| Autor: |
Barpi, Fabrizio, Deakin, Michael A B |
| Předmět: |
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| Zdroj: |
International Journal for the History of Engineering & Technology; Jul2012, Vol. 82 Issue 2, p159-175, 17p |
| Abstrakt: |
A trunnion-type drawbridge requires a lifting force that varies in the course of its operation. The so-called Bélidor design allows for this variation by providing a counterweight running down a curved track whose shape is calculated to provide the correct effective force during the course of the lift. The design is usually attributed to the eighteenth-century engineer Bernard Forest de Bélidor, but in fact is earlier. We provide a correct account of the origins of the design and go on to discuss its implementation in a variety of places and contexts. It was used in eight examples constructed in the Australian state of New South Wales in the first quarter of the twentieth century, where the consideration was to accommodate the competing demands of road/rail transport and of shipping. The same design had also been used somewhat earlier in the USA for the same purposes. We provide a guide to the literature dealing with both these sets of examples. Moreover, as well as the Australian and American examples, there are others in Europe, mostly as elements of castle fortifications. The reader is introduced to a number of these. We also discuss a very recent example (Forton Lake) developed for other purposes, as well as a further American example (Glimmer Glass). These two examples are noteworthy in that both are fully operational. We also provide the basic theory underlying the design and comment on the different ways in which it has been realized. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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