Animal-Drawn Carts: History, Engineering, and Improvements

Introduction

The animal-drawn cart has existed since — and possibly arose alongside — the discovery of the wheel, around the fifth millennium BCE. Since that time, the human mind has developed various strategies and engineering solutions to make these carts more efficient and better suited to human needs. Over the centuries, animal-drawn carts have been used to carry everything from supplies to other animals and human beings. Up until the creation of the train and the internal combustion engine, animal power was one of the primary forces in the transportation of goods and people. The only other major source of motive power was the waterways, and even then animals were used to pull canal boats upstream in order to deliver merchandise.

This paper examines the implementation of animal-drawn carts both historically and currently. Although trains, planes, and automobiles have taken over transportation in many countries, poorer nations still rely heavily on the "beast of burden." After analyzing the past history of this device and its current uses, suggestions are offered for how carts might be improved. Research encompasses both the actual design and engineering of the efficiency involved and the materials used and available, since material choice affects both initial cost and operational performance and must therefore be assessed carefully.

The history of the animal-drawn cart dates back to the creation of the wheel itself. Since then, there have been many interpretations and iterations of this system of transportation — many of which have improved over time, while others, owing to their simple design, have remained virtually unchanged. Carts have been mentioned in literature as far back as the second millennium BCE, and may be named for the animal that pulls them, such as horsecarts or oxcarts ("Cart").

Carts come in many different shapes and sizes, but the basic purpose of transporting material and/or living cargo remains the same. Carts generally have two or four wheels, although some have more than four. Those with four wheels — called drays or wagons — usually have a pivoting front axle with a pole connected to the collars or yoke of the two controlling animals ("Cart"). The traces from the animals are connected to the pivoting front axle and then, by chain or sometimes rope, to the rear axle.

History of the Animal-Drawn Cart

Two-wheeled carts, sometimes still referred to as wains, have two shafts — one along each side of the animal — which help to support the forward-balanced load. These shafts are connected by a saddle placed on the horse or other animal, and the traces then attach to the axle of the vehicle. In all such cases the traces are attached to a collar on horses, to a yoke on larger animals like oxen, or to a smaller harness on lighter animals. One-horse carts are the most common form of transportation for low-income or small-acreage farmers. As Ogwang observes, "Two-wheeled carts drawn by oxen and donkeys are used commonly for farm transport in the northern part of Uganda and generally in the rest of the country" (181).

Traces are made from a range of materials depending on the load and frequency of use. Heavy draught traces are made from iron or steel chain. Lighter traces are often leather or hemp rope, though plaited horsehair and other decorative materials can also be used. Builders of wains were known as Wainwrights, just as builders of carts were known as Cartwrights. These trades no longer exist, but the terms survive as surnames descended from those who practiced these crafts ("Cart").

While the installation of brakes on most carts is not common practice — especially in flat areas — brakes are a substantial and desirable feature in other contexts. On steep inclines they can spare animals from severe stress or pain: on the uphill run, brakes can be used to allow the animal to rest; on the downhill run, they ease the strain of the weight burden. This is in addition to the general safety benefits brakes provide to carts and their owners.

Carts may also be constructed for a very specific single purpose. A notable example is the Light Single Drum water carrier, developed in England for use in Kenya by the Development Technology Unit at the University of Warwick ("Light Single Drum").

The earliest devices for animal-drawn labor were probably plows, used by farmers to cultivate their fields. Usually pulled by oxen, horses, or other large draught animals, these plows had a large blade that split the ground as the animal dragged it forward. While efficient for the time and still in use today, the mechanics of a direct pull involve important trade-offs.

Such a pull has both an upward component and a forward component. If the pull were at an angle of 45°, the horizontal and vertical forces would be equal, meaning as much applied force is being used in "lifting" as in "pulling." If it were possible to change the 45° pull into one nearly parallel to the ground, the same force would have a much greater horizontal, or forward, effect (Starkey 12).

The use of a cart substantially increases the weight of the load that draught animals can handle compared with carrying loads on their backs or using a sleigh — which, in tractive terms, is closer to the plow idea. The lower rolling resistance of a wheeled cart makes tractive forces far more effective. Ideally a cart should be lightweight yet durable and should employ as efficient a wheel-and-axle system as possible. It is also necessary that carts be equipped with the appropriate harness system for proper use with the animal or animals involved.

Physics and Engineering Involved

Ogwang notes in his article "A Note on Improving Animal-Drawn Transport in Uganda" that, beyond these general principles, carts also need to be:

…adapted carefully to local operating conditions in terms of terrain, type of use and the characteristics of indigenous draft animals; designed to take account of local production conditions in terms of the availability of components, materials and manufacturing skills; manufactured in a way and on a scale that matches the capability of local industry; marketed at a price people can afford with credit available if necessary. (Ogwang 182)

After thousands of years of development, one might think that the designs of animal-drawn carts — especially in developing countries — would have reached an optimal level of efficiency in all these respects. However, Oram reports in "The Development of Low-Cost Animal-Drawn Carts" that developmental evolution is still occurring:

Working in Nigeria and the UK, members of the Development Technology Unit have developed cart components and cart designs which are significantly cheaper than existing designs. These cost reductions have been achieved by rigorous simplification of design, usually by providing only the minimum number of components. Such components as there are, are easy to make, of easily obtainable material and require only the minimum of skills and tooling to produce. (Oram 171)

Materials have certainly been one area that has driven an evolutionary step in making carts both more durable and lighter. While wood is a traditional and often readily available material for cart construction in many regions, it is not always the best option. Steel can produce a very durable and rugged cart that will often outlast the animals drawing it. However, aluminum is equally durable and resistant to the elements, while being extremely lightweight, making it the material of choice in many countries. Pneumatic, or inflatable, tires have also been a significant boon to cart design: they absorb shock and distribute weight over a wider surface area without significantly increasing drag on the vehicle.