The Babcock Test. ^ 61 



or friction application of power. Hand testers made 

 with cog-geared wheels can be depended on to give the 

 necessary speed when run according to the manufactur- 

 ers' directions; the earlier machines of this kind were 

 very noisy, but at the present time the best machines 

 on the market are of this type. These are provided 

 with spiral cog-gearing and ball bearings, are strongly 

 made and will run smoothly and with little noise (figs. 

 20 and 21) ; in cog-geared machines the bottles are al- 

 ways whirled at the speed which the number of turns 

 made by the crank would indicate. 



70. Power testers. For factory purposes, steam tur- 

 bine machines (figs. 22-25) are most satisfactory when 

 well made and well cared for. They should always be 

 provided with a speed indi- 

 cator and steam gauge, both 

 for the purpose of knowing 

 that sufficient speed is at- 

 tained, and to prevent what 

 may be serious accidents 

 from a general smash-up, if 

 the turbine "runs wild" by 

 turning on too much steam. 

 The revolving wheel of the 



tester should be made of FlG>22< Ty pe of ^ abcock steam 

 wrought or malleable iron, or lters - 



of wire, so that it will not be broken by the centrifugal 

 force and cause accidents. The swinging pockets 

 .which hold the test bottles in some machines should 

 be so made that the bottles will not strike the 

 center of the revolving frame when in a horizontal posi- 



