Pocket Balance

grabcad

A »Pocket Balance« from the good old days.I found the original product at random, in my garage, which I additional use for storage old tools, in a meanwhile rusty toolbox.A very small challenge for me to made a modification of the existing design.I used a compression spring instead of a tension spring and the hook is now rotatable by 360°.Notes:The geometry of the threads is really modeled (no cosmetic threads), but with theoretical values, means without clearance.Some of the inner threads are created by using the "Cut Out"-Function in the assembly.Explode the model in "3D-Viewer" and see, that every component of the assembly is existing in detail.I added some photos of the original product, just for comparision with my design.The calculated data of my compression spring (both spring ends flat grinded):Shear modulus (spring steel): 81425 N/mm^2Permissible shear stress: 1015 N/mm^2Wire Diameter: 2.1 mmOuter coil diameter: 14.95Neutral Length: 117.5 mm (spring ends flat grinded, as shown in the model)Number of springy coils: 22Number of total coils: 24Stroke: 58.75 mmSpring rate: 4.24 N/mmForce at end of stroke: 249.13 NIf someone is interested, try to define a new compression spring, with a dimensioning, to reach the same or better proper function.My model is available in following data formats:STEP-file (.stp) of the assembly and all native files (.prt) and (.asm) in a (.7z)-folder,for users of »PTC Creo Parametric 2.0« and later versions.