I work at a grain silo and I am trying to figure out if I should tell truck drivers to turn off their engines while the vehicle is being weighed. I don't know if the loads created by the vibrations from a running engine will significantly affect the reading while weighing heavy trucks. I hope somebody can give me an answer. Thanks.
Um no, i drove a heavy haul woodchip truck for 4 years, we never turned the truck off to weigh it. The vibrations will not affect an industrial truck scale so you are free to weigh with the engine roaring!
The weight of the truck is not changed by a running engine, but the vibration of the engine will produce a rapid, cyclic change in the measured weight of the truck that might make measurement more difficult. The average weight measurement will be the same, but over short periods (well below one second, depending on the idling speed of the engine), the measured weight will vary. So it's probably a good idea to turn the engine off if you notice any wavering of the weight measurement. It depends on the equipment you use. This assumes that the truck is stopped on the scale, of course.
FYI: weight is not a verb. Weigh is the verb. While there will surely will be vibrations that will yield instantaneous errors in the measurement, these errors do not amount to any AVERAGE steady state errors in the measurement. The midline of the scale reading as a function of time will measure the same value whether the engine is running or not. Many weigh stations actually tell the drivers to weigh while in motion, just to keep a good flow of traffic. In fact, it is possible to cheat these scales with clever braking and accelerating. Braking will load the front wheels more, and accelerating will load the rear wheels more. This is due to the wheel supports needing to constrain with a torque against the truck tipping forward and backward, as it accelerates. I actually know people who mastered this skill of cheating the scales. If done right, you can cheat the scales by 5%. Of course though, there are speed limits to the weigh stations. Plus it is very difficult to change the speed of such a massive truck.
The weight of the truck is not effected by the engine running. If it did you can rest assured that there would be demands by the owners that engines be (on/off) while being weighed. It wouldn't be left to the discretion of the operators.
