Fig. 47a. THE THEORY OF A SCREW
Fig. 47b. A SCREW CLAMP
Compound Machines.—Any of the above six simple machines can be combined with any or all of the others and every machine that has ever been invented for any purpose is made up of a combination of these six mechanical powers.
Since the beginning of invention there has been made by combining these six mechanical powers in different ways, a large number of simple machines called mechanical movements; and there has not been a single new mechanical movement invented in many years.
Hence when you begin to work on your machine don’t waste time and energy trying to devise the mechanical movement you need, or what is still more foolish attempting to invent a new mechanical movement but look at the pictures in Fig. 48 which gives over 60 of the most useful mechanical movements. If you cannot find one among them that will do the work then look for it in Gardner D. Hiscock’s book of Mechanical Movements which gives them all.
Books.—And it would be a good idea for you to read one of the following books which you can, most likely, get at any library:
- Elementary Physics: Elroy M. Avery.
- Elements of Physics: Edwin J. Houston.
- Elements of Physics: George H. Hoadley.
- College Physics: A. L. Kimball.
The first-named books go deeply enough into the subject of physics for all ordinary purposes while the last named is very thorough and has a lot of math in it; and all of them treat of liquids, air, electricity and magnetism, sound, heat and light. In whatever field you are working a general knowledge of physics will give you the key to a new and a mighty interesting world.