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The Leach Trench Catapult explained


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The Leach Catapult Explained

In October 1914 a gentleman by the name of Claude Pemberton Leach of South Kensington presented his machine to Louis Jackson of the War Department for evaluation and approval. He claimed that it could throw a golf ball nearly 200yds. Sadly such a limited performance would not bring the German army to its knees. A jam tin bomb weighed more than a golf ball, and 200yds was only just acceptable. Jackson must have seen something in the basic device and suggested to Leach that he improve the strength and durability of the catapult and the rubber bands that powered it. Mr Leach promised to return when he could reach 200yds with a 2lb bomb with a relative degree of accuracy.

Mr Leach must have decided that he needed professional help as he went with the contraption to Gamage’s “Cycling, Sports, and General Outfitters”. The result was that eight months later, on 22nd May 1915 they applied for a patent together which was granted as Pat No 7710/15. As Gamage’s were a co-patentee this must imply that they made a significant improvement over Mr Leach’s basic model. It would appear however that the catapult was already in use in France before the application of the patent, but it would also seem that Gamage’s were the manufactures

The final version was 7 feet in length and shaped much like a child’s catapult. The motive power was by between 6 to 12, ½” inch diameter rubber bandsper side individually lashed to the hornes of the frame by ropes passing through holes in the horns, and through worsted tape loops at the ends of each band. The bands are attached to the canvas pouch by shackles. the Pouchhas an arrangement of wire rope for strength and a loop at the rear to attach the trigger mechanism. This is a simple trip mechanism, as used in boat-yards to this day. The cable to the rear of the trigger is drawn down the length of the machine, and around a pulley to the underside, where the winch is attached. On the originals this was a very nice gunmetal yacht winch that must have accounted for most of the £12 cost of the contraption. A simple crank handle winds the winch, drawing down the cable, trigger, and pouch. These pass over a painted scale along the length of the main beam, to allow for a consistent repeatable amount of pull. There is a simple brass pointer inclinometer on the side of the main beam to set the catapult at its optimum angle of 42 ½ degrees. The bomb is placed in the pouch just as weight is applied. The pouch then grasps the bomb as it is drawn down. The catapult is then aligned with the target and the amount of pull required guesstimated. With bomb primed and pulled to the required strength, the fuse lit, the trigger is then struck with an entrenching tool helve, and the bomb flies off in a beautiful rainbow arc to its target. That’s the theory, in practice the unvulcanised rubber bands can stretch or break, the bomb can hang up in the pouch and remain dangling at the end of the catapult, or the bomb can fly off in a strange direction. Remember the catapults were supposed to be worked from the support trench, and shoot over the front line. With my working replica I certainly have had a bomb (sand filled Army sock) hung up in the pouch, but with a clean loose, I have found that the bomb will fly consistently and straight, and I can drop 80% of my shots into a trench width at the 30 to 40 yards demonstration range that we use at shows.

The catapult came into service early in 1915 and was a front line weapon for about nine months, although the poet Endmund Blundon found one to play with in 1916. About 300 were retained at home fore training, thus free up more effective weapons for frontline service. from one of the 300 the sole surviving example was taken and placed in the IWM.

I hope that is of interest, if you want any more I will post you a page about my replica…Gareth


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  • 14 years later...

Hello, I'd love to see photos of the replica. 

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Yes it's very original. The rubber bands are cracked and splitting with age. Wonderful example. 

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