THE newest type of tractor now being used by the Institution is a develop- ment of the 95 b.h.p. Challenger III diesel crawler tractor made by Messrs.

John Fowler and Company (Leeds) Limited.

The standard Challenger tractor has had to be adapted by the manufac- turers to meet the special needs of the Institution. It has to be powerful enough to haul a life-boat and carriage weighing up to 14 tons over various types of terrain, including soft sand and deep shingle. It has also to be capable of pulling the life-boat and carriage up gradients of 1 in 4 and to hold them by its brakes on these gradients. The haul down to the water at low tide at certain stations may amount to several miles.

The tractor must be capable of operating continuously at full power in water up to a depth of seven feet.

For this reason the engine has had to be completely encased so that it can run for considerable periods without the circulating water overheating. To allow access to the engine for mainten- ance the side casing has been fitted with portable watertight panels or side doors.

The tractor has been made com- pletely watertight, so that if it becomes bogged down in sand or mud on a rising tide it can be recovered at the next low tide. This has been done by fitting circular brass rubber-seated valves to the air intake and discharge ports, which can be quickly shut in emergency by turning a hand-wheel in the driver's compartment.

To prevent the engine from being damaged by, for instance, water which might be sucked in if the valves did not close properly, and also to prevent a vacuum being created in the engine- room, an automatic stop device has been incorporated in the mechanism.

The tractor develops a draw-bar pull of 21,100 Ibs. through its six- speed gear-box, and is also fitted with a specially designed winch which would enable it to exert a maximum pull of 38,500 Ibs. at its lowest possible speed.

This is necessary, particularly for inch- ing the boat back on to its carriage.

Steering is by means of a vertical hand-wheel on a marine type steering column in the centre of the driver's cockpit. This column not only oper- ates the brakes, but withdraws the clutches when the tractor is being manoeuvred. A partial turn of the steering-wheel de-clutches the drive on the inner side of the turn while the outer side continues to drive. In this way direction is altered. A further turn of the wheel applies the brakes more strongly on the inner side, and the tractor then turns in a smaller circle by pivoting on the inner track.

The engine speed control is operated by levers to the fuel pump mounted on either side of the steering column.

A powerful hand-brake is provided for emergency stops and for holding carriage, boat and tractor on steep inclines.

To allow the driver to have full control of his tractor when his cockpit is submerged, extended clutch and gear levers have been fitted.

When launching, the tractor hauls the carriage and boat across the beach to the water's edge, where it turns the complete unit until the boat faces the sea. The tractor uncouples and moves round to the rear, where it pushes the carriage and boat into some three feet of water by means of a specially de- signed front buffer-plate. Two ropes secured to the tractor and rove through pulleys on the front of the carriage are passed to the stern of the boat, where they are attached tosliphooks. These form the launching falls. When the tractor is reversed these ropes are pulled taut, and the tractor then ejects the life-boat from the carriage into the sea, where, with its engines going full speed, it carries on under its own power..