| 摘要 |
PROBLEM TO BE SOLVED: To reduce the weight of a frame bottom while securing its strength. SOLUTION: This frame bottom is a cross beam which has a channel form cross section whose shape is continuously changed over the whole length of the beam so as to secure its necessary strength, extends between left and right frame sides 13 and 14, and is fixedly bonded to them at both ends 18 and 18. |
