Mexican Plow
Staff posted on October 24, 2006 |
Mexican Plow

Problems with Small Plows

Obviously, given the price constraint, the engine is going to be small. Unfortunately, the small engine plows in use have numerous problems. These are enumerated in a very useful text by R.C. Gifford entitled Agricultural Mechanization in Development. Here are some of the difficulties of small plows (518 hp) according to Gifford:

  1. High operation cost. Small engines must operate at higher r.p.m. to gain the torque necessary to pull a heavy implement. Because of this, maintenance and repair costs will be higher than with larger engines that can operate at lower speeds.

  2. Low traction. The average tractive efficiency of regular tractors (say, 50 h.p.) is about 46%; for small tractors, the efficiency is 1734% less. Traction is a function of the weight of the tractor and its ability to turn that weight into traction for the tires. Obviously the smaller the tractor the less weight available.

    A second problem with traction in smaller tractors is the limitations in the size and width of tires they can use; this also leads to low traction. Low traction will lead to difficulty in cultivation in heavy or dry soil conditions.

  3. Low stability. A single-axle plow's stability is limited by the ability of the operator to prevent the machine from tipping. If the slope of the land where the tractor is used is steep and the ground rocky and hard, the plow can skip and twist over the earth. Small two-axle tractors are limited in the width and length of their wheel base. This leads to the same problem Jeeps have; namely, the tendency to tip over easily in sharp turns or on slopes. Yet a short wheel base and high ground clearance are necessary for a plow that can operate in difficult areas such as small, irregularly-shaped plots. Thus a tradeoff between stability and mobility is often made in the design of the machine.

  4. Low operator comfort. Operator comfort is often slighted in favor of power and design constraints. Yet being able to operate a machine comfortably for long time periods increases both productivity and safety. Unfortunately, price constraints limit the designer's ability to make both economical and well-designed tractors.

  5. Safety problems. Safety of operation can be improved by considering ergonomic factors, as well as the layout of proper driveshafts and moving parts. It can also be improved with features which protect the operator from the machine. In designing small tractors, however, ergonomic factors are often given scant attention.

    As for safety features, these may work well when the plow is new, but a scarcity of parts and proper servicing may result in their degradation with time. Usually, there is little in the way of operator training. This tends to increase safety problems. Finally, small tractors have fewer safety features to begin with than larger ones.

Referring to the small tractor, Gifford concludes that "in spite of the seemingly attractive low cost, it is more costly per horsepower to manufacture, and more costly per hectare of output to operate, than conventional tractors."

Questions for Discussion

Will the plow be perceived as foreign or alien?

Anthropologists who have studied peasant cultures in Mexico and Central America emphasize that anything brought into such cultures from the outside and perceived as foreign or alien can be very destructive to the culture. It can also be detrimental to the self- esteem of the people who use it.

The peasant farmers in Mexico, many of whom are Indian, are very sensitive to the differences between their way of life and the way of life of the "white man." The "white man" includes not only Anglo Saxons from the United States, but also Mexican descendants of the Spanish invaders. The Indians often view anything brought in from the outside as an indication of their own inferiority. The acceptance of such imports implies, they believe, that the white man knows how to do things better than they do. Sometimes they will reject the imported item and not use it. Sometimes they will use it, but the result will be culturally or psychologically destructive. At other times they can incorporate the item into their culture in a more positive way.

Thus a very serious question arises as to whether a mechanically powered plow would have a beneficent impact on the indigenous cultures into which it is introduced by making their method of farming more efficient and their way of life more sustainable, or whether it would tend to disrupt their culture and contribute to its destruction.

Here is a case where there is an ethical issue demanding choice, whereas one might not have seen an ethical issue at all. It is an example of the way ethical issues lie hidden under the surface of considerations that appear purely technical.

There are, however, several ways in which an engineer might attempt to evade any responsibility regarding the ethical questions that this issue raises. For example, she might argue that this kind of consideration is not her concern as an engineer. But this relies on a narrow conception of responsibility. If a person's being a causal agent with respect to an event gives one a share in the responsibility for it, then a designer has a share in the responsibility for the effects of the plow.

A second argument might be that the degree to which peasants can incorporate a plow into their culture is determined more by the way the plow is marketed to the peasants, and this is an issue over which engineers have no control. There is a considerable degree of truth in this response, but it still seems inadequate. As we shall see in the next section, some of the factors that determine the ability of the culture to assimilate the plow are directly affected by the design, and these are factors over which the engineer does have a say. So engineers do share in the responsibility for whether or not the plow can be assimilated.

Finally, an engineer might say that primitive peasant cultures should be assimilated into the dominant, more western-oriented culture of Mexico. If the plow he designs contributes to that end, this is one of the fortunate consequences of the creation of the plow. Whether or not this view is correct, it is clearly not a value-neutral position. It shows even more clearly that the engineer cannot wholly escape responsibility for the value dimensions of her work.

A number of factors might determine whether the plow will be perceived as an unwelcome import from a foreign and hostile culture, including such simple things as what color the plow is painted. Some colors may have special meanings for the culture, and they may be important determinants of who uses the plow and what significance it has in the culture. For example, some colors may be more associated with one gender than the other, or one social stratum rather than another.

For whom should the plow be designed?

If the plow is used by the wealthier and more competent and enterprising members of the peasant community, it may be used most effectively. This may have the result, however, of putting these members of the community even further ahead of their neighbors. If the plow is used by the less talented members of the community, it may not be used effectively, and the community may not make as much economic progress.

Which value is more important: community solidarity or economic progress? Is there any way to achieve both ends? Could this be incorporated into the design of the plow? For example, the cost of the plow is an important determinant of who will use it.

Several other factors might be important in deciding which group would be more likely to use the plow. The simpler the construction and the more easily repairable the plow is, the more likely it would be that the less advantaged peasants would use it. The important thing for the student to see is that these kinds of ethical issues are raised by the question about the group for which the plow is designed.

Will humans or animals be used to pull the plow?

Animals are an important part of many traditional cultures. Mechanical devices that make animals useless, or even less useful, can be important determinants of social change. We have already pointed out that it is possible to design a plow that is pulled by an animal, but has a motor to vibrate it or in some other way move the blades so the plowing can be done more easily. Human power is even an option in some cultures. Would this be desirable?

The care and association with livestock is important to peasants' sense of self and social place. Animals are also a kind of insurance for peasants. If times get too hard, the animals can be sold to help sustain the family. If animals are not used for draft purposes, they would be idle much of the time. On the other hand, animals may be a significant drain on the limited food resources of some groups. Perhaps the reduction in the number of animals the peasant would have to support would be a benefit to him.

Is the design of the plow sensitive to the gender of the operator?

In some traditional societies, women do most of the farming. If the plow is not suitable for women, the introduction of the plow into the community would be disruptive of traditional ways. What design considerations are relevant here? For example, some plows might be too heavy for women to use. A heavy plow might be too difficult for women to turn at the end of the row. If a heavy plow overturned, some women might not be able to set it up again.

If, in a given culture, women do not do farming and their exclusion from agricultural work is one of the reasons for their subservient status in the culture, a plow suitable only for men would perpetuate these conditions. A plow suitable for women would be a vehicle for raising their status in the society. But then this augmented status might be highly disruptive to the society, and the need to be "liberated" might be something that the women of the culture do not recognize. Is it morally permissible for outsiders to, in effect, mandate change by introducing revolutionary technology? Perhaps the engineer should strive to make the plow "gender neutral." If so, she must know how to do this.

Will the operator of the plow walk or ride?

The change from walking to riding or riding to walking is a significant one. In general, walking behind a plow is probably better for the operator's health, but it might not be desirable from a social standpoint. For example, riding might have more social status than walking. Whether one walks or rides might also be related to the perception of whether the work of plowing is appropriate for men or women. Finally, safety issues might be important considerations in whether the operator of the plow walks or rides.

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