求翻译：改向滚筒直径有250、315、400、500、630、800、1000mm等规格．选用时可与传动滚筒直径匹配，改向时其直径可比传动滚筒直径小一档，改向或时可随改向角减小而适当取小1—2挡。本次设计采用4个直径315mm的改向滚筒,改向180°，改向托辊组是若干沿所需半径弧线布置的支承托辊，它用在输送带弯曲的曲率半径较大处，或用在槽形托辊区段，使输送带在改向处仍能保持槽形横断面。输送带通过凸弧段时，由于托辊槽角的影响，使输送带两边伸长率大于中心，为降低胶带应力应使凸弧段曲率半径尽可能大．一般按织物芯带伸长率为%、钢绳芯带为0.2％计算．是什么意思？

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Changes has 250 to the drum diameter, 315, 400, 500, 630, 800, specifications and so on 1000mm. Selects when may with the transmission drum diameter match, change to time its diameter may compared to the transmission drum diameter small 13, changes to or when may along with change reduces to the ang

Bend pulley diameter, 250, 315, 400, 500, 630, 800, 1000mm and other specifications. Selection to match the drive pulley diameter, bend diameter can be smaller than the drive pulley diameter, bend or reduced and appropriate, he may bend point-min 1-2 gear. This design uses 4 of bend pulley diameter