I know there are a lot of rules for designing whatever you are designing but is it me or is it that since I did my degree in mechanical Engineering ( 22 years ago ) some of the basic ones have been forgotten or ignored . I have worked as a mechanic , ships engineer, field service engineer , project engineer and designer of various items and systems in a team or by myself . So forgive me if I whinge a bit when I say that some rules are definetley not being used 1. Design everything as though you your self was going to work on it ( or repair it ) 2. Not everything has to have Micro electrickery in it to work . The simplest ideas are some times the most ingenious and reliable .Don't re-invent the wheel. 3. design for the enviroment it is being used in . If it has to withstand volcano temps chose the materials for this not for polar conditions 4. If it has to be maintained try to use the philosophy of no tools needed . I put this in because so many machines are so complicated or time consuming to take apart that if you don't make it easy to get at those filters etc then they probably won't get done . I really feel good now because although there are probably other rules people could add these are my current and particular favourites that most items I get my way seem to fail on and I have at last put them out there . College lecturers please drum it into the younger generation as this seems to be getting worse from my point of view . You could save them some pain when they eventually meet the people they have been designing for Sorry this is a bit long but when you crack you crack !