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Question de largeur

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Question de largeur

  1. 1. Un peu de culture… (amusante)
  2. 2. Comment a été défini l’écartement des rails de chemins de fer US ???
  3. 3. La distance entre deux rails de chemin de fer aux Etats-Unis est de 4 pieds et 8,5 pouces (143,5 cm). Nombre particulièrement bizarre...
  4. 4. Mais pourquoi cet écartement a-t’il été retenu ?
  5. 5. Parce que les chemins de fer US ont été construits de la même façon qu'en Angleterre, par des ingénieurs anglais expatriés, qui ont pensé que c'était une bonne idée, car cela permettait également d'utiliser des locomotives anglaises.
  6. 6. Mais... pourquoi les Anglais ont-ils construit leurs lignes comme ça ?
  7. 7. Parce que les premières lignes de chemin de fer furent construites par les mêmes ingénieurs qui construisirent les tramways, et que cet écartement était déjà utilisé.
  8. 8. Mais... pourquoi cet écartement des rails de tramways ?
  9. 9. Parce que les constructeurs de tramways étaient les mêmes que les constructeurs de chariots, avec les mêmes outils et les mêmes méthodes.
  10. 10. Mais... Pourquoi les chariots utilisaient-ils un tel écartement ?
  11. 11. Parce que partout en Europe et en Angleterre, les routes avaient des ornières et qu'un espacement différent aurait causé la rupture de l'essieu du chariot.
  12. 12. ET... Pourquoi les ornières des routes étaient-elles ainsi espacées ?
  13. 13. Parce que les premières grandes routes ont été construites par l‘Empire Romain pour accélérer le déplacement des légions romaines. Et les premiers chariots ont été des chariots de guerre romains. Ces chariots étaient tirés par deux chevaux qui galopaient côte à côte et ils devaient être suffisamment espacés pour ne pas se gêner l’un et l’autre.
  14. 14. Afin d'assurer une meilleure stabilité du chariot, les roues ne devaient pas se trouver dans la continuité des empreintes de chevaux, et ne pas se trouver trop espacées pour ne pas causer d'accident lors du croisement de deux chariots.
  15. 15. L'espacement des rails US s'explique parce que 2000 ans auparavant, sur un autre continent, les chariots romains étaient construits en fonction de la dimension de l'arrière-train des chevaux. Nous avonc donc maintenant la réponse À notre question d’origine !!!
  16. 16. Il y a une extension à cette histoire d'espacement des rails et d'arrière-train des chevaux. Et maintenant, cerise sur le gâteau !
  17. 17. Quand nous regardons la navette spatiale américaine sur son pas de tir, nous pouvons remarquer les deux réservoirs additionnels attachés au réservoir principal. C’est la société Thiokol fabrique ces réservoirs dans son usine de l'Utah.
  18. 18. Elle aurait aimé les faire plus larges, mais ces réservoirs sont expédiés par train jusqu'au site de lancement. La ligne de chemin de fer entre l'usine et Cap Canaveral emprunte un tunnel sous les montagnes Rocheuses. Ce tunnel limite la taille des réservoirs à la même largeur ... que deux arrière-trains de chevaux !!! 
  19. 19. Ainsi, le moyen de transport le plus avancé au monde, la navette spatiale, dépend de la largeur d'un cul de cheval ! Les spécifications et la bureaucratie vivront pour toujours...
  20. 20. Donc, la prochaine fois que vous aurez des normes entre les mains et que vous vous demandrez quel cul de cheval les a inventées, vous vous serez peut-être posé la bonne question !
  21. 21. Puisque nous sommes dans l’espace... Une dernière question... Comment écrire dans l'espace ? Dans les années 60, lors de la conquête de l'espace, les ingénieurs se sont en effet rendu compte que les stylos à bille n'écrivaient pas dans l'espace : absence de gravité, donc l'encre n'adhérait pas à la bille.
  22. 22. Les Américains ont donc investi plusieurs milliers de dollars pour réaliser un stylo dont l'encre est sous pression, ce qui permet d'écrire dans toutes les conditions et positions. Les Russes eux n’ont dépensé que quelques kopecks : ils ont emporté des crayons à papier !!!
  23. 23. Voilà… Vous avez de quoi « épater la galerie » lors de votre prochain repas de famille !!! Fin…

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