Request for information on Panzer III/IV chassis

In OTL there were projects for a tank featuring elements of the chassis of both the Panzer III and Panzer IV, a so-called Einheitsfahrgestell (standardized chassis). Wiking started this thread some years ago and there is also this wikipedia article on the subject.

The chassis of the Hummel self propelled heavy field howitzer, and of the Nashorn self propelled anti-tank gun also featured a combination of elements from the Panzer III (the driving and steering system according to the wikipedia system) and the Panzer IV (suspension and engine according to the same source).

My question is: why were the components of the Panzer III used?
Did the driving and steering system of the Panzer III show a better performance?
Could they be manufactured more cheaply than the corresponding elements of the Panzer IV?
Or was it just that the engineers were looking for a way to utilize Panzer III elements or the machines to produce them, that otherwise would have been unused when the Panzer III itself was phased out of production?

I would be very grateful for any information on these points and also for links or book and article titles.
 

Deleted member 1487

The Panzer III components were more widely available until 1943, but then the Pz IV components were needed for the Pz IV, while the Pz III chassis was relegated to secondary roles as it was too small to remain a turreted panzer. Instead it operated as an assault gun and weapons carrier. IIRC the III/IV chassis started development in either 1941 or '42 so the Pz III stuff was just much more available.
 
I'm a believer in economies of scale and mass production which makes me think the Germans shot themselves in the foot with the Panzer III and Panzer IV.

I think they should have only built the Panzer IV chassis. 75% would have been completed as battle tanks armed with the 50mm gun and the rest fitted out as close support tanks with the short 75mm gun.

Even if there were no production economies I thought it might make the supply of spare parts in the field simpler. Also when the 50mm gun and short 75mm became obsolete it would be relatively simple for the assembly lines to switch to the long 75mm armed version of the Panzer IV. Furthermore the surviving battle tanks could be rearmed with the long 75mm which wasn't possible with the Panzer III IOTL.
 

Deleted member 1487

I'm a believer in economies of scale and mass production which makes me think the Germans shot themselves in the foot with the Panzer III and Panzer IV.

I think they should have only built the Panzer IV chassis. 75% would have been completed as battle tanks armed with the 50mm gun and the rest fitted out as close support tanks with the short 75mm gun.

Even if there were no production economies I thought it might make the supply of spare parts in the field simpler. Also when the 50mm gun and short 75mm became obsolete it would be relatively simple for the assembly lines to switch to the long 75mm armed version of the Panzer IV. Furthermore the surviving battle tanks could be rearmed with the long 75mm which wasn't possible with the Panzer III IOTL.

The Pz IV has the issue of its suspension make it tough to fire on the move. It would have been great as a universal chassis until the Panther with torsion bar suspension like the Pz III. Had they had the concept of a MBT and used the 1935 developed 75mm L40.8 by Rheinmetall and the short L24 for support they'd have had a very much better situation production-wise, especially as it was ready significantly before the Pz III chassis pre-war.
 
The Pz IV has the issue of its suspension make it tough to fire on the move. It would have been great as a universal chassis until the Panther with torsion bar suspension like the Pz III. Had they had the concept of a MBT and used the 1935 developed 75mm L40.8 by Rheinmetall and the short L24 for support they'd have had a very much better situation production-wise, especially as it was ready significantly before the Pz III chassis pre-war.

Talking of a universal chassis, I began writing an uberwank about the tanks and armoured fighting vehicles of an Even Greater Germany about 12 years ago. The preamble went:
In Scenario F Germany is a bigger country with more economic and human resources. The Low Countries joined the Second Reich in 1871 and in the 1910 Census the country had 80 million people who were 100% German. The Kingdom of Austrian had 28 million people in the 1910 Census 20 million of whom were German out of a total of 52 million in the Austro-Hungarian Empire.
The Central Powers still lost the Great War and had a humiliating peace settlement imposed upon them. Despite President Wilson’s wish for self-determination, union between Germany and Austria was forbidden. Germany lost large tracts of land to France, Poland and Denmark. The Republic of Austria was more fortunate. It had the territory of the former Kingdom of Austria, less Galicia and some border adjustments with Hungary.

Hitler still came to power at the beginning of 1933 and the 1934 Nazi coup attempt in Austria was successful. At the end of 1934 the Nazis controlled a nation of over 100 million people, including the important industrial regions of the Low Countries and Bohemia-Moravia, which they did not get his hands onto until much later in the real world.

After the territories lost in 1919 were returned to the Reich in 1939-40 it had a total population of around 120 millions instead of about 80 millions in the real world.
It goes onto say:

Although Union between Austria and Germany was forbidden, most Austrians and nearly all Germans wanted it. So did their governments who harmonised their policies as much as the League of Nations would allow. There was secret coordination between the armed forces to prepare for union. They standardised their weapons, equipment, uniforms, training and organisation so that when the time came the two parts fitted together perfectly. Joint specifications were issued for new types of equipment. Austria and Germany were forbidden to import or export arms, but it was hard to enforce at the sub-component level. This was fully exploited to maximise economies of scale.
In the 1924 they made a joint decision with far reaching consequences. They decided to develop a 75mm anti-tank gun instead of the 37mm weapon that was developed in the real world. They wanted a gun that could also deal with concrete emplacements and maximise the firepower of their armies.

The design competition that produced the Panzers I to IV IOTL was an Austro-German joint venture which BMM (CKD of OTL) won. The Light Training Tank competition was won by the an enlarged AH-IV and the Light Reconnaissance Tank competition was won by the LT-38. It's entry in the heavy tank competition was a tactical failure because multi-turret tanks proved too difficult to command, but it was a mechanical success.

An enlarged LT-38 with a longer and wider hull with an extra pair of road wheels won the competitions for the Medium Battle Tank and Medium Close Support Tank. The Schnelltruppen wanted 25% to be close support versions armed with the short 75mm gun and the rest to be armed with a faster firing gun in the 37mm to 50mm range. However, the Waffenamt forced them to arm all the "Super LT-38" tanks with an adaptation of the artillery's 75mm anti-tank gun in the interests of standardisation and the extra time it would take to design, test and put into production a 37mm or 50mm tank gun.

The "Super LT-38" was built instead of the Panzer III, Panzer IV and Panzer 38 of OTL. Furthermore the BMM heavy tank chassis was fitted with a new superstructure with sloping armour and the 75mm L/70 gun. This was built instead of the Panther and Tiger. It wasn't as unreliable as the early Panthers of OTL because its mechanical faults had been sorted out on the prototypes built instead of the Neubaufahrzeuge. This also leads to the Super LT-38 being redesigned with sloping armour so that it looks like a baby Panther tank.

If that wasn't a big enough wank/ASB they also develop a range of self-propelled artillery carriages (inspired by the later Light Weapons Carriage and Medium Weapons Carriage of OTL), armoured personnel carriers and logistics vehicles from the BMM tanks that are put into production in place of the half-track SPW and ZKW of OTL. E.g. the LWC was developed from the LT-38, the MWC was developed from the "Super LT-38" medium tank and the Heavy Weapons Carriage came from the heavy tank built instead of the Neubaufahrzeuge.
 
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The Pz IV has the issue of its suspension make it tough to fire on the move. It would have been great as a universal chassis until the Panther with torsion bar suspension like the Pz III. Had they had the concept of a MBT and used the 1935 developed 75mm L40.8 by Rheinmetall and the short L24 for support they'd have had a very much better situation production-wise, especially as it was ready significantly before the Pz III chassis pre-war.

turret ring diameters

Churchill 75NA 1378mm 75mm L/40
T-34/76 1420mm 76mm L/41
Valentine XI 1466mm 75mm L/40
M24 Chaffee 1524mm 75mm L/40
Panzer III 1560mm 75mm L/24

Germans didn't try hard enough.
 
The Pz IV has the issue of its suspension make it tough to fire on the move. It would have been great as a universal chassis until the Panther with torsion bar suspension like the Pz III. Had they had the concept of a MBT and used the 1935 developed 75mm L40.8 by Rheinmetall and the short L24 for support they'd have had a very much better situation production-wise, especially as it was ready significantly before the Pz III chassis pre-war.

I'm sorry, was it the gun that was ready or a torsion bar suspension system?
 
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