Sherman Crab Mark II Walkaround

The “Funnies,” the specialized armoured vehicles which Britain developed for the invasion of France, are legendary for their ingenuity and plain coolness. One of the more famous vehicles in the family was the Sherman Crab, a mine-clearing tank that used a huge flail to beat the ground in front of the tank. We are lucky to have an example of the Sherman Crab here at the CFB Borden Military Museum. Although it has been stored outside for many years, the vehicle at Borden, a later Mark II variant, is in fairly good shape.

Most, if not all, Sherman Crabs were built on the M4A4 Sherman V chassis, presumably because the Chrysler multibank engine generated sufficient power to divert to the flail. The longer hull of the Sherman V, along with the nose-down attitude brought about by the considerable added weight of the mine-clearing equipment.

The business end of the Crab. The huge drum on the front had 43 chains with weights on the end and cutters on the end of the drum to deal with barbed wire or other potential entanglements. The drum rotated at 142 rpm and would churn up huge amounts of dust and debris when engaged. While flailing, the Crab could move at approximately 1.25 mph.

Some details of the very substantial bow mounting for the flail can be seen here; behind the main cross tube can be seen a heavy blast shield, designed to protect the vehicle from the force of exploding mines. Like most Sherman Vs, this vehicle has a 3-piece transmission housing. The dirt buildup in the track chevrons is noteworthy.

Along the right side of the vehicle, behind the mounting for the flail arm, is one of the standard British spare track stowage racks. The construction of the cuff-type steel chevron track can be clearly seen, as can the various weld seams on the hull. Note how the arm is attached to one of the hull appliqué armour pieces.

Prominent on the rear are the station-keeping light arms, which allowed troops and vehicles following the Crab to be able to see it through the dust kicked up by the tank. Missing from this tank are the large slanted bins which were on the rear hull sides of Crabs that dropped lighted poles to mark the cleared path.

This photo shows details of the rear hull. The engine access doors are in the centre, with stops on either side to prevent them from hitting the idler mounts when they are opened. Below the left door is the mount for a moveable arm that held a towing clevis; the arm itself is missing. On the right door are dispensers that would release smoke grenades behind the vehicle.

Looking up the Crab’s skirt, so to speak, a number of interesting details are revealed. The upper bracket for the towing clevis arm is visible in the centre, with the cable that connected the smoke grenade rack controls to the fighting compartment just behind that. The exhaust louvres fill up the rear hull overhang. Unusually, this vehicle has portions of the rear fenders still attached, visible over the tracks.

Along the left side of the engine deck are brackets for securing the station-keeping light arms. Some details of the turret casting can also be seen, as can the distinctive bulge in the engine deck that gives this tank away as a Sherman V. The shield over the bulge (perhaps to protect the radiator cover from debris) seems standard for Crabs, but not for ‘normal’ Sherman Vs.

This view down the right side of the vehicle emphasizes the nose-down aspect of the Crab. Prominent on the right side of the hull, just forward of the spare track link stowage, is the armoured box covering the power takeoff for the flail; inside the vehicle the drive shaft is modified so that power is diverted directly from the engine to the flail via a pair of bevel gearboxes inside the armoured box on the outside. The shaft that goes from the PTO to the drum itself can be seen entering the upper portion of the arm. Below the arm can be seen a hydraulic ram for raising and lowering the flail. The flail is in the elevated travelling position on this vehicle – in action, the arm is basically parallel to the ground.

The left side of the vehicle shows that this is a Mark II Crab. Instead of another hydraulic ram on this side, there is a pair of weights, which help to automatically maintain the height of the flail above the ground. Unlike the earlier Crab Mark I, where the flail could not compensate for uneven terrain and hence could miss striking mines in a depression, the Crab Mark II was designed to keep the flail drum a constant 4 feet 3 inches above the ground. On the lower portion of the arm can be seen a deflector blade, intended to keep wires from fouling the tracks; one was fitted to the bottom of each arm. The long stowage box normally seen on rear of British Shermans is on the hull side, where an open rack for stowing spare flail chains would normally be. Perhaps the spare chains were stowed in this box? The special hooded covers on the drivers’ periscopes, necessary to protect them from flying debris, are also visible here.

Our final photo gives a good overall view of the right side of the vehicle. Of note is the fact that the turret appears to be fitted with a British-designed Mk II vision cupola. While the cover itself is missing, the fittings for a canvas mantlet cover, necessary to keep dust and debris out, can be seen around the mantlet.

Modelling options for the Crab are rather limited right now. Resicast has a resin conversion for the DML M4A4/Sherman V to make a Crab Mark I, while Airfix has announced a 1/76 scale Crab that will, presumably, be based on their ancient M4/Sherman I kit; hence, it will not be an accurate representation of the Crabs used in combat. Perhaps the pieces could be adapted to fit the Matchbox Firefly Vc to make an accurate braille-scale Crab.