OK, please.



I'm not necessarily talking about top speed, but speed over rough terrain. Churchill's rhomboid shape and numerous rollers gave it the shape and low MMP necessary to climb out of craters/ditches and cross soft ground, but it would be tough to cross rough terrain as fast as a tank with a more supple suspension. Suspensions are designed to minimize the forces created by the vehicle driving over uneven terrain, and therefore--even if a tank's top road speed is low--suspensions have a direct impact on the cross-country speed, as a tank's cross-country speed is generally limited by the crew's tolerance to these forces and the risk of injury that they impart.

As an example, the US staged a race between the T25E1, T26E1, M4A3E8, and M4A3 VVSS in Aberdeen's Churchville cross-country area. The T25E1 and T26E1 both ran on torsion bars. All tanks had the same engine, however: the GAF of the T25/26 was essentially the GAA of the M4A3 redesigned to present a lower height, but power output was the same. The T25E1 and T26E1 were the heaviest vehicles in the competition, and as was shown in Korea, the relatively low power-to-weight ratio of the M26 compared to the M4A3(76)W HVSS yielded poorer performance in climbing the steep mountains of that country. Steering was controlled differentials for all the vehicles.

So the stage was set. All tanks had the same engine power output, and steering, but the heavier tanks were running on torsion bars instead of the volute spring suspensions of the lighter and intuitively more nimble Shermans. The results, however, had the torsion bar tanks in first place by a healthy margin: M4A3 finished in 30:40, the M4A3E8 in 28:35, the heavy T26E1 in 26 minutes, and the T25E1 in 23 minutes.

Looking at a comparison of British tanks, Cromwell had bump suspension travel of 226 mm and rebound of 190 mm, yielding 416 mm total. Churchill had bump travel of 3" (76 mm) and rebound of 2" (51 mm) on its bottom suspension bogies. Churchill's springs would necessarily be stiffer than those of Cromwell or else Churchill would be bottoming out on its bump stops constantly. With these stiffer springs, Churchill would be imparting higher bounce forces to its crew over a given terrain, and these forces would limit the vehicle's speed through rough terrain. Churchill could cross ditches or soft ground better than Cromwell due to its shape and lower MMP, but Cromwell should be able to cross hard, broken ground faster.

Yes. That's all I was trying to say. Tanks with a lower number of wheels or thinner tracks or whatnot would stand a chance of bellying, but Churchill also had considerations.


I wish you the best of luck with that. Wish I could tag along.

Nice post .

Just one bit concerning (and post not specifically directed at you) :

Churchill could cross ditches or soft ground better than Cromwell due to its shape and lower MMP, but Cromwell should be able to cross hard, broken ground faster.

There is a good reason that tank tracks are not always super wide, giving low ground pressure.

Wider tracks will mean a wider tank. That inhibits transportability. Wider tracks also mean greater friction thus lower engine/transmission/track life, lower reliability and greater maintenance. The trick is to make the tracks just wide enough to cope with the damp, and why some tanks were pretty good in some conditions but not in others.

In general, the Matilda was an unbelievably worthless tank! I will tell you about one of the Matilda's deficiencies that caused us a great deal of trouble. Some fool in the General Staff planned an operation and sent our corps to the area of Yelnya, Smolensk, and Roslavl. The terrain there was forested swamp. The Matilda had skirts along the sides. The tank was developed primarily for operations in the desert. These skirts worked well in the desert-the sand passed through the rectangular slots in them. But in the forested swamps of Russia the mud packed into the space between the tracks and these side skirts. The Matilda transmission had a servomechanism for ease of shifting. In our conditions this component was weak, constantly overheated, and then failed. This was fine for the British. By 1943 they had developed a replacement unit that could be installed simply by unscrewing four mounting bolts, pulling out the old unit, and installing the new unit. It did not always work this way for us.

Source: http://www.amazon.co.uk/Commanding-Red-Armys-Sherman-Tanks/dp/0803229208/ref=sr_1_fkmr0_1?ie=UTF8&qid=1337471825&sr=8-1-fkmr0

[DogDodger]

Nice post .

Just one bit concerning (and post not specifically directed at you) :


There is a good reason that tank tracks are not always super wide, giving low ground pressure.

Thanks. And absolutely, there is a practicable upper limit to track width. A loading width without skirts of 3.5 m or so seems about standard nowadays. One Cold War exception was Conqueror, with a width of 3.96 m. It ran on 31" wide tracks! M103, for comparison, was 3.63 m wide, and its tracks were 3" thinner, a savings of 152 mm in track width alone. The nominal ground pressures of modern MBTs has been creeping ever higher, though, and that is definitely one factor.

[panther3485]

Like I said (with poor wording in retrospect...): OK, please.

Thanks Chris, all scores registered now.

"I'm not necessarily talking about top speed, but speed over rough terrain. Churchill's rhomboid shape and numerous rollers gave it the shape and low MMP necessary to climb out of craters/ditches and cross soft ground, but it would be tough to cross rough terrain as fast as a tank with a more supple suspension. ... <snip>

No worries, Chris; your explanation is very good but I do already get all that. What I was trying to say is, given that none of the WW2 tanks I know of were as fast cross-country (rough terrain) as they were on the road; and given the Churchill's top road speed of 15mph, would a crew travelling over less than smooth terrain at speeds of, say 8-10mph at the fastest be subjected to significantly greater shocks than those of a tank with more compliant suspension? I would not have thought it would make much difference when speeds are that low; or at least, that the shocks would be well within tolerance for the crew even if the ride wasn't so plush.

(Enjoyed reading your posts anyway)

[DogDodger]

Thanks, and I had a feeling that wouldn't be new ideas. But at the cross-country speed of World War II tanks, I think even small differences add up. The course in the US Army test referenced earlier was 4.3 miles long. The VVSS Sherman, therefore, completed it at an average speed of 8.4 mph. The blazing fast T25E1? 11.2 mph. Going from VVSS to torsion bars had gained less than 3 mph of average speed, but even on that short course it translated to huge savings in time. Again, it wasn't really the point of an infantry tank, but (it seems to me) gaining just a bit of speed due to a "better" suspension could make a big tactical difference on certain terrains. Ogorkiewicz cites references that suggest that very low frequency peak-to-peak vertical displacements of 100-130 mm are the maximum acceptable. If your total wheel travel is only 127 mm, wouldn't that cut your speed on a much larger portion of the terrain than a tank with wheel amplitude of 400+ mm?

[panther3485]

Thanks, and I had a feeling that wouldn't be new ideas. But at the cross-country speed of World War II tanks, I think even small differences add up. The course in the US Army test referenced earlier was 4.3 miles long. The VVSS Sherman, therefore, completed it at an average speed of 8.4 mph. The blazing fast T25E1? 11.2 mph. Going from VVSS to torsion bars had gained less than 3 mph of average speed, but even on that short course it translated to huge savings in time. Again, it wasn't really the point of an infantry tank, but (it seems to me) gaining just a bit of speed due to a "better" suspension could make a big tactical difference on certain terrains. Ogorkiewicz cites references that suggest that very low frequency peak-to-peak vertical displacements of 100-130 mm are the maximum acceptable. If your total wheel travel is only 127 mm, wouldn't that cut your speed on a much larger portion of the terrain than a tank with wheel amplitude of 400+ mm?

Yes Chris, I do see your point. Even small differences can add up. How much they would add up to in the 'real world' of the battlefield is hard to say, especially at the low speeds (all below 15mph) applicable to the Churchill but yes, they would be there.

[triggerjockey]

I had to go with the T-34 on this one too. I don't have much to say on this one either. The T-34 was made to cover some of the nastiest terrain out there. It had good enough mechanical stamina to get to where they had to go and fight when they got there. It's speed was nothing to scoff at for the times either.

[panther3485]

I had to go with the T-34 on this one too. I don't have much to say on this one either. The T-34 was made to cover some of the nastiest terrain out there. It had good enough mechanical stamina to get to where they had to go and fight when they got there. It's speed was nothing to scoff at for the times either.

Thanks Chad, your vote for the T-34 has been recorded on the spreadsheet.

[Michele]

The T-34. Fast on good ground, undeterred by soft ground. In particular, in the summer of its introduction it was way faster than the opposition, and in its first fall and winter, way superior in dealing with mud and snow.
Not the most reliable engine, transmission etc., OK, but many tanks had such problems and those who were more reliable than the T-34, were also slower, and/or had a higher ground pressure, and/or a worse power/weight ratio.

[panther3485]

The T-34. Fast on good ground, undeterred by soft ground. In particular, in the summer of its introduction it was way faster than the opposition, and in its first fall and winter, way superior in dealing with mud and snow.
Not the most reliable engine, transmission etc., OK, but many tanks had such problems and those who were more reliable than the T-34, were also slower, and/or had a higher ground pressure, and/or a worse power/weight ratio.

Thanks Michele, score recorded.

[llkinak]

Winner: T34

Excellent: M4, Churchill, Cromwell, BT 5/7

Good: M3, Crusader, Tiger I, IS2, KV1, Valentine, PzKpfw III, PzKpfw IV, PzKpfw 38(t)

OK: Somua S-35, Panther, M13-40/14-41/15-42, Type 97 Chi-Ha

Poor: Tiger II, Char B-1 bis, Matilda II

[panther3485]

Thanks Lance, all scores recorded.

[97th Foot]

It was a toss up between the T34 and Churchill for me. In the end I went for the Churchill, of course this may be down to my reading to many posts by Nick the Noodle

As to the rest;

Excellent (36) - T-34, M-4.
Good (24) - Cromwell, PzKpfw III, PzKpfw IV, PzKpfw 38(t), BT-5/7.
OK (12) - IS-2, Valentine, Somua S-35, Char B-1 bis, Tiger I, Panther,
M 13-40/14-41/15-42, Type 97 Chi-Ha, M3 Medium, IS-2.
Poor (0) - Tiger 2, Crusader, Matilda 2, KV-1.

[Nick the Noodle]

It was a toss up between the T34 and Churchill for me. In the end I went for the Churchill, of course this may be down to my reading to many posts by Nick the Noodle

As to the rest;

Excellent (36) - T-34, M-4.
Good (24) - Cromwell, PzKpfw III, PzKpfw IV, PzKpfw 38(t), BT-5/7.
OK (12) - IS-2, Valentine, Somua S-35, Char B-1 bis, Tiger I, Panther,
M 13-40/14-41/15-42, Type 97 Chi-Ha, M3 Medium, IS-2.
Poor (0) - Tiger 2, Crusader, Matilda 2, KV-1.

My belief in the Churchill is not based on absolutes, but the best tool for the job that was available to any army for every role in WW2. I can't think of a better all round tank for supporting infantry in an attack. It certainly helps if your tank can go where the others cannot. It also had the legs to for extended operations from 43 onwards.

My belief stems from the fact that while tanks tend to get the limelight, it is the infantry and artillery that hold the ground and kill the enemy. Many think of tanks like Macedonian cavalry crunching through part of an enemy line, and then falling on the enemies rear causing a breakdown in enemy capability. While this is one role, the main role of tanks in WW2 was always to support the infantry in taking an objective. To use an example, the British employed 3 armoured divisions in NWE, ie 12 tank regiments. They were also intended to use 8 tank brigades ie 24 tank regiment equivalents, that is twice as many for the infantry support role.

The US also had tank battalions for their infantry divisions, and Shermans were simply too thin skinned and lacked cross country mobility compared to A22s. This is especially true due to terrain and adverse weather conditions much of the time, andwhy I support such an odd choice for many, apparantly too slow and undergunned to be a decent tank.

What I believe I have voted for is the right tool for the right job most of the time. That's the theory anyway .

[panther3485]

It was a toss up between the T34 and Churchill for me. In the end I went for the Churchill, of course this may be down to my reading to many posts by Nick the Noodle

As to the rest;

Excellent (36) - T-34, M-4.
Good (24) - Cromwell, PzKpfw III, PzKpfw IV, PzKpfw 38(t), BT-5/7.
OK (12) - IS-2, Valentine, Somua S-35, Char B-1 bis, Tiger I, Panther,
M 13-40/14-41/15-42, Type 97 Chi-Ha, M3 Medium, IS-2.
Poor (0) - Tiger 2, Crusader, Matilda 2, KV-1.

Thanks Neil.
All recorded.