THE problem of finding the ideal method of providing a life-boat with mechanical power has occupied the minds of de- signers and engineers for more than a century. For many years experiments were made with steam. At the Great Exhibition of 1851 a model of a steam life-boat which was entered in the com- petition for the Duke of Northumber- land's prize was shown.

Steam Life-boats In 1886 the Committee of Manage- ment appointed a special committee to inquire into the practicability of using steam power in life-boats. The first order was placed in 1887 for a steam life-boat, although the method of propulsion was that of hydraulic ejection, in itself a forerunner of the Hotchkiss principle, later used by the Institution.

Steam Jife-boats had only a limited success, for many of the difficulties which they inevitably presented were found to be almost insurmountable.

Writing in 1874, Richard Lewis, who was then Secretary of the Institution, pointed out very rightly that the heavy seas which a life-boat would often ex- perience would prevent air from being drawn in for the fires; and as a result, engines would be disabled. Moreover, there would always be difficulty in find- ing men with sufficient skill to work these engines among the fishermen and long-shoremen who formed the bulk of the crews.

The Petrol Engine It was in 1904 that an internal com- bustion engine was first installed in a life-boat. The experiment was not an immediate success, and it was not until 1910 that a boat fitted with a Blake motor made a passage of 538 miles in 11 days without any serious mechanical trouble. In the same year another boat, fitted with a Tylor engine, made a passage of 425 miles in 4 days without mechanical trouble, and from then on- wards it became increasingly clear that the internal combustion engine provided the ideal method of driving a life- boat.

The petrol engine, although initially cheaper to make than the diesel engine, has a much higher fuel consumption for the same horse-power. It had been found that buses fitted with diesel en- gines were able to travel twice as far as those fitted with petrol engines, with the same fuel consumption. Diesel fuel was also cheaper, and because it is less volatile and inflammable, the risk of fire was greatly reduced. In short, apart from the higher cost of the engines in the first instance, it was clear that the diesel engine would be in every way more suitable.

Introduction of the Diesel Engine During the last half-century there have been many developments in the design of life-boat power units, but none has been more important than that of the use of diesel engines.

The first life-boat with a diesel engine was the Yarmouth boat, into which a single six-cylinder cell-type engine of the Ferry Engine Company's design was fitted in 1932. This boat gave good ser- vice, both at Yarmouth and while she was in reserve. The fitting of this engine gave an opportunity of comparing two boats at approximately the same time; the Yarmouth boat and the Portpatrick boat, which was fitted with CE.4 petrol engines of equal horse-power. The Yar- mouth boat could continue at full speed for 118 miles, using 29| pints of fuel per hour. The Portpatrick boat could continue at full speed for only 57 miles, with a fuel consumption of 64| pints per hour. At a cruising speed of 7| knots, the difference in petrol consump- tion, and therefore radius of action, was even greater.

The single six cylinder cell-type diesel engine was followed by the development of handed and watertight four and six cylinder engines, and the Institution has now as many as 122 of these engines in service.

The Small High-Speed Diesel Up to the recent war, most diesel engines for boats were modifications of the bus engine, ranging in horse-power from 40 to 60 and weighing close on a ton. For our smaller class of life-boat, it was clearly desirable to have a high- speed, lightweight type.

The only diesel in this class which would conform to our weight limitations was the Admiralty Coventry Kadenacy four cylinder supercharged two-stroke engine, developing 50 h.p. at 2,000 r.p.m. This was modified and made watertight and manufactured in a three- cylinder version to suit R.N.L.I. require- ments, developing 20 h.p. at 1,600 r.p.m.

For those not conversant with the Ka- denacy principle of aspiration, perhaps a brief description will not be out of place.

The essence of the principle developed by the Frenchman Kadenacy is that for a given swept volume much higher compression pressures and thus more power are obtainable. It works as follows:— Products of combustion in the cylinder under pressure, having done most of their useful work, are suddenly released or exhausted. There follows a vacuum in the space previously occupied by the exhaust gas. If the inlet ports are made to open at the precise moment when the vacuum is created, the incom- ing air will rush in at increased speed, and if the ports remain open long enough a natural supercharging effect or build-up of pressure will result, with consequent increase in compression and thus of efficiency.

Perkins Engines The first of the FKR.3 engines was fitted in the Rhyl life-boat in 1949. It has given good service ever since and there are now 24 life-boats fitted with these engines in operation.

The advent of the 37-ft. larger self- righting boats, with the need for greater horse-power, has necessitated the fitting of a Perkins P.4 43 h.p. engine, running at 2,000 r.p.m., instead of this Kadenacy engine. One boat at Scarborough is so fitted and has given excellent service, and two new boats recently built for Sheringham and Weston-super-Mare are similarly fitted.

Since this Perkins diesel engine is not fitted with hand starting, to provide an alternative method in event of the battery failing a Bryce Berger hydraulic starter has been incorporated.

This has for its operation the sudden displacement of a piston moving a rack coupled to the crankshaft. The hy- draulic pressure necessary to operate this device is pumped into an accumu- lator by hand. In the Sheringham and Weston boats a power-operated pressure pump has been incorporated, as it is impossible manually to pump to any high pressure at sea to recharge the accumulator in the event of the eng- ines failing to start with original pres- sure.

Commercial Engines: The Gardner Diesel Late in 1950 the Committee of Man- agement gave deep consideration to the possibility of fitting commercial engines into life-boats. The problem of cost, simplicity of maintenance and ready availability of spares influenced the decision which was eventually taken.

It had also become clear that it was extremely difficult to maintain engines in a completely watertight state, and that certain items deteriorated rapidly.

It was apparent, too, that there would be advantages in adopting an engine in daily use in the commercial world which had survived the fierce tests of competi- tion and which was made in a wide range of horse-power and cylinders, all with standard parts easily obtainable, and of proven long-running life and reliability.

In 1954 a new type of life-boat, fitted with two 4-L. W. Gardner diesel engines, was sent to Coverack. A boat of a simi- lar type was later sent to Troon. Since then, all 42-, 47- and 52-ft. boats have been fitted with Gardner engines, which have proved themselves extremely satis- factory in all respects for life-boat work and conditions.

As in all matters connected with the construction and design of life-boats experiments continue, but there is now no room for doubt that the policy of fitting commercial diesel engines has been a momentous and outstanding suc- cess and will result in a marked financial saving in running and upkeep..