. American engineer and railroad journal . the last few years, with .a view to throwlight upon the subject. At the outset we felt the want ofsome means of accurately indicating and recording the ex-tent and character of vibrations, and therefore devised aninstrument for the purpose, which has been named a vibrometer. This instrument is shown in the first en- graving given. It has been in use for the last six years,and is, 1 believe, trustworthy. It consists, as will be seen,of a heavily weighted drum, suspended by elastic connec-tions. This drum is provided with suitable clockwork tocause it t
. American engineer and railroad journal . the last few years, with .a view to throwlight upon the subject. At the outset we felt the want ofsome means of accurately indicating and recording the ex-tent and character of vibrations, and therefore devised aninstrument for the purpose, which has been named a vibrometer. This instrument is shown in the first en- graving given. It has been in use for the last six years,and is, 1 believe, trustworthy. It consists, as will be seen,of a heavily weighted drum, suspended by elastic connec-tions. This drum is provided with suitable clockwork tocause it to revolve, and is regulated to make one revolu-tion per minute. Attacheil to an upright fixed to the standof the machine is a pencil, which presses lightly againstthe drum, round which a sheet of paper is wrapped, in thesame manner as in an ordinary indicator. It will bereadily understood that if the base of this instrument beplaceil upon a platform or the deck of a vessel subject tovertical vibration, this movement will be transmitted to. the whole apparatus, excepting that portion which is sus-pended by the elastic connection, and this, being heavilyweighted, will not follovv the vibratory motion of the , if we place our instrument on the stern or any partof a steamer which is vibrating, and start the drum revolv-ing, the pencil, being pressed against the paper, makes aline, indicating the relative vertical positions of the penciland the paper, or, in other words, makes a diagram whichrecords the character and extent of the movement of thatpart of the ship upon which the instrument stands. I believe the cause of vibration in screw vessels, whenrunning in smooth water with their propellers well im-mersed, to be mainly due to the forces produced by theunbalanced moving parts of the machinery, such as thepistons, piston-rods, valves, gear, etc., excepting when itis the result of bad workmanship or bad state of example, as clearly pointed out by Mr. Barnaby in
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
