“Productivity science is scientific effort, that in any specific work situation, identifies the appropriate philosophy, culture, systems, processes, technology, methods and human physical action and behavior and elements of each of them of that will maximize positive (social, environmental and economic) outcomes relative to the resources consumed.” - Narayana Rao (IISE 2020 Annual Conference Proceedings)
Read the abridged version of Productivity Science of Human Effort by Frank Gilbreth in:
Frameworks for Productivity Science of Machine Effort and Human Effort
Rao, Kambhampati Venkata Satya Surya Narayana. IIE Annual Conference. Proceedings; Norcross (2020): 429-434.
https://www.proquest.com/openview/5786c4e6edff56abf808b4db26f083b3/1
CHAPTER IV
-VARIABLES OF THE MOTION
ACCELERATION - AUTOMATICITY - COMBINATION WITH OTHER MOTIONS, AND SEQUENCE - COST - DIRECTION AND USE OF GRAVITY - EFFECTIVENESS - FOOT-POUNDS OF WORK ACCOMPLISHED - INERTIA AND MOMENTUM OVERCOME - LENGTH
A discussion of variables of the motion opens up a field so large that it is only possible here to attempt to show the method of investigation, and to show that each variable is a necessary factor in making motions standard, leaving to the universities and to properly created and equipped bureaus of the national government the task of reducing motion study to an exact science.
ACCELERATION
In considering acceleration of speed as an element of any motion, we must determine:
1. The amount of acceleration that it is possible or economical to obtain.
2. The means by which the acceleration can be obtained.
3. The effect of the acceleration on
a. Economy in time required to make the motion.
b. Economy in time required for rest to overcome the fatigue of having made the motion.
Examples. 1. Laying brick on a wall from a floor, from the height of the floor level up to three feet eight inches high above the floor, can be done with greatest speed when the brick to be picked up are each maintained at a height of one foot three inches, plus two-thirds the height that the wall is higher than the level of the floor on which the bricklayer stands. The brick to be picked up should never be higher than three feet eight inches under any circumstances.
By maintaining the height of the brick to be laid in this relative position to the height of the wall, the brick will always be in a position that permits the bricklayer to accelerate the speed of transportation of the brick by using the path of the quickest speed.
While bricklayers know nothing about this in theory, they very soon discover it in practice by means of their higher recorded output. Greater outputs will be noticeable as an immediate result of maintaining the brick as nearly as possible at the heights above stated.
2. In laying the filling tiers in any one course, it is most economical to lay the farthest filling tier first and the next farthest tier second, and so on. This enables the brick-layer to accelerate the speed of transportation of the brick up to the instant that it is deposited in the mortar.
The above practice is, of course, much more important on shove-joint work than on brick-and-brick construction.
3. The possible benefits from acceleration should be taken into consideration when determining the sequence in which the tiers shall be laid. The position of the feet of the bricklayer is an important factor in obtaining the acceleration desired. For the best results the feet should be on separate springy planks, so that the transportation of the brick can be speeded up, in addition to the speed of the arms by simply throwing the body by the aid of the spring of the plank. (See Fig. 13.)
AUTOMATICITY
Nearly all often-repeated motions become automatic. This is especially true of motions that require no careful supervision of mind or eye.
The automaticity of motions is of great assistance to the worker whose training and methods conform to standardized motions. This fact makes it necessary to have the apprentice taught the right motions first, last, and always.
The automaticity of motions is a hindrance to the worker who has been accustomed to old-fashioned surroundings, equipment, and tools, and who must adapt himself to standard surroundings.
Example. A remarkable example of making unnecessary motions as a matter of habit is noticeable in places where the local bricklayers have been accustomed to laying brick that have a decided difference in the top and bottom. This difference makes it necessary to lay no brick upside down on the line. When these bricklayers first worked from packets with the brick in the right position to seize right-side up, they would invariably flop and spin each brick in their hands, first wrong-side up and then back again to the original right-side-up position.
The worker who has been trained wrong also finds it difficult to change his habits when he conforms to standard methods.
Example. Occasionally we find the bricklayer who will spin or flop a brick that is to be laid in the middle of the wall, although it makes no difference which face of the brick is uppermost in these tiers.
The best way to cure motions that are not necessary but that are made from force of habit is to count the motions aloud, endeavoring to keep down to the standard number of standard motions.
When work is done by both hands simultaneously, it can be done quickest and with least mental effort if the work is done by both hands in a similar manner; that is to say, when one hand makes the same motions to the right as the other does to the left.
Most work is accomplished when both hands start work at the same time, and when the motions can be made at the same relative position on each side of a central fore and aft vertical plane dividing the worker's body symmetrically.
Even if motions cannot be planned to be similar for each hand and performed simultaneously, the plane in which the work is to be done should be carefully located.
If motions are so arranged as to be balanced, as suggested, it is possible not only to take advantage of automaticity, but also to cut down jar to the body. It is on this well-known principle that the shockless jarring machine is built. Balanced motions counteract each other. The result is, less bracing of the body is necessary, and less fatigue ensues.
COMBINATION WITH OTHER MOTIONS, AND SEQUENCE
A motion may be combined with motions that are (a) similar to it, and (b) dissimilar to it.
(a) If the motions combined are similar to it, advantage must be taken of the automaticity. Care must also be taken that all the motions made in a series of similar motions are necessary. Sometimes one effective motion is preferable to several not so effective.
Examples. 1 . When tapping a brick down to grade with a trowel, one brisk tap will do the work as well as several light taps, and with much less time and effort.
2. If it is necessary to spread mortar on a face tier, one stroke of the trowel will do the work as well as several.
(b) If the motions combined are dissimilar, two motions may often be transformed into one.
Example. - - The motion used to spread mortar may be combined with the motion used to butter the end of the brick laid just before the mortar was thrown. Thus, the two operations may be transformed into one, and a saving of time and motions will result. In fact, so doing may have other distinct advantages, such as leaving better keying for plastering direct upon the wall.
This subject of combinations of motions can barely be touched here. Its full treatment involves all other variables, and it can never be considered standardized till each separate motion is a standard.
COST
The cost of motions, absolute and relative, is a subject too large for any person, firm, or corporation to hope to cover. If complete data are ever to be gathered on it, the cost keeping, recording, and deducing will have to be done by the government.
But
all work done by the individual investigator will result in real cost reducing, with increase of output, which is the ultimate purpose of all motion study.
The relative cost of labor and material must be considered.
Examples. 1. A bricklayer should never stop to pick up dropped mortar. The mortar dropped is not so valuable as the motions necessary to save it.
2. That quality of mortar that is easiest handled by the bricklayer is usually cheapest. The cost of grinding up the lumps in the sand, cement, and lime is less than the cost of the motions necessary to pick the lumps out with a trowel.
3. It is usually cheaper to fill a closer, say less than one-half a brick in size, on the interior tiers, with even the best of cement, than it is to cut a special piece of brick to fit or to walk a few steps to find one the right size. The extra cost of the mortar is negligible compared with the cost of the motions.
The relative cost of motions of higher and lower grades of labor must also be considered.
It is obvious that, other things being equal, it is cheaper to have a low-priced man instead of a high-priced man make the same motion; but only the most careful study can determine all of the motions that could be taken from the high-priced man and allotted to one or more grades of lower-priced men. This can never be wholly or properly accomplished until our present trades, with their inherited conditions and traditions, have been reclassified to meet modern conditions.
In some trades it is very difficult to effect such division of work, as unions are opposed to having anything relating to skilled work done by laborers.
Examples. 1. In the most highly unionized districts carpenters only are allowed to unload the rough lumber from the cars, and none but carpenters are allowed to transport, lift, and erect, as well as to fabricate it.
2. In bricklaying the case is slightly different. The work of transporting the brick to the place where they are to be laid has always been done by tenders and laborers. The bricklayer never wheels or carries brick. This is a tradition long handed down. Yet he is most jealous that no part of his own work shall be done by a tender or a laborer.
During the time that brick construction was practically without competitors in its field, the bricklayer could insist on his ancient privileges and prosper.
The inroads of concrete, both plain and reinforced, however, have changed conditions, and the bricklayer himself is, more than any other one factor, the cause of many cases of substitutions of concrete for brick.
The architecture of any country is determined by the relative cost of building materials in place, and the history of the world shows that the way to get the most of any one thing used is to make it the lowest in price.
The one thing that will reduce the price of brickwork more than any other is to reduce the cost of the motions,
After the
laws underlying motion study have all been applied, the cost of motions can still be reduced from one-third to one-half by separating the motions of the bricklayer into at least two classes, such as, for example:
1. Those that require skill.
2. Those that require nothing but strength, endurance, and speed.
Those that require skill should be divided into several classes, according to the amount of skill required; those that chiefly require skill should be handled by mechanics, and those that chiefly require strength, endurance, and speed should be handled by specially trained laborers. This is the only way to enable brickwork to compete with concrete, when all of the architects, engineers, owners, and contractors shall have learned the full possibilities of concrete.
It will be urged that such division of the work of bricklaying will lower the general skill of the bricklayers as a class. Far from it! All operations requiring skill will remain in the hands of the bricklayer, who, escaping all work that unskilled hands could do, will have the more time and energy to devote to the "art" element of his work.
But we are not at this time discussing " brickwork as a lost art" - we cite bricklaying here as an example of the cost of motions, the result of the effects of cost of motions, and of the possibilities and importance of motion study as a method of attack in cost reducing and in standardizing the trades for the greatest possible economy.
What greater service can the bricklayer do both his trade and the people who own or occupy houses than to reduce the cost of the motions in brickwork without reducing his own wages or increasing his hours?
The elimination of wastes is the problem that has been forced to the attention of the entire world to-day, and of America particularly. The elimination of wastes in the trades offers the largest field for savings.
Every trade must be reclassified, and must have the brawn motions separated from the skill motions. Scientific division of the work to be done is as sure to result in higher wages and lower production costs as did F. W. Taylor's separating the planning from the performing.
The reason that our country is not astounded and confused at the appalling unnecessary loss to its inhabitants on account of unnecessary, wasteful, and improper motions of its workers is due to ignorance of the existence of this loss, and to ignorance of any method of eliminating it.
The loss due to the present classification of the trades alone is probably more than sufficient to pension, under full pay, one-half of the workers of the country; is certainly enough to enable all of the women and children in the trades to remain out of the trades and be paid at their regular wages.
While such action is not even recommended, the illustration is used to emphasize the enormous waste going on daily and yearly.
That we go on year after year submitting to this waste because our present trades are handled in accordance with ancient conditions entirely out of place in our present civilization, is no longer necessary and without excuse.
Let the government call its scientific managerial experts together and make a test of one trade, reclassify it, and publish the data. The object lesson thus presented will cause to be taken the necessary further steps to remedy the present system of handling the trades. The workers will each be able to earn higher wages when the unions see that they are benefited, and the labor interests will cooperate. The cost of living will be reduced as by no other means, and all this by scientifically reclassifying the trades!
DIRECTION
In most cases, the direction of a motion that is most economical is the one that utilizes gravitation the most. Oftentimes delivering material to a high-priced workman by leaving the material in a high position also makes easy unloading for the low-priced workman.
Example. Stacking up packs 2 feet high saves motions, and saves stooping when the laborer unloads his trucket. (See Fig. 21.)
" Direction" admirably serves as an illustration of the close interrelation of the variables. It is closely connected with "path." It involves discussions of anatomy, acceleration, and speed. It demands consideration of all variables of surroundings, equipment, and tools.
The best ''direction of motion" is not only important in itself for increase of output; it must also be kept constantly in mind in standardizing the placing of both materials and men.
EFFECTIVENESS
Effectiveness has been touched upon in discussing " combination with other motions."
An effective motion is one that produces the desired result. Oftentimes whole processes, methods, and operations can be so changed as to make the succeeding motions much more effective.
Example. The introduction of the fountain trowel, used in connection with an ordinary trowel, made each motion in handling mortar much more effective. (See Figs. 19, 22.)
FOOT-POUNDS OF WORK ACCOMPLISHED
After all, a human being or a work animal is a power plant, and is subject to nearly all the laws that govern and limit the power plant. It is a law of motion study that, other things being equal, the less number of foot-pounds of work done by the workman, the smaller percentage of working hours he must devote to rest to overcome fatigue.
It is therefore of great importance in obtaining the largest possible output that the work shall be so arranged and the workman so placed that he can do his work with the least possible amount of foot-pounds of work done per unit of output accomplished. This is where the philanthropic employer has often been rewarded without knowing it. In his desire to make conditions such that the workman was most comfortable while working, he reduced the number of foot-pounds of work to that which was absolutely necessary to do the work. He surrounded the workman with conditions that enabled him to have no fatigue, except that which was acquired from the motions of the work itself. He made conditions such that the workman was enabled to overcome the fatigue from his motions in the quickest possible time. (See Fig. 23.)
INERTIA AND MOMENTUM OVERCOME
There are two ways by which the amount of inertia and momentum may be reduced.
1. By standardizing surroundings and equipment so that the inertia and the momentum are limited to practically that of the materials, and not the materials plus arms and body.
Example. Picking up ninety pounds of brick at one lifting.
2. By so standardizing motions that as few starts and stops as possible occur from the time the material leaves the stock pile till the time it is in its final resting place in the work.
Example. In laying brick by the " pick-and-dip " method on face tiers, a brick is lifted in one hand and a trowel full of mortar in the other. The brick must come to a full stop in the bricklayer's hand while the mortar is being laid and the bed prepared, and then move to its final resting place, unless brick and mortar are dropped in two different places.
In laying brick by the " stringing-mortar " method, the mortar is laid and the bed prepared before the bricks are lifted. The brick are conveyed from the pack to the wall without interruption or delay.
Standard methods of performing work may enable the worker to utilize the momentum.
Example. If the bricks are conveyed from the stock platform or pack to the wall with no stops, the momentum can be made to do valuable work by assisting to shove the joints full of mortar. If, instead of being utilized, the momentum must be overcome by the muscles of the bricklayer fatigue, not full joints, will result.
The ideal case is to move the brick in a straight path and make the contact with the wall overcome the
momentum.
LENGTH
A general rule of motion economy is to make the shortest motions possible. Eliminating unnecessary distances that workers' hands and arms must travel, will eliminate miles of motions per man in a working day as compared with usual practice.
Example. Put the wheelbarrow body as close as possible to the pile that is to be put into it, so that the distance the packets are carried from the pile to the barrow, or the sand from the pile to the barrow, will be the shortest distance possible.
Of the necessary distance to be walked or reached, have as much of it as possible done by the low-priced man, and have as little of it as possible done by the high-priced man.
Example. - With brick, have the tender put the pack of brick as near the final resting place of the brick as conditions will permit, so that when the high-priced man picks up a pack of, say, eighteen bricks, he requires a short motion only.
Have the high-priced worker always use first the stock that is nearest, this rule requiring the shortest motions in conveying the stock to its final resting place.
Example. In picking up brick from a packet or a scaffold the nearest brick should be picked up first. The brick that are farthest away serve as a reserve stock pile, to be picked up only in the emergency of not having any others nearer to pick up. It .may be that the brick farthest away may not need to be used on that piece of work at all, or at least their place will not be occupied so many times by bricks to be transported with longer motions.
Standard tools, equipment, and surroundings are essential if length of motions is to be made standard.
As already said when discussing clothes, the workman of the present should have even his overalls, belt, and clothes so designed that they will hold the different kinds of tools that are oftenest used, so that they may be picked in in the shortest time that is, with pockets for nails, clips, clamps, etc. The tools should be so placed that the least and shortest motions can be used after they are picked up, as cartridges are placed in a cartridge belt.
Next:
Part 6
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Updated 22 June 2021
3 September 2020, 11 June 2020, 11 September 2019, 30 September 2017, 19 August 2015
