Cardan Shaft Measurement – Working in Confined Spaces

30.3.2017

Winter Grün Markier-technologie GmbH produces, at their site in Wilnsdorf, machines specially designed for making road markings. In addition to this, trucks are fitted with special installations and equipped according to customer requirements.

Fig2

The image shows the output side of the gearbox for the auxiliary drive. The cramped conditions are clearly visible.

 

One of the company’s special installations is a Unimog, which is fitted with a high-pressure water pump made by Hammelmann. With the help of highly specialized spraying tools, water pressure of up to 2500 bar generated by this pump is used to remove rubber abrasion from runways at airports, to establish a defined traction on roadway surfaces or to remove roadway markings.

A Cardan shaft is guided to the high-pressure pump on the gearbox output side. This shaft then drives the high-pressure pump at the required speed.
Actually cardan shafts should not balance any angular offsets. If they do so, the offset has to take place in a narrowly limited angle range.

 

fig1

Unimog platform with the driver's cab raised. The high pressure pump is visible at the rear. 

Fig3

The deflection angle ß must be the same at both universal joints of the Cardan shaft.

 

 

Objective of the alignment: Deflection angle ß1 = ß2

There are two methods for measuring the Cardan shaft: one with the Cardan shaft disassembled and one with the Cardan shaft mounted.

The first check measurements showed that measurement with the Cardan shaft mounted is not possible as the spatial conditions simply do not allow for the Cardan shaft rotation mechanism to be mounted and be rotated congruently.

The measuring procedure with the Cardan shaft removed was thus the only option available. Removal of the Cardan shaft in this design is very quick. The possibility of straightforward disassembly of multiple components was taken into account during Werner-Grün’s development of this design.

 

fig4

Principle schema of the design. Laser with holder and on the opposite side of the receiver, mounted on the motor shaft.

The laser is now positioned centrally on the gearbox output side and set up. In this regard the laser must be placed exactly in the gap in the structure so that the laser can map out a measuring circuit of 90°. A smaller rotation range would indeed be possible but this would significantly impair the accuracy of the measurement.

The “Intelli-Point” measuring procedure patented by PRUFTECHNIK is used to take the measurements. In this context, the lasers and receivers are positioned together at different points. An angle display with an additional pointer shows the congruence of the sensors and also checks whether the relative angular difference always remains the same.

All measurements are repeated in order to rule out potential measurement errors. The measurement values are compared against each other using the “measurement table”. The measurement values are checked for potential discrepancies by means of quality analysis.

fig5

Laser set-up on the gearbox output shaft. The laser has already been set up to record the measurement values.

fig6

Receiver on the high pressure pump. The sensor head is mounted on a rotation mechanism. Only the angular error is recorded.

 

Conclusion:

Following the procedure explained above makes it very easy to measure potential errors or excessive strain on the body on-site and in a very straightforward manner. Subsequent corrections can also be carried out. The focus is now shifting towards even more demanding projects involving trucks. Moreover, some new features, which are also to be measured, will soon be available.

 

fig7

Measurement results in the overall view. The maximum alignment error is 0.2°. The unit is within the specified tolerances.

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