The weight of the production model was increased to 45 tonnes from the original plans for a 35-tonne tank. Hitler was briefed thoroughly on the comparison between the MAN and DB designs in the report by Guderian's tank commission. Armour protection appeared to be inadequate, while "the motor mounted on the rear appeared to him correct". He agreed that the "decisive factor was the possibility of quickly getting the tank into production". On 15 May 1942, informed MAN that Hitler had decided in favour of the MAN design for the Panther and ordered
series production of the tank. The upper
glacis plate was to be increased from to . Hitler demanded that an increase to should be attempted and that at least all vertical surfaces were to be ; the turret front plate was increased from to . although some of its design flaws, such as weak final drive, were never fully rectified. General
Hasso von Manteuffel considered the Panther Germany's "most satisfactory" tank, saying it "would have been close to the ideal, had it been possible to design with a lower silhouette."
Crew The Panther had five crew members: commander, gunner, loader, driver, and radio operator. The commander, loader and gunner were in the turret, while the driver and radio operator were in the hull of the vehicle. The driver sat on the front-left side of the tank and next to him was the tank's machine gunner, whose tasks also included operating the radio.
Engine The first 250 Panthers were powered by a
Maybach HL210 P30
V12 petrol engine, which delivered 650
metric hp at 3,000 rpm and had three simple air filters. Starting in May 1943, Panthers were built using the 700 metric horsepower (690 hp, 515 kW) at 3,000 rpm, 23.1 litre
HL230 P30 V12 petrol engine. To save on aluminium, the light alloy block in the HL210 was replaced with one made of cast iron. Two multistage "cyclone" air filters were used to improve dust removal. The engine's power output was reduced when low-grade petrol was used. With its fuel capacity of of petrol, a fully fuelled Panther's range was on surfaced roads and cross country. The HL230 P30 engine was a very compact
tunnel crankcase design, and it kept the space between the
cylinder walls to a minimum. The
crankshaft was composed of seven "discs" or main
journals, each with an outer race of
roller bearings, and a crankshaft pin between each disc. To reduce the length of the engine by an inch or so, and reduce
unbalanced rocking moment caused by a
normal offset-Vee type engine, the two banks of 6 cylinders of the V-12 were not offset: the "big ends" of the
connecting rods of each cylinder pair in the "V" where they mated with the
crankpin were thus at the same spot with respect to the engine block's length rather than offset. This required a
"fork and blade" matched pair of connecting rods for each transversely oriented pair of cylinders. Usually, "V"-form engines have their transversely paired cylinders' connecting rods' "big ends" simply placed side by side on the crankpin, with their transverse pairs of cylinders offset slightly to allow the connecting rod big ends to attach side by side while still being in the cylinder bore centreline. This compact arrangement with the connecting rods was the source of considerable problems initially. Blown head gaskets were another problem, which was corrected with improved seals in September 1943. Improved bearings were introduced in November 1943. An engine governor was also added in November 1943 that reduced the maximum engine speed to 2,500 rpm. An eighth crankshaft bearing was added beginning in January 1944 to reduce motor failures. The engine compartment was designed to be watertight so that the Panther could ford water obstacles; however, this made the engine compartment poorly ventilated and prone to overheating. The fuel connectors in early Panthers were not insulated, leading to the leakage of fuel fumes into the engine compartment, which caused engine fires. Additional ventilation was added to draw off these gases, which only partly solved the problem of engine fires. Other measures taken to reduce this problem included improving the coolant circulation inside the motor and adding a reinforced membrane spring to the fuel pump. Despite the risks of fire, the fighting compartment was relatively safe due to a solid firewall that separated it from the engine compartment. Engine reliability improved over time. The average service life expectancy without the need to dismount the engine from the tank was about 2000 km, or around 100 working hours. A French assessment in 1947 of their stock of captured Normandy Panther A tanks concluded that the engine had an average life of and maximum life of .
Suspension The suspension consisted of front drive sprockets, rear idlers and eight double-interleaved rubber-rimmed steel road wheels on each side – in the so-called
Schachtellaufwerk design on a dual
torsion bar suspension. The dual torsion bar system, designed by Professor , allowed for a wide travel stroke and rapid oscillations with high reliability, thus allowing for relatively high speed travel over undulating terrain. The extra space required for the bars running across the length of the bottom of the hull, below the turret basket, increased the overall height of the tank. When damaged by mines, the torsion bars often required a welding torch for removal. The Panther's suspension was over-engineered, and the
Schachtellaufwerk interleaved road wheel system made replacing inner road wheels time-consuming (though it could operate with missing or broken wheels). The interleaved wheels also had a tendency to become clogged with mud, rocks and ice, and could freeze solid overnight in the harsh winter weather that followed the autumn
rasputitsa (muddy season) on the Eastern Front. During its design phase, the problem of the running gear becoming blocked with mud or snow was reduced to a minimum. Shell damage could cause the road wheels to jam together and become difficult to separate. Interleaved wheels had long been standard on all German
half-tracks, with extra wheels providing better flotation and stability and more armour protection for the thin hull sides than systems with smaller or non-interleaved wheels; but its complexity meant that no other country ever adopted this design for their tanks. The Inspector General of Armoured Troops reported in May 1944: In September 1944, and again in March/April 1945, MAN built a limited number of Panthers with overlapping non-interleaved steel-rimmed 80 cm diameter road wheels originally designed for Henschel's
Tiger II and late-series Tiger I Ausf. E tanks. These steel-rimmed wheels were introduced from hull number 121052 due to raw material shortages. From November 1944 through February 1945, a conversion process began to use
sleeve bearings in the Panther tank, as there was a shortage of
ball bearings. The sleeve bearings were primarily used in the running gear; plans were also made to convert the transmission to sleeve bearings, but were not carried out due to the ending of Panther production.
Steering and transmission Steering was accomplished through a seven-speed AK 7-200
synchromesh gearbox from
Zahnradfabrik Friedrichshafen (ZF), and a MAN single radius steering system, operated by steering levers. Each gear had a fixed radius of turning, ranging from for 1st gear up to for 7th gear. The driver was expected to judge the sharpness of a turn ahead of time and shift into the appropriate gear to turn the tank. The driver could also engage the brakes on one side to force a sharper turn. This was a much simplified design compared to the Tiger tanks. The AK 7-200 transmission was capable of pivot turns but only when the ground resistance on both tracks was the same. This high-torque method of turning could cause failures of the final drive. The overstressed transmission system led to premature stripping of the third gear. This was compounded by alloy shortages which made gears more brittle and prone to failure. To reach the final drive for repair, the entire driver's compartment and transmission had to be disassembled and lifted out.
Final drive The Panther's main weakness was its final drive unit. The problems stemmed from several factors. The original MAN proposal had called for the Panther to have an
epicyclic gearing (planetary) system in the final drive, similar to that used in the
Tiger I. Germany suffered from a shortage of gear-cutting
machine tools and for mass-production numerous simplifications were made to the design and its manufacture, sometimes against the wishes of designers and army officers. Consequently, the final drive was changed to a double spur system; although simpler to produce, the double spur gears had higher loads, making them prone to failure. A report by Dr. Puschel of MAN said "The main cause of these failures was fatigue of the compound intermediate gear due to the low-core strength of the material used and the absence of case hardening at the critical sections" and "the use of split ring dowels with only a few bolts to retain the main drive gear to its flange proved unsatisfactory. This difficulty was subsequently overcome by...fitting bolts." German industry made a number of modifications to the final drive units on the Panther Ausf. G in September and October 1944 to increase the durability of the unit. Jacques Littlefield, of the Military Vehicle Technology Foundation, which restored a Panther Ausf. A, said "we found that the alloy and gears used in their construction were as good as we could make them today. I suspect the main problem with the final drive was that they were designed for a much lighter version of the Panther...Once they started to up-armor the Panther, there was no room to beef up the final drives to handle the extra weight."
Armour Initial production Panthers had a
face-hardened glacis plate (the main front hull armour piece), but as
armour-piercing capped rounds became the standard in all armies (thus defeating the benefits of face-hardening, which caused uncapped rounds to shatter), this requirement was deleted in March 1943. By August 1943, Panthers were being built only with a homogeneous steel glacis plate. The front hull had of armour angled at 55 degrees from the vertical, welded but also interlocked with the side and bottom plates for strength. The combination of moderately thick and well-sloped armour meant that heavy Allied weapons, such as the Soviet
122 mm A-19,
100 mm BS-3 and
US 90 mm M3, were needed to assure penetration of the upper glacis at normal combat ranges. The armour for the side hull and superstructure (the side sponsons) was much thinner at . The thinner side armour was necessary to reduce the weight, but made the Panther vulnerable to hits from the side by all Allied tank and anti-tank guns. German tactical doctrine for the use of the Panther emphasized the importance of flank protection and -thick
spaced armour or armoured skirts, known as
Schürzen were added. Intended to provide protection for the lower side hull from Soviet anti-tank rifles such as the
PTRS-41, the armour was fitted on the hull side.
Zimmerit coating against magnetic mines started to be applied at the factory on late Ausf. D models beginning in September 1943; an order for field units to apply
Zimmerit to older versions of the Panther was issued in November 1943. In September 1944, orders to stop all application of
Zimmerit were issued, based on false rumours that hits on the
Zimmerit had caused vehicle fires. Panther crews were aware of the weak side armour and made augmentations by hanging track links or spare roadwheels onto the turret and/or the hull sides. The rear hull top armour was only thick, and had two radiator fans and four air intake louvres over the engine compartment that were vulnerable to strafing by aircraft. As the war progressed, Germany was forced to reduce or eliminate critical alloying metals in the production of armour plate, such as
nickel,
tungsten and
molybdenum; this resulted in lower impact resistance levels compared to earlier armour. In 1943, Allied bombers struck and severely damaged the Knaben mine in Norway, eliminating a key source of molybdenum; supplies from Finland and Japan were also cut off. The loss of molybdenum, and its replacement with other substitutes to maintain hardness, as well as a general loss of quality control, resulted in an increased brittleness in German armour plate, which developed a tendency to fracture when struck with a shell. Testing by U.S. Army officers in August 1944 in Isigny, France showed catastrophic cracking of the armour plate on two out of three Panthers examined.
Armament The main gun was a
Rheinmetall-Borsig 7.5 cm KwK 42 (L/70) with semi-automatic shell ejection and a supply of 79 rounds (82 on Ausf. G). The main gun used three different types of ammunition:
APCBC-HE (
Pzgr. 39/42),
HE (
Sprgr. 42) and
APCR (
Pzgr. 40/42), the last of which was usually in short supply. While it was of a calibre common on Allied tanks, the Panther's gun was one of the most powerful of World War II, due to the large propellant charge and the long barrel, which gave it a very high
muzzle velocity and excellent armour-piercing qualities — among Allied tank guns of similar calibre, none had equivalent muzzle energy. Only the British
Sherman Firefly conversion's
Ordnance QF 17-pounder gun — 3 inch (76.2mm) calibre, and a 55 calibre long (L/55) barrel, with its access to APDS shot — had more potential armour perforation power, but it was considerably less accurate owing to disturbances caused by the separation of shot and sabot and at a cost of less severe damage inside the target after perforation of the armour. The flat
trajectory and accuracy of the full bore ammunition also made hitting targets much easier, since accuracy was less sensitive to errors in range estimation and increased the chance of hitting a moving target. The Panther's 75 mm gun had more penetrating power than the main gun of the
Tiger I heavy tank, the
8.8 cm KwK 36 L/56, although the larger 88 mm projectile might inflict more damage if it did penetrate. The 75 mm HE round was inferior to the 88mm HE round used for infantry support, but was on par with most other 75mm HE rounds used by other tanks and assault guns. The tank typically had two
MG 34 armoured-fighting-vehicle-variant machine-guns featuring an armoured barrel-sleeve. An MG 34 machine-gun was located co-axially with the main gun on the gun mantlet; an identical MG 34 was located on the glacis plate and fired by the radio operator. Initial Ausf. D and early Ausf. A models used a "letterbox" flap enclosing its underlying thin, vertical
arrowslit-like aperture, through which the machine gun was fired. In later Ausf. A and all Ausf. G models (starting in late November-early December 1943), a ball mount in the glacis plate with a K.Z.F.2 machine-gun sight was installed for the hull machine-gun. Initial Ausf. D were equipped with the
Nebelwurfgerät with the later Ausf. A and Ausf. G receiving the
Nahverteidigungswaffe.
Ammunition storage Ammunition storage for the main gun was a weak point. All the ammunition for the main armament was stored in the hull, with a significant amount stored in the sponsons. In the Ausf. D and A models, 18 rounds were stored next to the turret on each side, for a total of 36 rounds. In the Ausf. G, which had deeper sponsons, 24 rounds were stored on each side of the turret, for a total of 48 rounds. In all models, four rounds were also stored in the left sponson between the driver and the turret. An additional 36 rounds were stored inside the hull of the Ausf. D and A models – 27 in the forward hull compartment directly underneath the mantlet. In the Ausf. G, the hull ammunition storage was reduced to 27 rounds total, with 18 rounds in the forward hull compartment. For all models, three rounds were kept under the turntable of the turret. The stowage of 52 rounds of ammunition in the side sponsons made this area the most vulnerable point on the Panther since penetration here usually led to
catastrophic ammunition fires. The loader was stationed in the right side of the turret. With the turret facing forward, he had access only to the right sponson and hull ammunition, and so these served as the main ready-ammunition bins.
Turret The front of the turret was a curved thick cast armour mantlet. Its transverse-cylindrical shape meant that it was more likely to deflect shells, but the lower section created a
shot trap. If a non-penetrating hit bounced downwards off its lower section, it could penetrate the thin forward hull roof armour, and plunge down into the front hull compartment. Penetrations of this nature could have catastrophic results, since the compartment housed the driver and radio operator sitting along both sides of the massive gearbox and steering unit. Also, four magazines containing main gun ammunition were located between the driver/radio operator seats and the turret, directly underneath the gun mantlet when the turret was facing forward. From September 1944, a slightly redesigned mantlet with a flattened and much thicker lower "chin" design started to be fitted to Panther Ausf. G models, the chin being intended to prevent such deflections. Conversion to the "chin" design was gradual, and Panthers continued to be produced to the end of the war with the rounded gun mantlet. The Ausf. A model introduced a new cast armour commander's cupola, replacing the forged cupola. It featured a steel hoop to which a third MG 34 or either the coaxial or the bow machine gun could be mounted for use in the anti-aircraft role. Powered turret traverse was provided by the variable speed Boehringer-Sturm L4 hydraulic motor, which was driven from the main engine by a secondary drive shaft, the same system as on the PzKpfw.VI Tiger. On early production versions of the Panther maximum turret traverse was limited to 6º/second, whilst on later versions a selectable high speed traverse gear was added. Thus the turret could be rotated 360 degrees at up to 6º/second in low gear independent of engine rpm (same as on early production versions), or up to 19º/second with the high speed setting and engine at 2000 rpm, and at over 36º/second at the maximum allowable engine speed of 3000 rpm. The direction and speed of traverse was controlled by the gunner through foot pedals, the speed of traverse corresponding to the level of depression the gunner applied to the foot pedal. This system allowed for very precise control of powered traverse, a light touch on the pedal resulting in a minimum traverse speed of 0.1 deg/sec (360 degrees in 60 min), unlike in most other tanks of the time (e.g. US M4 Sherman or Soviet T-34) this allowed for fine laying of the gun without the gunner needing to use his traverse handwheel. ==Combat use==