P = percentage of a day required for rest and necessary delays.
T = time for shoveling one cubic yard.
Our formula, then, for handling any earth after it is loosened, is:
[Transcriber's note -- omitted]
Where the material is simply thrown without walking, the formula
becomes:
If weights are used instead of volumes:
[Transcriber's note -- omitted]
The writer has found the printed form shown on the insert, Fig. 5
(opposite page 166), useful in studying unit times in a certain class of
the hand work done in a machine shop. This blank is fastened to a thin
board held in the left hand and resting on the left arm of the observer.
A stop watch is inserted in a small compartment attached to the back of
the board at a point a little above its center, the face of the watch
being seen from the front of the board through a small flap cut partly
loose from the observation blank. While the watch is operated by the
fingers of the left hand, the right hand of the operator is at all times
free to enter the time observations on the blank. A pencil sketch of the
work to be observed is made in the blank space on the upper left-hand
portion of the sheet. In using this blank, of course, all attempt at
secrecy is abandoned.
The mistake usually made by beginners is that of failing to note in
sufficient detail the various conditions surrounding the job. It is not
at first appreciated that the whole work of the time observer is useless
if there is any doubt as to even one of these conditions. Such items,
for instance, as the name of the man or men on the work, the number of
helpers, and exact description of all of the implements used, even those
which seem unimportant, such, for instance, as the diameter and length
of bolts and the style of clamps used, the weight of the piece upon
which work is being done, etc.
It is also desirable that, as soon as practicable after taking a few
complete sets of time observations, the operator should be given the
opportunity of working up one or two sets at least by summing up the
unit times and allowing the proper per cent of rest, etc., and putting
them into practical use, either by comparing his results with the actual
time of a job which is known to be done in fast time, or by setting a
time which a workman is to live up to.
The actual practical trial of the time student's work is most useful,
both in teaching him the necessity of carefully noting the minutest
details, and on the other hand convincing him of the practicability of
the whole method, and in encouraging him in future work.
In making time observations, absolutely nothing should be left to the
memory of the student. Every item, even those which appear self-evident,
should be accurately recorded. The writer, and the assistant who
immediately followed him, both made the mistake of not putting the
results of much of their time study into use soon enough, so that many
times observations which extended over a period of months were thrown
away, in most instances because of failure to note some apparently
unimportant detail.
It may be needless to state that when the results of time observations
are first worked up, it will take far more time to pick out and add up
the proper unit times, and allow the proper percentages of rest, etc.,
than it originally did for the workman to do the job. This fact need not
disturb the operator, however. It will be evident that the slow time
made at the start is due to his lack of experience, and he must take it
for granted that later many short-cuts can be found, and that a man with
an average memory will be able with practice to carry all of the
important time units in his head.
No system of time study can be looked upon as a success unless it
enables the time observer, after a reasonable amount of study, to
predict with accuracy how long it should take a good man to do almost
any job in the particular trade, or branch of a trade, to which the time
student has been devoting himself. It is true that hardly any two jobs
in a given trade are exactly the same and that if a time student were to
follow the old method of studying and recording the whole time required
to do the various jobs which came under his observation, without
dividing them into their elements, he would make comparatively small
progress in a lifetime, and at best would become a skilful guesser. It
is, however, equally true that all of the work done in a given trade can
be divided into a comparatively small number of elements or units, and
that with proper implements arid methods it is comparatively easy for a
skilled observer to determine the time required by a good man to do any
one of these elementary units.
Having carefully recorded the time for each of these elements, it is a
simple matter to divide each job into its elementary units, and by
adding their times together, to arrive accurately at the total time for
the job. The elements of the art which at first appear most difficult to
investigate are the percentages which should be allowed, under different
conditions, for rest and for accidental or unavoidable delays. These
elements can, however, be studied with about the same accuracy as the
others.
Perhaps the greatest difficulty rests upon the fact that no two men work
at exactly the same speed. The writer has found it best to take his time
observations on first-class men only, when they can be found; and these
men should be timed when working at their best. Having obtained the best
time of a first-class man, it is a simple matter to determine the
percentage which an average man will fall short of this maximum.
It is a good plan to pay a first-class man an extra price while his work
is being timed. When work men once understand that the time study is
being made to enable them to earn higher wages, the writer has found
them quite ready to help instead of hindering him in his work. The
division of a given job into its proper elementary units, before
beginning the time study, calls for considerable skill and good
judgment. If the job to be observed is one which will be repeated over
and over again, or if it is one of a series of similar jobs which form
an important part of the standard work of an establishment, or of the
trade which is being studied, then it is best to divide the job into
elements which are rudimentary. In some cases this subdivision should be
carried to a point which seems at first glance almost absurd.
For example, in the case of the study of the art of shoveling earths,
referred to in Table 3, page 164, it will be seen that handling a
shovelful of dirt is subdivided into, s = "Time filling shovel and
straightening up ready to throw," and t = "Time throwing one shovelful."
The first impression is that this minute subdivision of the work into
elements, neither of which takes more than five or six seconds to
perform, is little short of preposterous; yet if a rapid and thorough
time study of the art of shoveling is to be made, this subdivision
simplifies the work, and makes time study quicker and more thorough.
The reasons for this are twofold:
First. In the art of shoveling dirt, for instance, the study of fifty or
sixty small elements, like those referred to above, will enable one to
fix the exact time for many thousands of complete jobs of shoveling,
constituting a very considerable proportion of the entire art.
Second. The study of single small elements is simpler, quicker, and more
certain to be successful than that of a large number of elements
combined. The greater the length of time involved in a single item of
time study, the greater will be the likelihood of interruptions or
accidents, which will render the results obtained by the observer
questionable or even useless.
There is a considerable part of the work of most establishments that is
not what may be called standard work, namely, that which is repeated
many times. Such jobs as this can be divided for time study into groups,
each of which contains several rudimentary elements. A division of this
sort will be seen by referring to the data entered on face of note
sheet, Fig. 2 (page 151).
In this case, instead of observing, first, the "time to fill a shovel,"
and then the time to "throw it into a wheelbarrow," etc., a number of
these more rudimentary operations are grouped into the single operation
of
a = "Time filling a wheelbarrow with any material."
This group of operations is thus studied as a whole.
Another illustration of the degree of subdivision which is desirable
will be found by referring to the inserts, Fig. 5 (opposite page 166).
Where a general study is being made of the time required to do all kinds
of hand work connected with and using machine tools, the items printed
in detail should be timed singly.
When some special job, not to be repeated many times, is to be studied,
then several elementary items can be grouped together and studied as a
whole, in such groups for example as:
(a) Getting job ready to set.
(b) Setting work.
(c) Setting tool.
(d) Extra hand work.
(e) Removing work.
And in some cases even these groups can be further condensed.
An illustration of the time units which it is desirable to sum up and
properly record and index for a certain kind of lathe work is given in
Fig. 6.