davebender
1st Lieutenant
http://www.tank-net.com/forums/index.php?showtopic=36959
Al a meeting on 15 September 1939, Wa Pruef 6 and Krupp discussed the design of a new chassis, the VK 20.01 (IV), as a further development of the Pz.Kpfw.IV series. The engine compartment and the Maybach HL 116 engine were to be adopted from the VK 20.01 (III). Maximum speed was to be 42 kilometers per hour, the same as the Pz.Kpfw.IV Ausf.C. The suspension was selected to support a vehicle weight of 20 metric tons with a hull width of 1820 mm and an overall width of 2900 to 2950 mm. The Schachtellaufwerk (interleaved roadwheel suspension) from the VK 20.01 (III) couldn't be used, since it resulted in an overall width of about 3040 mm and exceeded the weight specification. Krupp proposed a six- wheel suspension with leaf springs which could use components from the normal eight-roadwheel suspension for the Pz.Kpfw.IV.
At a meeting on 28 October 1939 with Wa Pruef 6, a diameter of 630 mm was set for a six-roadwheel suspension for the VK 20.01 (IV). New Kgs 61/400/120 tracks were to be utilized. The designation for VK 20.01 (IV) evolved to VK 20.01 (BW) in November and then was changed to B.W.40 in December 1939.
On 13 December 1939, the frontal armor for the B.W.40 was increased from 30 mm to 50 mm thick. The basic hull shape for the B.W.40 was the same as the Pz.Kpfw .IV Ausf.D. On 4 January 1940, Wa Pruef 6 notified Krupp that two armor hulls and one soft steel hull were to be produced for the three B.W.40 experimental chassis. Three superstructures and rear decks were to be made from soft steel.
On 16 May 1940, Wa Pruef 6 informed Krupp that in consideration of the wartime situation, the B.W.40 project was to be shelved.
Also in May 1940, Krupp initiated a new design in coordination with Wa Pruef 6, the VK 20.01 (K) with either the Maybach HL 116 or HL 115 motors. As recorded in Krupp's 1939/1940 fiscal year report, preliminary proposals had been completed for the VK 20.01 (K) with 5 cm armament and heavier armor. A full-scale wooden model was being completed, and a detailed design had been started. The experimental turret for the VK 20.01 was being designed by Krupp with 5 cm Kw.K. L/42 armament. Frontal armor was to be 50 mm thick, side and rear armor 30 mm thick.
By 24 October 1940, Krupp had received contracts for three VK 20.01 (K) developmental chassis and by 12 November 1940 a contract for production of a 0-Serie of 12 VK 20.01 (K) complete with 5 cm gun turrets. Wa Pruef 6 had awarded contracts to M.A.N, and Daimler-Benz for the design of new tanks with 7.5 cm gun turrets in the 20 ton class.
In March 1941, Krupp proposed to complete three developmental VK 23.01 (K) chassis and six experimental VK 23.01 (K) with torsion bars. The VK 23.01 (K) was to have the power train components designed by Kniepkamp and developed by M.A.N.
On 18 April 1941, Wa Pruef 6 informed Krupp that they were to concentrate on development of a new submersible turret with a 5 cm Kw.K. L/60 gun for the VK 20.01 (K). The experimental turret for the new VK 20.01 (K) was to be completed by 1 February 1942 directly followed by production of 12 turrets for the 0-Serie.
By July 1941, an additional contract had been awarded to Krupp for three developmental VK 23.01 (K) chassis in soft steel without turrets. The previous contract for a 0-Serie of 12 was revised to specify two redesigned variants: six VK 20.02 (K) and six VK 23.01 (K). The six armored VK 20.02 (K) were to have 5 cm Kw.K. L/60 guns in their turrets.
Both the VK 20.01 (K) and VK 20.02 (K), designed for a maximum speed of 56 km/hr, had the same leaf spring suspension with six roadwheels (700 mm diameter) running on 450 mm wide Kgs 62/450/120 track. The total weight of a complete VK 20.01 (K) including a turret was calculated to be 21.5 metric tons, compared to the VK 20.02 (K) at 23 metric tons.
To meet the requirement for standardization demanded by Kniepkamp, the VK 23.01 (K) was to have a Schachtellaufwerk designed by M.A.N, with six 880 mm diameter roadwheels, a torsion bar suspension, and 474 mm wide Kgs 63/474/110 tracks. The first VK 23.01 (K) developmental chassis with torsion bar suspension, outfitted for total submersion, etc., could be delivered, at the earliest, about 1 October 1942.
In designing their VK 23.01 (K), Krupp contacted Zahnradfabrik Friedrichshafen and Maybach on 19 September 1941 in order to obtain the latest installation drawings of transmissions for the Dreiradien-Lenkgetriebe (triple radius steering gear) designed by M.A.N.
In a report written in January 1942, Woelfert related how the design and completion of the VK 20.02 (K) had frequently been delayed due to the following reasons: Initially a 5 cm turret was specified with an inner turret ring diameter of 1350 mm without a traversing floor. Then, on 10 October 1941, a 5 cm turret with an inner turret ring diameter of 1400 mm was required, to allow the option of mounting a 7.5 cm gun turret. Finally, the 7.5 cm Einheitsturm (standard turret) with 7.5 cm Kw.K.44 was specified, at first with an inner turret ring diameter of 1560 mm, later increased to 1600. As a result of continuously increasing the turret ring diameter, the hull width was expanded from 1600 to 1650 mm and the hull (originally 400 mm shorter) had to be repeatedly lengthened. Also, the ammunition storage was fundamentally changed. Along with this came the requirement to slope the superstructure walls, especially the driver's front plate.
In a meeting on 17 December 1941 with Krupp, Oberst Fichtner (head of Wa Pruef 6) expressed his position on tank development as follows: Against the advice of Wa Pruef 6, higher authority had decided that the weight class for the future tank should be 30 tons and not the 24 ton tank proposed by Wa Pruef 6. Fichtner was opposed to this decision. In his opinion, time would be lost since the 30 ton tank had yet to be developed, whereas development of the 24 ton tank was almost completed.
