218 APPENDIX. 



they give 4'83 and 5-24. For short strokes, however, they ought to come much 

 nearer. 



21. To find the length of the radius bar. 



I. When the radius bar and piston rod are attached to the links at the same distance 

 from the beam. 



RULE. First, From the radius of the beam, divided by twice the length of the parallel bar, 

 subtract unity. 



Secondly, Find the square root of the difference between the square of the radius of the 

 beam, and the square of the half length of the stroke, and add this root to the radius of the 

 beam. 



Thirdly, Multiply together the numbers so found, and the product added to the length of 

 the parallel bar will give the length of the radius bar. (235.) 



Example. Let the radius of the beam be 11 feet, the length of stroke 5, and the length of 

 the parallel bar 4 feet. 



First operation. 



Parallel bar 4 feet 

 2 



8 



Second operation. 

 Stroke 5 feet 



Half 2-5 

 2-5 



8)11 



1-375 

 Subtract 1 



375 > 



Beam 11 feet 

 11 



121 



125 

 50 



6-25 6-25 



114-75 



Square root 10'7l 

 Beam 11 



21-71 



1 This difference may sometimes be negative ; in that case the final product must be subtracted from the length of the 

 parallel bar (see next Example). 



