StuG III ausf. A (Sd.kfz 142)
After the first 5 prototypes of the "O" series had been
constructed and tested, changes were made in the design of the vehicle, and a new chassis
was selected. The "O" vehicles had been built on the chassis of the PzKpfw
III ausf B, in itself a developmental design, and the production vehicles "Gepanzerte
Selbstfahrlafette für Sturmgeschütz 7,5cm Kanone ausf A, Sd.kfz 142 (later called StuG
III ausf A) were based on the chassis of the PzKpfw III ausf F .
The hulls were not tank components, being modified to suit the Stug III layout and having
heavier armor, but the power train and suspension components were the same as those of the
PzKpfw III ausf F (5/ZW).
The superstructure, bolted to the chassis with angles, was a low, relatively spacious
fixed compartment with a multi-angled roof design and heavy frontal armor of 50mm
thickness. The chassis nose plates were also 50mm thick as was the gun mantlet;
there was another 50mm plate behind the driver, at the foward end of the fighting
compartment, and from the front, the StuG III ausf A was very well protected against the
anti-tank guns of the period. The vertical side plates were 30mm thick, the glacis
plate was a 26mm, and the roof plates were 11mm. On the left side was a rectangular
armored pannier for the radio installation. In front of this box on the left, and
all along the right side wall, an angled series of plates of 9mm thick formed an outer
wall which extended over the part of the mudguards. These angled plates were
intended as a extra spaced armor; nothing was stowed behind them, and there was no access
to the space enclosed. The rear superstructure and rear hull plates were 30mm thick,
and the belly was 16mm thick, with 20mm lower nose and tail plates.
The gun was the standard 7,5cm L/24 KwK 37 then being fitted to the PzKpfw IV medium tank,
which was intended as a support vehicle for armored formations. Thus, since the
StuG had not be intended to fight tanks or other moving targets, it did not need a
turret, and slightly smaller PzKpfw III chassis could mount the same gun. The
mounting developed by Krupp was relatively primitive, consisting of a pedestal which was
bolted to the floor, and with the simple elevation and traverse mechanisms. No
bullet splash protection was provided; this was particulary serious at maximum
elevation. A canvas dust cover was provided to close the space around the mounting
and protect the crew and equipment from dust and rain.
Access to the fighting compartment was through 3 hatches in the roof; in an emergency, the
driver could escape through the inspection hatches in the glacis plate. The driver
sat in front on the left; behind him was the gunner, and the commander occupied the left
rear corner of the superstructure. The loader was at the right rear of the fighting
compartment. The gunner's sight was internal, requiring a small aperture in the
front plate, and a V-shaped cutout was made in the roof armor over the driver's
compartment to allow a wider field of vision for the gunner. Metal ribs wer welded
in place to deflect ricocheting bullets and fragments.
The mechanical details were the same as the PzKpfw III ausf F. The suspension
consisted of 6 pairs of roadwheels on each side, each set sprung by the torsion bars and
arms, with the shock absorbers on the first and last axles. Because the torsion bars
were paired, the wheels on the left were slightly behind those on the right side.
Three return rollers were fitted, spaced equally. A built up, solid rear idler was
used, and the cast drive sprocket had 8 lightening holes in the centers, driving 36cm cast
skeleton type tracks. The engine was a 12 cylinder Maybach HL120TR rated at 300hp,
and the transmission was the 10-speed preselective Variorex type. Steering was by
clutch and brake.
Production began early in 1940, and 4 batteries of StuG III ausf A's saw service during
the invasion of France in May, 1940. Additional units worked up to service status
after the end of the campaign.
A StuG III seen in Holland, 1940. Here can be seen the early
chassis layout, based on the chassis of the PzKpfwf III ausf F; note the early drive
sprocket, rear idler, and roller spacing.