Determining the spring rate of spring rods for roof windows
Special version of the universal testing machine inspekt table 10 KN
The inspekt table universal testing machine is an ideal testing system for determining the spring rate on window fittings, e.g. for roof windows. A special version of the testing machine with a centric through-hole in the lower crossbeam enables very long springs to be tested. These protrude downwards out of the test area. At 10 kN, the nominal load of the testing machine is matched to the forces required to determine the spring rate. The spring rate (also known as the spring constant or spring stiffness) describes how strongly a spring reacts to a load. It indicates how much force is required to stretch or compress the spring by a certain distance.
The spring rate is of crucial importance for roof window spring rods because it effects the comfort, safety, energy efficiency and durability of the window. It determines:
- How easy or difficult the window is to open or close.
- Whether the window closes tightly (important for thermal insulation and sound protection).
- How safe the window is (protection against uncontrolled slamming or child safety locks).
- How long the window fittings, bearings and seals will last.
The spring rate is influenced by various factors such as the material properties of the spring steel used, the geometry of the spring and the number of coils.
The test sequence for determining the spring rate can be precisely set up in the LabMaster testing software, which is developed in-house at Hegewald & Peschke, in accordance with the manufacturer's specifications. The spring is suspended in a special test fixture and then loaded and unloaded in several cycles. The required characteristic values are measured at various points in time, saved and used directly with the stored formulas to calculate the spring rate. The data can then be output in a customizable report and/or exported to the customer's own quality management systems.