Normandy: Immobilisations

[undead reindeer cavalry]

It makes a difference what you're comparing the number against. Since you are not comparing the wet ground numbers to relevant real world numbers (i.e. not the Soviet data), then it's numbers in a vacuum. That's what I detailed on the previous page.

So... does someone want to test on dry open ground and compare those numbers to the Soviet figures? Without further clarifications the comparison is utterly meaningless, but with some extremely rough guesswork I think we can at least have a better comparison than we've been able to have so far with bad ingame data.

sorry for confusion, but for some posts already i have talked about CM test vs CM test comparison. thus the misconnect.

i still haven't found more detailed information about that Soviet road march (the precise terrain travelled, weather and ground conditions etc), so i am not sure there is a justification to choose one ground setting over another in CM tests if we want to be really accurate.

there had been heavy rains on the region which turned large areas in the mud, but the actual dates of the march were mostly dry at least at Kursk itself. (yes i repeat myself endlessly)

Kursk belongs to the so called "black earth region", which caused rains to turn ground to mud very easily. it's hard to say how quickly the ground would dry up, as it's dependant on quite a number of factors like you yourself wrote.

the condition of roads on the march route is unknown. it's the rear of the Kursk salient so it might have seen considerable amout of traffic.

i'm still hoping to get some Soviet studies of this type of stuff on my hands. there are references to these studies on a number of books and some of the studies are apparently quite detailed. e.g. there's a study about the maintenance stuff about the 6th GTA's march thru Mongolian desert & mountains.

perhaps someone encounters a study by some other nationality.

then there are ordinary unit diaries and reports, from which we might, with hard work and good luck, collect some interesting data ourselves.

then of course there are all sorts of algorithms about ground pressure and such.

[undead reindeer cavalry]

That is not quite true.

it's hard to find a source discussing T-34 that doesn't say its good cross country mobility was one of its key strengths.

T-34 ground clearance is just the same as with Panzer IV etc. yes, modified Christie suspension. yes, great floatation on soft ground due to good MMP values.

i'd rather not get sidetracked with this. if you really want, perhaps open up new thread at CMBB forum?

[rune]

read the article from the Russian tank commander who commanded the Sherman tanks. in it, he states the Sherman had better cross country performance then the T-34 which surprised me at first. It used to be on the red army site, and it was also stated in the q&a section where he answered questions. not that it has any impact on the conversation.

Rune

[Battlefront.com]

URC,

i still haven't found more detailed information about that Soviet road march (the precise terrain travelled, weather and ground conditions etc), so i am not sure there is a justification to choose one ground setting over another in CM tests if we want to be really accurate.

Well, that's a primary problem. If the real data is taken from largely "good" terrain conditions, and you do game tests on "poor" terrain conditions, the numbers will look wildly different. And they should since the conditions are on opposite ends of the spectrum.

there had been heavy rains on the region which turned large areas in the mud, but the actual dates of the march were mostly dry at least at Kursk itself. (yes i repeat myself endlessly)

I live in an area where we claim to have a 5th Season called "Mud Season", so I'm very familiar with bad soil in the rain For us the issue is very shallow, often clay, based soil on top of glacial bedrock. Every town here has hundreds of acres of swamps, bogs, ponds, rivers, streams, and lakes (the largest lake here is 40 miles long). We're generally wet until the ground freezes. It's been raining steadily for 4 days now and the dirt roads around here are completely passable to my 2 wheel drive VW. Not comfortable for such a vehicle, because the roads haven't been graded, but largely dry. But try driving offroad around here... not a very smart idea as I will prove on Saturday when I have to haul an old vehicle out of a field with a tracked vehicle. I'm expecting to get stuck

Again, what I'm saying here is that road marches are not directly comparable to offroad use. The reason is quite simple, as I keep explaining, but I'll try again using a more simplistic example.

For paved roads, how much difference is there from day to day, season to season (assuming no snow/ice), in terms of the ability to drive on them without bogging? Extremely consistent, yes? How about dirt roads? More variable, true, but generally pretty good, right? I mean, that's why people go through all the trouble of making roads, isn't that true? If roads were really no better than open terrain, then why spend so much time and energy making them? So I hope there's no disagreement here.

Now let's talk about "open ground". How does the best conditions in the best "open ground" compare to a paved road? How about a dirt road? Inferior even under best conditions, true? Now what happens when the terrain gets a little wet? Does "open ground" suffer the same sort of problems as roads do, or does it get disproportionally worse? How about when the ground is saturated with rain for many days? Is it about the same as roads getting the same amount of rain?

HOPEFULLY nobody is going to say that "open ground" is proportionally the same as roads, because I think we can stop the discussion right here and now if that's the case If you agree with what I wrote in the previous paragraphs then you have to also agree that even dirt road marching won't change much based on fairly mild weather conditions (i.e. not the sort of quagmires that happen after prolonged rain in generally wet seasons). Yet open ground, which is already inferior to dirt roads, will see a dramatic, even exponential, increase in its ability to bog vehicles. At some point even the dirt roads become problematic, but by that time off-road conditions are so bad as to almost guarantee bogging. Therefore, even at the most extreme the bogging/immobilizations on dirt roads will be extremely modest compared to open ground.

Any disagreement here? I really, really hope not!!

This is why people doing tests have to be VERY careful to correctly identify, assess, and replicate the variables of a real world sample with in-game conditions. Extrapolations are extremely difficult to do for a large number of reasons that I've harped on for pages and pages of this thread (all unchallenged as far as I can see), but they are absolutely impossible if a couple of the basic variables are not assessed correctly.

The Soviet march data has the following critical components:

1. Predominantly, if not exclusively, on-road.

2. A mix of rain and non rainy conditions.

3. Travel most likely done on dirt roads vs. paved roads.

So far we have two recent tests with enough samples to be statistically relevant, but neither duplicates the above variables. The Vulture's test comes closest, and the results appear consistent in that they show a lower immobilization/bogging rate than the Soviet data. The other test, from URC, is so different that a meaningful comparison of results is impossible.

My recommendation is to do two sets of tests. One on dry dirt roads, one on dry open ground. After that test with the least amount of wetness for both. Some very carefully done comparisons can then be achieved by proportionally mixing the wet and dry tests against the Soviet data. HOWEVER!!! There are still major variables which must be accounted for, because the number of immobilizations itself is completely different in the Soviet data compared to the way CM does it. After the tests are done I can help come up with reasonable allowances for these differences. I've already mentioned a large number, but there are others (for example, did the road marches during wet days continue at the same pace as dry days? Or did they stop more frequently to allow for road repairs, less strain on vehicles, etc?).

Steve

[Battlefront.com]

Redwolf,

I think that some of the irritation about CMBB's bogging also came from oversimplifying this model. Just using weight/track-surface leaves you with an inaccurate picture.

Correct, there are a couple dozen major variables at work and we only simulate ground pressure, abstracted terrain characteristics, abstracted weather characteristics, and crew Experience. I don't remember if we have power:weight included, we definitely don't have arbitrary "reliability" figures. Nor do we have ground pressure simulated exactly to simulate the fact that weight distribution is more even on some vehicles than others. This just involves way too much work with far too many unknowns to be of any use. Just look at the "travelability" stuff that pmak1970 linked to! Nobody would be happy if we spent the time needed to simulate that stuff

Great discussion.

I agree now that we're finally inching towards some more meaningful comparisons. The last 10 pages or so show why it's so VERY important for people to take a scientific approach to testing instead of tossing some stuff on a map, see what it does, then compare it to something which is totally different.

Steve

[c3k]

My .02, having followed this for 23 pages.

The Soviet road march data, while interesting in and of itself, does not, in my view, lend itself to an interpretation of CMx1 or CMx2's immob/bogging rates.

I admit not knowing exactly what SOP's Soviet Mechanized/Armored units used when conducting a road march. However, I would assume that there were periods of time built into the march schedule for maintenance, etc. These times would get changed, in my view. Let's say a company of T-34's is grinding down the road. Suddenly tank number 4 throws a tread, drops its transmission, loses steering, whatever. The unit would stop, evaluate the condition of the tank, and either leave it behind for rear echelon repair units to pick up (not likely in the Soviet army), or repair it if able.

Here's the crux of the issue: the parent formation, conducting a multi-hour (multi-day?) long-distance march DOESN'T CARE how long a tank is broken, as long as it's at the start line when the attack starts. So, our tank may take 2 hours to fix. Whatever. The unit will then, having used the delay to accomplish whatever it can on the other tanks, attempt to make up the lost time. Typical road march speeds are not that fast. So, this tank would be totally inop for the duration of a CM scenario, yet it wouldn't cause a blip in the high level report.

The tank in question would have to be catastrophically out of service for it to be listed.

Now, let's look at how these things get reported in a bureaucracy. The Soviet commander is torn between a couple of priorities. If he reports breakdowns due to rear area factors (spares, fuel, poorly made tanks, etc.) would he possibly risk being shot for criticizing the state? Yet, if he has non-runners which he is keeping off the books so he doesn't look good (which one of the regimental commanders is the worst? is the number of non-runners important? you bet!), how does he eventually reconcile the numbers? In combat, you can add one or two extra into "destroyed by enemy action". If you're in the rear area, the best you can do is keep them on the books until a convenient road march, then you can list them as "fell out of march".

In short, I wouldn't put too much reliance on the precision of the numbers given, nor would I extrapolate the numbers into CM scale.

I _AM_ interested in bog/immob rates in tests made using the game engine.

Regards,

Ken

[pamak1970]

i'm still hoping to get some Soviet studies of this type of stuff on my hands. there are references to these studies on a number of books and some of the studies are apparently quite detailed. e.g. there's a study about the maintenance stuff about the 6th GTA's march thru Mongolian desert & mountains.

perhaps someone encounters a study by some other nationality.

I suggest you visit the armchair general forums. Specifically wwii forum- " PKKA in wwii (the Russianarmy in wwii)".

It has many Russian posters and a lot of them have Soviet studies (many not yet translated to English).

Recently i posted a question there about the rate of repair of Soviet maintenance formations and they were very helpfull.

[Vark]

I took a different tack, I looked at a situation that should result in a high number of bogging/immobilisations and ran a series of tests. 60 Ferdinand tank destroyers driving buttoned through thick mud at fast speed, the result after 30 mins was 29-34 immobilisations and 7-9 bogged (repeated the test 10 times). I have no expert knowledge if these figures seem realistic or not (if any Ferdinand grogs are out there, please reply) but they seem overly generous to me.

[Kwazydog]

My .02, having followed this for 23 pages.

I admit not knowing exactly what SOP's Soviet Mechanized/Armored units used when conducting a road march. However, I would assume that there were periods of time built into the march schedule for maintenance, etc.

C3k Interesting point, it actually reminded me of a chapter on SS Panzer Abteilung 102's march to Normandy.

According to it the Tigers were to halt every 10-15km to inspect engines and perform any needed maintenance. Generally the tracks were about to travel 45km with attention, but the hard roads were proving a problem for them.

Even with these halts several of the Tigers engines started to hit the 100c with fire shooting out of the exhaust and the rear deck plates smoking. Eventually one caught fire and had to have its cooling fans replaced. 3km further on the engine had stalled again, and even though it restarted the tank caught fire 10km further down the road as they had installed the fan backwards in their rush It was saved though.

Anyways just thought Id pass it on...interesting story of how even a road march with scheduled maintenance can be problematic.

Dan

[pamak1970]

maintenance time during road march is absolutely vital.

I do not have available right now wwii numbers for different nations (i have to dig for this and i do not have enough time).

I do have right now available times for modern operations .

For example

http://www.globalsecurity.org/military/library/policy/army/fm/100-61/Ch3.htm

Notice

Daily march performance calculations assume that units march from 10 to 12 hours of each day. The remaining 12 to 14 hours are spent as follows:

Maintenance: 3 to 4 hours.

Deployment and camouflage: 1 to 1 1/2 hours.

Movement to start line: 1 to 1 1/2 hours.

Rest: 4 to 8 hours.

Hot meal: 1 to 1 1/2 hours.

During a march of over 1,000 km, there is likely to be at least one rest day, for essential repair and maintenance work.

That is for modern (and more reliable equipment-manual of 1998)

Also i have some more interesting data for specific vehicles

For example

http://www.inetres.com/gp/military/cv/inf/M113_variants.html

XM806E1 Light Armored Recovery Vehicle

"Recovery Vehicle, Full-Tracked, Light Armored (M113A1) XM806E1." The XM806E1 recovery vehicle is an M113A1 APC modified for recovery of disabled vehicles comparable in weight to the M113A1. The vehicle was scheduled for operation at Aberdeen Proving Ground for 4,000 vehicle test miles, of which 1,000 were with an M113A1 in tow. Also, 100 winch operating hours and 12 crane operating hours were conducted.

Testing was under actual field conditions on missions which typify normal operational use of the equipment by troops in the field. The maintenance ratio for the test vehicle was 0.0815 hour of active maintenance time per mile of vehicle operation. Based on 4,001.2 miles of operation and 17 equipment failures, the MTBF was 235.3 miles. The total active maintenance time to repair failures was 133.2 man-hours and 46.5 clock-hours giving a MTTR of 7.78 man-hours and 2.73 clock-hours.

Where MTBF =mean time between failures

..........MTTR=mean time to repair

Notice especially the mean time to repair)(2.73 clock-hours).

This means that a large number of vehicles falling behind during a road march, will be able to join their parent unit at the end of the day.

(that is a 1969 technology by the way)

There will be a small percentage of vehicles experiencing a serious problem which will not be able to join the unit and you might see them as "out of action" in the unit report. However, the real percentage of vehicles experiencing breakdown is much larger and can not be revealed by high-echelon reports about the unit's march mission.

For wwii. although numbers maybe different, the concept is still the same. There are many repair jobs which will not be recorded in the unit's diary.

[Battlefront.com]

Excellent data, thanks!! I have a memoir of a gunner who wound up crewing the only Super Pershing to see combat action. Yup, the guy who took out a King Tiger actually wrote a small, and quite good, book. In the book there were all kinds of details about breakdowns and boggings. Including their first night march where his driver panicked, drove into the tank in front of them, and ejected their TC onto the deck of the tank in front! And the guy was unhurt!! The same could not be said for the Sherman, which IIRC had a broken sprocket. The crew had to sit all alone all night on the side of the road waiting for the rear repair guys to fix it up. Then they got lost on the way to their parent unit and wound up having a couple hundred Germans surrender to them when they accidentally drove into enemy territory. Or something like that, I forget the details and the book is buried at the moment

Another thing to consider is kinds of recovery elements that are on vehicles. Tanks have tow cables or tow bars, many vehicles have self recovery winches (all Strykers do), and in WW2 crews had all kinds of stuff strapped to their vehicles for recovery. Especially logs. So either all these nations making vehicles, and all their crews using them, were needlessly paranoid *OR* they had good reason to suspect they would bog and need to help themselves out. My money is on the latter explanation

I have a 1950s tank driver's manual which explains all kinds of really super cool ways to get a tracked vehicle unstuck from a variety of different obstacles. Having tracked vehicles myself, I've actually employed one of the tricks and had the stuff ready to do another one.

Trick 1 - general bogging. Put cable onto the top section of track that is most likely going to get the vehicle turned onto solid ground. Take cable and put it around something very solid, like a large diameter tree or another vehicle. Put power to that track in whichever direction you have it set up for, the cable stays taught, and the vehicle pulls itself along the cable. Kinda like going hand over hand up a rope. Works like a charm!

Trick 2 - if you mange to "belly" the vehicle by getting something between the tracks which reduces traction enough for the tracks to slip, take a log and strap it to both tracks either up front or to the rear (depending on which direction you want to extract. Slowly engage both tracks and the log moves under the vehicle, makes contact with the obstacle, and then forces the vehicle to slide off of the obstacle. This might work for other types of situations, depending on conditions.

The problem with #1 is that if you're in an open field without anything to anchor to, the technique doesn't work. #2 might work, but if you're really sunk into the ground it likely won't help much. Which is why recovery vehicles are still necessary to have around

An experienced crew could probably use either technique to free up their vehicle within 10 minutes after they have identified the need for such work. Both tricks should be avoided if possible because they risk damaging the tracks (and or other things), so crews wouldn't hop right out and give that a go straight away. But they do work and it's why you often see pictures of tracked vehicles with at least one log which is about as wide as the vehicle it is strapped to

Steve

[Michael Emrys]

...it's why you often see pictures of tracked vehicles with at least one log which is about as wide as the vehicle it is strapped to

Interesting. Yes, I have seen many such pictures and assumed the log was used for unbogging but never knew the exact procedure.

Michael

[Flanker15]

"A log" is pretty standard issue on Soviet tanks I've noticed.

[hcrof]

"A log" is pretty standard issue on Soviet tanks I've noticed.

I often wondered about that untill I saw a high rez picture of one - turns out it is a snorkel.

[undead reindeer cavalry]

read the article from the Russian tank commander who commanded the Sherman tanks. in it, he states the Sherman had better cross country performance then the T-34 which surprised me at first. It used to be on the red army site, and it was also stated in the q&a section where he answered questions. not that it has any impact on the conversation.

i think it's directly related to what Redwolf wrote about cross country mobility. usually when US tankers say Sherman's mobility was worse than that of German tanks, it's when ground conditions are bad, like mud or snow. they report stuff like they first observe German tanks cross a muddy field, but when they try to pass the same field they get bogged. this is related to "floatation", something in which tanks like T-34 or Panther really excel. when US tankers say Sherman's moblity was better than that of German tanks, it's usually when ground conditions are good but the terrain is a bit rough or contains strong elevation differences. compared to T-34 in the same conditions the ride is certainly going to be a lot more bumpy, harder (driving itself) and generally unpleasant inside the noisy and cramped tank.

[wisbechlad]

Bollocks, forgot my password. And the email address I registered with has long gone.

Oh well. Here is an interesting lecture on military geography of Normandy:

http://www.esci.keele.ac.uk/geophysics/People/Jamie/MilitaryGeology/M_G_6_Notes.pdf

Some interesting grog facts that I didn't know before reading this:

- Choice of Normandy was influenced by its suitability to build airfields

- Much of the airfield surfacing needed to be shipped in (50% in UK sector, 75% in US sector)

- Allies had a whole quarrying (and presumably road resurfacing) organisation

Oh yes, and on topic, has examples of cross country movement maps, showing soil types, areas where tracks are likely to break etc.

[Michael Emrys]

Here is an interesting lecture on military geography of Normandy:

That is indeed interesting. However, that looks like a mere outline. Any idea where the complete course/lecture/discussion might be found?

Michael

[undead reindeer cavalry]

Steve,

i totally agree about what you say about CM test settings and i think there isn't much point about comparing that Soviet data to CM test data as long as we don't have more accurate information about the road march. people already have some opinion about the subject and further tests aren't likely to make any difference.

the rest of this post does not relate to that Soviet road march data at all.

what comes to the difference between "wet" and "dry", "open ground" and "dirt road", i unfortunately suppose it all depends on what those things mean.

since CM also contains "mud" and "deep mud" ground conditions, i always thought "wet" means just wet ground (not mud). if we think about T-34 driving, with something like CM's "move" order, on open flat terrain, i don't think it's going to matter that much wether the ground is "wet" (not "mud") or "dry" -- other things will be far more important.

i think the same is partly true to "wet dirt road" vs "wet open ground", but to a lesser degree. having more firm ground is of course one reason why dirt roads were preferrable to open ground. there are others as well though, like not having to deal with terrain recon (e.g. wonder what the terrain is like behind "that hill" -- is it still "open ground" or something else like "soft ground"), having more direct path of movement, having a "systematized" path between two points (which is important for both having a control of forces on the larger level and being able to direct troops on the level of the guy who tells to "turn left here") and so forth. but yes, the difference does exist, i agree about it. i just do not agree that the difference is so huge.

[undead reindeer cavalry]

the maintenance stuff per km / hour can be found both from maintenance manuals and vehicle log books of tanks. should be trivial to find if you are willing to pay for the manuals. there are also all kinds of reports of what was the expected and actual life expectancy of various tank components.

if you are happy with modern data, there are extensive studies (due to having all the maintenance data on computers these days) about maintenance of various components of modern vehicles.

it's almost morbid how this type of stuff (e.g. five fast ways to tell when a specific bolt of Panzer IV tracks are starting to overheat) is quite easy to encounter, yet stuff like historical bogging frequencies are nowhere to be seen.

[undead reindeer cavalry]

Bollocks, forgot my password. And the email address I registered with has long gone.

Oh well. Here is an interesting lecture on military geography of Normandy:

http://www.esci.keele.ac.uk/geophysics/People/Jamie/MilitaryGeology/M_G_6_Notes.pdf

Some interesting grog facts that I didn't know before reading this:

- Choice of Normandy was influenced by its suitability to build airfields

- Much of the airfield surfacing needed to be shipped in (50% in UK sector, 75% in US sector)

- Allies had a whole quarrying (and presumably road resurfacing) organisation

Oh yes, and on topic, has examples of cross country movement maps, showing soil types, areas where tracks are likely to break etc.

that is almost sexy. the guy who run that course has his email listed in there. perhaps someone should drop him a mail.

[Battlefront.com]

Michael Emrys,

Interesting. Yes, I have seen many such pictures and assumed the log was used for unbogging but never knew the exact procedure.

I also wondered about it until I found the details in the tank driver's manual. Amazing what a couple of B&W sketched images can do to clear up some curiosity Fortunately I never had to use the log I carried around with me. However, I did "belly" a different vehicle which had a winch. Since my experience once again illustrates how easy it is to bog a tracked vehicle, here it is...

I was packing down a path in fairly deep snow. This involves going very, very slowly and carefully, often having to reverse and change forward vectoring a little bit to avoid getting stuck. Depending on the vehicle a single or multiple pass is needed to then proceed on the path with ease. The BEST way to do it is pack it down on a sunny morning and then wait until the following day since the sunlight tends to make the snow soft and night freezes it up really hard. But I digress

While going through a second or third time I came to a frozen decent sized fallen tree that lay nearly perpendicular across the path. I'd crossed over it without problems already, however now the snow cover was off the tree and the snow around it was packed down more. This made the height differential greater and also changed the characteristics of the top side of the log. I eased onto the log as perpendicularly as possible (the proper way to approach), but I must have been going a tiny bit too fast (i.e. not crawling speed) because my left track slipped and the right track spun me around very quickly so that my hull was resting fully on the log and both tracks had nothing but snow to grab. I was very, very stuck.

After trying all kinds of things, like putting bits of wood and what not under one track to try and get traction and elevation to get over the log, I gave up. The next day I started out fresh and approached the problem differently. I couldn't use my winch to pull my vehicle backwards off the log because there was no room for that. The only way was forward. Since the tree was my problem, I decided to use it to my advantage. I put the winch cable under the hull and attached it to the top end of the tree. I winched the vehicle to the top end and then I was all set because the diameter was small enough that I was now no longer bellied. And Mr. Chainsaw saw to it that Mr. Tree didn't bother me on future passes.

Anyhoo... just another example of how things can go quite quickly from a happy day driving around in the woods to a frustrating couple of hours getting back to business since firewood doesn't magically appear next to the stove

Steve

[Battlefront.com]

hcrof,

I often wondered about that untill I saw a high rez picture of one - turns out it is a snorkel.

No doubt the majority of those shapes you see are logs, though you are correct that there is a snorkel attachment which could look like a log if the image quality wasn't great.

URC,

i totally agree about what you say about CM test settings and i think there isn't much point about comparing that Soviet data to CM test data as long as we don't have more accurate information about the road march. people already have some opinion about the subject and further tests aren't likely to make any difference.

The primary problem is those variables matter a lot and without data can't be meaningfully accounted for. Which is why at the very start of this thread I said there really isn't good data to use. Whatever data does exist tends to be at a different level with different accounting goals. It's the difference between needing to know what your bank balance is before writing another check and trying to find out what the bank balance was on a particular day. If you just get the higher level balance you're never going to be able to figure out what the running balance was nor which checks had cleared for a particular day.

what comes to the difference between "wet" and "dry", "open ground" and "dirt road", i unfortunately suppose it all depends on what those things mean.

Absolutely. And as I already explained the real world is VERY complex. One patch of ground could bog an entire company one day and pose no problems a couple of days later depending on very specific circumstances.

since CM also contains "mud" and "deep mud" ground conditions, i always thought "wet" means just wet ground (not mud). if we think about T-34 driving, with something like CM's "move" order, on open flat terrain, i don't think it's going to matter that much wether the ground is "wet" (not "mud") or "dry" -- other things will be far more important.

You are correct that Wet isn't nearly as bad as Mud or Deep Mud. However, if there was no difference between Wet and Dry we wouldn't have included Wet, would we? Sometimes Wet is worse because if the drivers (or player, in our case) presume that it is the same as Dry then there will likely be problems. At least with Mud and Deep Mud the drivers (and player) presume that bogging is extremely likely and therefore take that into account when moving.

Also remember that bogging in perfectly Dry open ground conditions is still possible to do. Unlike PaulAU's request for certainty, there is no such thing in the real world. I've already mentioned I personally "immobilized" a WW2 tracked vehicle in perfectly dry conditions on an established trail. I have no problem admitting to operator error, but in this case my driving skills (which are very good) had nothing to do with it. Mother Nature just thought it would be funny to watch me spend an hour in the blazing sun trying to get a piece of tree out of my suspension system

i think the same is partly true to "wet dirt road" vs "wet open ground", but to a lesser degree. having more firm ground is of course one reason why dirt roads were preferrable to open ground. there are others as well though, like not having to deal with terrain recon (e.g. wonder what the terrain is like behind "that hill" -- is it still "open ground" or something else like "soft ground"), having more direct path of movement, having a "systematized" path between two points (which is important for both having a control of forces on the larger level and being able to direct troops on the level of the guy who tells to "turn left here") and so forth. but yes, the difference does exist, i agree about it. i just do not agree that the difference is so huge.

How much experience do you have driving vehicles, tracked or wheeled, off established trails in a variety of terrain conditions? I've got a pretty good amount and some of those with military experience have already chimed in long ago. It would appear that our opinions are shaped more by the differences in experience vs. theory.

the maintenance stuff per km / hour can be found both from maintenance manuals and vehicle log books of tanks. should be trivial to find if you are willing to pay for the manuals. there are also all kinds of reports of what was the expected and actual life expectancy of various tank components.

Very true. For my M29C Weasel (WW2 tracked cargo carrier, with the best floatation of any vehicle until the BV-206) it stated that when you came out of thick terrain you were to stop and clear the suspension system of any debris. I personally found it advisable to do this while driving through the terrain because if something was going to get kicked up and cause problems that was it. Since I didn't have anybody shooting at me I had the luxury of dismounting at my leisure

it's almost morbid how this type of stuff (e.g. five fast ways to tell when a specific bolt of Panzer IV tracks are starting to overheat) is quite easy to encounter, yet stuff like historical bogging frequencies are nowhere to be seen.

As I said, the reason for that is it was too frequent, yet so wildly random at times, to bother getting statistics for. And since those statistics couldn't possibly be useful in any military sort of way, they weren't kept. The military has far better things to do with its time than to document things like this. Instead it was better to get their commanders and drivers experience so they could figure these sorts of things out on their own.

Steve

[Battlefront.com]

BTW, earlier there was a point made about speed and the chances of bogging. It is true that in some circumstances it is better to be going fast because the momentum of the vehicle might carry you through the problem spot before other physics take control of the situation. However, these types of situations are usually self evident and are, IMHO, infrequent. More often than not going slow produces better results for the following reasons:

1. Unless you've personally done recon on the terrain you're hoping to speed onto, it's quite possible that the spot you're trying to get over is just a warning about even worse terrain to come. If you speed ahead you could pass easily through a moderate problem right into a serious one.

2. Generally speaking if you go slowly you can feel the vehicle starting to get stuck BEFORE it gets stuck. This gives you time to process the information and cease forward motion. At that point you have a range of options such as recon ahead, gunning the engine and going through the next patch faster, downshifting into a lower gear range, or best of all... backing up onto known solid ground.

3. Since speed x time = distance traveled, the faster you go the less time it takes to go a specific distance. If you go slowly and figure out the terrain is becoming worse you are more likely to be at the beginning of the trouble spot instead of in the middle of it. This means good terrain, which you already safely drove over once, is easy to get back to. Even if you get stuck at this point you have more options for recovery because you have less distance to get out of.

4. Velocity can do some very interesting things to a vehicle's mechanical integrity There's a big difference hitting a tree stump at crawling speed vs. 10 mph. vs. 20 mph. At crawling speed it's just a light bump which likely won't cause damage. At 10 mph you might break something. At 20 mph you might actually bounce up and over the obstacle (with or without causing damage), but then upon landing find yourself with compounding damage potential. Ever seen a picture of a tank with with a broken road wheel? With out knowing how it got to be broken I feel I can offer up a theory

5. Turning to avoid obstacles that come into view is super easy when going slow, very difficult to do when going fast. Anybody who drives a car on a road knows this already. A deer in your headlights at 65mph is almost a certain collision, but at 5mph it is almost certainly not.

6. Anybody who has hit a rock or a stump with a wheeled or tracked vehicle at anything over than a crawling speed can tell you how quickly and seriously your vector can change. Again, if you're going slow your vector will change less dramatically and quickly because of less momentum. You also will travel less distance off course when going slower than when going faster. Going off course in an open field might not matter much, but in other situations it matters a lot.

7. It's generally best to drive off road with the least traction option possible. That way when you start to feel the vehicle having problems you have options, such as shifting into 4 wheel drive, engaging a lower gear range, or doing combinations of things. The theory is that if you get yourself stuck with the best options you're screwed, but if you get stuck with the lowest options you have something left to play with. Personally I think it's a balance because if you go with a medium setting you're less likely to get stuck in the first place and yet still have at least a couple additional options. With my Pinzgauer (military 4x4) I would drive in 4x4 and still have the ability to lock front and/or rear differentials as well as shift into low range. Only got stuck once in deep mud just after I said to myself "maybe I should stop here"

Anyhoo... this is just more stuff to consider. I think people with off road driving experience have a very, very different concept of bogging/immobilization than people who don't.

Steve

[ASL Veteran]

Dammit! I had about thirty minutes worth of typing done and clicked on another link to add it to my post, and instead of opening up a new window it changed the one I was typing my post up in and my whole post was lost!! Oh well, here is a link that I found where someone was taking the Trafficability information and putting it into simulation form for the military

http://www.sedris.org/presentation/TTMS.pdf

Maybe I'll retype what I had earlier when I have more time and motivation again.

[Michael Emrys]

Dammit! I had about thirty minutes worth of typing done and clicked on another link to add it to my post, and instead of opening up a new window it changed the one I was typing my post up in and my whole post was lost!!

That's one reason why tabs can be nice. I've lost many fewer posts in the making since I started using them.

Michael