32

RULES FOR CALCULATING THE STEAM ENGINE.

•1847Link 2

•5357) -3694,0(0-69•3214,2

47980•3510Link 2

•5357) 7020( 1-315357

16630

16071

5590

The distance of the required point from the end of the beam is therefore 0 1 69 feet, or8 - 28 inches, and the distance from the end of the radius bar is 1'31 foot or 1 foot 3'72 inches.N.B. As a check against any gross blunder, the distances multiplied by the respectivelengths of the beam and radius bar ought to give nearly equal results. In thepresent case they give 4‘83 and 5 - 24. For short strokes, however, they ought tocome 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 distancefrom the beam.

Rule. —First, from the radius of the beam, divided by twice the length of the parallelbar, subtract unity.

Secondly, Find the square root of the difference between the square of the radius ofthe beam and the square of the half-length of the stroke, and add this root to the radiusof the beam.

Thirdly, Multiply together the numbers so found, and the product, added to the lengthof the parallel bar, will give the length of the radius bar.

Example— Let the radius of the beam be 11 feet, the length of stroke 5, and the lengthof the parallel bar 4 feet.

First operation.

Parallel bar 4 feet2

8

8)11

1-375

Subtract 1

• 375*

1 This difference may sometimes be negative; in that case the final product must be subtracted from the length of theparallel bar. (See next Example.)