# Specific ground pressure

The specific ground pressure is an indication that is used, especially in the case of tracked vehicles , to obtain a comparative value for off-road mobility , especially on soft ground. As a rule of thumb, the lower the specific ground pressure, the higher the potential mobility of a vehicle.

## Physical background

The weight of a vehicle is transferred to the ground via the contact surface of its wheels or its crawler track and puts a strain on it. This can lead to the vehicle sinking into the ground, especially on soft ground. This undesirable effect is greater the heavier the vehicle and the smaller the area over which the weight is distributed.

### calculation

The specific ground pressure is calculated from the total weight of the vehicle divided by the contact area. The SI unit is Pascal . Usually, especially for historic vehicles, it is given in kg / cm² , which means that from a physical point of view it is a mass occupancy and not a "pressure". In the case of tracked vehicles, the contact area is calculated from the width × the length of the track, and the total ready-to-drive weight (combat weight) is generally used.

## Measures to reduce the specific ground pressure

Wheel belt on a German 21cm mortar

To reduce the specific ground pressure, one can either reduce the weight of the vehicle or increase the contact area between the vehicle and the ground. This can be achieved in different ways, depending on the type of vehicle:

• Use of wider (or longer) crawler tracks (on tracked vehicles )
• Enlargement of the tire contact area (for rubber-tired wheeled vehicles)
• Use of wider tires
• Increase in the number of tires
• if necessary, reduce the tire pressure
• Use of bike belts (for rigid bikes)
• Placing objects under the vehicle, which distribute its weight over a larger area (mats, construction of a stick dam , etc.)

## Examples

specific ground pressure in kg / cm² Total weight in kg
Human (both legs, shoe size 44) 0.17 (approx) 90
DT-54 chain tractor 0.41 5,400
Panzer IV Ausf. G 0.82 23,500
T-34 /85 0.83 32,000
IS-2 0.82 46,000
Leopard 1 0.89 42,500
T-62 0.77 37,500
Excavator 288 1.74 (17.1 N / cm²) 12,840,000
Snailochod ZIL-2906 0.025 1,280
M1A2 Abrams 1.055 (15.4 psi ) 69,540
Leopard 2 A4 0.83 55,150
Leopard 2 A5 0.95 (9.3 N / cm²) 59,700
T-90 S. 0.87 46,500
Scraper walking excavator Esch 10/70 0.94 kg / cm² (working), 1.49 kg / cm² (walking) 680,000 kp

(Original information in brackets)

## literature

• AW Karpenko: Soviet-Russian tanks . 1905-2003. Ed .: Rudi Meier. Elbe-Dnjepr, Klitzschen 2004, ISBN 3-933395-44-5 (Russian: Обозрение отечественной бронетанковой техники (1905-1995 гг.) . Translated by Rudi Meier).

## Individual evidence

1. Krohn Mechanical Mine Clearance System KMMCS. Characteristics. In: krohn.de. Retrieved July 4, 2015 .
2. a b PanzerIVg. In: panther-panzer.de. Retrieved July 4, 2015 .
3. a b Karpenko, pp. 251-254
4. a b King Tiger. In: panther-panzer.de. Retrieved July 4, 2015 .
5. Tiger II Ausf. B. Panzerkampfwagen VI (Sd.Kfz. 182). In: waffenhq.de. Retrieved July 4, 2015 .
6. a b Karpenko, p. 420
7. a b Technical data. Leopard 1 (standard tank). In: The 314 tank battalion in Oldenburg. pzbtl314.de, accessed on July 4, 2015 .
8. a b Karpenko, p. 312
9. a b The largest excavators in the world ( Memento from July 17, 2012 in the Internet Archive )
10. a b c Svargaman in Voprosik: Шнекоход ЗИЛ-2906 ( Memento of the original from December 22, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , January 18, 2012. Accessed December 16, 2015 (Russian)
11. a b Main Battle Tank. M1, M1A1, and M1A2 Abrams. In: fprado.com. Retrieved July 4, 2015 .
12. a b Leopard 2. In: whq-forum.de. Retrieved July 4, 2015 .
13. a b Leopard 2 battle tank (Pdf, 6.86 MB) Bundeswehr, accessed on July 4, 2015 .
14. a b Karpenko, p. 393.
15. a b LMBV walking excavator goes on tour. In: lmbv.de. Retrieved July 4, 2015 .