BY the use of carefully considered designs, the authors contend, any transportation unit in use today can be made largely of aluminum and considerably lighter than the same unit made entirely of ferrous materials. In most cases, they declare, it is possible to make a weight reduction of approximately 50% from the weight of an iron or steel part when aluminum is used.
Results of a test made on a 36-passenger aluminum-alloy bus are reported, indicating that calculated stresses do not correspond very closely with measured stresses. This finding is attributed to the fact that a bus body is a complex, statically indeterminate structure and the accuracy of design calculations is wholly dependent upon the accuracy of the assumptions upon which they are based. Strain gages were used to measure the stresses actually occurring in the parts.
The authors emphasize the necessity of local stability, or the ability of the members in a bus body to withstand maximum loads, both service and accidental, without permanent distortion. The high tensile strength of the alloy steels cannot be fully utilized, they claim, because, to do so, would result in the use of sections so thin that they would buckle locally and collapse.
In concluding, the authors recommend materials to be used in different parts for buses and light railcars.
