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Chapter 1 - Human Muscle Power in History
By David Gordon Wilson
"The sweat of the brow is daily expended by millions, and daily millions of sighs are wrung from the tormented frame of the bent and weary in the pursuit of providing food." Rudolf P. Hommel wrote this after living for eight years in China in the 1920s studying Chinese tools and crafts. His aim was to "give a fairly complete picture of Chinese life, as lived by millions of people today, a life in which there has been no considerable change for thousands of years."
That picture is, I believe, one which we all have of our forebears in any culture except, perhaps, those few tropical paradises where we are taught to believe that the inhabitants just sat under the banana trees and coconut palms eating their fruits whenever they wished. My remembrances of growing up in England in the thirties and forties are certainly closer to the Chinese model than to that of the Pacific islands. During World War II we all had large vegetable gardens carved out of tennis courts and the like, and I look back without longing at the back-breaking weeding, watering, and the "double-digging" (double-depth trenching the plots, with manure in the lower part of the trenches). The only mechanization we had was my homemade bicycle trailer which carried the five-gallon cans of water and the manure. The fork, the spade, and the hoe were the principal tools; and they used, or misused, our bodies painfully. We could utilize only a small proportion of the energy output of which we were capable because of the twisting contortions which these implements demanded of us. How different from the relative comfort of a bicycle, with a choice of gear ratios to suit the load and the terrain.
I have worked on farms in England, Scotland, and Germany and have lived among farmers in Nigeria. In all these places the tractor was beginning to take over those tasks which could be most easily mechanized. But this meant that the manual labor which was left to be done was generally the least susceptible to relief given by the application of mechanical aids. We shoveled endless quantities of manure; we hoed the weeds from almost invisible crops; and we picked up potatoes from the mixture of earth and stones thrown up by a speeding tractor with a rotary digger. We did not feel that we were much better off than our more ancient ancestors.
What is remarkable about the historical use of muscle power is not only how crude it generally was, but that when improved methods were tried, they were generally not copied and extended. There were three ways in which the application of human muscle power could fall short of the optimum. First, the wrong muscles could be involved. We find time and again that people were called upon to produce maximum power output, for instance in pumping or lifting water from a well or ditch, using only their arm and back muscles. It seems obvious to us nowadays that to give maximum output with minimum strain we must use our leg muscles, not incorrectly called our second heart.
Second, the speed of the muscle motion was usually far too low. People were required to heave and shove with all their might, gaining an occasional inch or two. A modern parallel would be to force bicyclists to pedal up the steepest hills in the highest gears, or to require oarsmen to row boats with very long oars having very short inboard handles.
Third, the type of motion itself, even if carried out at the best speed using the leg muscles, could be non-optimum in a rather abstruse way. Here is the best example I know of: Dr. J. Harrison of Australia took four young, strong athletic men and a specially built "ergometer" a device like an exercise bicycle in which the power output could be precisely measured. He wanted to settle the controversy as to whether oarsmen produced more or less power than bicyclists, and he reproduced the leg and arm motions required for rowing racing boats (or "shells") and pedaling racing bicycles. He found (somewhat to his surprise, no doubt) that there was negligible difference between the power output produced in these two very different actions by the same athletes after they had practiced long enough to become accustomed to each.
Then he tried some old, and some possibly new, variations. He fitted elliptical chainwheels in place of the normal circular types to the cranks of the bicycle-motion devices. These chainwheels were made in Europe in the thirties to reduce the apparently useless time spent by the feet at the top and bottom of the pedaling stroke in bicycling, and correspondingly to increase the more useful time when the legs are going down in the "power" stroke. He found that some of his subjects, but not all, could produce a little more power with the elliptic chainwheel than they could before. Then he changed the ergometer so that, instead of the rowing motion usually found in racing boats where the feet are fixed and the seat slides back and forth, the seat was fixed and the feet did the sliding. This time all his subjects produced a perceptible increase in power output. The reason was apparently that they did not have to accelerate so high a proportion of their body mass at each stroke.
In normal rowing, after the oarsman has driven the oars through the water by .straightening out his legs and body, he must then use muscles to eliminate the kinetic energy produced with such effort in the body. Harrison investigated the effects of using mechanisms which automatically conserved this kinetic energy. He used various types of slider-crank motions, like those of a piston in an automobile cylinder. He called these "forced," as opposed to the normal "free," rowing motions; and he found that all his subjects produced a substantial increase over their previous best power outputs in rowing or bicycling. What is more, this improvement held for as long as the tests went on. One subject, apparently Harrison himself, could produce no less than 2 horsepower (1.5 kilowatts of mechanical output) for a few seconds, and a more-or- less continuous output after five minutes of a half horsepower, still 12 percent or so above his best output by other motions.
This careful, scientific work enables us to look with a better perspective at the use of human muscle power in the past. Until Harrison did his work, no one could agree as to which muscle action was best to use for racing or for steady, all-day work. Even now, six years after wide publication of his results, no one to my knowledge has grasped the significance sufficiently to apply this new in-formation to ease the lot of anyone who has to use muscles in his daily work or to increase the speed of people who race. And, incidentally, other research by Frank Whitt in England has shown that power output measured by ergometers may be substantially lower than that produced by the same persons using the same muscle actions when bicycling or rowing because the absence of the self-produced cooling wind results in dangerously overheating the body. As pointed out earlier, few of the motions used historically to harness human muscle power incorporated any intrinsic cooling action. They were mostly of the slow, heaving variety, so that our unfortunate forebears had to cope with heat stress on top of the use of usually inappropriate muscles moving against resistances which were too large at speeds which were too low. If in the future we run out of the earth's stored energy and have to resort to that of our bodies, we should be able to look forward to considerably greater comfort while we are working if the results of modern research are applied.
The Manpower Plow of Shantung
This was, and possibly still is, a plow operated by two men, one pushing and one pulling. Rudolf Hommel found it still being used in China in the twenties. "Shantung is very much overpopulated, and poverty is therefore much in evidence.... [I]t is therefore not surprising to find today a primitive plow, which for lack of draft animals has to be served by man to pull it. There is a baseboard with a cast-iron share at one end. Two uprights are firmly mortised into the baseboard, the rear one of which, farthest from the share and bent backward, resembles the handle of one of the ancient one-handled European plows, but is not so used. Instead of grasping the upper end of this upright in his hands, as in the old western plow, the plowman, leaning forward and down-ward, presses his shoulder against it, while his two hands grasp the two projecting ends of a cross peg-handle driven through the lower part of a curved upright. Thus in a very ingenious manner, he not only guides but pushes the plow."
Figure 1-1 The Shantung plow
For this arduous task, both plowmen used their leg muscles, which are the most appropriate muscles for the duty. The motions are too slow to be efficient (in engineering we call this a poor "impedance match"), and most of the other muscles and body frame are strained painfully to apply the force produced by the leg muscles. One hopes that it was used only in soft ground. In the rocky soil of New England its use would be exquisite torture.
I have started with this plow because we have so good a description of it, complete with a knowledge of how it was used. In most historical cases, we have just old illustrations which were made for purposes other than for showing the details of the mechanisms or the precise way in which they were used. We can usually guess intelligently enough. But before we leave the manpower plow, consider how you would perform the same task today. I know of no purchasable alternative to the fork and spade for either of which my back has no great affection. Certainly the Rodale winch described in Chapter Three is a solid advance. We will be discussing various other alternatives in the chapter on futuristic uses of manpower.
In the examples which follow, I am not attempting historical completeness: I have chosen them as interesting illustrations of how muscle power has been used in the past for a variety of tasks. I am grouping them by the muscles and motions employed.
This is perhaps the most obvious means of obtaining rotary motion, and man has been using it for centuries. The earliest known handcranked device was a bucket-chain bilge pump found on two huge barges used by the Roman emperors and uncovered when Lake Nemi was drained in 1932.
Figure 1-2 The bucket-chain bilge pump (Reproduced by permission of Doubleday & Company, Inc.)
Figure 1-3 Bucket-chain water lifter (Courtesy of Friedrich Klemm)
Figure 1-4 Chinese endless-chain water lifter (courtesy of Martha Hommel)
Agricola, writing in 1556, showed a complicated hand cranked transmission for driving a similar bucket-chain water lifter. He also showed a bucket-chain being assembled. An endless-chain water lifter was also used in China in much later times. It was different in two respects. Instead of buckets, the water was trapped by boards sliding in a trough. One would think, however, that this would be less efficient because of friction and leakage. In addition, levers were attached to the cranks, with all the lost motion and top-dead-center problems they entailed. Presumably the levers were used to give a more comfortable working position for the ground-mounted trough.
Leonardo da Vinci shows concern for the comfort of the user in his drawing of a textile winder with a handle at a convenient height and with a winder-drum of a diameter giving what will presumably be a near-optimum rate of action. Leonardo uses gearing for the same reason obtaining a good "impedance match" in his design of a file-cutting machine in which the crank is used to raise a weight at a speed to suit the operator, and the weight subsequently delivers energy at an optimum rate to the drop-hammer cutter.
Figure 1-5 Leonardo's file-cutting machine (Courtesy of Friedrich Klemm)
An earlier crank-driven screw-cutting lathe was obviously not designed by Leonardo.
Figure 1-6 Screw-cutting lathe (Courtesy of Friedrich Klemm)
One can imagine the difficulty of simultaneously turning a high-resistance load with a small crank in one hand while trying to control the cutting process with the left hand.
Two much more modern examples of handcranking are taken at random from the Science Record of 1872: the air pump for an undersea diver and what looks like a multiple stirrer for a nitro-glycerine-manufacturing process. These seemed to be low-torque applications of muscle power. A high-torque application which scarcely needs illustration was the old hand-wringer, which I used to try to turn for my mother. This was rather similar to the fifteenth century screw-cutting lathe in that while the right hand turned a heavy and fluctuating load, the left hand had to perform a difficult and hazardous control function.
A variation of the handcrank was used in China in the form of a "T-bar" attached to the crank. The use of this simple connecting rod enabled the use of both hands and/or ones chest or belly to contribute to overcoming the resistance.
Figure 1-7 Air pump for undersea diver
Figure 1-8 Nitro-glycerine factory
Levers Actuated by Arm and Back Muscles
Until the arrival of the sliding-seat scull, oars were moved predominantly through the action of the arms and back. Battles among warships were won by the boat which could pack in the most oarsmen. Ameinokles of Corinth in about 700 s. c. built boats to accommodate three rows of oarsmen in a staggered arrangement on each side; with al-most 200 oarsmen, it could travel at seven knots and became the standard battleship of the Mediterranean.
At the other end of the warlike scale were the pipe organs designed by Ktesibios in Alexandria in the third century before Christ. The air pump was a rocking lever which could be operated with two hands. There was little difference in the external appearance, at least, from the hand-pumped organ used in our church in England when I was a boy. (My father fitted it with one of the first electric blowers used for the purpose, at least in our area of the country.)
Figure 1-9 Pipe organs (Reproduced by permission of Doubleday & Company, Inc.)
Some tricycles were designed for lever propulsion by the hands, the arms, and possibly the back. Sharp showed a drawing
To be continued...
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