Mechanical Engineering Annual Report 2021 | Page 19

Figure 2 . Downward track motion is transmitted and converted into generator rotation : ( a ) the red arrows show the direcction of motion in response to track deflection due to a passing wheel ; ( b ) the green arrows represent the motion in rebound to return to undeflected track position .

One-way clutch engages

One-way clutch disengages

Gearhead Generator Gearhead( ) ( ) Generator

Wheelset

EHT

Transmission when a wheelset approaches and one-way clutch engages

( a ) ( b )

Transmission when a wheelset leaves and one-way clutch disengages

Wheelset

EHT

University of Nevada , Las Vegas

In rebound , the preloaded springs rotate the output shaft , bevel gear , and ball screw shaft in the opposite direction , along the green arrows in Figure 2b . The one-way clutch is disengaged from the gearhead ’ s shaft in rebound , disconnecting the generator from the gearbox . The generator can continue spinning with its momentum but momentarily receives no additional torque until the next compression cycle by the next railcar ’ s wheel shortly later .

A ½-tie prototype , shown in Figure 3 , was developed and fabricated to fit in a hydraulic load frame for testing . Comprehensive bench testing was performed in the lab with both sinusoidal excitation and field-recorded tie displacement on a ballasted track at 40 mph train speed . Testing with the sinusoidal excitation testing yielded

Figure 3 . A half-size energy harvesting tie prototype was fabricated and tested in the lab average electrical power of up to 150 W . The mechanical efficiency of the energy harvester proved to be as large as 78.1 %. The test results proved the energy harvesting tie to have a highly efficient , promising , and practical design .

With a recorded tie displacement input , an average 44.5 W power output was obtained , as shown in Figure 4 . The test demonstrates that the proposed system can generate sufficient power for powering various trackside electronics effectively . The implementation of such electronics promises to have a great influence on in situ track condition monitoring , which is essential for track safety and reducing maintenance costs .

Figure 4 . Experimental results under recorded tie displacement excitation with 2-ohm resistive loads

Displacement ( mm )

About This Project

This project is being conducted under the auspices of the RailTEAM UTC , a consortium of universities led by the University of Nevada , Las Vegas ( https :// www . unlv . edu / railTEAM ). The research is led by Dr . Mehdi Ahmadian , J . Bernard Jones Chair of Mechanical Engineering and Director of the Center for Vehicle Systems and Safety at the Virginia Tech Railway Technologies Laboratory . The project resulted in an innovative energy harvesting railroad tie that can convert track deflection under passing wheels ’ load into electricity , which can be installed readily on revenue-service tracks for powering various trackside electronics that are critical to improving track condition monitoring and safety . The energy harvesting tie can also be used to set up remote power stations that extend the flight range of drones that are highly desired by the U . S . railroads for track inspection .

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