When a truck scale exhibits a mysterious and inexplicable “weight gain,” workers begin to wonder if the place is haunted
By Contributing Writer Phil Ouellette
Years ago I used to repair truck scales. In those days, truck scales were mechanical with levers and pivots located in a pit under the scale platform. One customer had a recurring problem with a scale that wouldn’t hold zero. Intermittently the scale would have a sudden weight change of 50 - 100 lbs. The operator would re-zero the scale, and it would be okay for a while, until suddenly the scale changed back by the same amount.
There was no apparent reason for the changing zero and it was driving the customer and us crazy. We had been called out several times and each time we investigated we found something that could be improved, but nothing we did got rid of the changing zero. It got to the point that the operators would say “The ghost is walking on the scale again.”
Okay, so much for the fact that ghosts normally float, but they made their point.
After this had gone on for far too long, I was tapped to go figure out what was wrong with that scale. Typically, zero change in a mechanical scale is caused by friction or occasionally a broken part. First, I checked to see whether dirt or debris had built up to the point it was touching the scale platform or working parts of the scale. I checked to see whether the deck had shifted on the I-beams or the pit coupling was coming loose, which would cause the deck to rub against the pit wall. I also confirmed that the connections between the levers and the indicating beam (imagine a giant version of the beam you slide the weight along on a doctors scale) were not bound up with debris or rubbing on something.
I then checked to see if the bumper bolts, which are large bolts attached to the deck to prevent it from moving too far when a truck drives off or on, were out of adjustment. These take a pounding and it is not unusual for them to get bent out of shape.
I did notice while I was carrying out my investigations that the pit floor was wet, but the water wasn’t high enough to reach any of the working parts. Obviously this wasn’t causing the problem. Finally, after exhausting all of my diagnostic abilities, I decided to camp out under the scale until the problem reoccurred and hopefully get a clue as to what was happening.
After about 30 minutes the operator called down “that the ghost was back.” I turned on my flashlight and swept the working parts of the scale only to discover a large frog sitting on top of one of the levers staring grumpily at me. No, it wasn’t a giant frog. Due to the multiplying factor of the lever system that 1 or 2 lb frog was weighing 50 to 100 lbs on the scale readout.
At first, the owner of the scale didn’t believe me when I told him of my discovery, but I was able to show him the wet marks the frog had left on top of the lever. He was flabbergasted that a frog had caused him so much trouble. I recommended he install a sump pump in the pit to keep it dry.
The ghost never reappeared.
Contributing Writer Phil Oullette started working in the scale business in 1978 as a service technician (fixing and installing scales) in Arizona. In 1983 he started working for Toledo Scale as a startup engineer, which was a ton of fun and he learned a lot. He then worked in tech support for awhile and did a short stint in marketing, but engineering is where he says his heart is. He graduated from Franklin University in 1995 with a BSEE and today designs electronic scales. If you have ever been to a UPS, FedEx or Kinko’s store to ship a package, then you have used one of his scales.