This machine is used to test the compression and recoil force values of a shock absorber. A speed controlled motor is used to control the speed of a flywheel. A pneumatic clutch is used to connect the crakshaft to the flywheel. The shock absorber being tested is inserted between a loadcell at the top and the crankshaft at the bottom. First the correct speed for the flywheel is set, then the clutch is engaged and the shock absorber's bottom half moves up and down. The loadcell measures the force in Newtons of the shock absorber's resistance to the movement. At the point of maximum upward velocity the maximum compression value is measured, while at the maximum downward velocity the maximum recoil value is measured.
This project only upgraded the controller to a PC-based system. The rest of the machine, including the constant speed drive, was not altered. The PC contained a expansion card with 8 relay outputs and 8 optical inputs which was custom made by me. Four of the relay outputs were used to select the correct speed. The fith relay was used to control the pneumatic clutch. The first optical input was used to read in an inductive proximity sensor. This sensor sensed when the crackshaft moved through its index position. The PC also contained an analog to digital converson card which was connected via a loadcell pre-amplifier to the loadcell.
The software does not only test shock absorbers, it also contains a database of parameters of the different shock absorbers. A tested shock absorber can therefore very easily be compared to this data to see whether it operates correctly or not. Each shock absorber is tested at four different speed settings of the crankshaft.
Below is a screenshot of the database editing screen of the
Below are some print-outs from the program. The first one is a
versus position plot.
The two graphs below compares the measure compression and recoil
with the safety limits:
The printout below displays the results of testing a batch of shock
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