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Balance of Reciprocating Masses

Balance of Reciprocating Masses

Description:

A simple model four-cylinder engine that shows primary and secondary forces and moments in reciprocating masses and how to balance them. This product is an excellent follow-on from the Static and Dynamic Balancing equipment (TM1002). The pillar holds a cantilever that holds a model four-cylinder engine. The model engine has a crankshaft, connecting rods, bushes (as big-end bearings), pistons and a cylinder block. A separate Control and Instrumentation Unit (included) controls a motor that turns the engine crankshaft. The crankshaft has adjustable sections. Students can rotate each section relative to the others to change the crank angles. The crankshaft includes a sensor that works with the Control and Instrumentation Unit to measure and display engine speed. It also helps to give a trigger output at top dead centre of the first piston. Each piston includes a tapped hole to allow students to add weights (included) to vary its mass. The supporting pillar fixes to a workbench, so the engine’s centre of mass is on the cantilever axis. Strain gauges on the cantilever detect the bending and torsional strains. The gauges connect to the Control and Instrumentation Unit that calibrates and processes their signals and gives outputs for the oscilloscope (OS1). Students first find the engine’s resonant speeds. They then experiment with different engine arrangements to understand balancing and how to allow for unbalanced reciprocating masses. A removable transparent guard with a safety interlock protects students from the moving crankshaft.

Learning Objective:

Primary and secondary forces and moments in popular engine configurations - one, two and four cylinder

Primary and secondary forces and moments for different crank settings

The effect of adding additional mass to one or more pistons for any chosen crank setting

Comparing calculated forces and moments with actual results

Device component:

Pistons and cylinders

Crankshaft

Pulleys

Force and speed sensor

Epicyclic Gear

Description:

The planetary gear is a special type of gear drive, in which the multiple planet gears revolve around a centrally arranged sun gear. The planet gears are mounted on a planet carrier and engage positively in an internally toothed ring gear. Torque and power are distributed among several planet gears. Sun gear, planet carrier and ring gear may either be driving, driven or fixed. Planetary gears are used in automotive construction and shipbuilding, as well as for stationary use in turbines and general mechanical engineering. This expermenal unit allows the investigation of the dynamic behaviour of a two-stage planetary gear. The trainer consists of two planet gear sets, each with three planet gears. The ring gear of the first stage is coupled to the planet carrier of the second stage. By fixing individual gears, it is possible to configure a total of four different transmission ratios. The gear is accelerated via a cable drum and a variable set of weights. The set of weights is raised via a crank. A ratchet prevents the weight from accidentally escaping. A clamping roller freewheel enables free further rotation after the weight has been released. The weight is caught by a shock absorber. A transparent protective cover prevents accidental contact with the rotating parts. To be able to determine the effective torques, the force measurement measures the deflection of bending beams. Inductive speed sensors on all drive gears allow the rotational speeds to be measured. The measured values are transmitted directly to a PC via USB. The data acquisition software is included. The angular acceleration can be read from the diagrams. Effective mass moments of inertia are determined by the angular acceleration. The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

Learning Objective:

- determine the transmission ratio for a locked gear

- measure transmitted forces for a locked gear

- gear acceleration under constant driving torque

- influence of the transmission ratio

- determine reduced mass moment of inertia

- conversion of potential energy into kinetic energy

- determine friction

- determine gear efficiency

Device component:

Planetary gear

Weights

Dial gauge

Hand crank

Protective cover

One Degree Free Vibration

Description:

The mass-spring system is one of the most easily explainable oscillatory systems. This is because students may already be familiar with Hooke’s Law, showing the force exerted by a spring is proportional to the extension. Therefore, students can easily make the link to simple harmonic motion - defined as the oscillatory motion where the restoring force is proportional to the displacement. A back panel fixes to the Test Frame. The panel holds two vertical guide rods and a non-contacting displacement sensor. A test spring suspends a balanced mass platform which vibrates (oscillates) vertically in the guide rods. Students fit additional masses to the platform, and a second spring is provided to test various system combinations. The displacement sensor measures the vertical oscillations of the platform. An additional sensor (accelerometer) built into the platform measures the acceleration of the platform as it moves up and down. Both sensors measure the motion, yet create negligible damping. The back panel has a printed scale. Students use it with a cursor on the platform to measure accurately the spring extension, to show Hooke’s Law and find the spring constant.

Learning Objective:

Investigate simple vibrational system mass spring

Investigate effect of spring stiffness on vibrations

Observation of natural frequency 

Device component:

Spring

Mass

Damper

Sensors for measurment