The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

de o De ees Fic. 2, The speed in miles per hour being | made by the vessel is always the "source of a great deal of interest to passengers and transportation lines catering to the passenger traffic can attach a tachometer indicator calib- rated in knots or miles per hour, to the same generating outfit employed in connection with the revolution in- dicators, thereby making the equip- ment complete. The current necessary to operate these indicators and provided by the generating unit is so very infinitesi- mal that it is claimed that the break- ing of a wire surrounded by inflam- mable material will not cause com- bustion and that the wires may also be short circuited indefinitely without producing any heat or injuring the magnetos in any way. . The wires connecting the generating unit with the indicators are, in addition, run through approved armored conduit and are thereby protected from all mechanical injury. "THE. Marine REVIEW Tachometers are not new, but the designers of tachometer claim for it. that: it is the first perfectly the reliable Hutchison and marine Satistac- December, 1909 tory instrument of the kind yet pro- duced commercially. Why Centrifugal Tachometers Have Failed in This Service. It is claimed that centrifugal tacho- meters fail to meet marine require- ments because of the impracticability of transmitting the rotation to the bridge or pilot house continuously without failure of shafting, etc.,' and that furthermore, such an instrument, kept in constant use, will eventually change calibration because of fatigue. of the spring control. It is further claimed for the Hutchison tachometer that it maintains its calibration abso- lutely and is not susceptible to dam- age other than from physical abuse. The Pointer of the Hutchison Marine Tachometer Is Steady. Most tachometers are affected by the variation in angular velocity' of the propeller shaft of a reciprocating engine, causing the pointer to swing rapidly between a maximum and min- imum value which renders accurate reading difficult. The Hutchison avoids this by an arrangement of flat spiral springs which smooth out the effect of these variations of angular velocity and cause the shaft which actuates the generators, "to, srotate "at> a<=.constant speed resulting in a steady pointer. Some of the Troubles of Electrical Tachometers. Efforts have been made to provide an electrical tachometer which would give simultaneous readings of engine speed at engine room and bridge. A direct current magneto was geared to the propeller shaft, and direct current voltmeters connected to it. These meters were calibrated to show en- i oe ai etal be Ma as cree