Panjandrum folly

Britain’s greatest mistake was one of the most spectacular follies of the entire war. It was a secret weapon that was doomed to fail from the start – the giant Panjandrum. This was to be a large explosive wheel that could roll up the beaches and destroy German fortifications on the coast of Normandy, France. The unlikely name came from the theatrical writings in London of Samuel Foote in 1754: ‘The grand Panjandrum himself … playing the game of catch-as-catch-can till the gunpowder ran out at the heels of their boots.’

In construction it was to be a pair of large wheels, each some 10ft (3m) in diameter and with a tread around the periphery about 1ft (30cm) in width. In the middle, at the hub, there was to be a substantial explosive charge fitted with a fuse that would detonate on impact. Around the rim of the two wheels would be cordite rocket charges that would spin the whole device up the beaches of northern France during the Allied invasion. In use, it would look like a pair of Catherine wheel fireworks.

The original idea was approved by the British Royal Navy’s Directorate of Miscellaneous Weapon Development based on rough sketches prepared by a Combined Operations group-captain. In August 1943, at Leytonstone in East London, construction of a prototype began. Within a month it was ready for testing. Let us step back and examine the idea in principle. At once a serious defect in the design becomes apparent. If the wheels were propelled forwards by rockets that burned only when facing to the rear, it would be driven along at increasing speed like any other reaction-propelled vehicle. This dramatic concept of the rocket-propelled weapon was no doubt what immediately appealed to the designers. But think about it: the Panjandrum was not a reaction-propelled vehicle at all. The rockets burning around the periphery were going to exert their effects in turning the wheel – in creating torque, as an engineer would say – and it was the torque, rather than the backward thrusting rockets, which was going to drive the device forward.

There are clear differences between a reaction-propelled rocket vehicle and one driven by torque. For instance, if the number or power of the rockets on a reaction-driven trolley (where all the rockets point backwards) is increased, then the contrivance will go correspondingly faster. This is not, however, the case with the Panjandrum. In this case, more rockets, or an increase in their power, could well lead to an increase in torque but that might just as well manifest itself as wheel-spin, rather than forward movement. Half the rockets are pointing backwards, true; but half are directing their thrust forwards, against the direction of movement. This is what the experimenters were to find. If the number of the rockets was too low, the device would not be able to overcome the rolling resistance of the sandy beach. However, if the number and power of the rockets were substantially increased, then wheel-spin could set in. There was no means, as it were, of slipping the clutch as the giant wheels slowly gained forward velocity.

There was an added problem: the device was not a carriage fitted with wheels – rather, it was a large pair of wheels. It would have only to run over a relatively small object (like a rock) to tilt sideways and substantially change course. One or two such perturbations could cause it to change direction several times, with possibly drastic results.

The mathematics of all this is involved, though not obscure; and even common sense would show that the Panjandrum was unlikely to succeed. A wheeled mine, driven by rear-mounted rockets, might well have been practicable. It would have no problems of torque, and would tend to maintain its straight course, as any four-wheeled vehicle would tend to do. Furthermore the manufacturing technology, being more conventional, would have posed fewer problems. I can see several alternatives. One would be the trolley, as I have already said. If the wheels were really necessary, then it might have been feasible to mount the rockets near the hub, on gimbals fitted with weights that caused them always to point to the rear. Another design that could have worked would be to have had the rockets mounted around the edge of smaller wheels that were geared to drive the larger, outer wheels. That way, the drive wheels would be spinning round at speed, and reduction gears would have transmitted their energy to the main wheels, turning more slowly as they gathered momentum.

But to the minds of the Directorate, the uncomplicated image of a vast, rotating, fiery wheel spewing its way up towards the enemy fortifications was romantic, bizarre, frightening even; the practical problems did not commend themselves to anyone on the team. The prototype was constructed under conditions of the greatest secrecy. When it was finished, it was transported under the closest security to the West Country with a police guard, moving only under cover of complete darkness. Once it arrived safely at the seaside town of Westward Ho! in Devon the security measures were forgotten about and the Panjandrum was unveiled, ready for the tests. Local residents, even people on holiday, crowded round the device with bemused interest.

On its first run it was clearly underpowered. Had anyone calculated thrust values (assuming that the complication of torque did not exist) they would have seen that the rolling resistance of such a vast, heavy object against sand was going to be considerable. But they did not take this into account, and the first test run came to an ignominious end as the ‘secret weapon’ trundled down a ramp with its rockets feebly firing and rolled steadily to a dead stop. The plans had been for the Panjandrum to storm across the beach at up to 60mph (almost 100km/h) and the depressing exhibition the device gave of itself must have been profoundly disappointing. So the number of rockets was increased; and they were clamped to the inside edges of the wheels, as well as the outside. The next firing was a failure because of the excessive torque. Not only that, but one of the wheels sank into the sand which threw the vehicle off course, and several of the rockets broke free and zoomed crazily across the beach. The spectators looked on in astonishment and not a little fear.

To correct the instability was the next priority. But how could this be achieved? It was decided to try fitting a third, central wheel. It is fairly obvious that, on even slightly rough terrain, this would add to the instability rather than correcting it. The test that followed proved the point. The huge contraption ran a little way up the beach, powered by a total of 70 rockets instead of the original 18. It lurched to one side, then turned back on itself, ran back into the sea and fell on its side, the rockets boiling the water around. Other rockets became detached and flew off low across the sands. Clearly, the middle third wheel was not an improvement. It was found to have been bent and buckled after this test run, and was abandoned.

During the month of October 1943 further trials were arranged in which heavy cables were attached to each end of the hub and secured to two winches which could, it was hoped, steer the contraption safely up the beach. Of course, when the test was run the clouds of smoke and flame from the combustion of the rocket fuel obscured the direction of travel from the controllers manning the winches, and the increased drag from the cables was itself an added disadvantage.

There was yet another practical problem in the design that began to emerge. The breaking-up of the rocket units was clearly very dangerous, yet it was obvious that the rockets might disintegrate. They were designed, as rockets always are, to produce a steady backwards thrust and by being fixed to the periphery of the Panjandrum wheels they were being submitted to centrifugal forces for which they were never intended. These acted laterally against the casings and the force would become considerable when we consider the dimensions involved. A 20lb (9kg) rocket whirling on the edge of a large wheel moving at speed is clearly subject to lateral forces of considerable magnitude and the break-up of some of the rockets was clearly probable. Yet this hazard was also ignored, and was omitted from the design calculations.

A further test took place over an uneven surface. The wet sand was specially cratered for this trial run. After a distance of only 140 yards (about 130m) the wheels of the Panjandrum buckled, the winches seized and the cables became entangled; its trajectory this time had been a wild zigzag pathway across the sand, ending up with the giant device lying pitifully on its side, spent rockets still smoking. If any further evidence of the impracticality of this absurd contraption were needed, this surely was it. But no – development work continued, in spite of all the accumulated evidence. Two new prototype Panjandrums were constructed. They were ready early in the New Year and an official demonstration was arranged in January 1944. A number of senior government officials came to witness this latest test run and several senior members of the Armed Forces were also in attendance. It was to be an auspicious occasion.

The rockets on the first Panjandrum were successfully ignited and the monster began to roll forward. But within a short distance, the first rocket exploded violently and disintegrated, soon to be followed by others. The great wheel, as it gathered speed, began to weave dangerously from side to side and then erratically to change direction. It was completely out of control, and began to head straight towards a group of terrified photographers. The VIPs leapt behind a sand-dune and fell into a tangle of barbed wire. The roaring device turned again, headed down the beach back towards the sea, then in a cloud of smoke and a series of explosions it crashed heavily on its side. Rockets broke away and screamed across the beach in all directions, at least one being vainly pursued by a holidaymaker’s dog. All that remained of the secret weapon was a scorched and twisted hunk of metal beneath a lingering cloud of black smoke.

So, at last, the project was terminated. All the scientific and engineering data should have shown that it could not work. Even a cursory examination of the elementary physics involved would have shown that it was doomed from the start. The cost of the project is unknown, but was clearly considerable, and the wastage of time was immense. At the time, a financial saving, or the release of a few thousand man-hours, would have been of the greatest value to the war effort. Householders were giving up their kitchen saucepans in order to supply light alloy to the aircraft industry and railings were being torn up and melted down to make steel sheet for weapons manufacture. To have these resources diverted to the Panjandrum project was unjustifiable.

This was not the last we heard of the wasteful Panjandrum fiasco, however. It has re-emerged in more recent times. A lightweight reconstruction featured in the BBC’s wartime comedy series Dad’s Army, first broadcast on 22 December 1972. This episode featured the many problems that befell the device, and paralleled the original trials in some ways. The only time a Panjandrum ran successfully was in 2009 when a 6ft (1.8m) diameter replica was constructed to mark the 65th anniversary of D-Day. Like their wartime predecessors, these designers also envisaged that it would speed along the beach, heedless of the problems caused by the question of torque and the backward pointing rockets. It was ignited in a ceremony for the Appledore Book Festival in Devon, and ran down a small ramp. Although it worked to a fashion, the model trundled for several yards, mostly moving at walking pace, before it slowed to a halt and its rockets burned out.

And so attention turned to designing an explosive landing craft. It was planned that this could deliver a load of explosives to breach a protective Atlantic Wall of concrete and allow the Allied troops through to the plains of France. It was being argued privately, that – even if the Panjandrum had delivered its load of explosives – they would not have exerted the desired effect. To give full benefit, an explosive charge would have to be clamped firmly against the wall. The blast would otherwise be dispersed and dissipated as it produced a huge crater in the sand. The proposed landing craft were designed with hydraulic rams which would provide the desired result – they would extend to force the explosive charge firmly against a concrete wall, maximizing its effect.

The vehicles chosen were Alligator landing craft made in the United States. They were based on the amphibious DUKWs vehicles but had caterpillar tracks instead of conventional wheels. Attached to the tracks were spoon-shaped paddles which propelled the craft through the choppy seas until it came to land, when it would rise from the water and proceed up the beach like a conventional tracked vehicle. The Directorate planned to fit each craft with a 1-ton bank of high explosive mounted on a mattress base; this – on contact with the concrete wall – would be firmly clamped in position by the hydraulic rams and automatically detonated.

The Alligator itself was a formidable device. Each was 26ft (10m) long overall and more than 10ft (3m) wide, weighing about 11 tons. But once in the water they were cumbersome and slow, and under sea trials they ran into repeated problems of instability that are reminiscent of the Panjandrum tests. On one occasion the hydraulic ram mechanism was actuated while the craft was still at sea. Its 1-ton mattress of explosive, ballasted with sand, tilted the whole contraption upwards at a crazy angle and a serious accident was narrowly averted. The Alligator took with it more casualties than its fiery predecessor had done as it spiralled up the beach.

As with the Panjandrum, eventually someone realized that they were unlikely so succeed with this project and the Alligator too was cancelled. It was just as well. Both devices were being specifically designed to blast through an impenetrable wall of concrete behind which the Germans would be hiding. But, as intelligence showed (and as the Allied landings would confirm), the concrete wall simply did not exist. The Germans had never thought to construct an impregnable wall, and the Allied strategists had been developing weapons against a target that had never even been built.

There was one final attempt to use rockets as a secret device for the Normandy landings that would aid the Allies, and intimidate the Germans. This was a novel idea: to drop containers of vehicles and equipment from low-flying bombers, using retro-rockets to slow the descent and cushion their landing on the beaches of Normandy. The Army proposed this novel idea to the Admiralty’s Directorate of Miscellaneous Weapon Development, who had been working on parachuting equipment during the invasion. Using parachutes to drop heavy equipment was no problem, but the relatively heavy impact was causing damage. Surely a retro-rocket assembly could cushion the landing. The preliminary designs seemed perfectly satisfactory, and the device was code named Hajile.

The idea was to set off a battery of rockets when the container was a few yards from the ground. Solid-fuel rockets could not be relied upon to ignite at exactly the same time, and early tests showed – when the smoke had cleared – that the container was often left crunched into the ground. It was decided that it would be safer to carry out some tests over the open sea, and the site chosen for the observers was the holiday pier at Weston-super-Mare, which was designated HMS Birnbeck during the war. It was decided to drop a large container, fitted with its retro-rockets, from a Lancaster bomber but the pilot’s aim was not accurate and the horrified technicians realized that it was heading straight towards the buildings. They ran back along the pier, just in time to avoid the container as it crashed through the roof and demolished the workshops.

There were plenty of other tests. One of them involved dropping containers from a tall crane. On the second attempt, the container hit the ground just as the rockets fired with a massive roar – this propelled the container back up into the air, where it smashed into the jib and demolished the crane that had dropped it. Several of these containers were built for the D-Day landings, but the device was never formally commissioned and remains a peculiar sideline to the war effort. The only remaining secret was the strange name given to the device: Hajile. Unlike Panjandrum, it seems to have no meaning at all, but its roots lie in the Old Testament. Elijah is said to have ascended unto heaven in a pillar of fire, remember?

Suddenly, all is clear: Hajile in simply Elijah in reverse.

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