A spring controlled lever is shown in Fig. 23.34. The spring is to be inserted w
ID: 1852817 • Letter: A
Question
A spring controlled lever is shown in Fig. 23.34. The spring is to be inserted with an initial compression to produce a force equal to 125 N between the right hand end of the lever and the stop. When the maximum force at A reaches to a value of 200 N. the end of the lever moves downward by 25 mm. Fig. 23.34. Assuming a spring index as 8, determine: 1. spring rate, 2. size of wire, 3. outside diameter of the spring. 4. number of active coils. and 5. free length, assuming squared and ground ends. The allowable shear stress may be taken as 420 MPa and G= 80 KN/mm2. [Ans. 0.33 N/mm; 27.2 mm; 10; 77 mm]Explanation / Answer
force at spring =P conserving momentum P1*200 =125*400 P1 =250 .... p2 *200 =200*400 P2 =400 ... difference =150 .. also deflection at spring =x hence x/25 =200/400 hence x =12.5 .... hence sping rate = 150/12.5 =12 N/mm