| 摘要 |
<p>A cross bar 1, a lower bar 2, a bridge 31, a saddle stem 3, and rear forks 11 and 12 are cast in one piece from a magnesium-based alloy. An important feature of the frame is the additional stiffening of the frame against torsion by means of the structural bridge 31. The bridge is cast solid with the cross bar 1 and lower bar 2 and acts as a torsion arm so that any twisting of the frame due to deflection of the head 4 out of the plane of the frame is not resisted by the ends of the cross bar 1 and lower bar 2 remote from the saddle stem 3, but at locations considerably nearer the saddle stem 3. A further improvement is achieved by shifting the junction of the bottom bar 2 upwardly from the lower end of the saddle stem 3 as illustrated in Figure 1. By this means, the overall length of the bottom bar is reduced, thereby further reducing the length of the beam it forms, and also saving material and therefore weight. In addition, there is some reinforcement of the saddle stem 3 itself. <IMAGE></p> |
