Front view of torsional scale
Say David, have you priced those heavy duty scales lately? They are extremely costly. There has to be a cheaper way to find the weight of these crates. David, you are the engineer, how about designing a simple torsional weighing system to find the weight of these heavy crates?
What is known:
- The thin-walled tube is 2 meters long.
- The torsional arm is 60 cm long.
- The tube is made from steel with a shear modulus, G, of 80 GPa.
- The shear stress limit of the steel, τmax, is 350 MPa.
- The cross section of the tube is 10 cm by 5 cm as shown at the left.
- The tube wall thickness is not known but the top and bottom is twice the thickness of the sides.
- The torsional arm is stiff enough that it will not bend.
- The system should be able to weigh crates up to 12.5 kN.
- Assume the tube thickness is small when compared to the cross section dimensions and can be considered a thin-walled tube.
- Assume the applied moment due to the load is about the center of the tube and there is no out-of-plane twisting or deflection.