Introduction

The RSO is a World War 2 era prime mover of Nazi German origin. It was developed early 1942 as a prime mover for towed anti-tank guns and towed howitzers in the Eastern front. Here in the muddy season in 1941 both wheeled vehicles and horse drawn limbers of the German forces suffered significantly. A cheap, yet capable, towing vehicle suitable to difficult off-road conditions was required. With the help of Ferdinand Porsche the Austrian firm Steyr developed the tracked RSO. There also was a wheeled RSO by Skoda, which is described in a separate article. The name RSO stands for Raupenschlepper Ost, describing it as a "tracked towing vehicle for use in the east".

Design

The RSO is a small tracked vehicle with a cabin with two seats located over the engine. A flatbed with tarpaulin cover makes up the rest of the vehicle. Early model RSO had a distinctive rounded cabin. This was replaced by an easier to produce straight angle cabin. As designed the RSO was fitted with a 3.5-lieter V8 petrol engine. About half the production volume was of a derivative model by KHD using both the square cabin and their 5.5-liter diesel engine.

Protection

The RSO is a soft skin vehicle without any armor protection.

Cargo capacity

The RSO can carry a load of about 1.5 t on its flatbed. This often included the additional gun crew. The maximum towed load is 3 t. In photos it is most commonly seen towing the 75mm PaK-40 anti-tank gun or 105mm leFH-18 howitzer. Photos also show it sporadically towing the 150mm sFH-18, which is twice the maximum towed load.

Mobility

The RSO vastly improved the mobility of towed gun on the Eastern front. Although prototypes were tested with speed of up to 30 km/h, in practice the RSO moved at very modest speeds of 17 km/h or 14 km/h with petrol or diesel engine respectively. Steering was found to be janky and even led to gun sights losing their calibration. Apparently some crews of the PaK-40 used improvised limbers to reduce burden on their guns.

Users

About 25.000 RSO were produced and used from 1942 up to the end of the war. These were mainly used on the Eastern front, but were also seen in the Italian and Western theaters in smaller numbers. After the war small numbers were used by various nations until replaced by trucks or other prime movers. The RSO was not a design worth restarting production after the war. A derivative vehicle was produced for civilian use such as agriculture and forestry.

The list on the right hand side lists the types of towed weapon systems for which the RSO was often employed as a prime mover.

For weapon systems up to the 10.5-cm leFH-18 the RSO worked quite well. For anything heavier the fuel consumption went up and the performance degraded quickly.