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Bogging and Immobilized: is it right?


IanL

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There has been some discussion recently about bogging / immobilization of tanks. I am currently playing Huzzar! and I ran into a real problem. I have a ford that is clogged with immobilized vehicles. I suppose theoretically it is still passable but given that 5 tanks and 5 HTs tried to cross it and now 3 tanks and one HT are immobilized I do not think I will risk it. I realize that crossing fords constitutes some risk so I was not expecting to get a free pass but just under 50% losses from a ford. Ouch!

Ford%20clogged%20up%20with%20Immobalized%20vehicles.jpg

I have re arranged my plans and will now be conducting a two pronged attack :-)

Given how bad that experience was I decided to conduct some tests. I am still working on them but I have created a cross country course for testing and conducted tests for Shermans, PzIVs and Panthers.

Here is the test course map: http://lesliesoftware.com/forforumposts/Bogging%20Test.btt

There is about 100m of each of the following terrain types:

Mud

Sand

Rocky

Cobble Stone

Plow NS

Crop 2

Grass XT

Grass

Hard

Dirt

Ford

Gravel

The ford itself is about 70m the rest of the 100m is taken up with banks. I put 15 tanks on the map and ran them back and forth three times for a total of 7km trip over those 12 terrain types. I created allied and axis setup areas in the gravel so if you want to do your own tests all you have to do is purchase your units (for one side at a time) and save under a different name then you can play 1 player WEGO and setup the initial moves from end to end of the map and press the big red button over and over until all your vehicles are either home or immobilized.

Here are the saved games with the back and forth movements already plotted for the test I have conducted already:

http://lesliesoftware.com/forforumposts/Bogging%20Test%20Dry%20Shermans%20001.bts this is 2Mb big because I saved after starting and not before - oops

http://lesliesoftware.com/forforumposts/Bogging%20Test%20Dry%20PzVs%20001.bts

http://lesliesoftware.com/forforumposts/Bogging%20Test%20Dry%20PzIV%20001.bts

Here are the results of running these test 5 times. With 15 tanks per trial this is like running 75 tanks for a 7km trip over my cross country course. I measured the percentage of vehicles that remained operational - all others were immobilized.

Vehicle Conditions

Dry

Sherman 22.67%

Panther 44.00%

PzIV 36.00%

Percentage of vehicles immobilized in which terrain type under dry conditions

Vehicle Terrain Type Immobilized

Sherman Mud 34.67%

Sand 2.67%

Rocky 2.67%

Grass XT 2.67%

Ford 34.67%

Panther Mud 28.00%

Sand 1.33%

Rocky 0.00%

Grass XT 0.00%

Ford 26.67%

PzIV Mud 38.67%

Sand 0.00%

Rocky 0.00%

Grass XT 0.00%

Ford 25.33%

Clearly there are lots of tests to do yet - other vehicles and other conditions and I plan to add them but I wanted to post the results I had.

I was surprised at poorly the Sherman's did. Actually I was surpised at how bad they all did. Remember this is dry conditions so only the mud and the ford are gooey. Is this really what should be expected?

I realize that given the testing on multiple terrain types is problematic for determining the true immobilization rate for a terrain type but I don't have time to create a 1000m map of each terrain type and run a test for each vehicle under each condition. This test cannot give you an immobilization rate for terrain but it can compare the performance of different vehicles.

How worth while is continuing with this test?

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very nice test ian...

in my opinion the number of immobilized/bogged down tanks shown in your tests are too high especially for dry conditions.

after 7km driving cross country at dry conditions only 22,6% of the shermans remained operational...thats a joke ;). i have no hard data at hand but i would suggest you eventually continue with the test and send the complete results (with save game links) and eventually some sources regarding real number of immobilizations to phil from bfc ! the devs should really take a look into it in my opinion.

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One big factor in bogging is - as far as I understand it - speed.

Unless I´ve overlooked something, you haven´t told us which speed the vehicles where travelling at when you made your test.

Oh, man huge oversight on my part. Yes, these are all fast - I do need to do different speeds. So, this should be the worst case.

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You can't assume that FAST = more immobilizations as one would think would happen in RL. After posting about my own bogging problems in the Hoffnung campaign where I moved all tanks SLOW all the time (assuming that would result in lowered immobilizations), the folks who were suffering minor boggings said they moved FAST or QUICK as that seemed (to them) to reduce the distance traveled/immobilization ratio.

So, your results will be very interesting.

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Then heaven help us, my tanks were bogging and immobilizing all the time on SLOW - but out 10 AFV's, after 3 battles in a campaign, I had lost 6 to immobilization.

Way too high (and no fun at all when one considers this is an entertainment product). I increasingly feel that in trying to be "more realistic" that also means more hard work and more misery.

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Then heaven help us, my tanks were bogging and immobilizing all the time on SLOW - but out 10 AFV's, after 3 battles in a campaign, I had lost 6 to immobilization.

Previous discussions and tests of CMx2 codebases have shown that people's assumption that movement problems are worse when using fast aren't correct. We have seen no evidence that the code takes this into effect to an observable degree. Or maybe it is the BFC typical 3% or something else insignificant.

And that's good that way. Everybody who ever tried to get as much as a simple car through mud or snow knows that simply driving through a rough patch slower is not the right strategy. You need just the right momentum (which comes from speed) to plow through the bumps inside that patch but slow enough that you lose control.

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I have been finding that my wheeled vehicles seldom bog, it's the tracked armor (that was designed to move across ground that bogs wheeled vehicles) which seem to bog/immob. most.
(emphasis added)

I don't think this is a completely accurate statement, speaking generally. Heavy armor is almost always built on a tracked chassis because tracks are the only way to carry the heavy weight of all that armor and armament off-road, and even on-road in some cases. For vehicles weighing over about 30 tons, tracks are really the only reasonable option if the vehicle needs to be able to move across anything other than hard, prepared surfaces. It's not so much that tracked armor is "designed to move across ground that bogs wheeled vehicles" as that the weight of armor forces this design choice.

But once you start comparing vehicles of different weight classes, all bets are off. 2.25-ton Jeep will beat a 35-ton Sherman in off-road performance in almost any ground conditions. It's not really a fair comparison; the Jeep is so much lighter that it has far better ground pressure, and the high torque-to-weight ratio combined with 4-wheel drive and differential lock enable a decent driver to take that Jeep places a Sherman will just never go.

So you need to be specific about what tracks vs. wheels comparison you're talking about. If you are observing that Shermans are bogging more often than Jeeps in CM, then this is probably accurate and there is no reason for concern. On the other hand, if Shermans are bogging more often than M8 Greyhounds in CMBN, then maybe we have something to talk about -- the M8 had good hard ground off-road performance, but also had relatively high ground pressure, so didn't do very well on soft ground.

In summary, I really think any meaningful conversation needs to be about specific tracked vehicle X vs. specific wheeled vehicle Y, rather than just "tracks vs. wheels".

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I seem to remember that ground pressure for each vehicle was available in the UI in CM1.

If we had this info available, it may help mitigate our perceptions re: bogging.

Ground clearance is also a factor. Once the frame/body hits the ground... it's over.

I do think that immobilizations on roads may need a tweak.

-3% extra chance of bog on any road tile maybe?

-

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It's not really a fair comparison; the Jeep is so much lighter that it has far better ground pressure, and the high torque-to-weight ratio combined with 4-wheel drive and differential lock enable a decent driver to take that Jeep places a Sherman will just never go.

Fully agree with the statement you made: the tracks are there to give a 30-50 ton vehicle some cross country mobility and to move it at all. Even today we always tried to keep our tracked vehicles on a road or a track as long as possible when the ground was wet or muddy (which is quite often the case in Europe).

One thing: IMHO the 1940's Willys Jeeps didnt' have a differential lock they were just 4WD.

In addition there is quite a difference between a Sherman with .962kg/cm² and a Panther with .88kg/cm² ground pressure. Interestingly enough the Tiger I was worse with 1.05kg/cm² and the T-34/85 had just 0.81 kg/cm2.

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For what it's worth nearly all my boggings/immobilizations of tracked vehicles took place while I was moving them SLOW on roads. To have 20% of your tanks out of action in this way in each scenario of a campaign seems over the top. Hence my frustration. People say that they have fewer immobilizations by moving tanks QUICK or FAST offroad, but that doesn't seem right.

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For what it's worth nearly all my boggings/immobilizations of tracked vehicles took place while I was moving them SLOW on roads. To have 20% of your tanks out of action in this way in each scenario of a campaign seems over the top. Hence my frustration. People say that they have fewer immobilizations by moving tanks QUICK or FAST offroad, but that doesn't seem right.

Odd, mine don't bog anywhere near that often. I have had one that had had me scratching my head as to why it bogged (dry conditions, roadway, using regular moverment etc) however as a one off I didn't think about it much. Now crossing fords is another thing. I approach them with some trepidation mainly because if one vehicle bogs, then the ford beomes that much more difficult to negotiate.

I also use multiple move modes depending on situation, mostly slow, hunt and quick. I don't often use fast.

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I also use multiple move modes depending on situation, mostly slow, hunt and quick. I don't often use fast.

True I very rarely use fast. For tanks often quick (at least on roads) and then move or slow, when I get across obstacles or off road. and naturally hunt which seems to be somewhere around move.

I might be superstitous, but I think that move and slow also reduce track damage when driving across obstacles (walls etc). but that's more like a feeling than a empirical insight.

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In addition there is quite a difference between a Sherman with .962kg/cm² and a Panther with .88kg/cm² ground pressure. Interestingly enough the Tiger I was worse with 1.05kg/cm² and the T-34/85 had just 0.81 kg/cm2.

Yeah but that's not all either. The T-34 with it's simple loaded-spring mechanism would fall very hard into anything uneven, and then get stuck. It's low ground pressure on the tracks are nice if you move over even, soft ground. But the springs actually have less resistance as they compress, and that make it bounce hard when it bounces. The reason why the Germans bothered with the torsion bar suspension was to overcome things problem. Now the suspension gets harder as it compresses. Of course there are other disadvantages starting from the tank getting quite a bit taller (the Jagdpanther in particular because it couldn't recoil it's large gun between the torsion bars and they didn't want to limit elevation too much).

The T-34 also had very low ground clearance.

The Sherman went from suck suspension on narrow tracks not only to wider tracks, but also to a suspension system that would work against that "acceleration of bumps".

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