| Animal Powered Systems |
"A Merciful Man is merciful to his beast. Moral: Buy a J.l. Case Horse Power!" Behind that appeal by an American manufacturer of agricultural machinery to the Christian conscience of the American pioneer of 1878 (figure below) lurks a psychological barrier that - more than a century later - could represent an impediment to the propagation of animal- power technology via development projects: whoever uses or recommends the use of an animal power is a potential tormentor of animals. The significance of such suspicions, especially with regard to public interest in the development policies of industrialized countries, should not be underestimated. Time and again, organizations dedicated to the prevention of cruelty to animals have spoken out against the promotion of systems- based on tractive animal power in developing countries.
Add to that the associations with days gone by that animal-power technology can call forth at the drop of a hat. Thoughts of treadmills and slavery crop up. And so, it could happen that the only feasible alternative to one or the other case of slave-like manual labor is rejected without even having been tried.
Do animal powers really just make slaves of poor dumb beasts? Love of animals derives from the knowledge that, in many ways, animals are not unlike human beings. Such insight is most readily acquired through close, daily contact with animals.
Within the framework of Christian morality, man's love and respect for animals grew primarily out of the relationship between beasts of burden and their keepers' and so polemic the remark may sound - that love and respect seem to be disappearing at about the same rate that draft animals are being replaced by factory farming and pointless animal experiments. Anyone who is in some way dependent on the services of draft animals must sooner or later recognize the fact that he can get more work out of them - and increase his own profits - by paying heed to how his animals express their needs, learning to understand their "signals", and trying his best to keep them as contented as he can. This includes proper feeding, grooming and preventive health care as well as the use of harnessing techniques adapted to the needs of the animal and attention to its naturral working habits. A draft animal will feel all the better, the more intensively and conscientiously it is put to work.
But, what are the needs of a draft animal at work in an animal power? How can its energy best be utilized and, to the extent possible, increased? Due to the circular track that the draft animals are forced to follow in a sweep power, as much as one-half of the animal's normal "straight path" efficiency may be lost due to the slow pace in combination with a waste of strength that is inherent to such systems.
The first way to improve efficiency is to maximize the diameter of the track in order to make the drawbar as long as possible (not less than 3.50 m), though the attainable advantages must be carefully weighed against the increased cost of construction and the lower speed of rotation.
The energy losses in a sweep power can be further reduced by ensuring that the tractive power is tangentially applied to the circular track. If oxen or castles are serving as draft animals, that is relatively easy to manage by securing the drawbar at the animal's withers. In the case of donkeys or horses, a somewhat more complicated harnessing arrangement must be used.
In addition, achievement of optimum performance on the part of a draft animal is also decisively dependent on the selection of an optimum work cadence. In this connection, it is interesting to note that both the Delou and the Persian Wheel - two animal-powered water- raising systems with completely different modes of operation - are well-designed and widely used. The technical aspects of the purely intermittent Delou and the purely continuous Persian Wheel, together with some intermediary forms of water-raising facilities, are described in detail in Chapter 7. At this point, it is deemed sufficient to point out the fundamental differences in the two approaches to the organization of work and working time.
All work and no play? In the case of the Delou (the name derives from an Arabic word for "water bag"), the raising sequence - lifting, emptying, lowering and filling of the buckets - is in harmony with the rhythmic motion of the draft animal: pulling (away from the well on a straight path), turn/rest, returning without load (to the starting point), turn/rest. Together, the bag, rope and water often weigh more than 60 kg, so that the drover has to pull together with the animal at certain points of the raising process. For both the man and the animal, then, there is a rhythmic succession of great exertion and relative ease.
The Persian wheel, the forerunner of the sweep power, has a completely different mode of operation. The animal trots steadily along on a circular track, thereby transmitting its energy to an endless bucket ladder (potgarland) via an angular gear. The various steps of the cycle intermingle: filling, raising and emptying of the buckets and the pulling and turning efforts of the animal all overlap. Neither of the two systems can claim superiority in principle. Both have their advantages and disadvantages. The Delou involves a certain amount of idle time, and the Persian wheel - like all sweep powers - wastes a certain amount of energy. The Persian wheel is also characterized a relatively high initial outlay and maintenance costs, though even children can operate it. The Delou is less complicated and cheaper, but its operation requires an adult with whom the animal is familiar and whose guidance it will accept. The only meaningful difference, though, lies in the attainable drawing depth, which is greater with the Delou.
No thorough, comparative analysis of the two systems has as yet been conducted, but would certainly be worthwhile. In any case, the reason for the emergence of two such dissimilar methods of raising water was a "non-technical" one: the Persian wheel was developed in Egypt or Mesopotamia, that is, in areas where life has always been decisively influenced by the eternal flow of large rivers. Most likely, bucket wheels driven by those rivers served as early models for the development of the Persian wheel.
With the sudden rise in the use of water power during the High Middle Ages, a great many new machines, all utilizing rotary motion as the most universal driving force. also appeared in Europe. Where water power was not available, sweep powers had to fill the gap as the most obvious technical solution.
The concept of perfect rotary motion determined the development of animal-power technology in Europe. At a very early stage, efforts were undertaken to relieve the animal power of its, well, "barnyard aroma" and to at least minimize, if not entirely eliminate, the disruptive effect of the natural, unpredictable, drive-side factors on the power take-off side.
Especially with regard to nonagricultural applications, that motive soon came to be a decisive factor in most new and improved systems such as water-raising facilities in castles and fortresses, where more and more treadwheels and treading disks had come into use since the 17th century. Finally, with great structural intricacy, the aim of becoming independent from the will and moods of the animal and simultaneously minimizing the output fluctuations was accomplished by tying the animal in place - often enough with a noose around its neck - in a treadwheel or on a disk. By permanently pulling the ground out from under the animal's feet, so to speak, the animal was automatically forced to deliver the power required on the output side. The conventional animal power is an appendage to the animal, as it were; in the case of treadwheels and disks, the opposite is true.
This eliminated the necessity of someone who was familiar with the animal being in constant attendance, which certainly provided a major incentive for the use of treadwheels and disks. Moreover, fascination with the engineering feat embodied in such ponderous new machines doubtlessly contributed to their rapid rise in popularity. (An ox-powered treading disk that was used well into the third decade of this century at Schillingsfurst Castle in Franconia is still on display there.) Without having conducted a thorough study of pertinent literature, and in the absence of practical test results, it would be difficult to say to which extent treadwheels and disks were able to effect a real increase in efficiency. Judging by the data on a water-raising treadwheel that was in operation until the mid-'30s at Conradsburg in the Harz Mountains, one could easily come to the opposite conclusion, since the system was veritably ridden with friction losses: the bearing had to support not only the weight of the disk or wheel, but also that of the animal.
With the onset of industrialization, initial improvements to the handmade wooden structures were introduced in the form of metal friction bearings and cast-iron bevel gears, which had a positive impact on the overall efficiency and reliability of animal powers.
From about 1870 on, the focus of interest shifted to other aspects, including safety of operation. Above all in the field of agriculture, the animal power was regarded as a rather dangerous instrument, though that was at least partially attributable to the frequent practice of having them operated and attended by children.
Safety problems also gave rise, at least in part, to the development of automatic coupling and braking mechanisms, for which 15 patent applications were submitted in Germany alone between 1870 and 1910. During that same period, 10 patents were issued for strain equalizers (for the simultaneous use of several draft animals) and for spring mountings.
While such modifications tended to further enhance the animal's "comfort" (and, hence, to improve its performance), they usually entailed high costs in time and effort for their design and construction.
Also around 1870, the tread power appeared as the industrial form of the old treadwheel and disk. In addition to the advantages already discussed in connection with the latter, the new tread powers also featured a much more modest space requirement.
Nonetheless, tread powers were widely criticized because of their high price and frequent breakdowns, and because the animals often fell down or were otherwise injured in them.
Above all else, though, nature took revenge for being forced into the role of a mere appendage to the machine: the draft animals were often overworked to the point of complete exhaustion and at least temporary uselessness.
By comparison, the two automatic ("self-acting") whipping machines patented in 1886 and 1895 for use in sweep powers appear ludricrous and harmless.