# ADVICES OF DESIGNER

### Advice 2

about computation

** Engineering Calculations ** in engineering played a key role. From their
accuracy depends on the appearance of the car and its specifications.
In the calculations should follow two basic classical
Rules:
** Rule number 1 ** The results of calculation ** can not only use, but even
consider ** until after the calculation will not proveren.Horosho if checking account
is not the one who does it, and another person.
** Rule number 2 ** Even if the calculations are correct, ** calculation results
Do not use **, has not ruled out possible errors in input data and
used formulas.
Errors often creep into the formula for several reasons:
1. When you print a confused character variables and indices of the characters (subscript
and superscript);
2. The authors of technical literature does not take into account the different dimensions
of physical values ??(in a formula using centimeters and inches, pounds force and Newtons, etc.).
** curious example: ** In the old 70's on a course in descriptive geometry
at the Moscow Aviation Institute, where this writer learned the basics of knowledge
our teacher gave a good xtextbook, but the book contains many errors in
notation and xindexes. On the puzzled questions of students, "Why can not fix typos?"
The author replied as follows: "The clever student will find the error itself, and it will
play in his favor, and a fool mistakes and not notice! "
Now the formulas in the books - ** FORMULA NOT BELIEVE! **. You can believe only
simple in mathematical terms, the laws and their use should be
need to understand their physical meaning. Such laws in mechanics are
Newton's laws, conservation of energy, Hooke's law, the formula sopromata (stretching,
compression, bending, twisting, stability ...), etc. In electrical engineering - is Ohm's
law and other simple patterns.
Formulas should be such that for calculations on them could have done even
** without a calculator. **
Especially a lot of mistakes in the ad hoc technical literature devoted enough
narrow fields of technology (such as "transporters"). This is explained partly by the fact
that the authors of books, knowing full well the technical and physical side of the subject, were
uncomfortable with the mathematical expressions of these patterns, and sometimes especially
do not hesitate to copy the formula from one workbook to another.
In these cases it is necessary to understand the physical nature of the formula and bring
it yourself,
based on the classical laws of physics, the stability of which is beyond doubt.
** Results ** of any calculation (that results, not the calculation) must be
test (identify), comparing them with characteristics closest analogues.
For example, if you define power drive your car, compare the resulting
value to the capacity of the closest analogue, the data is not in doubt.