Mechanical & Materials Engineering, Department of
Date of this Version
Summer 8-2011
Document Type
Article
Abstract
Railroad grade crossings are locations of significant interest for prevention of collisions, injuries and fatalities. Another area of concern is derailments resulting from mechanically deficient track structures. Many of these incidents occur in remote areas due to the lack of electrical infrastructure to power automated warning systems and/or track health monitoring sensor networks.
Providing electrical infrastructure to railroad crossings in remote areas is often not economical, and other alternative sources of electricity such as solar and wind energy are not reliable or robust. This motivated development of devices for in situ energy harvesting.
Initially, an improved mechanical energy harvesting device capable of harnessing the vertical deflection of the railroad track due to passing railcar traffic was developed. It is mounted to and spans two rail ties and converts and magnifies the track’s entire upward and downward displacement into rotational motion of a PMDC generator. Simulation and testing results of the device show the capability of harvesting power on the order of 40 Watts under loaded train conditions traveling at 60 mph.
If the vertical deflection of the railroad track is small for any reason such as freezing weather conditions and/or unloaded train cars, the mechanical device is constrained to very small amounts of output power levels. This motivated the design of a device generating electricity by passage of each train wheel. The device consists of two ramp-levers oscillating with cycloidal motion with passage of each train wheel, independent of the direction of the train, and a mechanism to return the ramp-levers to their initial positions.
A hydraulic system was also designed and built, addressing the mentioned shortcomings and limitations of previous approaches. A hydraulic cylinder is mounted under the bottom of the rail such that it directly harnesses the downward deflection of the rail due to railcar traffic. The hydraulic cylinder is compressed and relaxed by passage of each railcar, forcing the hydraulic fluid towards a hydraulic motor and converting the hydraulic pressure and flow into rotational motion and torque. The rotational motion is scaled appropriately to drive a PMDC generator.
This thesis describes the design, development, and testing of these devices. The intent is that this work represents a significant step towards safer and more robust railroad track systems.
Comments
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Mechanical Engineering, Under the Supervision of Professor Carl A. Nelson. Lincoln, Nebraska: August, 2011
Copyright 2011 Abolfazl Pourghodrat