Shop Management, Frederick Winslow Taylor [most important books of all time .txt] 📗

if the element is very small, the total time of,

say, ten may be entered as a fraction, with the time for all ten

observations as the numerator, and the number of observations for the

denominator.

 

In the illustration given on the note sheet, Fig. 2, the operation

consists of a series of elements. In such a case, the letters

designating each elementary unit are entered under the columns “Op.,”

the stop watch is thrown to zero, and started as the man commences to

work. As each new division of the operation (that is, as each

elementary unit or unit time) is begun, the time is recorded. During

any special delay the watch may be stopped, and started again from the

same point, although, as a rule, Mr. Thompson advocates allowing the

watch to run continuously, and enters the time of such a stop,

designating it for convenience by the letter “Y.”

 

In the case we are considering, two kinds of materials were handled sand

and clay. The time of each of the unit times, except the “filling,” is

the same for both sand and clay; hence, if we have sufficient

observations on either one of the materials, the only element of the

other which requires to be timed is the loading. This illustrates one of

the merits of the elementary system.

 

The column “Av.” is filled from the preceding column. The figures thus

found are the actual net times of the different unit times. These unit

times are averaged and entered in the “Time” column, on the lower half

of the right-hand page, preceded, in the “No.” column, by the number of

observations which have been taken of each unit. These times, combined

and compared with the gross times on the left-hand page, will determine

the percentage lost in resting and other necessary delays. A convenient

method for obtaining the time of an operation, like picking, in which

the quantity is difficult to measure, is suggested by the records on the

left-hand page.

 

The percentage of the time taken in rest and other necessary delays,

which is noted on the sheet as, in this case, about 27 per cent, is

obtained by a comparison of the average net “time per barrow” on the

right with the “time per barrow” on the left. The latter is the quotient

of the total time shoveling and wheeling divided by the number of loads

wheeled.

 

It must be remembered that the example given is simply for illustration.

To obtain accurate average times, for any item of work under specified

conditions, it is necessary to take observations upon a number of men,

each of whom is at work under conditions which are comparable. The total

number of observations which should be taken of any one elementary unit

depends upon its variableness, and also upon its frequency of occurrence

in a day’s work.

 

An expert observer can, on many kinds of work, time two or three men at

the same time with the same watch, or he can operate two or three

watches—one for each man. A note sheet can contain only a comparatively

few observations. It is not convenient to make it of larger size than

the dimensions given, when a watch-book is to be used, although it is

perfectly feasible to make the horizontal rulings 8 lines to the inch

instead of 5 lines to the inch as on the sample sheet. There will have

to be, in almost all cases, a large number of note sheets on the same

subject. Some system must be arranged for collecting and tabulating

these records. On Tables 2A and 2B (pages 160 and 161) is shown the form

used for tabulating. The length should be either 17 or 22 inches. The

height of the form is 11 inches. With these dimensions a form may be

folded and filed with ordinary letter sheets (8 1/2 inches by 11

inches). The ruling which has been found most convenient is for the

vertical divisions 3 columns to 1 1/8 inches, while the horizontal lines

are ruled 6 to the inch. The columns may, or may not, have printed

headings.

 

The data from the note sheet in Fig. 2 (page 151) is copied on to the

table for illustration. The first columns of the table are descriptive.

The rest of them are arranged so as to include all of the unit times,

with any other data which are to be averaged or used when studying the

results. At the extreme right of the sheet the gross times, including

rest and necessary delay, are recorded and the percentages of rest are

calculated.

 

Formulae are convenient for combining the elements. For simplicity, in

the example of barrow excavation, each of the unit times may be

designated by the same letters used on the note sheet (Fig. 2) although

in practice each element can best be designated .by the initial letters

of the words describing it.

 

Let

 

a = time filling a barrow with any material.

 

b = time preparing to wheel.

 

c = time wheeling full barrow 100 feet.

 

d = time dumping and turning.

 

e = time returning 100 feet with empty barrow.

 

f = time dropping barrow and starting to shovel.

 

p = time loosening one cubic yard with the pick.

 

P = percentage of a day required to rest and necessary delays.

 

L = load of a barrow in cubic feet.

 

B = time per cubic yard picking, loading, and wheeling any given kind of

earth to any given distance when the wheeler loads his own barrow.

 

[Transcriber’s note — formula and Tables omitted]

 

This general formula for barrow work can be simplified by choosing

average values for the constants, and substituting numerals for the

letters now representing them. Substituting the average values from the

note sheet on Fig. 2 (page 151), our formula becomes:

[Transcriber’s note — formula omitted]

 

In classes of work where the percentage of rest varies with the

different elements of an operation it is most convenient to correct all

of the elementary times by the proper percentages before combining them.

Sometimes after having constructed a general formula, it may be solved

by setting down the substitute numerical values in a vertical column for

direct addition.

 

Table 3 (page 164) gives the times for throwing earth to different

distances and different heights. It will be seen that for each special

material the time for filling shovel remains the same regardless of the

distance to which it is thrown. Each kind of material requires a

different time for filling the shovel. The time throwing one shovelful,

on the other hand, varies with the length of throw, but for any given

distance it is the same for all of the earths. If the earth is of such a

nature that it sticks to the shovel, this relation does not hold. For

the elements of shoveling we have therefore:

 

s = time filling shovel and straightening up ready to throw.

 

t = time throwing one shovelful.

 

w = time walking one foot with loaded shovel.

 

w1 = time returning one foot with empty shovel.

 

L = load of a shovel in cubic feet.

 

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