Bélidor, Bernard Forest de, La science des ingenieurs dans la conduite des travaux de fortification et d' architecture civile

Table of Notes

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            <p>
              <s xml:id="echoid-s7291" xml:space="preserve">
                <pb o="38" file="0328" n="342" rhead="LA SCIENCE DES INGENIEURS,"/>
              que le bâtiment de deſſus ſeroit trop en vûë auſſi-bien que la façade.
                <lb/>
              </s>
              <s xml:id="echoid-s7292" xml:space="preserve">Cependant, c’eſt une neceſſité que le paſſage des Portes ſoit couvert
                <lb/>
              à l’épreuve de la bombe, pour prévenir les accidens qui pourroient
                <lb/>
              arriver en tems de Siége, puiſqui’il n’en faudroit qu’une pour y
                <lb/>
              cauſer un grand deſordre.</s>
              <s xml:id="echoid-s7293" xml:space="preserve"/>
            </p>
            <p>
              <s xml:id="echoid-s7294" xml:space="preserve">Le Profil, qui eſt ſur la Planche 13, repreſente une fermeture de
                <lb/>
              Portes meilleure que la précédente; </s>
              <s xml:id="echoid-s7295" xml:space="preserve">à l’extrêmité I du tablier eſt
                <lb/>
                <note position="left" xlink:label="note-0328-01" xlink:href="note-0328-01a" xml:space="preserve">
                  <emph style="sc">Planch</emph>
                .
                  <lb/>
                13.</note>
              une chaîne IG de chaque côté, qui étant attachée par l’un de ſes
                <lb/>
              bouts, l’autre va paſſer ſur deux poulies G & </s>
              <s xml:id="echoid-s7296" xml:space="preserve">F, & </s>
              <s xml:id="echoid-s7297" xml:space="preserve">eſt arrêtée en-
                <lb/>
              ſuite à l’endroit K de la Porte HK, qui eſt ſuſpenduë en l’air quand
                <lb/>
              le Pont eſt baiſſé, & </s>
              <s xml:id="echoid-s7298" xml:space="preserve">ſe ferme quand le Pont eſt levé en tournant
                <lb/>
              ſur des tourrillons H: </s>
              <s xml:id="echoid-s7299" xml:space="preserve">car tandis que le Pont en ſe levant décrit
                <lb/>
              l’arc IG, la Porte décrit l’arc KL, ce qui ſe fait en tirant la chaîne
                <lb/>
              KE vers L; </s>
              <s xml:id="echoid-s7300" xml:space="preserve">&</s>
              <s xml:id="echoid-s7301" xml:space="preserve">, pour juger encore mieux comme ſe ferme cette
                <lb/>
              Porte, il n’y a qu’à jetter les yeux ſur le Profil qui eſt coupé ſur la
                <lb/>
              largeur CD, on y verra les poulies Mm, & </s>
              <s xml:id="echoid-s7302" xml:space="preserve">la diſpoſition de leur
                <lb/>
              crapaudines: </s>
              <s xml:id="echoid-s7303" xml:space="preserve">j’ajouterai, qu’on pratique un Guichet dans la Porte,
                <lb/>
              afin que lorſqu’elle eſt baiſſée on puiſſe aller fermer les verroux de
                <lb/>
              la baſcule.</s>
              <s xml:id="echoid-s7304" xml:space="preserve"/>
            </p>
            <p>
              <s xml:id="echoid-s7305" xml:space="preserve">Comme il y a long-tems qu’on s’eſt aperçû que les Ponts-Levis à
                <lb/>
              flêches étoient ſujets à pluſieurs inconveniens, on les a fait a baſ-
                <lb/>
              cule comme on le voit dans le Profil qui eſt ſur la Planche 15; </s>
              <s xml:id="echoid-s7306" xml:space="preserve">ce
                <lb/>
              Pont eſt compoſé de pluſieurs poutrelles, comme IF, qui ont en-
                <lb/>
              viron 28 pieds de longueur. </s>
              <s xml:id="echoid-s7307" xml:space="preserve">Une partie de ces poutrelles, étant re-
                <lb/>
              couverte de madriers, compoſent par leur aſſemblage le tablier
                <lb/>
              HF, & </s>
              <s xml:id="echoid-s7308" xml:space="preserve">le reſte comme HI, (qui eſt ce que l’on nomme baſcule)
                <lb/>
              ſert de contre-poids pour donner le mouvement au Pont par le
                <lb/>
              moyen des tourrillons qui ſont à l’extrêmité d’une bare de fer, qui,
                <lb/>
              étant entretenuë avec les poutrelles, traverſe toute la largeur de la
                <lb/>
              Porte à l’endroit du ſole: </s>
              <s xml:id="echoid-s7309" xml:space="preserve">cette baſcule eſt logée dans une cave que
                <lb/>
              l’on nomme auſſi Cage de la baſcule, qui eſt couverte par un Pont dor-
                <lb/>
              mant compoſé de poutrelles & </s>
              <s xml:id="echoid-s7310" xml:space="preserve">de madriers. </s>
              <s xml:id="echoid-s7311" xml:space="preserve">Quand on met le Pont-
                <lb/>
              Levis en mouvement, la baſcule décrit l’arc IK, tandis que le ta-
                <lb/>
              blier décrit l’autre FG pour deſcendre dans la cave; </s>
              <s xml:id="echoid-s7312" xml:space="preserve">on fait un eſ-
                <lb/>
              calier pratiqué dans l’un des piés-droits, comme il eſt figuré au Plan
                <lb/>
              de la Porte qui répond au Profil dont nous parlons.</s>
              <s xml:id="echoid-s7313" xml:space="preserve"/>
            </p>
            <p>
              <s xml:id="echoid-s7314" xml:space="preserve">On ne fait plus preſentement de ces ſortes de Ponts, parce qu’à
                <lb/>
              le bien prendre ils ſont encore plus défectueux que les autres à flê-
                <lb/>
              ches; </s>
              <s xml:id="echoid-s7315" xml:space="preserve">car la cage eſt d’une grande dépenſe, & </s>
              <s xml:id="echoid-s7316" xml:space="preserve">affoiblit beaucoup
                <lb/>
              le mur de face: </s>
              <s xml:id="echoid-s7317" xml:space="preserve">ils ſont ſujets à des réparations continuelles, & </s>
              <s xml:id="echoid-s7318" xml:space="preserve">diffi-
                <lb/>
              ciles à manœuvrer. </s>
              <s xml:id="echoid-s7319" xml:space="preserve">Un autre inconvenient, c’eſt que la cage qu’il </s>
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