LAUGHTON ELECTRONICS |
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On the Road Again - Not! Driving simulations in the lab |
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This article describes an ambitiously conceived product test apparatus. |
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I had a call some years ago from a Product Test Engineer seeking my assistance. This fellow was on contract with a manufacturer of automotive rubber products, and his assignment was to establish an evaluation process for vibration-damping engine mounts. I soon discovered he wasn't afraid to tackle the problem head on! He had a well-developed plan, and I became part of a team, managing some of the wiring and building power supplies for the resistance bridge load cells we were using. Part one of the plan was to collect some vibration data. The info came straight from the horse's mouth, so to speak. He had been given access to a vehicle of the type using the engine mounts in question, and what he did was load the vehicle with accelerometers and recording gear. Then he made tests drives over every kind of road he could find — and the more potholes and railway crossings the better! The accelerometers recorded the actual, real-world stresses on the engine mounts. Part two was to select
and reproduce excerpts from the recorded data. This amounted
to a "torture
test," performed indoors, for various
prototype engine mounts to be evaluated. The test rig consisted of
a complete
vehicle engine and transmission,
mounted in midair at a height of about
6 feet. But there was no
vehicle or chassis; the engine mounts attached
instead to four computer controlled hydraulic actuators. These cylinders were brutally powerful, fully capable of reproducing the abuse and the g-forces previously experienced by the actual engine in the real vehicle. In fact, the concrete floor in the test lab was deemed not to be an adequate foundation for the rig. The floor and the earth underneath were excavated and replaced by a reinforced slab two feet thick. That's because the original floor — besides being inadequately stable — would've gotten shaken to pieces! |
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