Problem:
| A class-I Railroad was having serious classification retarder control problems and contacted a major university for engineering & physics guidance to assist in a solution. Feedback circuits from a mechanical scale using a conventional strain gage was being fedback to the retarder control system. This was causing significant rail-car damage and other car handling logistics problems. | |
| Need: | An in-motion non mechanical rail-car scale was needed up-track from the retarders for significantly more accurate retarder control. | |
| Solution: | A scale which electronically senses the speed change in a free rolling rail-car over a fixed distance of free rolling, with known slope of grade. Once this change in speed is measured Newtons equations relating mass, speed and acceleration are applied to accurately calculate the rail-cars rolling weight. The rail cars weight was used directly in the retarder control system to properly control the rail cars speed through the classification yard. | |
Design: |
Hall Effect sensors were used to magnetically sense the proximity of the
rail-car's wheels. Optical sensors were deemed useless because of dirt
and moisture that would inhibit the sensor from sensing car position.
Two senosrs were used immediately after the rail-car release point and
after the rail car was located completely on the yard "hump" glide
grade.
These sensors were loacted 20 feet apart. Another pair of sensors were located approximately 60 feet down grade . Each set of two sensors would time the car between a fixed distance. A velocity was calculated from this time differnce. With the known initial velocity of the dropped rail-car and the velocity of the rail-car 70 feet down track, this differnce, in veolocity, track grade, distance and gravity acceleration constants were used to accurately calculate the rail-cars weight. |