Alternative History Armoured Fighting Vehicles Part 4

As of 1940 the Germans thought that a short 75mm direct-fire gun, i.e. KwK 37 L/24, was the optimal main armament for infantry support AFVs, because smaller-caliber guns' HE shells were much less effective against infantry-battlefield targets. Arguably, the Germans were right. Perhaps the French would have had a similar realization before too much more time had passed.

If the French tank program had continued to evolve, it...much like the early-war German program, with the PzKpfW III and IV, plus the StuG III...might have featured a convergence toward a medium tank armor-powertrain-crewing approach, but a continued divergence of main weapons between tank-fighting and infantry-fighting versions of that otherwise-converged medium tank until the later time when tank-fighting main armament finally evolved to 75mm caliber.

France had at least two short 75mm cannons available...the hull gun from the B1 tank series, and the leftover 75mm Schneider guns from WWI, some of which were in use in casemate versions of the Renault FT. The former probably was much more expensive to build than the KwK 37, so not optimal as a tank weapon. The latter was very old and low-performance. But, either could have provided a starting point for prototypes and battlefield trials.
I suspect that the French were seeing infantry tanks in the same way as the British and the Soviets (T-26 and T-50), with small caliber armament able to take out the odd tank and MG nest. Tougher defenses were to be dealt with by the B series (which were meant to far more common than simple breakthrough/heavy tanks, with more than 60/month in production by mid-1940 and 100/month intended in the future*, same as the Pz III's production rate at the time), or ARL V 39 SPGs. Pz IVs were not produced at very high rates at the time.
It's hard to say. The future battle tank spec had a heavier AT armament than the infantry tanks, so maybe the 47mm SA35 would still be accepted even after facing uparmored German tanks and they would just deal with them using AT guns, tank destroyers and battle tanks. The thing is that by French estimates, a turret suitable for the long 47 is similar in weight to one using the full power 75mm, so if infantry tanks are now required to engage heavier tanks, they will indeed die out in favor of only using medium tanks.

The 75mm hull gun happens to use a cartridge of the same length as the German short 75, but muzzle velocity is higher due to pressure and powder loading being closer to normal guns, so it's probably indeed more expensive to build than your typical infantry/pack howitzer. I suspect the French would also consider it to require a dedicated loader (unlike the 47mm SA35 with tiny light ammo), which would lead to the same weight creep which would kill normal infantry tanks.

So yeah... Either the future infantry tanks still happen in their intended form regardless, or they go the way of the T-50 versus T-34 and are abandonned. This is one bit I did not mention: since the future infantry tanks would no longer use simple truck engines, are heavier and would require 60mm of armor which is more difficult to make than 40mm, their tooling/facility requirements would start approaching those of full-blown medium tanks. They may simply not be spammable enough to be worth it. But we will never know for sure.
 
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Driftless

Donor
This is one bit I did not mention: since the future infantry tanks would no longer use simple truck engines, are heavier and would require 60mm of armor which is more difficult to make than 40mm, their tooling/facility requirements would start approaching those of full-blown medium tanks. They may simply not be spammable enough to be worth it. But we will never know for sure.

Interesting. I hadn't considered there is a leap of scale for the metallurgy of armor manufacture. Sometimes the infrastructure isn't there at the time it's wanted.

Also, I seem to remember that one of the issue for the British 6lb cannon that needed development was the long tool (yeah, yeah, yeah) for boring the barrel - that it was somehow different from other 57mm tools in British industry of the time. Maybe that's a BS idea.
 
Also, I seem to remember that one of the issue for the British 6lb cannon that needed development was the long tool (yeah, yeah, yeah) for boring the barrel - that it was somehow different from other 57mm tools in British industry of the time. Maybe that's a BS idea.
Early marks of the British 6lber were 43 calibers, until tooling for 50 caliber versions was available, while American built 57mms were always 50 caliber- that may be what you're remembering.
 
The British had planned to switch the QF gun factory system over from the two pounder to the six pounder beginning in July-August 1940. Plans and blueprints were prepared, contracts were let, construction and installation engineers and skilled workers were hired and ready, and all the needed equipment was purchased and already on site, ready for installation as soon as the old equipment was removed...except the new, longer barrel bore lathes, which were a very long leadtime item. So initial production was to proceed at the maximum barrel length that would fit on the old lathes.

To compensate for the shorter barrels so that those guns would have the standard muzzle velocity and could be fired with standard sights, and so that all six pounder gunners would have "standard" trajectory and penetration experience when they eventually switched over to standard-length guns, the shorter guns would use different ammo with more propellant.

The plan of course assumed that British and Commonwealth forces would continue to be fully equipped with two pounder towed guns and two pounder equipped tanks, with any needed field replacements during the changeover-shutdown period coming from gun/vehicle inventories in the various theaters of deployment...there being very few towed guns in inventory at the factories, and only enough guns at the tank factories to support continued production operations until it was time to switch over that tank-type.

As the factory system came back into operation after several weeks of shutdown, initial production was to be 100% dedicated to towed guns. As the process of replacement of towed two pounders among all of the first line British and Commonwealth forces began to approach completion, a substantial part of production was to switch over to guns for cruiser tanks. That was anticipated to begin around the end of 1940. Once enough guns for six pounder armed cruiser tanks had been built ahead of the production use-rate to allow that tank production to continue at full speed, new six-pounder-armed infantry tanks were to begin production. That was anticipated to begin around April to June of 1941.

Of course, none of that happened because of the BEF's loss of all equipment shipped to Europe, plus unanticipated losses in North Africa.
 
What would the potential of Romania 75mm/L48 m1943 as a tank gun be? https://en.wikipedia.org/wiki/75_mm_Reșița_Model_1943

According to this source (https://www.deviantart.com/wingsofwrath/art/Resita-75mm-AT-gun-shell-comparison-chart-V5-903141895)
with first hand information, it fires a 6.6kg AP at 840m/s, which is 15% higher muzzle energy than the L48 KwK40. Using 7.2kg AP shell from KwK 42, it should have a muzzle velocity of about 805m/s and similar penetration with KwK 36.

Given it has been installed on the 8.5 ton Maresal tank destroyer, and the ammunition length is only slightly longer than KwK 40. Could it be put on Panzer IV with minimal modification? Would it make continuing production of Panzer IV (perhaps with sloped armor like Ausf.K/L) more attractive than switch to Panther?
 
What would the potential of Romania 75mm/L48 m1943 as a tank gun be? https://en.wikipedia.org/wiki/75_mm_Reșița_Model_1943

According to this source (https://www.deviantart.com/wingsofwrath/art/Resita-75mm-AT-gun-shell-comparison-chart-V5-903141895)
with first hand information, it fires a 6.6kg AP at 840m/s, which is 15% higher muzzle energy than the L48 KwK40. Using 7.2kg AP shell from KwK 42, it should have a muzzle velocity of about 805m/s and similar penetration with KwK 36.

Given it has been installed on the 8.5 ton Maresal tank destroyer, and the ammunition length is only slightly longer than KwK 40. Could it be put on Panzer IV with minimal modification? Would it make continuing production of Panzer IV (perhaps with sloped armor like Ausf.K/L) more attractive than switch to Panther?
It might be a good reason to keep the Panther to 35 tons rather than allowing it to grow to 45 tons, but there were other reasons like the Panzer IV drivetrain and suspension to move to a new tank.
 
What would the potential of Romania 75mm/L48 m1943 as a tank gun be? https://en.wikipedia.org/wiki/75_mm_Reșița_Model_1943

According to this source (https://www.deviantart.com/wingsofwrath/art/Resita-75mm-AT-gun-shell-comparison-chart-V5-903141895)
with first hand information, it fires a 6.6kg AP at 840m/s, which is 15% higher muzzle energy than the L48 KwK40. Using 7.2kg AP shell from KwK 42, it should have a muzzle velocity of about 805m/s and similar penetration with KwK 36.

Given it has been installed on the 8.5 ton Maresal tank destroyer, and the ammunition length is only slightly longer than KwK 40. Could it be put on Panzer IV with minimal modification? Would it make continuing production of Panzer IV (perhaps with sloped armor like Ausf.K/L) more attractive than switch to Panther?
Well I am not sure what the space claim of the gun itself would be compared to KwK 40 and whether the cartridge can be retained or needs to be necked and shortened, but it might work. I suspect the cartridge as is would be too long since Germany settled on the specific length of the KwK 40 cartridge as opposed to the straight PaK 40 cartridge.

That does not make the tank itself necessarily more attractive though, because as mentionned there was a need for armor and mobility improvements which, considering the chosen layout, were bound to reach 45 tonnes, and even 840 m/s wasn't completely satisfactory for what Germany wanted to do (beyond the need to counter potential enemy armor upgrades, the early ammunition on the KwK 40 had a fairly modest margin of superiority against the upper front armor of a T-34 (improved ammo changed this but Germany wanted to guarantee a safe margin).
 
Kick
My apologies for the lack of posts. A combination of having work done on the house, sailing around the Greek Islands, and a lack of motivation to paint 3 models at the same time! Anyhoo... A bit of a re-post to get people back up to speed...

An Alternative Take on Bristish Cruiser Tanks:

I have always wondered what might have happened to British Cruiser tank designs (specifically their suspension) had Walter Christie’s dalliance with the USSR resulted in an earlier intervention by the US Government which precluded Britain accessing his unique suspension design.

The RL Historical Bit (Educational)…
As it happened, at the same time Mr Christie was upsetting all and sundry in Washington, two British engineers (namely Sidney Horstmann and John Carden) were working on independent horizontal-spring suspension designs. Horstmann’s ‘slow motion’ system ultimately equipped the A9, A10 and Valentine tanks whilst Carden’s designs were fitted to the Vickers light tanks and hugely successful series of Universal Carriers. Unfortunately, Carden’s untimely death removed him from any future design consideration.

Coincidentally, Harry Knox, an engineer with the Rock Island Arsenal, was developing a similar two-wheeled bogey suspension unit not unlike Horstmann’s design but using a double vertical volute spring instead of a coil spring. Knox’s design would eventually find its way onto the US Army’s M1 Combat Car and the M3/M5 series of light tanks.

The AH Made Up Bit (Fun)…
Now, what if Horstmann, who was fully aware of Knox’s work, managed to convince the UK Government to approach the US Government for licencing rights to the more efficient volute spring suspension design. Easier to produce and easier to maintain and replace in the field than Christie’s design, the VVSS seemed like an idea solution to the UK’s future cruiser tank designs.

Fortunately, for this whiffing project and the AH AFV thread, the US Government were favourable in their response to this request and the rest, as they say, is alternative history…

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Ramontxo

Donor
My apologies for the lack of posts. A combination of having work done on the house, sailing around the Greek Islands, and a lack of motivation to paint 3 models at the same time! Anyhoo... A bit of a re-post to get people back up to speed...

An Alternative Take on Bristish Cruiser Tanks:

In October 1928, Christie’s M1928 was demonstrated at Fort Myer, Virginia. There the Army's Chief of Staff, General Charles P. Summerall, and other high-ranking officers were impressed, however, the Tank Board was less enthusiastic. They noted that the vehicle's armour was very thin and could not survive penetration by the smallest armour-piercing antitank rifle or artillery piece. The Board also differed with Christie on its guidelines for tank capabilities, which were based on a radically different theory of armoured warfare than that used by Christie. For the Infantry Tank Board, armour and firepower were more important design criteria than mobility, and the M1928 prototype was passed to the Cavalry for further evaluation. The Cavalry's thinking at that time was based on armoured cars, and it wanted to develop the M1928 as an armoured car chassis. Once again, Christie's concept of how his vehicles should be used, together with his difficult nature, resulted in disputes with Army officials. Ultimately, the Secretary of War rejected mass production of the M1928, citing excessive acquisition costs.

Christie then, somewhat foolishly, felt he was justified in selling his inventions to the highest bidder. A long and complex series of exchanges between Christie and foreign governments followed. These were technically illegal since Christie never obtained approval of the US Department of State, Army Ordnance, or the Department of War to transfer his designs to potentially hostile governments.

Initially, in early 1930, Christie promised to sell his M1928 tank design to the Polish government, but the deal fell through and, to avoid potential litigation, he eventually returned the payment made by the Polish government, which never obtained the tank they had ordered.

Although the USSR did not have diplomatic relations with the USA at the time, and was prohibited from obtaining military equipment or weapons, Soviet OGPU agents at the trade front organization AMTORG managed to secure plans and specifications for the Christie M1928 tank chassis in March 1930 using a series of deceptions. On 28 April 1930, Christie's company agreed to sell AMTORG two Christie-designed tanks, documented falsely as agricultural farm tractors, and without prior approval of the U.S. Army or Department of State. They were successfully shipped to the USSR where the Soviets used them to develop the BT series of tanks, forerunners of the massively produced T-34 tank of World War II.

Needless to say, the US Government, and the Department of State in particular, were not amused and Mr Christie was promptly arrested by the FBI and imprisoned on dubious charges of failing to gain export licences and tax fraud rather than aiding and abetting potentially hostile governments.

After favourable reports on observation of Soviet tank activities in 1936, the British War Office tentatively approached the US Government regarding the possible purchase of a license of the Christie design. Not unsurprisingly, the request was politely but firmly turned down.

Meanwhile, across the Pond in Britain, Sidney Horstmann had been developing suspension designs from the 1920s and through his Slow Motion Suspension Company had by 1930 produced a new design using two road wheels on a single bogie, each connected to a bell crank with a horizontal coil spring between the crank arms, and double-acting shock absorbers to control recoil. In 1934, John Carden of Vickers-Armstrongs had a "bright idea" for a new type of tank suspension and partnered with Horstmann's Slow Motion to turn it into a working design. Unfortunately, Carden was killed in an air crash in December 1935, but by this time he had designed a lighter tank platform that had been taken up as the A9, although later known as the Cruiser Mk I. In this version, one large wheel was fitted on one bell crank, and two smaller wheels to a shared arm on the second crank. This went into production in 1937 as an interim type until the Army could develop something better. The same suspension was then used on the larger A10 Cruiser Mk II which came to its ultimate form as the Valentine tank.

At much the same time in the US, Harry Knox an engineer for Rock Island Arsenal, was developing a similar two-wheeled bogey suspension unit but with an innovative double vertical volute spring in place of Horstmann’s coil spring. The suspension was developed in 1933 and was first tested on a T2E1 light tank prototype in 1934. The Rock Island Arsenal would go on to produce the M1 Combat Car, which entered service with the US Army in 1937.

Horstmann and Knox were fully aware of each other’s work, and it didn’t take long for Horstmann to convince the UK Government to approach the US Government for licencing rights to the more efficient volute spring suspension design. Easier to produce and easier to maintain and replace in the field than Christie’s design, the VVSS seemed like an idea solution to the UK’s future cruiser tank designs. Fortunately, the US Government were more favourable in their response to this request and the rest, as they say, is history…

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Have you thought of licensing torsions bars from Sweden? Say in 1935 some British officer in holiday in Ireland gets an close look to an L 60... And Carden* gets an Cruiser with torsion bar suspension**

*The accident was in December 1935 wiki says Ireland bought the tank in 1935 let's say he left the project in its way to success...


**Just for a wank (with the RN 6-pdr / 10cwt QF Mark I and a Twin Bedford for engine, if they could develop it for the Churchill they could have developed it before...)
 
Have you thought of licensing torsions bars from Sweden? Say in 1935 some British officer in holiday in Ireland gets an close look to an L 60... And Carden* gets an Cruiser with torsion bar suspension**

*The accident was in December 1935 wiki says Ireland bought the tank in 1935 let's say he left the project in its way to success...


**Just for a wank (with the RN 6-pdr / 10cwt QF Mark I and a Twin Bedford for engine, if they could develop it for the Churchill they could have developed it before...)
Given they were bought due to the Army pushing for a scenario of a British attack, bit of handwaving to have a British office get access to the only one, also given the general view between Ireland and the UK at the time, most likely the easiest way to get the reverse of whatever we bought/did.
 

Ramontxo

Donor
Given they were bought due to the Army pushing for a scenario of a British attack, bit of handwaving to have a British office get access to the only one, also given the general view between Ireland and the UK at the time, most likely the easiest way to get the reverse of whatever we bought/did.
Thanks for the info, let's say the officer was passing his holidays in Sweden.
 
Have you thought of licensing torsions bars from Sweden? Say in 1935 some British officer in holiday in Ireland gets an close look to an L 60... And Carden* gets an Cruiser with torsion bar suspension**

*The accident was in December 1935 wiki says Ireland bought the tank in 1935 let's say he left the project in its way to success...


**Just for a wank (with the RN 6-pdr / 10cwt QF Mark I and a Twin Bedford for engine, if they could develop it for the Churchill they could have developed it before...)
It’s a possibility, but the end product would look very similar to the original Christie suspension vehicles. I went for the VVSS/HVSS option because they would look radically different.
 
An Alternative Take on Bristish Cruiser Tanks:

Early days on the Alt Comet Cruiser Tank (A34). The Tamiya base model I am using is, as always with Tamiya, very well molded and fits together like a dream but just for once Takom's / Bronco's irritating habit of having every bit of detail as a separate piece might have served me better. I am having to cut away all of the beautiful pre-molded Christie suspension detail in order to clear the sides for the new HVSS units. Ah well, no rest for the wicked, as they say!

WIP pic show (on the left) the original detailed starboard side plate and (on the right) the cleaned port side - a thin sheet of plastic card will cover the various unwanted holes. 👍

Early 1.jpg
 
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