908 



Popular Science Monthly 



This bolt takes r^::^ 

 the thrust \ 'I 



-J Key to shaft 



V 



The ball seated// 



heads take the/" \ Flexible pir\s, 



reverse pMll do the driving 



The center bolt gives the required 

 rigidity to the coupling, the lami- 

 nated steel pins of the flange 

 give it the necessary flexibility 



Flexible Coupling Takes Side Strain 

 Off Shafting 



UNLESS there is perfect alinement of 

 the propeller shaft with the engine 

 or reverse-gear shaft there is sure to be 

 trouble in any engine-propelled marine 

 craft. Binding bearings, with resulting 

 friction, hot journals and loss of power, 

 or excessive vibration 

 and consequent wear 

 are the natural results 

 of the side strain 

 caused by the imper- 

 fect alinement. As a 

 truly perfect aline- 

 ment is possible only 

 in theory, some pro- 

 vision must be made 

 to compensate for de- 

 fects in the alinement 

 which may develop 

 from various causes at 

 any time. It was 

 found that a flexible 

 coupling for connect- 

 ing the propeller shaft with the engine 

 constituted the best remedy. One of 

 these flexible couplings, which has been 

 successfully tried for marine engines of 

 various types, is here shown in cross 

 section. 



The coupling consists of two cast-iron 

 or steel flanges con- 

 nected by flexible lami- 

 nated steel pins instead 

 of rigid bolts. The con- 

 struction of the coupling 

 is made plain by the 

 diagram. The center 

 bolt takes the push or 

 pull, as the case may be, 

 from one shaft to the 

 other. The flexible 

 laminated steel pins, 

 which connect the two 

 flanges, allow sufficient 

 play to give the coup- 

 ling universal action 

 within its intended 

 limits. The pins take 

 no push or pull, their 

 business is to drive. It 

 is expected that this 



arrangement will elim- ^,^ . ,^. 



° , , , The student sin(>b 



mate much trouble into the tubes to 



hitherto encountered. test quality of voice 



E^ 



A First Aid to the Singing-Teacher. 

 It Analyzes the Voice 



VERY tone of the human voice is 

 composed of fundamentals and over- 

 tones, according to the musical authori- 

 ties. It is the presence or absence of the 

 overtones which decides whether a tone 

 is musical or otherwise. Hence overtones 

 constitute the essen- 

 tials of the singing 

 voice. 



Professor Howard 

 H. Hanson, of San 

 Jose, Calif., has per- 

 fected a device which 

 determines what over- 

 tones of a particular 

 voice need cultivating 

 or subduing for the 

 sake of bringing the 

 voice up to its maxi- 

 mum beauty. The de- 

 vice is constructed 

 principally of tin and 

 resembles a huge 

 from which tubes of 



stove-pipe jomt 



various lengths and sizes protrude hori- 

 zontally. 



There are sixteen of the tubes, and each 

 is tuned to a different overtone of middle 

 "C." When a voice is to be tested, the 

 student sings the five vowels on middle 

 "C" into the protrud- 

 ing end of a tube. The 

 sound waves of the tone 

 enter a resonating cham- 

 ber where the presence 

 or absence of the desired 

 overtone is recorded. 

 The test is repeated 

 through each of the six- 

 teen tubes and the 

 records thus obtained 

 clearly show the teacher 

 on which vowel 

 sounds most 

 ^ork is re- 



Each of the 

 tubes regis- 

 ters a certain 

 overtone of 

 middle "C" 



