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TM 180 Balance of Reciprocating Masses
Education / GUNT Hamburg / Engineering Mechanics and Machine Elements / Dynamics /

Using the benchtop model, mass forces can be investigated on a reciprocating piston machine. The model has four pistons with plastic sleeves that do not require lubrication. The quadruple cranked crankshaft is driven by an electronically commutated DC motor via a toothed belt. The rotational speed is regulated and displayed digitally. Forces and moments are measured using strain gauges on the elastic boom of the model mounting bracket. All electrical functions are integrated into the control unit that also provides an analogue output for an oscilloscope. The crank offset for each cylinder can be continuously adjusted, as an aid marks are provided at 90°, 180° and 270°. The natural frequencies are defined such that resonant oscillations are easy to detect even without instrumentation.

Learning Objectives / Experiments
- Run up curve
  * effect of mass forces
- Comparison of different crank arrangements
  * four cylinder, symmetrical, 180° crank offset
  * four cylinder, unsymmetrical, 90° crank offset
  * two cylinder, 180° crank offset
  * single cylinder

[1] Benchtop model for investigating oscillating and rotating mass forces and moments on a reciprocating piston machine with four cylinders
[2] Simulation of 4, 2 and 1 cylinder machines
[3] Electronically commutated and speed-controlled DC motor with digital display and potentiometer
[4] Continuous adjustment of the crank offset
[5] Force and moment measurement using strain gauges, measuring amplifier with digital displays
[6] Measuring amplifier / control unit fitted with laboratory sockets to connect external oscilloscope or FFT analyser

[7] Vibration decoupling from the laboratory environment using rubber components and matching


Technical Data

Cylinder machine

- number of cylinders: 4
- piston mass: 36g
- additional mass: 41g

Crank mechanism

- crank radius: 15mm
- piston stroke: 30mm

- connecting rod length: 70mm
- cylinder centre distance: 35mm

DC motor

- speed range: 100...3000min-1

- nominal power output: 36W

Resonant speeds (±50min-1)
- for 1st order forces: n=1825min-1
- for 2nd order forces: n=900min-1
- for 1st order moments: n=2555min-1
- for 2nd order moments: n=1285min-1


Dimensions and Weight

l x w x h: 420x370x320mm (model)

l x w x h: 370x320x160mm (control unit)

Weight: approx. 45kg

Required for Operation
230V , 50/60Hz, 1 phase or 120V, 60Hz/CSA, 1 phase
Scope of Delivery
1 4-cylinder model
1 control unit
1 instruction manual
Order Details

040.18000  TM 180  Balance of Reciprocating Masses