Somua S35 unbuilt variants

[Elan Vital]

Hi everyone,

This thread will be about unbuilt variants of the Somua S35 family, in the same vein as my previous thread about Keller program vehicles, based in part on my research at the Vincennes archives.

This will include (as of current knowledge):
- Somua S40
- Somua S40 with FCM multi-man turrets
- SARL 42
- Somua SAu 40
- other Somua S35-based SPGs.

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I will be starting with the FCM turret projects for a modified Somua S40.

Work on these projects is explained in a descriptive note from the 24th of April 1942 from the FCM (Mediterranean Foundries and Shipyards), based notably in Marseille. Here is a translation of the note:

A - Project of 2-man turret with 47mm SA 35 gun.

1°) Mandatory conditions

- Turret ring of 1505mm (ball center distance), fitting within a 1490/1605mm wide hole
- Electric and manual traverse mechanism
- Turret body armored at 40mm on all plates but the roof and floor which are 20mm thick.
- Armament: 1 47mm SA 35 gun with a coaxial 7.5mm machinegun
- AA armament: twin 7.5mm machineguns with increased rate of fire (author's note: analogous to the aircraft MAC 34 M39 machineguns)
- Crew: 2 men: 1 commander with an observation cupola located on the right of the guns with a hatch to observe directly outside, and a gunner located on the left.
- Communication means: radio, signal flags and openings

2°) Description

The turret body is made of rolled armor plates, bent and assembled with joint covers or welding.
The mantlet and the cupola are made of rolled, stamped and welded plates.
The turret body is mounted on a turret ring placed in an opening of the tank's roof.
Turret traverse is done with a manual mechanism or an electric motor.
The controls are doubled so that both the gunner and commander can traverse the turret.
The armament is composed of a 47mm SA35 gun coupled with a coaxial 7.5mm MAC 34 machinegun with a firerate reducer which brings the ROF back down to 600 rpm.
The main gun can be shot with a manual or electric trigger.
AA defense is done by the tank commander who has a twin mount of MAC 34 machineguns firing at 1200rpm each. Elevation angles are from 0 to 80° above the horizontal plane.

The means of observation are as follows:
- for the commander: 3 PPL episcopes with a total forward field of view of 180°, 4 vision slits, one aiming sight and one target designation sight.
- For the gunner: 1 Gundlach periscope, 2 vision slits and one aiming sight.

20 rounds of 47mm ammunition and 15 MG magazines are stored in the turret itself.
Good comfort is ensured by a turret basket in which access to the different observation levels is obtained by adjustable floors.
The turret can be accessed from inside the tank and from the observation hatch on the roof.

The weight of the turret without the basket and ammunition is roughly 3800kg.

B - Project of a 3-man turret with 47mm SA37 gun.

The first project can mount a 47mm SA37 gun instead of the SA35 gun. In this case, proper servicing of the weapon requires a 3-man crew: 1 commander designating targets and ensuring continuity of observation, one gunner and one loader.

The project has been established to fulfill these requirements without modification of the turret basket and traverse mechanism..
The commander and gunner are located on the left of the weapons which are moved slightly further right.
The loader is on the right of the weapons.
The weight of this turret is similar to that of the 2-man turret.

The pictures of the turret are the first accessible in Part 1 of my Vincennes archives album:

Les Archives de Vincennes · Shared album ð¸

Tap to view!

photos.app.goo.gl

Sadly, this was my very first visit there so the quality on those was less than stellar. Higher quality ones are in spoilers

Spoiler: Turret plans

My observations on the plans:
- the 3-man SA37 turret carried 24 ready rounds rather than 20.
- the AA twin MG mount was stored inside the turret near the cupola's hatch, with a mechanism to lift it over the hatch.
- the 2-man turret is 1870mm long, 1670mm wide, and 865mm tall (a little taller than the APX-1 CE on S35 and early S40).
- the inside diameter of the turret ring, so the real diameter accessible to the crew, was 1435mm or 56.5 inches, so a little bigger than/comparable to the T-34-76 and many British tanks of the time with a turret ring diameter of 54 inches.
- a complete revolution of the turret could be done in 20s (18°/s) with the electric motor, 1min20s with the manual mechanism.
- complete weight with the aluminium turret basket and ammunition was 4373 kg. In comparison the APX 1 CE weighed 2000-2200kg fully loaded (not sure if everything is included), so in the most pessimistic esimate the turret would have added 2.2 tonnes to the weight of the S40, notwithstanding the weight increase/reduction caused by modifications to the hull.

It is not known what modifications would be needed on the S40's hull to accept the larger turret ring, nor what modifications were contemplated unrelated to the new turret itself. However, the location of the radio in the turret all but guarantees that the radioman located in the hull of the S35/40 would be removed in favor of...something else.
This project had been apparently done in the context of restarting production of the Somua S40 in Vichy France for the Axis in 1942. Nothing came of this until the invasion and occupation of this part of the country after November 1942.

Overall, the FCM turret project was a natural follow-on to the projects that had been undergoing since before the Fall of France for turrets using welded and bent rolled plates rather than castings, and fixed observation cupolas instead of small rotating cupolas like the cast APX turrets. Both FCM and ARL (the latter with patents and major contribution from the Five-Lilles steelworks) had been designing 1-man turrets to replace the APX-1/4 cast turrets, with introduction starting in July 1940.

It was claimed by a well-known French historian, Stéphane Ferrard, that work on such a type of 3-man turret had started at FCM in April 1940, but to this date I cannot confirm this claim.

It is interesting to note that, unrelated to this program, a report on the lessons of the battle of France and on the creation of a new armored division written in 1940/41 envisionned the use of Somua derivatives with a 2/3-man 47mm turret and a 75mm turret, which are eerily similar to this project and the clandestine SARL 42. It is quite possible that thinking from armored officers inspired these programs or that this simply was convergent evolution.

Regardless, the FCM project was a logical way of using the limited French tank production capabilities which may have been accessible to France in the case of a program approved by the Axis authorities or launched after a very early liberation of France. It allowed the use of a well-known chassis that would be easier to put back in production, while adressing many of the problems of the Somua: it brought one or even 2 crew members in the turret, improved observation capabilities, added a more practical access hatch and more ready ammunition and greatly improved antitank capability in the case of the 3-man turret (to the level of a Pz III with a 5cm L60 gun).

This tank would obviously have been obsolescent from day one by the standards of major powers even if it could enter production in 1943, as it retained now very thin 40mm armor, and modest level of mobility (potentially fast, but only around 10 hp/t). Nonetheless, for non-German Axis powers and co-belligerents like Italy, Hungary or Romania, it was better than nothing and could even compete with a lot of their designs, like the M15/42 which was no better armored, nor more mobile, and more poorly armed, or the Turan I/II which also had poorer antitank capability and barely better armor and mobility. Whether this could have been an actual net gain for the Axis considering their production capability and ressources is however very uncertain.

 

[Elan Vital]

In November 1935, the SOMUA offered a few SPG projects based on the SOMUA AC3 chassis (S35 prototype), long before the more well-known SOMUA SAu40 (also called CAM 2 or AC4).

Here is a translation of the offer:

Mister General Inspector,

We have the honor of sending you hereby attached, a preliminary project for a self-propelled field gun obtained by installing a 75mm Schneider 12 or 14km gun on the fast tank SOMUA AC3.
As we explained on the "General" section of the associated note, this preliminary study has been established in order to set the rough lines of a self-propelled field gun featuring an armament of the greatest power compatible with the space available on the SOMUA AC3 fast tank prototype.
The envisionned solution allows the combination of firepower, tactical and strategic mobility, quick deployment, offroad capability and sufficient protection to not fear infantry projectiles or schrapnel.
This solution, built on the principle of the integral use of a proven vehicle and of existing and proven weapons, gives the advantage of envisioning an eventual realization which would present the minimum of risk.

Translation of the note:

Such a realization would lead to a type of equipment which could be logically used as the element of self-propelled batteries. This materiel used alone (commented: No) could also be an excellent infantry support asset.
The gun used is a powerful 75mm Schneider, firing a 6.5kg explosive shell at a muzzle velocity of 715 m/s, providing a range of 14km.

The ammunition capacity of this equipment could be at least 76 rounds stored as indicated on the attached project.
Servicing of the vehicle could be done by 3 crew members:
1. A driver sitting on the left
2. A gunner sitting on the right.
3. A loader standing on the right
Eventually, a 4th standing crew member could also be in the fighting compartment to work as second loader or radioman.

Summary Description

The cavalry armored car SOMUA which we suggest to turn into a self-propelled piece is composed of:
1. A rear section exclusively dedicated to the engine, transmission and controls of the tracked running gear.
2. A front section called "fighting compartment" in which everything regarding the armament with ammo and personnel and the driving compartment are organised and gathered.

The oscillating mass includes:
1. The gun with its muzzle brake and vertical wedge breech.
2. The housing for the hydraulic brake with counter-rod and the hydro-pneumatic recuperator.
3. The chassis on which the housing slides during recoil, holds the brake and recuperator attachments, the trunions and the mobile mantlet and the vertical traverse gear
4. The automatic breech opening and closing mechanism.

(Rest is just typical carriage and gun control suff):

Vertical traverse range is -5 to 45°
Horizontal traverse range is +-5°

The aiming equipment is a monobloc assembly located on the right trunion containing: an elevation cam, an elevation goniometer, an elevation mechanism and a x4 panoramic goniometer. This device allows direct and indirect fire.

When moving, the oscillating mass is locked at an angle of 30° and recoiled the maximum recoil distance (1.2m) inside the tank.

The fighting compartment is ventilated by the engine fan. There is a small hatch to dispose of spent cases, and ammo racks possess an evacuation device for gases.
Side access doors are available.

Ballistic data:

Calibre	75 mm	75 mm
Muzzle velocity	715 m/s	600 m/s
Projectile weight	6.5 kg	6.5 kg
Weight of complete round	9.5 kg	9.5 kg
Maximum range	14 km	12 km
Ammo capacity	76	76
Weight of ammo	700 kg	700 kg

Length of the barrel	3150 mm	2820 mm
Number of calibre lengths	42	37.6
Firing height above ground	1430 mm	1430mm
Above floor	1000 mm	1000 mm
Elevation angle	-5/+45°	-5/+45°
Traverse angle	5° either side	5° either side
Recoil force (horizontal)	3790 kg	2560 kg
Recoil distance	1200 mm	1200 mm
Weight of oscillating mass	658 kg	605 kg
Weight of the artillery piece (roughly)	1000 kg	950 kg

The final weight of the SPGs will be determined at a later date dependent on the armor thickness and width that will be approved after a more thorough study.
However we can estimate that the total weight of this vehicle will be on the order of the SOMUA AC3 with an APX1 turret (20 tonnes).

Translation of the reply from December 1935:

The general organisation of this materiel presents the following major defects:

1. The tank is blind

The only observation equipment is a panoramic sight fixed on the carriage and whose method of employment would only make sense if the vertical walls of the fighting compartment were deleted.
To use this panoramic sight, one would have to lengthen the sight body so that it emerges on the roof; but the disposition envisionned by the SOMUA seems to be hardly suitable for this organisation.

2. No tank commander is intended

The driver being the only crew member with good view of the exterior, it seems impossible to give command of the tank to another crew member. I also add that it seems pretty much impossible to direct the movement of the tank under enemy fire without having all-around vision.

3. The artillery piece is poorly protected.

The chassis and tray of the gun stick out of the armor but are too fragile to be exposed to enemy fire without special protection. It will be necessary to protect these elements with armor which would increase the weight of the oscillating mass.
Moreover, when moving, the forward part of the hull extends beyond the idlers. Is it to be feared that the hull, when moving offroad, would dig into the ground much like happened on numerous occasions with the first 75mm SPG studied by Général GARNIER.

4. The equilibrator of the oscillating mass will not work.

While it is possible to balance a field gun with springs as the joint is mostly vertical, this solution is not acceptable for a tank able to fire in any position, especially when the seating plane can be 15° away from the horizontal plane. The greater this unbalance, the more serious the drawback.

5. The ball joint of the gun is of excessive dimensions.

A ball joint of such size presents the following drawbacks:
a) it makes sealing of the joint difficult
b) it gives a large attack area, and thus increases enemy hit probability on the trunions and aiming equipment
c) reinforcing the ball joint armor may increase unbalance of the gun and make the work of the equilibrators worse

6. The organisation of the aiming sequence is not rational

The gunner is a separate crew member from the driver. It is to be feared that the gun will never be aimed roughly where the target is. (Author's note: this might be why the driver was the main gunner on French casemate guns of the time like the B1 and ARL V 39 SPG. One can obviously question this assessment considering that workable WW2 SPGs had a separate gunner).

In these conditions, I consider this project of no interest.

Plans of these vehicles can be found on 2nd part of my archive album here, relatively early:

Les archives de Vincennes Partie 2

1511 new items added to shared album

photos.app.goo.gl

The project that was discussed here is better-known as the SOMUA CAM 1:

There is another SOMUA SPG plan here which is somewhat different as it features a more normal mantlet with -10/+20° elevation and a machinegun turret. It also retains the weird front roller that was on the AC3 prototype and previous SOMUA vehicles.


Overall, a fairly flawed but imaginative initial project. The rather high elevation angle and big ball joint was likely intended to provide best conditions for dual use in the direct and indirect role, as HE throwing seems to have been the main intended mission rather than anti-tank duties.
The most interesting aspect remains the sheer power of the envisionned weapon. The 75mm Schneider 14km (based on an AA gun following the 75mm mle.1928 ballistics) eventually became the basis for the ballistics of the clandestine/postwar 75mm SA 44 gun, and was an intermediate between the typical medium 75mm (Sherman, T-34) and the medium-high velocity 75mm (KwK 40 L/48). The Schneider 12km was a more modest type roughly close to the gun of the Sherman.

 

[Elan Vital]

Finally doing the SOMUA S40, the least "secret project" S35 variant. But there are still quite a few elements that are often not mentioned about it. Also doing SARL 42 as I have time.

Basic history:

The SOMUA S40 was the culmination of developments studied throughout 1938 and most of 1939 to improve the general ease of use, reliability and safety of the S35. Unlike other programs like the B1 Ter, it did not feature any direct improvements to the firepower and armor of the tank. The scale of the modifications led the Cavalry to set a new production standard encompassing all modifications from the 451st SOMUA tank onwards, starting the 5th batch of tanks (the last one being S35s numbers 326th to 450th, originally meant to be completed in September 1940).
The outbreak of WW2 changed the plans a little, resulting in the first complete S40s being expected in July 1940 instead of October. 14 in July, 27 in August, 32 in September. The mobilization production target was updated shortly after the outbreak of the war, increasing from 28/30 to 36/month. SOMUA managed to constantly outdo army expectations, so would have likely met their targets.

3 orders were made throughout 1939, respectively for 50 tanks, 100 tanks, and finally 3 months of mobilized production (108 tanks, prolonged until March 1941. This translated to 374 tanks and 26 spare cast hulls. The first 150 of which would (not accounting for losses) complete the full equipment of the first 3 DLM armored divisions with SOMUAs only, replacing the Hotchkiss H39 (200 tanks per division).

The Fall of France killed those plans, with Germany getting their hands on a few cast hull bodies. A complete pilot hull with a mockup of the new ARL 2C turret was made in April 1940, but all complete hulls were lost in the chaos of WW2 France. In late May 1940, the desperate French government enquired the US about the possibility to build a whopping 12 000 SOMUA S40s at a rate of 50 per day, to be delivered starting in early 1941. This was quickly changed for B1 Bis tanks.

Per Rickard, J (11 March 2016), Somua S40 , http://www.historyofwar.org/articles/weapons_somua_S40.html, the Vichy government and the Germans were apparently approached by Japan to envision the possibility of ordering S40s for the Imperial Army. Negociations led to the May 1941 Protocols of Paris to increase cooperation between Vichy France and Germany, with a ground and air element.

These protocols led to the Improved SOMUA S40 with FCM 2- and 3-man turrets I mentionned early on. 200 were to be built for French colonies, and 600 for Italy and Germany. In February 1942, an agreement was in the works for 250 such tanks for the IJA to be delivered 12-18 months after the contract was signed. Production was to be set up in FCM's factory in Marseille. In September 1942, this was updated to 135 tanks for Vichy, 250 for Japan and as many as Italy and Germany wanted. The plan was killed by Operation Torch and the subsequent invasion of Vichy France, Italy capturing the FCM factory in the process.

Technical history and description:
The very core of the S40's design was the new so-called "inclined track" suspension. This had roots as far as 1936-37 when SOMUA participated in the 20t/G1 battle tank program. The Infantry requested a greater wall-climbing capability than the S35's, which was even worse than that of the Renault R35 light tanks (merely 50cm instead of the required 80cm). SOMUA's entry thus featured a reworked suspension which raised the idler and inclined the upper run of the track by 2 degrees. SOMUA left the G1 program in 1938, but applied the idea to the SOMUA SAu 40 self-propelled gun.

With the idea of an improved S35 taking shape in the latter half of 1938, the new suspension was now envisionned. Preliminary testing was done by reducing the weight of the SAu 40 prototype to 20.5 tonnes, the only difference being the width between the tracks (2.4m instead of 2.05m).

Inclined suspension, revized hull and battery setup
The new suspension improved wall-climbing and trench-crossing capability, reduced mud buildup and vibrations/shocks during offroad movement. The new inclined track moved the idler 300mm further forward and 183mm further upwards. An additional elastic roadwheel was added, an extra return roller and 12 extra track links. This increased the weight of the tank by 475kg.

This new setup, if implemented as is, would have inclined the hull by 2-3°, increasing total height to 2.735m instead of the 2.626 of the S35. It did actually improve the field of view of all episcopes, but those of the driver. SOMUA suggested modifying the hull to bring the driver's vision devices back to their original position, but ARL opposed this as this would delay production of hulls.

SOMUA nonetheless went forwards with the idea. The solution found was to bring the upper part of the hull to its original position, but to rework the entire bottom front half of the tank to angle the floor at 2-3° like the suspension. This meant reducing the physical height of the front hull by some 14 cm. The lowered hull had the following advantages:
a) it reduced the tank height, reducing its vulnerability compared to the S35
b) it improved the shape of the front hull for protection

It also saved some 400kg, almost fully compensating the extra weight of the new suspension.

The driver's seat would be lowered by moving the braking accumulator at the current location of the oil tank, the latter being moved beside the oil radiator in an accessible manner. The radio operator's seat would also be lowered by moving the current battery.

On the S35 two sets in 4 blocs of batteries (SAFT 9-8 Type JN 18 with 130 Amps.h) were used in groups of two. One powered the electrical equipment of the tank while one powered only the radio.
The first solution proposed was to add a filter to the dynamo to use the same group of two blocks to power the equipment and the radio and to delete the 2nd group, just like on the SOMUA SAu 40.

The second solution, was to move the battery of the radio operator in the place of a toolbox on the escape hatch, but this setup presented fire risks due to inconvenient position to maintain the radio and it wasted time. It also would be inconvenient for the escape hatch. So the 2nd solution was preferred.

Ammo capacity would be reduced in the lower hull, 113 projectiles instead of 119 and 19 machineguns drums instead of 24. However the first battery solution could allow more rounds to be fitted as it saved substantial room.
The deletion of the 2nd battery was facilitated by the increased capacity of the JN batteries and the fact that the ARL 2 C turret traverse not longer took electricity from the battery, but from a special generator driven by the engine.

The opportunity was also taken to standardize the hull floor thickness to 20mm instead of 20mm at the front and 15mm under the engine compartment.

Improved V8 engine:

In June 1939, the SOMUA informed the Cavalry Technical Section led by Colonel DARIO that they had completed development of an engine able to replace the existing one on the S35. This modified engine featured an enlarged bore of 125mm instead of 120mm (125x140mm bore and stroke) and better designed valves to improve the air intake and the regularity of the engine torque. Displacement increased to 13.7 L.

This engine was tested between late September and November 1939 in an existing S35 tank over 935 km on road and offroad terrain.

The engine retained certain defects of the original engine:
- a rattle/clicking noise between 800 and 1200 rpm
- auto-ignition
- excessive heating of the gases in the intake manifold
- deterioration of the upper parts of the cylinder liners

However, it provided an extra 22 horsepower at 2000 rpm at the cost of an 18% fuel consumption increase. This additional power allowed much better performance on all types of terrain while being undeniably superior in ease of use and movement speed.
This engine could be mounted on existing tanks without any modifications.

As a result, the Cavalry Technical Section decided to adopt this engine not only for the S40 (so from the 451st tank onwards) , but would also be adopted as the only spare engine type for the 450 S35s. The SOMUA would continue working to adress the defects of the engine and in particular the wear on the liners. However, it's not quite certain if it would have been ready in time for the first S40s.

Work continued to improve the intake piping in hopes of further improving the air feed.

Output was normally 220 PS at 2000 rpm and 230 PS at 2300 rpm (max regime), instead of 190-200 and 200 PS respectively. It more than made up for the increased weight of the S40 (around 500 kg, approx 20.5 tonnes in total).

Intercom:

The same Bronzavia intercoms tested on the B1 Bis and Ter would also be adopted for all SOMUA tanks, with approval to start work on the first 450 sets for the S35 released in January 1940. They would appear as standard on the S40.

New radiator setup:

In April 1939, the SOMUA suggested the adoption from the 451 st tank onwards of a new radiator layout. Much like the B1 Ter, the radiator would be put horizontally, joint with the upper rear armor plate. The new radiator was designed to account for the heat of the new engine. It would significantly increase the available space inside the engine bay and facilitate access to certain parts (the spark plugs). This modification would work best if the SOMUA was allowed to add access hatches at the rear of the tank for easier access to the steering clutches.
This would also allow increased fuel capacity by 100 L, increasing range by 70 km, with the S35 already achieving around 200 km.

However, nobody knows yet if this modification was approved for deployment on the S40.

New clutches:

The 2-disk clutches would be replaced by single disk clutches which were more durable and facilitated driving.

Electrical installation:

In January 1939, the following defects of the electrical installation were reported:

a) The battery charging circuits and the lighting circuit were relatively complex due to the use of shielded wires. It was suggested to add a filter to the generator to allow use of ordinary wires (easier to maintain and repair).

b) Engine ignition left something to be desired due to the use of electrical shielding. A Faraday cage was under study to remove the need for electrical shielding and thus improve ignition.

c) The SAFT company replaced its Type JD cadmium nickel batteries with a new JN type which had an increased capacity for the same size. It was suggested to do the replacement on the SOMUA tanks to exploit the greater capacity. The new JN type would end up being adopted indeed.


More minor changes relative to the qualify of life/ease of maintenance and use were to be implemented:
- Modified left access hatch to open from back to front.

- Increased opening angle for the two upper access hatches to the oil and fuel tanks. They can open fully, this preventing any sudden closing.

- Modification of the right side door on the rear armor plate.

- New access hatch created for access to the brakes and steering clutches.

- Modified lubrication circuit

- Addition of an extra lubrication system for cold weather.

Some modifications required new studies, and it hasn't been confirmed if they would be present on the first S40s, if at all:

- Increased waterproofness of the cable gland on the water pump.

- Modification of the intake piping to improve the air feed to the engine.

- New CALEX fireproof bulkhead. It is about 50% heavier, more costly and thicker (23 instead of 14mm) but supposedly improved protection.

- Modified fuel circuit to allow the full use of the complete capacity of the two fuel tanks.

- New needle bearing for the pinion of the final drives. This improved their operation. This was to be used only on the tanks with the 220 PS engine.

- Hydraulic assistance/command for steering. This avoids the difficult tuning of the steering clutches and facilitates driving.

- Auto-serve Kegresse automatic (hydraulic control) transmission which facilitated driving, efficiency and improve the life of the general transmission and gears. This allowed the complete deletion of the clutch pedal, eliminating special training for drivers. The engine could no longer be stalled, and it was possible for the driver to set a maximum speed and allow automatic drive between 0 kph and said speed. This transmission had 5 forward speeds including 4 synchronized ones, and a single rear speed.

ARL 2C turret:
The new ARL 2C (likely C for Cavalry) turret was suggested in January 1939. This was identical to the variant developped for the B1 Ter save for the armor being reduced to 40mm on most faces (60mm in the rear for balance, 35mm on the cupola and 20mm on the roof). It shared the same advantages already mentioned in my post on B1 Ter.
It was especially beneficial because its traverse mechanism was powered by a generator driven by the engine, facilitating the deletion of the 2nd set of batteries.

55, but eventually 80 S40s would run with the existing APX 1 CE turret instead. Originally, it was intended to prepare the hulls for the ARL 2C and use an adaptor to use the APX 1 CE on the first tanks, but this was apparently not done. Using the ARL 2C on the S35s was abandonned due to the increase in weight and especially height driven by the adaptor.

The ARL 2C added less than 500 kg to the weight of the tank, and was the main source of the modest weight growth on the S40. Due to delays with APX 1 CE deliveries, delivery of both APX 1 CE and ARL 2C S40s would happen simultaneously. The types were not to be mixed in the same unit.

Source: GBM n°88, SHD Châtellerault file GR 9 NN 12 146 (Improvements and defects of the S35).

Pictures: to be found on Chars.Français

1940 SOMUA S 40

www.chars-francais.net

Spoiler: S35 (top) vs S40 (bottom) hull outline, reproduction of a plan made during development of the SARL 42, featured in the magazine GBM issue n°88.

Spoiler: 1941 plan of the S40, with APX 1 CE turret

SARL 42:

Regarding the SARL 42, the article on Tanks Encyclopedia gathers pretty much all we know on this tank, so I recommend it: https://tanks-encyclopedia.com/sarl42/

The only additions I would make is that per GBM n°90 this article was based on, the Aster 6-cylinder inline diesel engine (discussed in my thread on Keller Tank Program's vehicles) was also a candidate for the SARL 42's powerplant.

Moreover a project for a new armored division drawn in the Vichy era (late 1940, 1941) by General De LA FONT envisionned the use of a "medium support tank" based on the proposed combat tank (itself a 2-man turret S40 reminiscent of FCM's project), with armor reduced to 30 mm but a suitably large hull and turret for a 3-man turret with a 75mm gun and able to intervene out to 3000m, well provided with observation and gunnery capabilities. This effectively matched the SARL 42. We know that the requirements for the SARL 42 were apparently suggested by an officer. This would suggest that the concept was well-spread within the post-Fall French Army.
(Source: GR 3 P 146 at SHD Vincennes)

Incidentally, a postwar interview from an officer as part of the Enquiry on the events that happened in France between 1933 and 1945 by Charles Serre (1951) mentioned the idea of a 75mm turret SOMUA in 1939 as part of discussions about the fire support of the DCR division (in fact, it General GAMELIN himself brought this idea).
(Source: Page 193 of Rapport fait au nom de la Commission chargée d'enquêter sur les événements survenus en France de 1933 à 1945. Partie 1-4 / par M. Charles Serre, 1951 on gallica.bnf).