Floor-standing apparatus for demonstrating the pressures around a journal bearing at diff erent speeds.
Key features
• Acrylic bearing allows clear observation of the oil fi lm at all times.
• Pressure profi les, along and around the bearing, continuously monitored on large manometer panel
• Theoretical pressure profi les (Sommerfeld analysis) may be tested and compared with practical results
• Exaggerated clearance makes oil wedge clearly visible
• Shaft/bearing eccentricity easily visible and can be determined by experiment
• Provides striking demonstration of self-excited vibrations (half-speed whirl)
• Fully adjustable speed, direction and loads
Description
This fl oor-standing apparatus allows students to study the performance of a journal bearing during diff erent test conditions.
It is a plain steel shaft encased in a clear acrylic shell and directly driven by an electric motor. The bearing is freely supported on the motor shaft and sealed with a rubber diaphragm. The clearance is especially large to clearly show the oil in the bearing. Supplied with the equipment is a container of suitable oil.
A control unit adjusts the motor speed, which can run in both directions. A display shows the motor speed.
An adjustable reservoir supplies oil to a low pressure region at both ends of the bearing.
The bearing contains 12 equi-spaced pressure tappings around its circumference and four additional ones along its topside and on a vertical radial plane. All are connected by light and fl exible plastic tubes to the rear manometer panel, to clearly show the pressure head of oil at all 16 points at all times.
Students load the bearing by attaching weights (included) to arms connected to the bearing.
A strong steel frame with a worktop holds the bearing, the motor, the manometer panel and the control unit.
Recommended Ancillaries
• Stroboscope (ST1)
Learning Outcomes
Simple demonstrations:
• Observation of oil wedge (fi lm thickness) and hence eccentricity variations for diff erent speeds and loads
• Observation of the pressure profi les at these conditions
• Observation of the critical bearing whirl
Experiments:
• Measuring pressure profi les for chosen conditions and plotting the cartesian and polar pressure curves
• Measuring pressure profi les for chosen conditions and plotting the theoretical Sommerfeld curve
• Measurement of shaft speed and journal speed at the critical whirl
All tests may be conducted for either direction of rotation of the shaft.
