THE TMB AUTOMATIC SHIP'S MOTION RECORDER 



by 

 Norman H. Jasper 



ABSTRACT 



This report describes the development of an automatic ship's motion recorder 

 which records the ship's rolling, pitching, and heaving accelerations as well as the 

 rolling and pitching angles. The recorder has provision for automatic sampling of 

 data at preselected intervals of time, and it can operate continuously for weeks on ship- 

 board without requiring human attention. The apparatus may also be used to record 

 quantities other than those mentioned, for example, pressures and strains. 



The recorder and the transducers are evaluated on the basis of their perform- 

 ance so far, and further worthwhile developments are suggested in the report. 



INTRODUCTION 



The function of the TMB automatic ship's motion recorder is to re- 

 cord automatically the heaving, rolling, and pitching accelerations as well as 

 the rolling and pitching angles of ships. Its record provides the data needed 

 for a statistical analysis of ships' motions. Briefly, the recorder registers 

 the output of five transducers as a function of time, for a predetermined dura- 

 tion, at preselected intervals of time; that is, it performs a sampling opera- 

 tion. The unit described in this report is set to record for a duration of 

 two minutes at hourly intervals. 



This device was developed as part of a program, authorized by the 

 Bureau of Ships, 1 to study the strength of ships at sea.* There are many oc- 

 casions when it would be of considerable value to know the actual motions 

 which ships may be expected to have at sea, for example in designing masts, 

 flight decks, hulls, and supports for machinery and instruments as well as in 

 the design of equipment mounted aboard ships and — to mention quite a different 

 field — in the study of physiological aspects of ship motions. 



References are listed on page 26. 



*A general discussion of a proposed program for the study of the strength and motion of ships at 

 sea will be given in another TMB report. See also References 2 and 3. 



