1911] on Recent Advances in Turbines. 97 



We mentioned before that de Laval had in the 'eighties introduced 

 helical tooth gear for reducing the speed of his little turbines. For 

 twenty-three years it has worked well on a small scale. Recent experi- 

 ments, however, have led to the assurance of equal success on a large 

 scale for the transmission of large powers of many thousand horse. 



After some preliminary experiments some years ago on helical 

 reduction gear, which showed a mechanical efficiency of more than 98 

 per cent., a 22-feet launch was constructed in 1897 ; the working 

 speed of the turbine was 20,000 revolutions per minute, which was 

 geared in one reduction of 14 to 1 on to the twin-screw shafting 

 driving the propellers at about 1100 revolutions. The speed attained 

 was 9 miles per hour, and this little boat was many years in use as a 

 yacht's gig. 



The next step was the purchasing of a cargo boat in 1908, the 

 Vespasian, of 1350 tons displacement, and triple expansion engines 

 of 900 horse-power. After thoroughly overhauling and testing her 

 existing machinery for coal and water consumption, the engines were 

 replaced by geared turbines, the propeller, shafting and boilers 

 remaining the same. On again testing for economy a gain of 15 per 

 cent, was shown over the original machinery, and subsequent minor 

 alterations have increased this gain to 22 per cent. There are two 

 turbines, a high pressure and a low pressure, each driving a pinion at 

 1400 revolutions, gearing into a main wheel on the screw shaft making 

 70 revolutions per minute. The gearing is entirely enclosed in a 

 casing, and is continually sprayed with oil by a pump. Ordinary 

 centrifugal governors on the turbines control the speed, and because 

 of the enormous angular momentum of turbines (some fifty times 

 that of an ordinary marine engine) the acceleration is so slow that the 

 governors have time to act, and consequently no racing has ever 

 occurred in the heaviest weather, and it is certain that if geared tur- 

 bines come into use there will in their case, as in other turbine vessels, 

 be no more cases of broken screw shafting as has hitherto been 

 common Avith reciprocating engines. 



The vessel has now been carrying coal from the Tyne to Rotter- 

 dam for about a year, and has covered about 20,000 miles and carried 

 90,000 tons of coal across the North Sea. The pinion on the lecture 

 table was specially removed from the vessel last week for this lecture, 

 and shows a wear on the teeth of under to^oq- i^- i^ this time, and 

 its life will therefore be equal to or greater than that of a vessel. 



Gearing promises to play an important part in war vessels for in- 

 creasing the economy at cruising speeds. We explained the difficulty 

 in obtaining good, economy at the high-pressure end of marine tur- 

 bines, and in replacing such portions by geared high-speed turbines 

 we have a complete solution. The Turbinia Company are now con- 

 structing two 30-knot destroyers of 15,000 horse-power, wherein the 

 high-pressure portion and cruising elements are geared in the ratio of 

 3 to 1 and 5 to 1 respectively to the main low-pressure, direct-coupled 



Vol. XX. (No. 105) h 



