PROGRESS IN TURBINE SHIP PROPULSION. 83 



gears. Nothing could remedy that until a Lanchester damper was put on, about Si/^ or 6 

 inches in diameter, after which all the trouble immediately disappeared. 



The trouble in that case was apparently due to the fact that it was a seven-bearing and 

 not a three-bearing shaft, because in a three-bearing shaft the torsional vibrations would 

 be of a higher period and would not interfere. In the seven-bearing shaft the period is low, 

 being about 1,400 revolutions, and it was immediately and entirely chocked by the Lan- 

 chester damper. 



I would like to know what has been done so far to ascertain that the failure of the geared 

 drive is not due to this torsional vibration. Should this actually be the fact, the natural 

 remedy would probably be in applying some f rictional device similar to the Lanchester dam- 

 per in practically the same way as described above. Of course a great deal O'f vibration may 

 be due to sloppy balance. It then can be remedied only by careful balancing, but in re- 

 gard to torsional vibrations it is of importance, first, to establish their presence, numerically, 

 and then to take them out. Can Mr. Emmet give us any information on that subject? 



Mr. Em'met.' — In reply to Mr. Akimofif's question, I cannot say whether torsional vi- 

 brations of shafts do or do not play a part in these gearing difficulties. Very marked dif- 

 ferences have been observed between conditions in s'hips in which the machinery is for- 

 ward and those in which the machinery is near to the propellers. With gears of the Alquist 

 type in which the engagement between gear and pinion is a flexible, or, so to speak, an elas- 

 tically compressible one, it would seem possible that torsional vibration might be a contribut- 

 ing factor which has not yet been considered or observed. If such torsional vibration was 

 discovered in propeller shafts connected to Alquist gearing, a cure might be somewhat incon- 

 venient, but I feel sure that it would be possible. 



Mr. Ernest H. B. Anderson, Member (Communicated) : — This paper is of special 

 interest to the members of the Society, largely for the reason that this form of ship propul- 

 sion is at the present time receiving a great deal of criticism owing to breakdowns, most of 

 which have taken place in the gearing, rather than with the turbines. 



A feature of the paper appears to show that geared turbine marine installations can only 

 be a success provided that gears are built having a patented device which is manufactured 

 solely by the company with whom the author is associated. 



The author refers particularly to Sir Charles A. Parsons exploiting a design of gear 

 in 1910 which has rigid bearings, and it may be of interest to add that this so-called exploit 

 is to-day the pioneer mechanical reduction gear installation for a very large fleet of vessels 

 consisting of freighters, passenger vessels, transatlantic liners, cross channel craft, and for 

 every type of war vessel afloat. 



On the other hand, no marine development of geared turbine installations took place in 

 this country until 1915. In the summer of this year (1915) the U. S. T. B. D. W'adsworth 

 completed official trials and was placed in commission. This vessel was built and engined 

 by Bath Iron Works, Ltd., of Bath, Maine, and the ship now stands first in the Navy as 

 regards economy of fuel for propelling purposes, reliability in service and saving of ma- 

 chinery weights. 



Further, it was this vessel that led the first flotilla of American destroyers that crossed 

 the Atlantic in May, 1917. 



Plate 3 1 shows curves, giving particulars of gear tooth pressures in relation to pinion di- 



