Ethical issues in engineering design - 3TU.Centre for Ethics and ...

Ethical issues in engineering design
requirements stated that 32 tonnes of sand would be carried, an allowance for
overloading was not required. Liz and Hans said that if a trailer was consequently
overloaded and a driver drove too fast such actions would take out a part of the
safety margins designed into the trailer. Therefore, overloading would reduce the
safety margin. Hans wondered in his interview whose responsibility it was to
decide to include overloading. Hans drew the conclusion that the customer
should do this and change his requirements. Hans and Liz indicated that the
customer knew more about use and misuse of trailers than they did and therefore
the customer should include this in his requirements if necessary. Liz also
indicated that overloading would not really cause problems as the design was
stiffness dominated. Hence, the strength of the trailer was sufficient to withstand
the overloading, the floor will displace more than with a load of 32 tonnes but this
will not cause failure of the trailer.
Another possible problem might be that misuse with regard to the use of the
rods in the trailer might occur. As said before the trailer had no roof. The absence
of a roof can make a trailer unstable when loaded. The load pushes against the
side panels which are only fixed on the floor. The side panels can deflect
outwards as sketched in figure 7.3.
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Figure 7.3: sketch of trailer loaded with sand and rods open
To prevent this, three rods were inserted at the upper side between the side
panels. These rods will stay in place most of the time during use but need to be
removed before loading a trailer with long materials, once loaded the trailer rods
need to be reinserted. 9 While discussing misuse of trailers, Hans asked the
customer whether the rods are always inserted. Failing to insert the rods will
compromise the stiffness of the total trailer. The side panels can move
independently. The customer answered that he had not often seen rods left out
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9
The trailer was designed to be loaded from above and the rods are in the way when loading
long materials.