Quote:
Originally Posted by Efthreeoh
Engineers rarely ever guess. If they did, there'd be a lot of dead people in the world. If anything, BMW is an engineering-driven company that advances the state of the art in some areas as engineering challenges, yet there is an economic factor to be considered in the design and manufacture of parts and components and subassemblies.
MTBF can be calculated for almost any machine, component, or part. There is hardly any mystery to automotive design and manufacturing at this point in an industry that is well over 100 years old and over billions of product manufactured. Reliability is designed into each component, varibility depends mostly on adherence to manufacturing process and deviation in part tolerence and the buildup of tolerances between mating parts.
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I agree to an extent. Engineers work within very tight tolerances depending on the materials. Metals and mechanical parts such as a transmission are usually much tighter in tolerance, if not having virtually no room for error. Plastic door panels and fuel doors, under-body plastics, less so. They can be a millimeter off or more and still pass muster depending on the vehicle and it's price point
I did not mean they estimate the tolerances in this case. I meant that they estimate the level of testing to prove out a durability factor under X,Y, and Z conditions. Some parts I worked with had durability testing nearly double the number of cycles without any material changes between model years. It was the economic factor you are referring to. It became a cost analysis of having higher levels of testing vs. the amount of warranty that will come out the back end, wear and tear and replacement life, etc. But the engineer seemingly pulled the number out of the air when we were in discussions with the supplier, with recommendations provided by the supplier.