Cat D4 Modified Caterpillar Tractor
Photograph is courtesy of Jim Christie, Crook of Devon, a former senior mechanical engineer in the Forestry Commission.
This unmistakable machine with super wide track plates may have been the only one of its type in GB. From memory the overall width was just over 12 feet in old terms. The drive shafts and cross members fixing the track chain carriages would have all been extended. The driver for most of its ploughing life was Donnie Junor from the Black Isle. The machine was designed to operate on flat peat ground and almost all of its operations were in Caithness and Sutherland in the forests (at that time) of Rumster, Naver and Shin.
The plough was similarly modified by having a larger cross section main beam but in lighter gauge steel and had large terra tyre type wheels added. The other significant advantage of the track plate and tyre design resulted in far less surface damage and allowed the machine to pass over soft terrain and not tear the surface vegetation matt and expose the soft wet peat mass below. See Picture No 2797
Note the apical track plates which enabled the machine in turning to skid around more easily and cause only limited damage to the surface vegetation. Additional steel extension wings were added to both ends of the apical track plate resulting in a total overall length of around four feet. These additional wings were very vulnerable to deformation on stone and rocky ground.
The machine was normally used for ploughing with a double furrow plough but was also used occasionally with a second machine to cross drain in more rolling terrain where water was often trapped in the hollows. On side slopes it did have a tendency to slip sideways were easily and not ideal.
Transport by lorry from site to site was also a bit of a performance and at that time required a police escort which was often time variable and they liked to move the convoy quite fast. Not ideal on some of the narrow single track roads. Martin Mackenzie as one of main lorry drivers remembers these episodes well.
Can anyone give an exact date of this image and say where the modifications were carried out?
Groups: Forestry Mechanical Engineering Reports , Tractors Ploughs and Drainage Machines
Group: Forestry Areas - 3222 pictures
4 Comments
I think this tractor was sold some years ago to a chap from Burnley. He was a crawler tractor and plough enthusiast who had a collection of several interesting machines.
The tractor was collected by him from the Forestry Commission Longman workshop and from memory the track plates had to be removed to reduce the width for transportation. I think I have a photograph of it prior to sale and it looked a fairly sorry sight.
I will see if I can find the photo and put it on the web site. Comment left on 21 March 2022 at 10:23 by David McQuillan