No. 

 two 



16 in 

 corks 



EXERCISE 51 

 HOW DOES A LIFT PUMP WORK ? 



Materials. A glass model of a lift pump or the following materials: some wire 

 size; glass tubing from 1 to 2 inches in diameter and from 12 to 18 inches in length; 

 large enough to fit the tubing tightly ; a piece of thin shoe leather or harness leather ; 

 tacks and shingle nails ; a glass jar or pan. 



Directions. This exercise is best demonstrated by a model lift pump. 



If such a demonstration apparatus cannot be had, a crude one such as is shown in 

 the diagram may be constructed by the teacher or students. Secure a glass tube from 

 1 to 2 inches in diameter and from 12 to 18 inches long. Cut two flat corks to fit 

 the tube rather snugly. Bore a small hole through the center of each cork ; then place 

 a small, square piece of rather heavy sheet rubber or soft leather over the hole, and 

 tack the piece along one of its edges. These pieces of rubber or leather will act as 

 valves. Place one cork in the bottom of the tube, as in the diagram. A few small nails 

 driven into the cork will keep the pump from the bottom of the jar when the pump 

 is operated. 



Cut three lengths of No. 16 ordinary iron wire 10 inches longer than the glass 

 tube. Thrust these wires through the cork and clinch them below the cork, as shown 

 in the diagram. Bend them above the cork as shown, and then twist the wires together 

 to form a piston rod, making a circular handle above. Soak the valves well ; place the 

 piston in position and force it down, observing the position of the valves. Now raise it 

 and observe what occurs. Again push downward and observe. Repeat, and see if the 

 valves work in the same way as above. Why does the water rise in the tube during 

 an upstroke ? Write an explanation of the working of a lift pump, and make drawings 

 to show the principal features. 



Additional problems. How can a lift pump be made to lift water from a well more than 33 feet below 

 the surface ? 



Why must a pump be " primed " ? Why does water flow from the spout only on the upstroke of the 

 lift pump ? 



How does a force pump differ from a lift pump ? 



[70] 



