Happy New Year to all!
My first high school physics lab was to " Find the coefficient of linear expansion of a brass rod" I knew that things expanded when heated but to find a ratio was beyond me.
Later in the year we finally covered that subject.
Once out in the real world of mechanical work I realized the importance of that information. The ratio of expansion determines the clearances required to prevent two moving parts from seizing when heated.
Designers calculate this information into the design of a device to allow for the operation in different temperatures.
In practical terms that when doing things such as rebuilding an engine it is very important to adhere to the specifications given in the overhaul instructions. Ring gap is a good example. Serious damage will happen if the gap is not correct. Clearance may change over time.
Some can be checked on a regular basis. Spark plug and distributor are two that most people think of.
Brake clearances change with wear, when did you last check them?
Some gaps can only be checked during overhaul. Understanding the need for tolerances is important.
"Good enough" is not an option if you expect perfect operation of a system.
Sid Gough - Technical Editor
