===============++=========================++==================== || Fly-wheels. || Dimensions of ||Made when Practicable to || Cylinders. ||Serve also as Belt-Drums.|| Driving Belts. -------+-------++-------------+-----------++---------+---------- | || | Weight of || | Bore. |Stroke.|| Diameter. | Rim. ||Velocity.| Width. -------+-------++-------------+-----------++---------+---------- | || | ||Feet per | Inches.|Inches.||Feet. Inches.| Lbs. || minute. | Inches. 6 | 12 || 3 | 350 || 3300 | 9 single. 7 | 12 || 3 6 | 400 || 3850 |10 „ 8 | 16 || 4 | 650 || 3520 |12 double. 9 | 16 || 4 6 | 700 || 3960 |12 „ 10 | 20 || 5 | 1300 || 3610 |14 „ 11.5 | 20 || 5 6 | 1450 || 3970 |14 „ 13 | 24 || 6 6 | 2100 || 4084 |18 „ 14.5 | 24 || 7 | 2350 || 4400 |20 „ 16 | 30 || 8 | 4000 || 4150 |26 „ 18 | 30 || 9 | 4000 || 4670 |30 „ 20 | 36 || 10 | 6000 || 4400 |38 „ 22 | 36 || 11 | 6000 || 4840 |42 „ 24 | 42 || 12 | || | 26 | 42 || 13 | || | 28 | 48 || 16 | || | 32 | 48 || | || | 36 | 48 || | || | 40 | 48 || | || | 44 | 48 || | || | -------+-------++-------------+-----------++---------+---------- The powers are those given by an initial pressure of 85 lbs. on the square inch, cut off at about one quarter of the stroke. For the best economy steam should not be cut off earlier than this, unless a higher pressure is carried. At the latest point of cut off, the powers developed are double those given in the above Table. The engines can be worked under locomotive pressures, with corresponding increase of power. After considerable study I finally adopted the above table of standard sizes and speeds, covering the ground from 25 horse-power up with nineteen sizes. As the bed could not be reversed, I needed both a right-hand and a left-hand bed for each size. I avoided half of this expense in patterns by planning two diameters of cylinders with the same stroke, and making one bed answer for both. Until I found something else to do, I employed myself in preparing complete drawings for three or four smaller sizes of engines; a work which afterwards proved exceedingly useful. CHAPTER XXI Production of an Original Surface Plate. I will introduce here a description of the method of producing an original surface plate.