Model cart designed by Constantino Botelho de Lacerda

19.5 x 55 x 26.8
Carved and inlaid wood

CAT. 1824 : D.II.33

Outro carro como o de Boulard, só com a differença do seu eixo gyrar sobre tres cylindros moveis para que o atrito seja da segunda especie. Esta addição é do Sr. Constantino Botelho de Lacerda Lobo.- Jornal de Coimbra.

Another cart like Boulard's, differing in that its axle turns on three moveable cylinders so that friction is of the second kind. This addition is by Sr. Constantino Botelho de Lacerda Lobo. - Jornal de Coimbra.

Constantino Botelho de Lacerda Lobo's article "Report on the defects of our military carriages and how to improve them, and an addition to Boulard's invention", in Vol.I of the Jornal de Coimbra, has an editor's comment to the effect that transport is "the soul of the army'". The comment refers to an article by the Marshall General, Count Lippe, published in n.º VII of the Investigador Português, in which the author states that the armed forces should be equipped with carriages and carts suitable for transporting a variety of artillery.

Botelho de Lacerda's article claims that the army, responsible for the defence of the realm, commanded by "the best general in the world", the "Most Illustrious and Most Excellent Marquis of Torres Vedras", could no longer be expected to produce one victory after another if it did not have adequate transport at its disposal.

Due to the scarcity of oxen, he continues, it was desirable that all transport should use mules, as economically as possible. A very few oxen would be enough if carts were not so defective; mechanical defects were responsible for exhaustion of the animals, and precise identification and correction of defects would make the transport system more efficient. Vehicle failure in general contributed to the poor mobility, overloading and insecurity of military transport.

There were many causes for this poor mobility, in Lacerda's opinion, one being the frictional resistance of axles. As these were made of wood, they had to be very thick to be sufficiently strong. In addition, the wheels and axles were excessively heavy, and the cart floor was made of unnecessarily thick planks and beams. Traditionally, the axle of a cart was underneath the floor; this adversely affected stability because the centre of gravity was therefore quite high. The narrow rims of the wheels made them fragile, and the small area in contact with the earth caused damage by making ruts. Paved roads also suffered damage, as the cobble stones were pushed into the ground by the weight of the cart wheels.

Carts in Lisbon were the worst in Portugal, according to Lacerda. They had shafts measuring twelve spans in length, floors six spans wide and eleven spans long, and wheels of about five spans in diameter, decreasing in thickness from the axle to the rim. The wheel rims were not only narrow, but also covered with iron and studded with large nails, making them very uneven. The cart floor was supported on the axle by two bearings over two spans high, so that the centre of gravity was much higher than the axle, leading to instability of the cart.

As a result of his research, Botelho de Lacerda presented a report to the Lisbon Academy of Sciences in May 1806, suggesting possible alterations for carriages. For example, to increase mobility, he proposed fitting wheels of greater diameter, able to pass over obstacles, and with smooth wide iron-covered rims. The axle of each wheel should turn on cylinders similar to ball-bearings, which would substantially reduce the friction between the wheels and the axle. To lessen the overall weight, the wheels should not be solid, but instead have sturdy spokes running from a cylinder near the axle out to the rim. The floor of the carriage need not be made of thick bulky planks and beams; the wood could be thin, as long as it was strong enough to bear the weight of the load. Finally, to increase stability, the floor should be mounted below the level of the axle; this could be done by positioning the bearings on top of the floor rather than below.

Lobo, Constantino Botelho de Lacerda, "Memória sobre os defeitos, que têm os nossos carros de transportes militares; modo de os diminuir e additamento ao da invenção de Boulard", Jornal de Coimbra, Vol. I, 1812, p. 329, Fig. 1-3.

Back                 Index                 Forward