They would be slower on average and maximum and roadwheel life is likely to be poorer, but in the proposed configuration, the side armor could be made single plate and more resistant and the turret ring diameter would be less constrained by width.
Alternative History Armoured Fighting Vehicles Part 4
- Thread starter Claymore
- Start date
Ramontxo
Donor
While you are at it, can you send to the Penguin Proctology Station in the South Sandwich island to whoever decided to design the Cromwell Turret for an internal mantlet, while the gun designers were working with the expectation of an external one?
Slower - probably, potential for future development/up gunning - much improved.
Generally speaking, OTL British cruiser tanks had a top speed of 30mph (exception being the Cromwell which could hit 40mph). The M3/5 light tank, which weighed much the same as the Mk IV cruiser, could manage 35mph so the light VVSS itself would not be the limiting factor - more likely to be the power train. However, a reasonably high speed might still be achievable. The M2 Medium and M3 tanks were capable of 26mph (340hp) so the 340hp Covenanter and 340hp Crusader might be capable of similar speeds. The alt Cromwell might be limited to the top speed of the M4 (30mph) although the meteor engine was powerful (600hp v 450hp). The Comet was governed down to 32mph for better durability so I doubt that the alt Comet’s max speed would be too different.
I agree for top speeds. The difference in performance between the two suspensions will be greatest on difficult ground where the VVSS bottoms out more often. The life of VVSS type road wheels was also pretty low for vehicles in the weight class of the Sherman. This would prevent the Meteor Cruisers from using the maximum capacity of their engines.
The second factor you mentionned (potential) would matter when compared to internal Christie. Less so for external. Arguably that path did not see much focus for much of the Christie Cruisers' development period due to the British neglecting large turret rings until bigger guns than the 6 pdr were considered.
Totally agree and in my Alternative TL would very much be the reason for the subsequent Centurion design giving up VVSS/HVSS in favour of the large road-wheel Horstmann suspension (and, incidentally, the US moving to torsion bar suspension.)
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I scale those low angle 8 inchers on Lexington as being about 44 inches apart, CL to CL. Pretty close. And those guns were built with very heavy chambers.
Seems like there wouldn't have been room for horizontal recoil cylinders, even if one ignores maintenance/inspection space. So were the cylinders above/below? That'd even further limit the potential elevation angle, per the side view of the upper turret.
Your comment above got my little grey cells churning and made me realise that I had missed an opportunity.
Although my modified cruisers could (and would) have a wider interior and, therefor, the potential for a wider turret ring, the fitting of a larger turret would not be a foregone conclusion. Generally, the size of early turrets was dictated by the gun size and crew requirements - any increase in volume beyond the required size would only necessitate extra armour (requiring extra power or slowing the vehicle) and increase the vehicle’s profile. With the 40mm 2pdr being the only gun of choice in the early days, there would be no need to increase the turret size of my Alt Mk III, Mk IV, Covenanter and Crusader I vehicles. Likewise, the Cromwell and Comet were designed for the 75mm and 17pdr respectively so are also good to go as is. The one that stands out as needing attention is the Crusader III which OTL carried a 57mm 6pdr wedged Into the old Crusader I turret. Without the ability, OTL, to increase the turret ring, the only option to incorporate the 6pdr was to reduce the turret crew to two - not ideal. My Alt Crusader III would have the capacity to accept a larger turret ring and associated larger 3-man turret to house the 6pdr - also get rid of existing turret shot-traps.
I will go back and rework the design - and alter my model too… 🤔👍
Edit: At 1410mm, the Crusader’s turret ring was big enough, the problem was actually the design and restricted layout of the weird shaped turret. With no need to increase the turret ring would they have altered the turret design rather than accept the 2-man turret. OTL, they didn’t. Consequently, as my alternative cruiser premise is really only looking at changing the Christie suspension to VVSS/HVSS, I should perhaps stay loyal to other OTL design limitations/decisions. 🤔
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RamscoopRaider
Donor
46 inches apart to be exact
The guns of the 8" twins and early 8" triples were located in a common sleeve, elevation of up to 41 degrees. Recoil system was over/under with a recoil length of 29.65 inches
If you wish to up-gun your cruiser from the 40mm 2pdr there is an available 6lb gun from 1936, this is the coast defence 6lb 10cwt, using a 57 x464mm round at a respectful 726m/s with a recoil of only 12 inches. Now early war that can kill any armour it meets but also has a decent HE round which would make for a formidable tank.
Acknowledged and an interesting find but I am not looking to replace any of the cruiser tank’s armament. My musings were whether or not I should enlarge the Crusader III’s turret to give it a 3-man crew. However, as the OTL POD for my alternative British cruiser tanks was removing Christie‘s suspension as an option and replacing it with VVSS and HVSS, I didn’t see the need to change any of the other decisions that lead to the OTL series with all of their other limitations. And, of course, care should be taken with AH designs not to overdo hindsight! 😉
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57mm HE is only about half as effective as 75mm...and many WWII ordnance-effects designers considered medium-wall 75mm as the lower boundary of effectiveness for infantry support and general anti-soft-target bombardment. So that's an argument against 57mm tanks for general purpose use, and of course the gist of why the US M3 and M4 mediums went straight to 75mm armament.
It would be a sort-of-armament-change to replace the CruIII's original six pounder with the bored-out-to-75mm version...same gun on the outside, different sized hole in the outbound end...provided with a British version of Edgar Brandt's 1940 tungsten carbide APCR to keep it effective against hard targets, plus a legitimate 75mm HE round. Would that also be an overdoing of hindsight?
Arguably the CruIII's potential combat effectiveness increase would be greater if upgunned to medium-pressure 75mm, than by being re-suspensioned with VVSS/HVSS.
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The 6 pounder AT gun was more or less designed, but then production got delayed for no good reason, then Dunkirk made it more important to have a 2pounder now than a 6 pounder later.
I know it's better to try not to overdo multiple PODs but it wouldn't be too big a step to have different tank mind set meaning 6 pounder AT and tank gun are ready to be manufactured in mid 1940, so they are made alongside 2 pounder. The Crusader can now be fitted with one sooner. That bypasses the need to use a naval gun, and still meand the Crusader I and maybe II have a 2 pounder.
My understanding has been that contracts for the disassembly of elements of the two pounder production capacity and the installation of six pounder production capacity had been let, and additional engineers, draftsmen and skilled tradesmen had been hired and had created plans and schedules for that work; and the requisite new machinery and tooling (except for the longer barrel lathes, which were delayed), and elements of existing machinery that was to be converted for the new gun, had been ordered, built and received and were ready for installation, as of mid May 1940. The production changeover was scheduled to begin in early June.
Production of towed six pounders was to begin by late summer 1940, initially involving guns with barrel lengths at the maximum possible with the existing two pounder barrel lathes, retooled for the larger caliber. Production of six pounder armed cruiser tanks was to begin in early 1941, as soon as demand for towed guns was met. That production was expected to be able to commence using guns of full design barrel length. A production schedule for infantry tanks wasn't yet set, but was expected to be later in 1941.
So it was only the ramifications of loss of essentially all of BEF'S heavy weapons, but also military events and resulting equipment needs for North Africa and the engineers' realistic determination that six pounder production inevitably would start slowly but two pounder production could continue at a high rate, that caused the changeover to be postponed.
My understanding is, that wasn't the plan. Two pounder production was to entirely cease prior to commencement of six pounder production, with a period of no production while the conversion of the same factories and the same production machinery took place.
I hadn't realised they were quite so close to production. Bringing something forward by a few month or two looks a reasonable secondary POD since the initial change implies slightly better thinking in the right circles.
All very interesting points my good fellows and something for another day perhaps. However, you have kind of missed the point of what I was postulating. I was never attempting to improve the series of British cruisers rather I was only contemplating what might have happened had Mr Christie’s suspension not been available and the US VVSS/HVSS been selected instead - just that - nothing else… 👍
Go on, we know you're secretly looking to justify putting the gun from the French GPF194 [1] in the turret of an alt-CS Crusader and we're just helping you find a way..
[1] Deep down I'd prefer the CH280 (purely to reduce muzzle overhang), but sometimes we have to accept a compromise. .
I visited the French archives once again, a bit less content found this time. It was about the organisation and equipment of French armored forces between 1919 and 1924, as in what they intended to do in the long run.
The French were envisionning the following types of tanks
- a light tank armed with machineguns (or a machinegun and a 20mm gun/autocannon or a 37mm gun) around 8-11 tons with a 90hp engine and greater mobility (10kph minimum on tracks), armor against expected infantry weapons (20mm in the front). Basically meant to fight forward, of minimum size and weight to be fielded in large numbers and be easily transportable and use light pontoons.
- two types of support tanks armed with a short 75mm gun. One with good protection and firing directly at targets and in particular tanks, the other was a sort of open top SPG firing indirectly from a safe position.
- a recon tank with minimal armament but greater speed (20kph minimum) and/or protection to be able to move ahead of other formations and probe enemy defenses. Equipped with a radio.
- support tracked vehicles: an APC, a fuel/ammo carrier, a radio tank, a carrier tank or bridgelayer to cross obstacles.
- eventually a heavy breakthrough tank on the lines of the FCM 2C.
One can imagine that the use of tracked carriers for 105, 155 and 194mm guns as seen in late WW1 would continue.
Overall the French system was rather logical and complete for the early 20s, but the lack of funding meant that obviously none of the replacement and special vehicles mentionned saw the light of day in the expected timeframe (by 1925-26). It is only in the early 30s that the B1 and D1 series matured enough to somewhat fill the expected roles of 75mm direct fire tank and light tank imagined since 1920 respectively.
I have learnt about a few specific developments however. One from 1922 or so was a proposed upgrade of the Renault FT as a stopgap until a new tank is fielded in 1926, to remain relevant against the potential proliferation of the German MG 18 TuF heavy machinegun. The core idea was to increase the armor thickness by 10mm in places (so about 26mm at the front and 18mm on the sides if done), adding 700kg. This increase in weight would be compensated by an interesting development of the time: a new cooling and fuel delivery system. The existing cooling system (radiator + fan) was problematic because fan belts broke regularly. A solution by the Bloch-Sautter-Harlé company was what we call an ejector type cooling system, where the energy required to suck the air in and out of the tank is provided by the exhaust gases going through a nozzle. This system would be successfully used in some Soviet vehicles much later, but it was hoped for the FT that it would save an additional 7hp and greatly reduce maintenance requirements.
The other developments were from much later in 1929 or so. There was an idea to modernize the FCM 2C heavy tank by replacing the existing German 2*175hp engines by 2*250hp and increase armor thickness to 45mm everywhere instead of just the front. Additionally, it appears that the French were working on a new model of FT BS casemate (the FT BS was a casemated variant of FT with a short 75mm howitzer), as well as Junkers and Peugeot diesel engines for some unknown tank.
I also read reports from the French advisory committee on weapons from 1936 to 1939, but nothing out of the ordinary concerning tanks, just developments that we already knew about; bar some small info about 37mm SA 38 gun development and tank gun AP performance. More spicy for other weapon categories however.
The French were envisionning the following types of tanks
- a light tank armed with machineguns (or a machinegun and a 20mm gun/autocannon or a 37mm gun) around 8-11 tons with a 90hp engine and greater mobility (10kph minimum on tracks), armor against expected infantry weapons (20mm in the front). Basically meant to fight forward, of minimum size and weight to be fielded in large numbers and be easily transportable and use light pontoons.
- two types of support tanks armed with a short 75mm gun. One with good protection and firing directly at targets and in particular tanks, the other was a sort of open top SPG firing indirectly from a safe position.
- a recon tank with minimal armament but greater speed (20kph minimum) and/or protection to be able to move ahead of other formations and probe enemy defenses. Equipped with a radio.
- support tracked vehicles: an APC, a fuel/ammo carrier, a radio tank, a carrier tank or bridgelayer to cross obstacles.
- eventually a heavy breakthrough tank on the lines of the FCM 2C.
One can imagine that the use of tracked carriers for 105, 155 and 194mm guns as seen in late WW1 would continue.
Overall the French system was rather logical and complete for the early 20s, but the lack of funding meant that obviously none of the replacement and special vehicles mentionned saw the light of day in the expected timeframe (by 1925-26). It is only in the early 30s that the B1 and D1 series matured enough to somewhat fill the expected roles of 75mm direct fire tank and light tank imagined since 1920 respectively.
I have learnt about a few specific developments however. One from 1922 or so was a proposed upgrade of the Renault FT as a stopgap until a new tank is fielded in 1926, to remain relevant against the potential proliferation of the German MG 18 TuF heavy machinegun. The core idea was to increase the armor thickness by 10mm in places (so about 26mm at the front and 18mm on the sides if done), adding 700kg. This increase in weight would be compensated by an interesting development of the time: a new cooling and fuel delivery system. The existing cooling system (radiator + fan) was problematic because fan belts broke regularly. A solution by the Bloch-Sautter-Harlé company was what we call an ejector type cooling system, where the energy required to suck the air in and out of the tank is provided by the exhaust gases going through a nozzle. This system would be successfully used in some Soviet vehicles much later, but it was hoped for the FT that it would save an additional 7hp and greatly reduce maintenance requirements.
The other developments were from much later in 1929 or so. There was an idea to modernize the FCM 2C heavy tank by replacing the existing German 2*175hp engines by 2*250hp and increase armor thickness to 45mm everywhere instead of just the front. Additionally, it appears that the French were working on a new model of FT BS casemate (the FT BS was a casemated variant of FT with a short 75mm howitzer), as well as Junkers and Peugeot diesel engines for some unknown tank.
I also read reports from the French advisory committee on weapons from 1936 to 1939, but nothing out of the ordinary concerning tanks, just developments that we already knew about; bar some small info about 37mm SA 38 gun development and tank gun AP performance. More spicy for other weapon categories however.