Technical Knowledge: Basic Engineering
Basic Engineering checks the mechanical and electrical fundamentals behind warehouse plant: units, stress, simple machines, power transmission, and basic circuits. The maths is simple; the marks are lost on units.
Core rules
- Force in newtons (N), pressure and stress in N/m2 or N/mm2 (1 N/mm2 = 1 MPa), torque in N m, power in watts.
- Stress = load/area; strain = change in length/original length; Young's modulus = stress/strain.
- Lever: mechanical advantage = effort arm/load arm. Class I has the fulcrum between load and effort; Class II has the load between; Class III has the effort between.
- Pulley system: MA equals the number of rope segments supporting the load, ignoring friction.
- Gears: speed ratio = driven teeth/driver teeth; speed and torque change inversely.
- Belt speed v = pi D N/60, with D in metres and N in rpm.
- Electrical: P = VI; energy in kWh = watts x hours/1000; fuses and earthing protect against fault current.
Worked example
A 20-tooth gear drives a 60-tooth gear at 600 rpm. Speed ratio = 60/20 = 3, so the driven gear turns at 600/3 = 200 rpm. Torque is multiplied by about 3, ignoring losses, because speed falls by the same factor.
Traps
Entering diameter in mm in the belt formula; mixing stress (N/mm2) with force (N); forgetting efficiency in pulley and gear problems; treating torque and power as the same quantity; and ignoring the difference between mass (kg) and weight (N).