The Definition of Mobility ?

I have noticed that some people manage to reach the conclusion that tank "a" has better mobility than tank "b" because tank "a" has a higher cross-country speed. Cross-country speed can be the determinant when comparing mobility ( between the PzKpfw III and Matilda for instance ), but statements like the above is in my opinion illogical by definition because the mobility of a tank depends on many factors, not just one.

So, how should we define mobility ? What follows is not supposed to be guidelines, only my present opinion.

I judge a tanks mobility mainly by speed ( road and cross-country ), range/durability, reliability, manoeuvrability, and by its ability to negotiate obstacles. I also distinguish between strategic mobility and tactical mobility ( I hope I´m using the terms "strategic" and "tactical" correctly ? ). Strategic mobility includes the tanks ability to be moved from one place to another, either by means of transport ( train etc. ) or by its own power ( road speed, reliability etc. ) and if it can make use of bridges, bridging equipment etc. Tactical mobility includes the factors important to a tank under combat operations; Cross-country speed, manoeuvrability, range/durability, reliability etc.

 

4 factors determine "mobility"
1. Mechanical Reliability -breakdowns
2. Horsepower to weight ratio - engine size
3. Ground pressure - track width
4. Range - fuel storage and consumption

3 other factors apply:
1. Ground clearance - ability to clear obstacles
2. ammo load - length of time between resupply
3. fuel load - distance between resupply

going by that you can easily determine which vehicle was the most mobile.

take a basic list for example:

Panther V ausf G - 46kmph road 24kmph offroad.
1. reliability - Fair
2. 15.6 HP to ton
3. o.88 kg per sq cm on 65cm tracks with a 391 cm contact length
4. 730 litre tanks 4.12 liter per kilometre consumption twice that offroad
range 177km road 89km offroad. slightly over 4 hour range between refueling.
5. 56 cm ground clearance
6. 82 rounds main gun , 4200 mg
* Turn Radius 10 metres
* Fording Depth 170cm.


Tiger I - 38 kmph road - 20 kmph offroad
1. reliability - poor
2. 12.3 HP to ton
3. 1.04 kg per sq cm on 72.5cm tracks with a 361 cm contact length
4. 534 litre tanks 5.35 liter per kilometre consumption twice that offroad
range 100km road 60km offroad. slightly under 3 hour range between refueling.
5. 43cm ground clearance
6. 92 rounds main gun , 4000 mg

Pzkw IIIN - 40 kmph rd - 19 kmph offroad
1. reliability - good
2. 13.5 HP to ton
3. 0.94 kg per sq cm on 40cm tracks with a 286cm contact length
4. 320 liter tanks 1.83 liter per kilometre consumption twice that offroad.
range 175km road 97 km offroad. Roughly 4 1/4 hour range between refueling.
5. 41cm ground clearance
6. 64 rounds main gun, 3500 MG

so the difference between the 2 vehicles :
reliability good to poor IIIN wins.
range under 3 hours to over 4 hours IIIN wins
ability to negotiate rough terrain - ground pressure is a tie ( but IIIN wins if ability to cross bridges is factored in ) and ground clearance is a tie.
raw power equal - HP per ton both tanks would run without overtaxing the engines.

Tiger has better ammo load so it would be able to hold ground longer waiting for resupply. close defense its a tie.


So if ya want to move further faster and engage enemy targets longer...
ya go with the IIIN based simply on the fuel load and ability to cross bridges. But its duration in combat is lower due to the ammo load.
Mobility wise aside from the reliabity issue which throws the whole thing in favor of the IIIN its almost a draw.


Panther VG just added. VG would definitely be close to the IIIN almost a draw with the HP to ton and ground pressure in the Panthers favor pointing to fantastic offroad performance.. then we look at track contact length and the alarms go off.. first thing we check is turn radius.. can it manuever out of a tight situation ? negative.. fording ability is great on level ground but with that much length the tank would go nose down tryin to negotiate a bank.. its still too large to cross most bridges.
its lighter ( at point of ground contact ), faster ( HP to wieght shows it has reserves of power ) and runs cooler than either of the other tanks, but the legth of contact, sluggish turning and potential nosegrinding wear is gonna send it to position 3. a tank that has to constantly back out and find more stable paths isnt my definition of "mobile" its a tank thats utterly dependent on ground recon.

Strategic mobility is really a non factor as there werent enough large tanks to really stretch the capacity of countries to move em on a strategic level.

tactical level mobility ive described.
operational mobility ( the ability to transport quickly within a specific theatre, the ability to recover and repair damaged vehicles and return them to units ) was definetely a factor but too random to really be taken into consideration on a general level. )
strategic transport is from factory to theatre.. definetely well within the bounds of any combatant prior to the destruction of the german rail network late 1944. ) but thats not something a tank or its design would affect to an appreciable degree.

 

I agree with your 2. and 3. point because mobillity is all about how the tank performes when in motion, and not about its fuel consumption or ammo supply...and niether is reliabillity.

KBO

 

I agree that mechanical reliability might be a little outsie the relm of mobility. But range of a tank is definitely part of the equation. For instance the Russian KV-1 lacked range compared to the T-34, that was the reason why that the T-34 was often used as the spearheads for Russian armor breakthrus. Also, the KV-1 was more prone to breakdown mechanically than the T-34. As for the Germans, during the Battle of the Ardennes, one of their many mistake was using the gas-consuming Tiger II to spearhead their assaults. As a matter of fact one of their main objectives was to capture the allied gas depots in order to refuel their machiens. Well we all know what happened, the Tigers didn't go very far before they ran out of gas and became "immobile".

 

shouldn't that be 3 factors.

:lol:

 

yipe =) im havin a bad day =)

 

How would you rate the Panther VG for a medium tank's mobility? I believe the Panther VG varient was the best medium tank during WW II; with or without the IR equipment.

 

ill add it to that last and see how it stacks up to the first 2. It would be nice to determine an optimal tank as a comparison =)

yer tank got hammered =(.. apparently they tried to resolve the ground pressure issue by adding length... not a good move mechanically or performance wise. greatly limits its ability to negotiate rough terrain and cross obstacles, harms handling under ideal conditions and increases track, suspension, bearing and transmission wear by dragging the nose down.

speed , ground pressure, fuel loadout, ammo loadout, clearance, fording all have excellennt marks.. tanks incredible for its size and had reserves of power for up armoring or upgunning... just too long =(

 

I would classify "mobility" as being able to reach the point on the battlefield where and when it is needed.

 

its gotta get there with enough fuel to be able to manuever on the battlefield, and taking a lot of detours to find suitable ground and having to wait in place while the terrain is reconned lowers its mobility. Sure a tank can get there in a straight line.. but moving across terrain that isnt level and crossing streams and rivers and negotiationg ravines and gullies is part of the game. case in point is the exploits of peiper when he saved the 320th division then had to detour 50 miles to find a suitable crossing point to get back.