342 SOME SIMPLE MACHINES IN THE HOME 



plane placed in the form of a spiral. We have seen the 

 use of the jack screw under automobiles in case of tire 

 trouble. Again it is simply the use of force or energy 

 exerted on an inclined plane which runs round and round 

 the jack. Pulleys are not used so often 

 in the home although a familiar example 

 is seen in the supports of the painter's 

 staging. A glance at the diagram will show 

 how they are used. 



The small vacuum washer. Many homes 

 nowadays have washing machines. A small 

 hand washer using the vacuum principle does 

 good work. The cone-shaped metal washer is 

 fastened to a handle and the large end is 

 open. There are holes in the sides of this 

 cone. If this washer is pushed down and 

 lifted up alternately with a great deal of vigor, 

 air will be forced out on the down stroke, and 

 the vacuum produced on the up stroke sucks 

 the water up through the clothes under the 

 washer. The use of such an instrument as 

 this is very effective in washing blankets and 

 delicate materials which may be injured by rubbing. 

 What is the explanation of suction ? 



Washing machines. Washing machines are of two 

 kinds as far as the inside working is considered. In one 

 the system of vacuum domes is similar to the one just de- 

 scribed and is operated mechanically inside of the closed 

 tub. In the second type the clothes are held in a perforated 

 drum which revolves first in one direction and then in the 

 other. This drum sets in water held in the outside con- 

 tainer. The constant whirling of the water back and forth 



With this pulley 

 a weight of 600 

 pounds can be 

 supported by 

 a force of 100 

 pounds. 



