The cyclegraph method permits us to record, measure, and see this orbit or exact path of a motion or cycle of motions. Small electric lights are attached to the hands, or any other members of the body involved in the motion. A photographic plate or film is then exposed while the motion is made, with the result that a path of light, which resembles a white wire, is seen upon the developed plate, representing the path of the motion. The effect is best gained by a stereoscopic photograph, which shows this path in three dimensions.
The chronocyclegraph method enables us not only to see the path of the motion, but also its directions, and the duration of the entire motion and of its elements. These chronocyclegraphs are made by attaching lights to the moving parts of the body, or machine, as in the cyclegraph, and by introducing a properly timed, pulsating interrupter in the circuit, which may be adjusted not only to record the time and duration, but also to record these with different graphs, representing the paths of each of several motions made by various parts of the body and their exact distances, exact times, relative times, exact speeds, relative speeds, and directions.
Fig. 20
This picture shows a lamp attached to the hand for the purpose of taking cyclegraphs or chronocyclegraphs of motions in connection with obtaining motions of least fatigue.
Fig. 21
This picture shows an experiment that was carried on by us some time ago for determining the laws pertaining to the times and fatigue of motions of different lengths.
The operation studied is that of moving a seven pound weight. The times are divided into three parts: Length of time from starting to picking up weight; length of time from picking up weight to depositing; and length of time of recovery to standing position from depositing. The experiment proved that the time of motions of different lengths is practically the same unless those of the same length are consecutively repeated. The quantity of work that can be done in a day is, of course, much less with long motions than with short ones, due to extra time needed to overcome the fatigue of the long motions.
By means of the “penetrating screen,” it is possible to pass a cross-sectioned plane in any direction through any desired plane, or through any number of planes in the cubic space under observation. This makes it possible to record the data with great accuracy in three dimensions, and to read the information from the data easily.
These various types of motion study supplement rather than supplant one another. Motion study is primarily for the purpose of observing the variables that affect such study, and for arousing such co-operation between observed and observer, as will make possible the testing of the differences of the effects of the variables. Micromotion study provides for an accurate record of what happened, with all such attending circumstances as appeal to the eye. It is the greatest aid in transference of skill and experience from a worker who has it to one who does not possess such skill and experience. The cyclegraph is useful in providing a simple, easily understood record of the path that any activity followed. The chronocyclegraph is most valuable when the activity is complicated, and when the time and direction of the elements of the motion must be visualized continuously in order to analyze, measure, synthesize, and standardize the process. The penetrating screen, finally, is useful in recording the three dimensional paths and speeds of even the smallest unit of activity.
These methods of applying motion study have been patented, but have been for years freely at the disposal of the colleges, which have begun to use them as means for recording accurately scientific data of various kinds. They have justified themselves as more accurate than ordinary records of activity, and have within recent times been put on a basis which makes their cost compare favourably with less accurate methods of measurement. What is more, we have discovered in our data, especially in the chronocyclegraphs, direct records of fatigue, that we believe are the first records of fatigue ever made under industrial conditions. The micromotion films also show breaks in well established habits of several motions that are undoubtedly due to fatigue, but the irregularities in the orbit line, that appear in the cyclegraphs, and that must, because of close control of the variables, be due to the fatigue alone, are more impressive from the physiological viewpoint.