| Animal Powered Systems |
|7. Profiles .|
This last profile is devoted to the sweep-power/runner-wheel combination, which operates on an ingenious and hardly known principle of operation. Its greatest advantage is that at least part of the gearing can be dispensed with, thanks to a runner wheel that is attached to the end of the drawbar and runs along behind the animal. Its speed of rotation far exceeds that of the drawbar. The power is transmitted to the machine via shafts, gearwheels or belts and can be varied in steps by using runners of different size. In addition to increasing the speed of rotation, the runner wheel also serves as a friction clutch, i.e. as a safety device. Thus, this combination is often referred to as a "friction power".
The principle of the sweep-power/runner-wheel combination was probably first applied by the French company Tertrais et Carliers, of Chatelerault, which exhibited a power of that description at the Paris World's Fair of 1867. Incidentally, in the German literature, this principle was presented years later as an entirely new invention and attributed to at least three different inventors. In 1888, a German patent was even granted for the sweep- power/runner-wheel combination.
The experts' evaluation of the principle was contradictory. Some described it as "by no means worthy of imitation", while others expected that "within the next few years, this system will have completely supplanted all other types of geared powers in use up to now".
At least the latter prognosis has not been fulfilled. The sweep-power/runner-wheel combination has continued to lead a shadowy existence and was not incorporated into the product lines of any big manufacturers. In part, this may have been attributable to the necessarily complicated design (with steed wheel and circular runner rail).
The combination did not last long enough to experience the birth of the rubber tire (which was instrumental to the success of the tractor). If, however, such combination powers were to make a modern-day comeback, it would most probably be thanks to automobile tires -a mass-produced - and therefore lowpriced - industrial product in use all over the world. Accordingly, the three new constructions best-known to date and described briefly in following are based on the use of a car tire as their main component. A photo by Swiss engineer Oehler-Grimm shows an animal-powered pump in Botswana, about which, unfortunately, no further information is available. It is apparently a series product with a reciprocating pump installed at the bottom of the well and driven by the runner wheel via a crank mechanism, reversing chain and appropriate linkage. At the time this shot was taken, the pump had apparently been out of service for some time; the tire was dismounted. The outage may have been caused by accidents mentioned in Mr. Oehler-Grimm's report. Allegedly, a child was run over by the runner wheel. The extent to which such a unit could be manufactured by manual means (e.g. in combination with a "Sahores pump") should be determined by way of practical experiment. There is a Dutch proposal for a hand-made version' in combination with a rag pump (in the form of a rope pump with its rope running through a plastic sheath). At copy deadline, it was not yet known if the design in question had already been tried out in practice. Also, there is the prototype of a universal animal power developed by two students of engineering (Boie and Krause, Cologne) that works along the lines of the sweep-power/ runner-wheel combination. The design was deliberately adapted to the requirements of developing countries and includes, to the extent possible, only such components as would be locally available. Allowing for the correction of a few design deficiencies, this model should be very well suited for imitation and trial in a developing country. The photo was taken on the occasion of a demonstration organized by GATE in August of 1982.