Springs are used in engineering to store energy or to provide restoring forces. Both compression and tension (extension) springs may be encountered. The deflection of a spring depends on the load applied to it, an observation enshrined in Hooke's Law (Within the limit of proportionality, the strain is directly proportional to the stress producing it).
Applications of springs are found in spring balances which indicate loads by measuring spring deflections and in car suspensions where they absorb energy caused by wheel vertical movement due to potholes and bumps.
The HSM7 apparatus is designed to be mounted to a rigid vertical support approximately 1.5metres above floor level. It is used to test tension springs up to 200mm in length. The maximum spring diameter is 38mm.
A steel, powder coated wall housing has a spring support at its top and a through hole at its lower end. A loop ended extension spring is hooked over the spring support and its remaining loop secured to a load hanger.
Attached to the shaft of the load hanger is an extension indicator. This has a small horizontal mark inscribed which reads up against the extension scale on the wall housing. The indicator can be moved up or down the load hanger shaft to accurately adjust the start position of extension measurements and to cater for different length springs.
The load hanger has a solid base onto which the set of calibrated weights supplied is suspended.
Students load the spring with incremental loads and record the extension created for each load. From these results a load versus extension graph is plotted from which the spring stiffness is calculated.
Alternatively the students can measure the spring key dimensions and from this they can also calculate the spring stiffness. Both results can then be compared against manufacturers data.
To expand on the experiment, a further set of three springs (HSM7a) is optionally available (sold separately), which gives the students further work with springs of different length, outside diameter, coils and wire diameter.
A comprehensive instruction manual for student and lecturer is provided along with a 2 year warranty.