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Mr. F. "W . Lanchester on 



of the pendulum aecelerometer ; and fig. 3 shows the actual 

 proportions of my present (1904) model. Referring to fig. 2 in 

 which a resolution of forces is given, let the angle of deflexion 

 of the pendulum be denoted by 6 } "W" = forces on pendulum- 

 bob due to gravity, and "F" = force due to acceleration u /," 

 then we have : — 



f-=g.Y/W=;ff.tea6. 



It will be seen, therefore, that the motion of the recording 

 pencil in order to give a uniform acceleration scale must be 



Fig. 3. 

 PENDULUM ' ACCELEROMETER 



19 04. 



proportional to the tangent of the angle of deflexion. It is 

 the form of " tan angle mechanism " that constitutes one of 

 the improvements in the new model. 



In the 1889 model the pencil was mounted on a sliding 

 carriage (fig. 4) actuated by a forked arm, being an upward 

 prolongation of the pendulum : in this arrangement, in addition 

 to the pencil friction, two additional sources of sliding friction 

 existed, those of the carriage mounting and forked operator. 



