Equilibrium of Moments on a Two-Arm Lever
Using this benchtop unit, the lever principle and the equilibrium of moments are investigated in experiments. The unit consists of a centrally ball bearing mounted, symmetrical lever and the riders that slide along it with sets of weights. Millimetre scales are attached to the lever arms to read the distances from the pivot. A vertical column carries the lever, a sturdy base plate ensures that the unit sits securely on the table.
Learning Objectives / Experiments
- Investigation of the lever principle
- Fundamental principles of the equilibrium of moments
One of sixteen mechanisms built on an A3 board equally suitable for the classroom, drawing office or laboratory. The principal components are made from amber coloured Perspex, pivoted with hollow rivets, and mounted on a white melamine board for contrast and visibility. To see the mechanisms move is far more instructive and convincing than listening to a static lecture. The hollow rivets accept a pencil for transferring the loci of the joints to a sheet of paper, clipped to the board.
A link that slides in two in-line guides has a right angled cross frame that contains a symmetrically disposed slot. A wheel whose centre is also on the centre line of the guides carries a pin that turns in a slider running in the slot. As the wheel turns the linear motion of the link is exactly simple harmonic. The amplitude can be varied by altering the radius of the pin.
This equipment is part of a range designed to both demonstrate and experimentally confirm basic engineering principles. Great care has been given to each item so as to provide wide experimental scope without unduly complicating or compromising the design. Each piece of apparatus is self-contained and compact. Setting up time is minimal, and all measurements are made with the simplest possible instrumentation, so that the student involvement is purely with the engineering principles being taught.
This experimental unit demonstrates the conversion of smooth rotary motion into reciprocating motion.
The input angle is set on a ball bearing mounted crank disc made of anodised aluminium and read off on an angle measuring scale integrated into the base plate. A millimetre scale is fitted for the outlet stroke. The crank radius can be adjusted in three positions.
The simple insertion of a bolt enables the swivelling cylinder to be locked, thus a crank drive with either a fixed or oscillating cylinder can be demonstrated.
The components are attached to a solid, painted base plate. Two handles make the unit easier to carry.
|Learning Objectives / Experiments|
- crank drive with fixed cylinder