NO. ^ UNia.KV MKMOIH ON MECHANICAL ll.h.HI 17.") 



the engine shaft. Since (he efficient transmission of power through bevel gears 

 requires that they be verj accurately placed with reference to each other, and 

 maintained very accurately in tins position while they are at work, it was nec- 

 essary to make the transverse frame very rigid, especially at its extreme ends. 

 This was accomplished by the use of what were called " propeller shaft bed 

 plates." They are designated by the numeral 27 in Plate 54, and are shown 

 in detail in Plate 58 as of a very deep [-beam section, having very narrow 

 flanges top and bottom, the web of the I-beam furnishing the strength in a 

 vertical direction, while sufficient stiffness laterally was obtained from the flanges, 

 assisted by the brace tubes, which acted as struts between the bed plates and 

 the main tubes of the transverse frame. These struts, while very light, added 

 enormously not only to the lateral stiffness of the propeller bed plates, but 

 furnished for a minimum weight a maximum prevention against twisting of the 

 plates. The propeller-shaft bed plates were originally planned to he made 

 of sheet metal with the flanges brazed to the web. But at the time thai they 

 were constructed the pressure of the work was so great in the Institution shops 

 that it was found necessary to have some of the work done outside, and the 

 parties who undertook the construction of these bed plates were unwilling to 

 attempt to braze them up, and accordingly worked them from steel forgings 

 made for the purpose. The expense of this plan of construction proved la rue 

 and unnecessary, as both previous and later experience proved that it was not 

 only practicable to braze up bed plates more complicated in their design than 

 these, but that equal strength for equal weight could thus be obtained for less 

 than one-quarter the cost of constructing them from solid forgings. Further- 

 more, where such parts are made from the solid, changes which later tests 

 prove advisable can frequently not be carried out without very serious cost 

 and delay, while with the bed plates formed by brazing less hesitancy is felt in 

 removing parts which are brazed thereto and substituting new parts, or even 

 discarding the bed plates altogether and substituting new ones. Particular em- 

 phasises laid on this point for the reason that much expense and delay would 

 have been avoided had these very expensive propeller-shaft bed plates been dis- 

 carded as early as 1901 and replaced by others which would have permitted a 

 considerable strengthening of the ball-bearings, which, while strong enough to 

 stand even more power than they were originally designed for, were far too 

 weak to be safe when working under the greatly increased stress due to the 

 very much higher engine power which was later used. Instead of discarding 

 these bed plates then for new ones, they were strengthened by brazing to them 

 crescent-shaped pieces, as shown in the drawings and photographs. This 

 strengthening was made necessary by the larger hole cut in the bed plates for 

 the larger bevel gears. The bed plates for the engine, which are later de- 

 scribed, besides other bed plates which were made for other purposes, were all 



19 



