The barrels were usually employed in groups of four – a hit from a single barrel could immobilize a vehicle but the narrow beam from each barrel meant a greater chance of a hit if four barrels were fired together. The barrels were buried in the bank obliquely, facing the enemy and with between one to four yards between each barrel. A length of 4” drainpipe was buried behind each barrel so the charge could be inserted when required. The greater the depth of earth and the tighter it was packed around the trap, then the better the trap worked, as more of the force of the charge was directed towards the end of the barrel. A minimum of two ft of earth above the rap and four ft behind was recommended. As a barrel was two ft in diameter and 3 ft long, a minimum roadside bank would be four ft high and seven ft thick. However the range varied greatly due to the density and wetness of the soil.
Above: Flame Fougasse
There were two types of Barrel Traps, each using standard 40 gallon drums. It was recommended that they be employed at not less than four barrels at each site. They had the advantage that they could be set up quickly provided a charge was already made up.
Demigasse – a charge was placed in a hole about 8” deep and 6” wide and the barrel rolled over the charge with its rear strengthening rib lying over the charge. When fired a sheet of flame and burning oil about 36 yards square was produced, the barrel being projected about six yards.
Hedgehopper – consisted of a drum standing on end either on the side of a road or concealed behind a wall or hedge. The charge was buried as for the Demigasse. The charge should not be closer than five ft to the wall/hedge it had to jump. When fired it jumped about 10 ft high and 10 yards horizontally and flooded the area it landed on with a sheet of flame.
Above: Left - Demigasse. Middle and right - Hedgehopper
Fougasses and Barrel Traps were widely installed by Commands. By May 1941 Commands had made demands for 30,000 barrels (which would require 800 tons of steel), 14,000 batteries and two million yards of cable. In June 1941 instructions were issued that each Chemical Warfare Group should hold a supply of 600 barrels for installation after any invasion began, as required by the tactical situation. As no further barrels were to be issued, Commands had to find the barrels from their existing stock. Eastern Command, which had one Chemical Warfare Group attached, had been issued with 6,000 barrels and so had to find 600 out this stock for the Chemical Warfare Group.
Home Guard Flame Throwers
These were similar to the static Flame Traps developed by the Petroleum Department, except that they were mobile and could be pulled or pushed by a team of five or six Home Guard. They were cumbersome weapons and only mobile in the sense that they could be stored centrally and moved to a position under threat; they were still essentially to be employed for the defence of a selected strong point or road block. Selected positions for the Flame Thrower should be prepared in advance.
The “Home Guard” Flame Thrower was a 50 to 65 gallon drum mounted on a car axle. It used a fuel of 40% motor spirit and 60% diesel oil. A pump was supplied along with approx 90 ft of 1½” flexible delivery hose. A section of 1½” steel pipe was attached to the hose, which had the jet attached. Ignition was achieved by attaching a small tin can to the jet which would throw out one or more small spray jets into the can, which when lit remained alight and so kept the main jet alight.
Above: The "Home Guard" Flame-Thrower
The Harvey Flamethrower consisted of a 22 gallon cylinder filled with creosote and was mounted on wheels. A 25 ft flexible hose fitted with a nozzle was connected to the cylinder. It could throw a jet of flame to a range of 50 yards with a full cylinder, the range decreasing as the cylinder emptied. Harvey Flame Throwers were certainly issued to some Home Guard in Suffolk from 1941.
Above: The Harvey Flame-Thrower