A CRANE MOVED into the boatshed at William Osbornes one day last autumn to lift first the twin engines and then the superstructure aboard the 37ft 6in Rother class lifeboat which will be RNLB Shoreline.

The engines are twin Ford 2712E four cylinder 4.165 litre marine diesels developing 52 SHP at 1,750 RPM and they are fitted with 2:1 reverse reduction PRM gearboxes. These engines are supplied in handed pairs, one with right-hand rotation for the starboard side, and one with left-hand rotation for the port side. Thus the starboard propeller will be turned clockwise and the port propeller will be turned anticlockwise so that when both engines are running at the same speed the opposing torques of the two propellers will coun- terbalance each other. The bias of the torque, or twist, of each individual propeller can, of course, be used to advantage when the boat has to be manoeuvred in a confined space.

Before the engines are lifted aboard, the bearing pads on which they will be bedded down are machined so that the engines, when put in place, will automatically be aligned with the shaft coupling. Each engine is bolted in its position through the bearing pads with four 'Ain bolts, two on each side.

Now the aluminium superstructure can be lifted aboard. It is fitted down over the wooden forward engine room bulkhead and faired to the deck sheer; then it is bolted in place with aluminium angle.

Within one day the building of the lifeboat has suddenly made an impressive move forward and work which had been waiting until these important members were in place can now go ahead; the fitting, for instance, of the after engine room bulkhead (aluminium); the fitting of pipework such as the exhaust, closed water cooling and fuel systems; the fitting of the engine controls; the fitting of toughened glass windscreen and windows; on deck the fitting of stanchions, guardrails, capstan, searchlight socket . . . and so it goes on.

The diagram (left) shows the steering system, which is also being assembled at this time. The steering wheel is mounted on a pedestal which in turn is mounted on a support taking its weight right down to the centreline structure of the boat, thus ensuring complete rigidity. As the wheel is turned to port or starboard, its rotation is transmitted through two pajrs of bevel gears to the vertical intermediate shaft and on via the tail shaft and steering gearbox to the rudder.

Movement of the boat's hull in a seaway would make the working of the entire system very rough if it were not for the flexibility of the connections between the pedestal and the gearbox.

This is achieved by universal joints and a spherical bearing where the intermediate shaft passes through the end box bulkhead. The tail shaft is also splined at its lower end, allowing a limited travel of the universal joint along it.

The rudder is mounted on a square shaft on which it can be raised and lowered by means of tricing lines. It is raised to avoid risk of damage on slipway or carriage when the lifeboat is launched or recovered and lowered as soon as there is enough water under the beat as she gets away from the beach after launching.

(To be continued).