The Rastrick Notebook

[Page 38] 10 Octr. 1829 Saturday Mr. Braithwaite & Ericksons Engine Wheels - - 4’ .. 2 2/10” diamr. From Centre to Center – 6’ .. 0” Two Steam Cylinders 6” dr. One Foot Stroke. Cranks on Boiler Axletree 8 inches Radius. Water Tank 4’ .. 11 ¾” long 1’ . 8 ¾” deep & 2’.. 3” wide Inside. Cubic Content = 19.38 Cubic feet – 121 1/8 Imp Gallons or 1211.25 Pounds Wt. = 10 Cwt . 3 q .. 7 lbs. Wt. of Iron Case of Tank 1/8 In thick 2 Cwt 1 q 0 lbs. Wt. of 2 Straps to Hold it up Forcing Pump 2¼ diamr. 6 2/3 Inch Stroke. Steam Valve 1.2 Dr. 1.13 sq. In Area Pressure per Sqr. Inch 50 Pound Load on Valve 56.50 Pressure produced by the Valve Leaver 8.00 lbs Wt. of Valve .25 8.25 - - - - - - - - -8.25 Pressure to be produced by the Weight on the Leaver 48.25 Ratio of distance of the Weight to distance of Valve 1/7 ⁂ 48.25/7 = 6.89 lbs the Wt. ought to be, say 7 lbs Messr. B & E call their Engine an Eight Horse Power [Page 39] 22 Octr. 1829 Mr. Ericesson says that – 20 Cube feet Per Mt. is the Quantity of Air at ¼ lb. density that the Bellows must blow but, if 15 Cube feet of Air is actually delivered into the fire Place for each Horse Power it will be enough there are three Copper Tubes in the Horizontal Boiler each 2¾ Inches diamr. inside and 10½ feet long, thro’ which the air is forced with a Velocity of 50 feet per second. 2 feet double Stroke x 67 Strokes per Mt. = 134 feet Velocity of Piston per Mt. 6 In dr. equal to 28.27 sqr. Inch area of Piston x 25 Pounds effective Pressure per square Inch = 706.85 Pounds load upon the Piston. 706.8 x 134 = 94,717.9 Pounds raised one foot high per Minute. 94,717.9/33,000 = 2.87 Horse Power for one Cylinder & 2.87 x 2 – 5.74 Horse Power of Engine at ten Miles per Hour supposing the Steam kept constantly up to 50 Pounds per square Inch on the Safety Valve. But if the effective Pressure per square Inch can only be maintained upon the Steam Pistons at 20 Pounds per Square Inch then the Power of the Engine would be only 4.6 Horse Power.