Tank Off Road Performance Tests and Possible Wackiness

[Vanir Ausf B]

I've was intrigued by the observation that the Tiger I has a 4-bar Off Road rating while it seems every other medium or heavy tank in the game has a 3-bar rating. This would suggest the Tiger I has the best off road performance of any tank in the game. In reality the Tiger I was surprisingly good off road, but was not the best in that category.

So of course I had to test this.

Test is 20 vehicles -- Regular/Normal/+0 -- moving Fast over muddy terrain for a distance of 4km or until immobilized. Test was repeated for each vehicle until a total of at least 100km had been traveled.

Tiger I: 153043m traveled, 66 immobilizations, 1 immobilization per 2318.8m

Sherman Firefly VC: 132122m traveled, 73 immobilizations, 1 immobilization per 1809.9m

Panther G: 107427m traveled, 76 immobilizations, 1 immobilization per 1413.5m

Tiger II (Porsche): 100347m traveled, 77 immobilizations, 1 immobilization per 1303m

Hummm. We may have an issue here.

In CMx1 vehicle bog and immobilization rates were based on the nominal ground pressure rating.

Nominal Ground Pressure

There is significant variation for German vehicles from different sources, but the rankings are generally consistent.

Panther 12.5psi (.88kg/cm²) (CMBB) - 12.8psi (.9kg/cm²)

Tiger II: 14.1psi (.99kg/cm²) (CMBB) - 14.6 (1.03kg/cm²)

Tiger I: 13.9psi (.97kg/cm²) (CMBB) - 15.0psi (1.05kg/cm²)

Firefly: 15.1psi (1.06kg/cm²)

Ground Clearance

Panther: 56cm

Tiger II: 50cm

Tiger I: 47cm

Firefly: 43cm

A better measure of off road performance on soft ground specifically is Mean Maximum Pressure.

http://www.angelfire.com/trek/mytravels/militarygp.html

http://ciar.org/ttk/mbt/soil-mechanics/

Long ago, a helpful soul calculated the MMP for most common WW2 vehicles.

Here we go....

Was doing this out of interest, thought I may as well post it. A more complete list, in order of best to worst of ability to traverse soft ground.

Panther 150-155

M-24 Chaffee 175

BT-5 175

T-34/76 174-186

Churchill M IV 177 (11 roadwheel)

Tiger II 184

Tiger I 185-192

Churchill VII 182-223

Churchill Mk IV 217 (9 roadwheel)

Panzer IV 184-191

T-34/85 196

Sherman HVSS 205

M3 Stuart 216

Panzer III 220-232

BT-7 240

JS-II 245

Universal Carrier 253

Sherman VVSS 282

E-100 290

Cromwell VII 300

Cromwell IV 352

M3 Halftrack 363

US 2 1/2 ton 367 (6X6)

Elephant 370

SD KFZ 231 (8 rad) 415

M8 Greyhound 460

Maus 470

Opel Blitz 525 (4X4)

Opel Blitz 700 (4X2)

For comparison

M29c Weasel 27

Caterpillar D7 32.5 (widepad)

Caterpillar D7 80 (regular)

Leopard II 201

M-60 221-236

T-62 242

M-47 246

AMX-30 249

http://www.battlefront.com/community/showthread.php?t=38553&page=2

Conclusion

By any conventional measure the real world off road performance of the 4 tanks tested should be ranked as follows, from best to worst:

1. Panther

2. Tiger II

3. Tiger I

4. Sherman Firefly

The way they perform in game is much different, ranking as follows:

1. Tiger I

2. Sherman Firefly

3. Panther

4. Tiger II

This calls into question whatever mysterious methodology the game uses to gauge vehicle off road performance. I'm not trying to bash the game, which in general I find to be addicting to roughly the same degree as crack cocaine, but to point out that his particular aspect seems to be whacked.

Or perhaps my tests are crap, prove nothing, and the game is correct. I hope to find out...

[Vanir Ausf B]

From:

United States Vs. German Equipment: As Prepared for the Supreme Commander, Allied Expeditionary Force:

"I have compared the depth to which our tanks sink along side of German Mk V and Mk VI tanks in soft ground. Before the addition of track extensions our medium tanks sank six to eight inches while the Mk V tracks were not over four inches... The new E8 suspension with the wider track is about equal on our M4 tank to what the German Mk V has always been."

"Wherever we have seen Tiger and Panther tanks they have not demonstrated any inferior maneuverability. Near Puffendorf, Germany, several Tiger Royal tanks were encountered. These Tiger Royals were able to negotiate very soft ground and their tracks did not sink as deeply into the soft ground as did our own."

"The Mark V and VI in my opinion have more maneuverability and certainly more flotation. I have seen in many cases where the Mark V and VI tanks could maneuver nicely over ground where the American M4 would bog down. On one occasion I saw at least ten Royal Tigers make a counterattack against us over ground that for us was nearly impossible."

[Vanir Ausf B]

.................

[akd]

I wonder if having the highest max speed is disadvantaging the Panther in this test? Also was this a straight run to 4k, or did the course involve reversing direction?

[Vanir Ausf B]

I wondered the same. But the in-game off road ratings suggest the game does not consider the Panther to be as good as the Tiger I, at least, and my test results certainly back that up. Unfortunately the 1-5 bar system lacks granularity so outside of test results we don't know how the game views the Panther, Sherman and Tiger II in relation to each other. In fact, IIRC every medium and heavy tank in the game has a 3-bar rating in the game except for the Tiger I.

Also was this a straight run to 4k, or did the course involve reversing direction?

Straight run.

BTW, I found that the best way to test this was in real time (scenario author test). I just set it up and let it run and then checked back in an hour or so. The real work is measuring the distance traveled for every immobilized tank... and not many made the full 4km.

[RT North Dakota]

Panther 12.5psi (.88kg/cm²) (CMBB) - 12.8psi (.9kg/cm²)

Tiger II: 14.1psi (.99kg/cm²) (CMBB) - 14.6 (1.03kg/cm²)

Tiger I: 13.9psi (.97kg/cm²) (CMBB) - 15.0psi (1.05kg/cm²)

Firefly: 15.1psi (1.06kg/cm²)

Ground pressure is not the only factor. Power to weight ratios, and suspension have significant effect. I don't know how accurate those figures are but there is no real functional difference between 1.03 to 1.05 to 1.06kg . Actual track design and layout could well make a far bigger difference than that margin.

..... and avoid "veterans" opinion. It's mostly worthless unless very strongly qualified and set in context. Some guy saying he's seen tanks sink in X-inches is meaningless. Same field? Same day? Same mud? Tanks parked next to each other? Did you actually measure it? etc etc etc.

The reason the Brits created operational analysts were because soldiers were/are such unreliable observers.

[Vanir Ausf B]

"The capability of the Panther to negotiate obstacles and cross terrain was better than all other German and Allied tanks encountered by the Panther."

-- Thomas L. Jentz, German's Panther Tank pg 127.

Ground pressure is not the only factor.

I know that.

"On the whole, NGP has proved useful as a measure of the ability of tanks to move over soft soils and in particular for assessing their relative capabilities. Thus, tanks with a low NGP have generally performed better over soft soils than similar tanks with a high NGP. However, NGP is no more than a gross approximation to the pressure exerted by tanks on the ground and fails to take into account the fact that the pressure varies along the length of the track. In particular, it fails to take into account that peaks of the pressure, which occur under the road wheels, can be considerably higher than the average values."

Actual track design and layout could well make a far bigger difference than that margin.

Which is perhaps why I included Mean Maximum Pressure values?

"Physical reasoning leads to the conclusion that the maximum pressure under a track P(max) must be directly related to the weight acting on each of the road wheels and inversely related to the width of the track, the pitch of its links and the diameter of the road wheels...

Such an expression was derived by D Rowland who correlated it with pressures recorded during the experiments carried out in Britain with some 21 different tanks and other tracked vehicles, mostly in cohesive soils.

Rowland proposed that MMP should replace NGP as a design parameter and be used as the basis of comparing the soft soil performance capabilities of vehicles. This has happened to some extent since the use of MMP was first proposed in 1972 and comparisons of the values it calculated with known records of the performance of a number of tanks have shown that it is a far more accurate measure of their capabilities than NGP. For instance, the NGP of 84.9kN/m² of the German Panther of the Second World War and the 94.6kN/m² of the contemporary US M4 medium tanks did not reflect how superior the performance of the former was generally considered to be in relation to that of the latter. But their respective MMPs of 157 and 272kN/m² reflect this very clearly"

http://ciar.org/ttk/mbt/soil-mechanics/

and avoid "veterans" opinion. It's mostly worthless unless very strongly qualified and set in context.

On their own they may not mean much. But in this case they are not on their own.

[dieseltaylor]

Good foundations to the observations VAB

* mmp - Nice to see that at least one aspect of the Greyhound's sterling cross-country ability is shown : )

[Fizou]

Love it that you do these tests Vanir. Very interesting results.

[RT North Dakota]

"The capability of the Panther to negotiate obstacles and cross terrain was better than all other German and Allied tanks encountered by the Panther."

-- Thomas L. Jentz, German's Panther Tank pg 127.

Jentz was a nice guy and good researcher, but I'd be very careful of making such an all encompassing statement as that. Given vehicles with better power to weight ratios, its slope climbing performance was certainly not as good as say the Cromwell.

"Physical reasoning leads to the conclusion that the maximum pressure under a track P(max) must be directly related to the weight acting on each of the road wheels and inversely related to the width of the track, the pitch of its links and the diameter of the road wheels...

Such an expression was derived by D Rowland who correlated it with pressures recorded during the experiments carried out in Britain with some 21 different tanks and other tracked vehicles, mostly in cohesive soils.

Very familiar with Rowlands work. He's a bit of legend in the UK Ops Research World. The issue I was driving at is more to do with the ingress of mud/soil/debris into the track space and running gear itself. I perhaps did not explain that very well as I took it as given.

Overall, based on the data you are showing I'm not seeing this a major "game" problem. Would altering the figures make a significant difference to tactical conduct?

If I was designing the experiment, I'd want to see the failure rates based on a series of terrains, and not just one homogenous type. Not criticising your research method. I am merely suggesting another course of enquiry that you may want to pursue.

[c3k]

VAB,

Good stuff. Keep it coming...

Ken

[dieseltaylor]

RT North Dakota/VAB

Don't you find it a little odd that the breakdown rate is as high as it is. I mean they are travelling in a straight line in moderately difficult conditions but no shrubs/trees etc.

I have several books on tanks, regiments, and autobiographies and breakdowns did occur but not AFAIK at the rate in this test. There are of course many accounts where there are multiple breakdowns of Tigers but generally you find that this is from doing stupid things like towing or poor driving. IMO the game should reflect higher risk for behaviours .. as it does and dispense with this sort of apparently random breakdown.

[c3k]

As shown in Vanir Ausf B's screenshots, he used "Muddy" ground conditions. I have no accurate knowledge of what BFC's "Muddy" correlates to in the real world.

It could be pigsty-like, bottomless, clay, type of mud. To get through that would need constant high, fluctuating rpms in low gear, "snowplowing" an ever-thickening blanket of goo ahead of the armor. (Hmmm, is straight vs. downsloped armor better or worse? Is it modeled?) Huge goblets of mud cloying to the tracks and clogging every piece of running gear?

Or is it just a little softer than normal? A tank may sink to 4" instead of 3"?

I don't know. Because of that lack of knowledge, I don't think there is a basis to assess whether or not the breakdown rates are correct or not. The RELATIVE breakdown rates could certainly be looked at.

Flotation, MMP, NGP, etc., may be more important for SPEED rather than reliability. The heavy stress of deep mud would strain transmissions, drivetrains, and engines. Of course, "Bog" and "Immobilized" don't differentiate between terrain bog and mechanical breakdowns. (Unless you can see it under the wrench icon for the tank? E.g., terrain bog shows no broken systems, whereas mechanical breakdown would show a red "x" for engine or track or whatnot? VAB?)

So, I'm curious about how close to their maximum DRY speed can they drive over mud?

Manueverability vs. Reliability.

Ken

[RT North Dakota]

RT North Dakota/VAB

Don't you find it a little odd that the breakdown rate is as high as it is. I mean they are travelling in a straight line in moderately difficult conditions but no shrubs/trees etc.

These are not breakdowns. If I understand VABs data these are the vehicles becoming immobilised, due to factors unknown or unspecified.

I don't know. Because of that lack of knowledge, I don't think there is a basis to assess whether or not the breakdown rates are correct or not. The RELATIVE breakdown rates could certainly be looked at.

When you assess the reliability of any tank, you take what is called the Mean Distance Between Failure (MDBF) of each major automotive component. Boat loads of data exists for almost every modern design if you know where to look.

In terms of historical data these are quite hard to ascertain. I have seen post-war debriefs of German formation commanders who are basically disgusted with the reliability of their tanks compared to the Allies, but I have never seen figures where these are quantified in a reliable way.

Yes some data sets may exist, but I suggest they are utterly irrelevant for a game where not tank can really drive more than 20km and only lasts for 4 hours - so company and battle group tactics.

It would be very relevant if you wanted to play Divisional or Corps level stuff though.

[Lt Belenko]

There has to be factors other than ground pressure taken in to account by BFC. In running the test there is no way to determine which variable actually caused the breakdown. The King Tigers were notorious for breakdowns. And the Sherm was reliable.

But any way 1.5 to 2 kilometers between breakdowns just seems like they occur way too frequently.

[YankeeDog]

But any way 1.5 to 2 kilometers between breakdowns just seems like they occur way too frequently.

Fast moving over Muddy terrain? I don't think so. Navigating a tracked vehicle across mud is a royal b*tch. Trying to do so at top speed is downright foolhardy. The vehicle yaws all over the place due to differences in how much traction each individual track gains. It's very hard on the vehicle and it takes a lot of skill and attention on the part of the driver.

A quick dash across a short patch of muddy ground might make tactical sense, but going hell bent for leather hundreds of meters across muddy fields is going to get you stuck, sooner or later.

[akd]

There has to be factors other than ground pressure taken in to account by BFC. In running the test there is no way to determine which variable actually caused the breakdown. The King Tigers were notorious for breakdowns. And the Sherm was reliable.

But any way 1.5 to 2 kilometers between breakdowns just seems like they occur way too frequently.

They are not breakdowns. There is no "reliability factor" in CM that I am aware. Unreliable tanks are represented by their absence from the battlefield. If tanks are immobilizing without suffering battle damage, it is due to terrain.

Deep, water-logged mud would be incredibly challenging terrain.

[dieseltaylor]

These are not breakdowns. If I understand VABs data these are the vehicles becoming immobilised, due to factors unknown or unspecified.

A very fine distinction to make. I help myself by viewing immobilisation as a running gear related problem and breakdown to cover this and all other events also which may have the effect of immobilsing such as engine overheating, clutches and gearboxes breaking down. The sum of these should be considered.

So taking into account we are talking of tanks driving in a straight line and running through what is probably light mud in European terms the breakdown rate is way too high in the game.

If someone wishes to establish how muddy this is then perhaps a test with other vehicles like Dingos , Universal carriers, and Greyhounds might be interesting.

PS Perhaps more tests at slower speeds would be helpful. But in any event fast surely is a relative term according to the terrain circumstances. And of course relative to each tank with Churchills being notoriously slow. Fast therefore being less than 15 mph for most tanks across country I guess.

[akd]

I think it is safe to say that combining mud tiles with "muddy" ground conditions represents more than light mud.

[RT North Dakota]

A very fine distinction to make.

Not a fine distinction in real world military terms. Bogged down or grounded vehicles are an easy problem to solve. Busted transmission maybe a long job.

So taking into account we are talking of tanks driving in a straight line and running through what is probably light mud in European terms the breakdown rate is way too high in the game.

I strongly disagree. Terrain, such as soft ground and/or tree stumps will immobilise a vehicle quicker than you can say spit. I've seen a Leopard immobilised by sheet ice, and another tank foul it's tracks with concrete ribar. Nothing mechanically wrong with either tank.

What we are discussing is the granularity of the immobilisation frequency based on factors such as ground pressure (because it is simple to model as a number.)

There is no point in having mechanical reliability in the game, unless you want to have poor troops break the gear boxes on the Panthers... and good drivers get 150km out of them, etc etc etc.

[YankeeDog]

I think it is safe to say that combining mud tiles with "muddy" ground conditions represents more than light mud.

Agreed. Considering this is basically the worst type of natural, flat terrain vehicles will even attempt to cross in CMBN, I think it's safe to assume that this combination of weather & ground conditions is intended to model something worse than "light mud". AFAIK, the only way to make things worse would be to actually use marsh tiles, but if I'm not mistaken, marsh tiles are "no go" for vehicles in-game.

[RT North Dakota]

Actually if you want to model ground that really screws up tanks, go for terrain inside woods...as in lying logs and tree stumps or worse woods hit by shell fire or rubble around destroyed houses.

[dieseltaylor]

Given the screenshot shows , apparently, ploughed fields I cannot see the point of discussing rebar and tree stumps which are not routinely found in European fields. The dangers of rebar and tree stumps, gullies etc we would agree on.

I put forward the suggestion of wheeled vehicles [and the Universal] so that if they do not move much or at all we will know whether it is light or heavy mud. Until that happens it remains a moot point.

[akd]

Given the screenshot shows , apparently, ploughed fields

mud tiles.

[YankeeDog]

mud tiles.

So basically, we're looking at a WWII tank version of one of those redneck events were some guy in a souped-up truck goes flat out and tries to make it as far as possible across a mud pit before he bogs down, blows the engine/tranny, or loses control and flips the vehicle (or some combination of the three). Fun.