A new line of development was opened by Frank B. Gilbreth, one of Taylor's most prominent followers. He added to time study the concept of motion study: that is, the investigation and classification of the basic motions of the body, regardless of the particular and concrete form of the labor in which these motions are used. In motion and time study, the elementary movements were visualized as the building blocks of every work activity; they were called, in a variant of Gilbreth's name spelled backward, therbligs. To the stopwatch were added the chronocyclegraph (a photograph of the workplace with motion paths superimposed), stroboscopic pictures (made by keeping the camera lens open to show changing positions assumed by the worker), and the motion picture; these were to be supplemented by more advanced means. In its first form, motion study catalogs the various movements of the body as standard data, with the aim of determining time requirements and making the procedure “primarily a statistical problem rather than a problem of observation and measurement of particular workers."
Therblig charts used by industrial engineers, work designers, and office managers give to each motion a name, a symbol, a color code, and a time in ten-thousandths of a minute. The basic motion symbols are given in a recent textbook by the chairman of the Industrial Engineering Division at the University of Wisconsin as follows:6
G Grasp UD Unavoidable Delay RL Release Load AD Avoidable Delay P Position H Hold PP Pre-position R Rest A Assemble PN Plan DA Disassemble Inspect U Use W Walk SH Search B Bending ST Select SI Sit TL Transport Loaded SD Stand Up TE Transport Empty K Kneel
Each of these motions is described in machine terms. For example, Bending, we are told, is “trunk movement with hips as hinge." These defined motions are in fact classifications of motion types, for each is in turn broken down into finer motion types. Thus G, Grasp, has four basic subclassifications:
Transport Empty is further defined according to the distance the hand must extend, and Transport Loaded is broken down not only according to distance but also to the weight of the load. To pick up a pencil, therefore, would involve the proper categories of Transport Empty, Pinch Grasp, and Transport Loaded, each with a standard time value, and the sum of the time categories for these three therbligs, given in ten-thousandths of a minute, constitutes the time for the complete motion.
The combination of motions required to perform each operation is worked out on a therblig chart: "The therblig chart (Therb CH) is the detailed symbolic and systematic presentation of the method of work performed by the body members."7 As a rule, the therblig chart is a two-column affair, representing separately the activities of each hand, whether in motion or at rest, during any part of the time sequence.
The therblig was only the first of a series of standard data systems, which are now constructed by many large corporations for their internal use (see Chapter 15, “Clerical Workers"), or provided by research organizations. Of these various systems of “predetermined work time," the most popular is Methods-Time Measurement, put out by the MTM Association for Standards and Research in Ann Arbor, Michigan. This association publishes “Application Data" in booklet form.\* In this system, the time standard used is the TMU, which is defined as one hundred-thousandth of an hour, equal to six ten-thousandths of a minute or thirty-six thousandths of a second. It offers refinements of the therblig to apply to many conditions. Reach, for instance, is tabulated separately for objects in fixed or varying locations, for objects jumbled with others, for very small objects, and so forth, and for distances varying from three-fourths of an inch up to thirty inches. For example, to reach a single object the location of which may vary slightly from cycle to cycle, twenty inches away, consumes according to the MTM chart 18.6 TMU, or .6696 second (not, we ask the reader to note, two-thirds of a second, which would be .6666 second; a difference which, in an operation repeated a thousand times a day, would add up to three seconds).
Move is defined for objects from 2.5 to 47.5 lbs.: to either hand or against stop; to approximate or indefinite location; to exact location.
Turn and apply pressure is given for pressures up to 35 lbs., and for vectors of 30 degrees to 180 degrees, in increments of 15 degrees.
Position: loosely, closely, or exactly; for easy-to-handle and difficult-tohandle objects (its opposite, Disengage, is also given for the same conditions).
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The Scientific-Technical Revolution and the Worker
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G2 Pinch Grasp (thumb opposes finger).
G1 Contact Grasp (pick up wafer by touching with fingertip).
G3 Wrap Grasp (hand wraps around).
G4 Regrasp (shift object to gain new control).
\* The front cover of the booklet bears the boxed legend: "Do not attempt to use this chart or apply Methods-Time Measurement in any way unless you understand the proper application of the data. This statement is included as a word of caution to prevent difficulties resulting from misapplication of the data."