Page Four

The Prototype

On my return to Le Khroub, I found that both the new Churchill from R.A.O.C. and clear instructions from A.F.H.Q. had preceded me. I was met with little enthusiasm. The C.O and several other officers in the Company were regular soldiers. Being of a conservative nature, they were dubious about the project, and diffident about being connected with what they thought was an almost certain failure, which could have unfortunate repercussions on their future careers. I was given to understand quite clearly, that whereas I would be given every possible assistance, all decisions regarding the conversion were my affair- I was in fact completely on my own.

By this time somewhat daunted, but irretrievably committed, I got to work. A corner of the main workshop was roped off, the new Churchill was put into it, and a crew of Artisans was selected and detailed to the job. Fortunately the diffidence of the officers’ Mess did not extend to the ranks. Armament Sgt, Major Sim Verity, an armament artificer (guns), L/Cpl Lowry, a welder, and a couple of other fitters from my old field detachment, were more than enthusiastic, and were delighted to have the opportunity to do something out of the ordinary, which could prove constructive to the war effort. Throughout the production of the prototype, and later when the job went into quantity production, these men, particularly Sim Verity, were to prove a tower of strength.

It was decided that the first step would be to mount the gun in the Churchill turret, purely to prove out the space problem. The 6 pdr. Was removed together with it’s mantled and auxiliary gear, the turret was cleared, and the internal guide ribs for the 6pdr mantlet were cut out. A gun complete with mantlet and mounting was removed from a Sherman. The mantlet/ mounting of the Sherman gun had a flat peripheral flange which was bolted to the front face of it’s turret. To accommodate this, a large hole was marked off on the front of the Churchill turret, and cut out with oxy/ acetylene.

The die was now well and truly cast – the British Taxpayers’ money was being cut to ribbons – and my nerves were in pretty much the same state.

The front face of the Churchill turret was curved in the vertical plane, whereas the Sherman was flat, and it was necessary to rebate the cheeks on either side of the hole to accept the flat flange of the Sherman mantlet. When a satisfactory seat was obtained, the Sherman, mantlet complete with gun was offered up and arc welded into position. The only arc welding equipment available was the standard single operator workshop set, and the largest electrodes available were 8 s.w.g. it took many hours of work and some 400 electrodes before the mantlet was satisfactorily appliquéd.

At this stage, all the people working on the job took fresh heart. It looked right, the 75mm in the Sherman looked a bit top heavy-the 6 pdr in the Churchill looked ridiculously small. The 75mm and the Churchill were proportionally suited and the consensus of opinion was that ‘they were meant for each other’.

The accuracy of the preliminary measurements was confirmed. The gun was pulled back on to full recoil with ample clearance, and there was quits enough room around it not to interfere with the normal crew positions, and to permit of the gun being served and fired.

The physical fitting of the gun was only a start. Many other aspects had to be covered, and modifications devised and executed before the tank could be considered a viable fighting machine. Most of these arose from the diametrically opposed crew positions in the Churchill as opposed to the Sherman, and the different configuration of the turrets.

The first and most obvious snag was in the limit of elevation of the gun. In the Sherman the front face of the turret and consequently the gun mounting was laid back from the vertical some 30 degrees. The gun barrel protruded through the mantlet and moved in a slot. The effect of welding the mantlet to the front face of the Churchill turret was to limit the elevation to a little over the horizontal, and to permit depression to a much greater degree than was required. To compensate for this came the simple expedient of elongating the top of the slot by some 8” and welding the piece which was cut out, back into the bottom of the slot.

The major snag, and the factor which gave rise to the bulk of the modifications necessary, derived from the respective national origins of the Churchill and the Sherman. The American Sherman was left hand drive. The driver sat to the left of the centre line, with the loader behind him and the gunner to the right with the tank commander behind him. Consequently the breach opening of the 75mm gun faced to the left hand side. The English Churchill was right hand drive. The crew positions were reversed and the breach opening of the 6 pdr, faced to the right.

Many solutions which would have the effect of turning the breach of the gun through 180 degree were considered, but all presented complications, most of which involved extensive rework of the gun and mounting, and called for machining facilities which just did not exist. The job hung fire for nearly two days. Brains were exercised to the limit. Eventually I came up with the solution off, turning through 180 degrees, and welding back, only that portion of the mounting which enclosed the breech. Leaving the main portion of the mounting as original. The mounting consisted of a large boss mounted in trunnions. Through the centre of the boss, a bore some 10” in diameter was extended rearwards into a tube fitted with a phosphor bronze liner. The barrel of the gun was supported in the liner, and slid in and out as the gun recoiled and ran up. At the rear of the mounting were extensions carrying cam tracks for the semi automatic function of the gun, firing mechanism etc, and it was these extensions which overlapped the breach. The plan was to remove and replace at 180 degrees, the rear portion of the tube carrying the extensions. This really called for a very large lathe with something like a 2’ clearance, which we just did not have. The method used was, even to my mind, conditioned as it was by years of field improvisations, a bit ‘Heath Robinson’, but – it was successful. The gun was removed from its tube. The rear and of the tube was marked off with a circumferential line-many methods of scribing this line were tried with varying degrees of accuracy, until we hit on the idea of using an oversize pipe cutter which gave us a deep groove around the circumference with complete accuracy. The rear end of the tube was then cut off by hacksaw a laborious process. The edges of the cut were chiseled to a chamfer, the piece was reinserted with the breach turned to the right, and the rear and of the tube turned through 180 degrees, and the cut was stitch welded at interval of 2” around the circumference to secure it in position. To avoid damage to the piece, it was again removed, and the cut was arc welded around the circumference. All very primitive, but it worked.

We now had the breach opening facing the right way, with the auxiliary mechanisms of the gun functioning correctly. The remaining problem with the main armament were in laying and firing from the left hand side.

Sighting was relatively simple. It was possible to accommodate the Sherman ‘Peritelescope’ in a circular hole in the Churchill turret situated over the Gumner’s head which normally carried a fume extractor, to link the ‘Peritelescope’ with the gun mounting via an adjustable link, and to re-site the fume extractor elsewhere in the turret roof. Firing was also easy. The Sherman gun was fired by either a foot operated cable or by an electric solenoid, and re-siting the controls for these on the left hand side presented no problems.

Elevation and depression did pose problems. The elevating gear was at the right of the gun and the repositioning of the arc of operation of the gun i.e. more elevation and less depression, meant that the toothed quadrant of the elevating gear was now misplaced. The toothed portion of the quadrant was carefully cut off, repositioned further around, and welded back with a strengthening gusset. The elevating gearbox was turned over in it’s mounting to bring the operating hand wheel shaft higher up, an extension shaft was mounted in a bracket welded to the turret roof, and the hand wheel repositioned closer to the Gunner on the left hand side.

The only remaining problem was the co-axial machine gun. This in the Sherman mounting was a Browning-300 as opposed to the Churchill’s Besa. The configuration of the Browning was such that at full elevation, the butt grounded on the Churchill power traverse mechanism. The Browning mount was modified so that it followed the main gun up to the point where it grounded and then remained static whilst the main gun went on to it’s full elevation. Although this limited the elevation of the co-axial m/c gun, the degrees of elevation was considered adequate. To standardize ammunition, the lap machine gun, also a Besa The gun was now fitted and ready to fire.

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