Rough Models.—After you have made the drawings and experiments which your invention calls for and both have worked out to your satisfaction you will then have a burning desire to see the result of your efforts in a more substantial form.
Some machines in which there are only a few moving parts need not be built up very carefully, or to exact scale or even of the materials the marketable product is to have in it. Very often a model can be made of wood and scrap metals that will do and show everything that you want it to. See Fig. 64.
Should you have to employ a patent attorney who lives at a distance from you, say one who has an office in Chicago, Philadelphia or Boston, a rough model of your invention will be of great help to him for it will give him an insight into its workings and its possibilities that he is not apt to get from studying your drawings and description unless you are a good mechanical draftsman and he is above the average in his profession.
Fig. 65. A SCALE MODEL OF AN AEROPLANE
Scale Models.—Scale models are usually miniatures of the full sized machine, that is every part of the scale model is reduced in proportion from the dimensions of the big machine, say 1 inch to the foot or whatever you want to make it.
Like rough models scale models need not be actual working models, indeed in many cases it is very hard if not impossible to make a scale model which will run or work like a full sized machine, unless the model is made very large, as for instance model aeroplanes fitted with motors of any other kind than those made of rubber strands. Fig. 65 shows a scale model of an aeroplane.
Fig. 66. A TOY HELIOCOPTER
Then again sometimes a scale model will work to perfection and when a full sized machine is built it will not work at all as in the case of the heliocopter, that is, a flying machine having a screw with blades like a propeller and which when it is rapidly spun by means of a string like a top will rise in the air to a height and sail away to a distance of a hundred feet or more. Fig. 66 shows a toy heliocopter, or aerial top as it is called. Many attempts have been made to build full sized flying machines on the principle of the toy heliocopter but so far none of them have been able to get off of the ground.