Here's a short history of Allen Trenchers.
John Allen of Oxford started to produce trenchers to the designs of the American " Parsons Co." in 1933.
Below are two pics. of the original 1933 model which was the predecessor to the 16-60 of the 1940s/50s.
These were powered by a 38 hp. petrol engine and would dig to a depth of 14 ft. Side cutters to the buckets allowed trench widths to be varied between15.1/2 and 42 inches.
The boom could be moved across the machine to allow trenches to be dug centre or to either side and the transverse discharge conveyor could be moved and reversed to dump to either side.
The telescopic boom was lifted in and out of work and held against the dig by cables and worm drive winches all functions were controlled from one operating position.
Available digging speeds from 11" to 139" per min. were controlled through a gear box from the driving position and travel aped was 1.66 mph.
Allen's also introduced a small model in 1933 for trenches 4ft. deep and 6" to 12" wide. I have no details of that machine.
Details of later models to follow in next post.