Office of Research and 

Development 

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DOT/FRA/ORD-06/14 April 2006 

 Final Report 

This document is available to the

U.S. public through the National

Technical Information Service

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Federal Railroad

Administration

U.S. Department

of Transportation

Use of Dynamic Rail Deflection as a Means of 

Determining Changes in Top of Rail Friction
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April 2006 

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS 

Use of Dynamic Rail Deflection as a Means of Determining Changes in 

Top of Rail Friction

6. AUTHOR(S) 

Kevin Oldknow, Kelsan Technologies 

Richard Reiff, TTCI

DTFR53-00-C-00012 

Task Order 205 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION 

REPORT NUMBERS

Transportation Technology Center, Inc. Kelsan Technologies 

P.O. Box 11130 1140 West 15th Street 

Pueblo, CO 81001 North Vancover, B.C. V7P 1M9

9. SPONSORING/MONITORING AGENGY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY 

REPORT NUMBER 

U.S. Department of Transportation 

Federal Railroad Administration 

Office of Research and Development, MS 20 

1120 Vermont Avenue, NW 

Washington, DC 20590

DOT/FRA/ORD-06/14 

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

This document is available through National Technical Information Service, 

Springfield, VA 22161 

13. ABSTRACT

To determine if the use of dynamic rail deflection (RDG) data can be used to determine the effectiveness of top of rail (TOR) 

systems, Transportation Technology Center, Inc. and Kelsan Technologies Corporation, with funding from the Federal 

Railroad Administration (FRA), engaged in a collaborative effort to assess the suitability of RDGs in assessing TOR friction 

modifier effectiveness. Phase I of the test plan, included in this report, involved testing at the FRA’s Facility for Accelerated 

Service Testing at the Transportation Technology Center, Pueblo, CO, using existing lubrication equipment to produce a range 

of lateral forces and correlate RDG response with truck performance detector measurements. 

14. SUBJECT TERMS 15. NUMBER OF PAGES

Dynamic rail deflection, top of systems, truck performance detectors 35 

16. PRICE CODE

17. SECURITY 

CLASSIFICATION 

18. SECURITY 

CLASSIFICATION OF THIS 

PAGE 

19. SECURITY 

CLASSIFICATION OF 

ABSTRACT 

20. LIMITATION OF 

ABSTRACT 

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED SAR 

NSN 7540-01-280-5500 Standard Form 298 (Rec. 2-89) 

Prescribed by ANSI/NISO Std. 

239.18 

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iii

Table of Contents 

EXECUTIVE SUMMARY..............................................................................................................1

1.0 Introduction .........................................................................................................................3

2.0 Objectives............................................................................................................................5

3.0 Test Site Overview ..............................................................................................................7

4.0 Traffic Overview ...............................................................................................................11

5.0 Data Collection..................................................................................................................13

5.1 RDG Measurements .............................................................................................13

5.2 TPD Measurements ..............................................................................................14

5.3 Tribometer Measurements/Event Log..................................................................14

6.0 Test Sequence....................................................................................................................17

7.0 Data Analysis ....................................................................................................................19

7.1 Rail Deflection and Lateral Force Signal Characteristics ....................................19

7.2 Spectral-Analysis of Raw RDG and L/V Signals.................................................22

8.0 Correlation of Peak L/V and RDG Signals .......................................................................25

8.1 RDG Analysis Software .......................................................................................25

8.2 RDG Measurement Site 1 (Soft Track, Co-Located TPD)...................................25

8.3 RDG Measurement Site 2 (Stiffest Track, No TPD)............................................28

8.4 RDG Measurement Site 3 (Stiff Track, Co-Located TPD) ..................................29

8.5 RDG Measurement Site 4 (Softest Track, No TPD) ............................................30

9.0 Suggested Equipment Improvements................................................................................33

Acronyms .......................................................................................................................................35
iv

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v

List of Figures 

Figure 1. HTL Marked Up to indicate RDG Measurement Sites, TPD Sites, Lubricator Sites, 

and Running Directions ..............................................................................................7 

Figure 2. RDG Installation at Section 25, Tie 199 (RDG Site 1, Co-Located with TPD) .........9 

Figure 3. FAST Loop Lubrication Site in Section 24, with Gage Face Grease (High/Outside 

Rail) and TOR Oil (Low/Inside Rail) Applicator Bars Indicated..............................9 

Figure 4. Lubrication Site in Section 26, with Gage Face Grease (High/Outside Rail) and 

TOR Oil (Low/Inside Rail) Applicator Bars Indicated.............................................10 

Figure 5. Sample (Raw) RDG Data showing Wheel Sensor (Blue), Low Rail (Red) and High 

Rail (Green) Signals—Wheel Sensor Values are in Volts, and Rail Deflection 

Signals are in Millimeters .........................................................................................14 

Figure 6. Low Rail Lateral Force Signal from 6.5-Degree Curve with Standard Cut-Tie 

Fasteners ...................................................................................................................19 

Figure 7. Example (Raw) RDG Signals from Site 1, showing Wandering Baseline due to 

Gross (Quasi-Steady State) Lateral Shifts ................................................................20 

Figure 8. Simplified Diagram Indicating External Forces Applied to the Rail Section, as well 

as the Internal Bending and Net Deflection Measured by the LVDT Probe ............21 

Figure 9. FFT Magnitude Plots for Raw TPD (Left) and RDG (Right) Signals Taken at 

Measurement Site 3 (Stiff Track–Direct Fixation, Wood Ties)................................22 

Figure 10. FFT Magnitude Plots for Raw TPD (left) and RDG (right) Signals Taken at 

Measurement Site 1 (Soft Track–Cut Spikes, Wood Ties).......................................23

Figure 11. FFT Magnitude Plot for Raw and RDG Signal Taken at Measurement Site 2 (Stiff 

Track–Direct Fixation, Wood Ties)..........................................................................23

Figure 12. FFT Magnitude Plot for Raw and RDG Signal taken at Measurement Site 4 (Soft 

Track–Cut Spikes, Wood Ties).................................................................................24

Figure 13. Average Lateral Forces and Deflections Calculated Per Lap ...................................25

Figure 14. Average Lateral Forces and Deflections Calculated Per Lap ...................................25

Figure 15. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .26

Figure 16. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .26

Figure 17. Scatter Plot of Peak Lateral Forces and Deflections Calculated Per-Axle ...............27

Figure 18. Scatter Plot of Peak Lateral Forces and Deflections Calculated Per-Axle ...............27

Figure 19. Average Lateral Forces and Deflections Calculated Per Lap ...................................27

Figure 20. Average Lateral Forces and Deflections) Calculated Per Lap..................................27

Figure 21. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .28

Figure 22. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .28

Figure 23. Average lateral Forces and Deflections Calculated Per Lap.....................................28

Figure 24. Average Lateral Forces and Deflections Calculated Per Lap ...................................28

Figure 25. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .29

Figure 26. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .29

Figure 27. Average Lateral Forces and Deflections Calculated Per Lap ...................................29
vi

Figure 28. Average Lateral Forces and Deflections Calculated Per Lap ...................................29

Figure 29. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .30

Figure 30. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .30

Figure 31. Average Lateral Forces and Deflections Calculated Per Lap ...................................30

Figure 32. Average Lateral Forces and Deflections Calculated Per Lap ...................................30

Figure 33. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .31

Figure 34. Correlation Between Average Lateral Forces and Deflections Calculated Per Lap .31
vii

List of Tables 

Table 1. Descriptions of Measurement Test Sites.....................................................................8 

Table 2. Tribometer Measurements and Event Log for Night 1 (6/6/2005-6/7/2005)............15 

Table 3. Tribometer Measurements and Event Log for Night 2 (6/7/2005-6/8/2005)............16 
viii

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1

EXECUTIVE SUMMARY 

To determine if the use of dynamic rail deflection (RDG) data can be used to determine 

the effectiveness of top of rail (TOR) systems, Transportation Technology Center, Inc. 

(TTCI) and Kelsan Technologies Corporation, with funding from the Federal Railroad 

Administration (FRA), engaged in a collaborative effort to assess the suitability of 

RDGs in assessing TOR friction modifier effectiveness. Phase I of the test plan, 

included in this report, involved testing at the FRA’s Facility for Accelerated Service 

Testing (FAST) at the Transportation Technology Center (TTC), Pueblo, CO, using 

existing lubrication equipment to produce a range of lateral forces and correlate RDG 

response with truck performance detector (TPD) measurements. 

Summary of Test Conduct and Preliminary Findings: 

• Testing of a prototype RDG unit was conducted on the High Tonnage Loop 

(HTL) at FAST. RDG, TPD, and tribometer data were collected, allowing 

correlations to be established in range of track conditions. Data was collected at 

four measurement sites over two consecutive nights. 

• Existing lubrication systems at FAST (high rail (HR) gage face grease/low rail 

(LR) TOR oil) were used to produce a range of rail friction patterns that altered 

truck curving performance and resulting lateral forces. 

• Because the only variation during these periods of operation was rail friction, the 

intent was to evaluate the feasibility of RDG use in assessing the effectiveness of 

TOR friction control. 

• Correlations between average values of peak lateral force and rail deflection 

(calculated for leading axles using a custom algorithm to remove nonlinear 

signal components) are strong, with R2

 values ranging from 0.83 to 0.99 where 

direct comparisons are possible. This suggests that rail deflection measurements 

are a valid way to assess TOR friction modifier performance, provided other 

variables are known and controlled. 

• Deflection magnitudes were sufficient to provide good signal resolution across 

the range of track structures tested. 

• Non-zero intercepts in the correlation equations suggest that the correspondence 

between percent reductions in lateral force and rail deflections will not be exact. 

It is expected that stiff track structures will perform better than soft structures in 

this regard. In addition, analysis of loaded cars will minimize the impact of nonzero intercepts via higher lateral forces and deflections in relation to the intercept 

values. This represents an opportunity for further improvement to the rail 

deflection analysis algorithms. 
2

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3 

1.0 Introduction 

The introduction of TOR friction modification is being considered by a number of railroads. A 

primary benefit from implementing TOR friction control is the reduction in lateral curving forces 

applied to the track from freight car trucks. Typically, reductions of 30 to 40 percent have been 

observed on a 5-degree curve from gage face (GF) only to GF + TOR. 

Once applied, most TOR materials currently in use are invisible to the eye, taking the form of a 

very thin coating to the rail surface. Conventional methods used for measuring typical track 

lubrication (tribometer, rail temperature, and visual) are not always effective with TOR 

materials. Most evaluations of TOR systems at FAST and in the field have utilized strain-gage 

based load measurement stations. While such systems are accurate, they are expensive to install 

($10,000), require expensive equipment (valued at $12,000+) to monitor loads, and are not 

portable. Should a nearby location become more appropriate for monitoring TOR effectiveness, 

the equipment must be relocated and another set of strain gages installed, at an additional cost of 

$10,000. 

To reduce the cost of field monitoring of TOR effectiveness, it has been proposed that measuring 

dynamic gage widening could provide a lower cost measurement method. 

Limited demonstrations of a portable deflection system during TOR implementation have 

demonstrated performance suggesting that such an approach is viable. This was first observed at 

the FRA’s FAST at TTC, Pueblo, CO, when railhead deflections using a static gage were noted 

to increase with increased curing forces. Currently FAST uses static gages to record the highest 

rail deflection during the passage of a train to alert wayside inspectors of higher than normal 

lateral loads. While these high deflections are generally associated with a bad acting car/truck, 

high deflections have also been observed when track lubrication changes to form a pattern 

leading to increased lateral loads. 

Recent correlation work, conducted by Kelsan Technologies at several field sites where TOR 

friction control has been implemented, has shown that variations in TOR effectives can be seen 

in changes in dynamic gage widening. In addition, data from Norfolk Southern (NS) track 

geometry inspections has shown that, when operating over territories where TOR has been 

implemented, dynamic rail cant (railhead deflection or tipping) is reduced when compared to the 

immediate previous run. 

To determine if the use of RDG data can be used to determine effectiveness of TOR systems, 

TTCI and Kelsan Technologies Corp. with funding from FRA, engaged in a collaborative effort 

to assess the suitability of RDGs in assessing TOR friction modifier effectiveness. Phase I of the 

test plan, included in this report, involved testing at FAST, using existing lubrication equipment 

to produce a range of lateral forces and correlate RDG response with TPD measurements (TPDs 

are strain-gage based lateral/vertical force measurement sites). 
4 

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5 

2.0 Objectives 

Objectives for Phase I testing included: 

• Install a prototype RDG unit (developed specifically for this work) at a number of 

locations on the HTL at FAST, representing a range of track conditions (structure, 

stiffness). 

• Obtain data to facilitate a correlation between rail deflection (as measured by the 

RDG unit) and lateral forces (as measured by TPDs). 

• Obtain data to examine the sensitivity of the RDG instrumentation with respect to the 

range of deflections seen under different track stiffness conditions. 

This report describes testing undertaken at FAST during June 6-8, 2005. 
6 

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7 

3.0 Test Site Overview 

As stated in the introduction, Phase I of this collaborative project involved RDG testing at FAST 

on the HTL. Figure 1 illustrates the test loop. 

RDG Site 1

Night 1

(Soft track)

RDG Site 2

Night 1

(Stiffest track)

RDG Site 3

Night 2

(Stiff track)

RDG Site 4

Night 2

(Softest track)

Lubricator

Lubricator

TPD Site

TPD Site CCW Running CW Running (Night 1) (Night 2)

RDG Site 1

Night 1

(Soft track)

RDG Site 2

Night 1

(Stiffest track)

RDG Site 3

Night 2

(Stiff track)

RDG Site 4

Night 2

(Softest track)

Lubricator

Lubricator

TPD Site

TPD Site CCW Running CW Running (Night 1) (Night 2)

Figure 1. HTL Marked Up to Indicate RDG Measurement Sites, 

TPD Sites, Lubricator Sites, and Running Directions 

As Figure 1 shows, RDG measurement sites were established at four locations. Table 1 lists and 

describes these locations. Measurement Sites 1 and 3 are co-located with TPDs and represent 

soft and stiff track conditions, respectively. Soft track at Site 1 is constructed with wood ties and 

cut spikes, whereas stiff track at Site 3 is constructed with wood ties and direct fixation fasteners. 

In this case, because there is generally good track at FAST, track designated as soft is expected 

to exhibit less gage widening strength, and track designated as stiff is expected to exhibit more 

gage widening strength. 

Site 2 is a wood tie/direct fixation location with the track structure in excellent condition and 

good fastener toe-loads. This represents the stiffest available track on the HTL and is 

representative of structures, such as concrete tie/direct fixation in the field. Site 3 is a wood 

tie/cut spike location with relatively (for FAST conditions) significant tie degradation. This 

represents the softest available track on the HTL. 

Figure 1 also shows the lateral/vertical force measurement sites (i.e., TPDs). As previously 

mentioned, RDG Measurement Sites 1 and 3 were chosen so the RDG unit could be located with 

a TPD site (facilitating a direct comparison of raw and processed signals). The photos of 

Measurement Sites 1 and 3 in Table 1 and Figure 2 show the strain gage measurement points 

(installed with protective covers). 

(Softest Track)

(Stiff Track)

(Soft Track)

(Stiffest Track)
8 

Table 1. Descriptions of Measurement Sites 

Section 

(Tie No.) Description Picture 

Site 1 25 (199) 6o

L 

Cut Spikes 

Wood Ties 

Soft Track 

Site 2 25 (1319) 6o

L 

Direct Fixation 

Wood Ties 

Stiffest Track 

Site 3 7 (306) 5o

R 

Direct Fixation 

Wood Ties 

Stiff Track 

Site 4 3 (522) 5o

L 

Cut Spikes 

Wood Ties 

Softest Track 
9 

Instrumentation Box 

(Signal Conditioning, 

Data Logging, Comm.)

LVDT Displacement Probe

(1 per rail)

TPD Strain Gauges

and protective cover

Wheel Sensor 

(Gauge Side)

Instrumentation Box 

(Signal Conditioning, 

Data Logging, Comm.)

LVDT Displacement Probe

(1 per rail)

TPD Strain Gauges

and protective cover

Wheel Sensor 

(Gauge Side)

Figure 2. RDG Installation at Section 25, Tie 199 (RDG Site 1, Co-Located with TPD) 

During testing at FAST, truck steering was manipulated through rail lubrication strategies to 

produce a range of lateral force levels. Specifically, two lubrication sites (shown in Figures 3 

and 4) were used to control the application of grease on the outside rail GF and oil on the inside 

rail TOR. 

Gauge Face

Grease Bars

(Outside Rail)

Top of Rail

Oil Bar

(Inside Rail)

Gauge Face

Grease Bars

(Outside Rail)

Top of Rail

Oil Bar

(Inside Rail)

Figure 3. FAST Loop Lubrication Site in Section 24, with Gage Face Grease (High/Outside 

Rail) and TOR Oil (Low/Inside Rail) Applicator Bars Indicated 

Gage Face 

TPD Strain Gages and 

Protective Cover 

(Gage Side) 

 TOR 
10 

As Figure 1 shows, the inside/outside rails correspond to the low/high rails in all curved sections 

except the reverse curve centered at Section 7. In this section, the lubrication strategy results in 

grease being applied on the low rail GF and oil on the high rail TOR. 

In general, application of oil to the inside rail TOR surface was used as the primary control 

variable while grease application on the GF was held constant. Dry-down of the low rail TOR 

surface was used to generate high lateral forces through increased friction forces and antisteering moments. Over application of oil to the top of the low rail (versus nominal running 

conditions) was used to create minimum lateral force levels. This can be done at FAST without 

detrimental side effects as the locomotives are not under full-tractive effort nor is train braking 

usually required. Such a lubrication pattern, even though it leads to reduced curving forces, is 

generally not recommended for revenue service application because of potentially detrimental 

side effects to tractive effort and braking related issues. When measuring deflections in Section 

7, grease application was varied on the outside rail GF in an effort to produce a range of lateral 

forces. Variations in friction were produced using a variety of lubricants (grease and oil)—not 

friction modifiers. This was done to reduce costs and fit in with normal FAST lubrication 

policies, as past experience has shown that improperly adjusting these lubrication systems can 

lead to increased lateral curving forces. These changes in forces are due strictly to variations in 

friction as train speed, wheel/rail profiles, and other variables are kept constant. 

Gauge Face

Grease Bars

(Outside Rail)

Top of Rail

Oil Bar

(Inside Rail)

Gauge Face

Grease Bars

(Outside Rail)

Top of Rail

Oil Bar

(Inside Rail)

Figure 4. Lubrication Site in Section 26, with Gage Face Grease (High/Outside Rail) and 

TOR Oil (Low/Inside Rail) Applicator Bars Indicated 

Gage Face 

TOR 
11 

4.0 TRAFFIC OVERVIEW 

As Figure 1 shows, the HTL is a closed-loop test track. A single freight train runs on the track at 

a nominal speed of 40 mph, resulting in a complete lap occurring (approximately) every 

4 minutes. 

During the testing described here, four 4-axle diesel locomotives were configured at the headend of a 78-hopper consist. All cars were loaded to 125 tons (62.5 kip axle load), resulting in a 

nearly uniform consist (some minor variability in hopper carbodies/trucks was present). This 

type of configuration is well suited to the evaluation of RDG instrumentation, as many variables 

(e.g., vertical load, car type, truck type, and wheel base) are held constant. 

The running direction at FAST is typically alternated between clockwise (CW) and 

counterclockwise (CCW) directions to promote even wear of track components and remove 

effects associated with consistent directional running. During the testing described, the running 

direction was: 

• Night 1 (6/6/2005-6/7/2005): CCW 

• Night 2 (6/7/2005-6/8/2005): CW 

These running directions were convenient as they were conducive to manipulation of lateral 

force levels at the RDG measurement sites. As Figure 1 shows, CCW running results in the train 

passing the lubricator at Section 24 just before RDG Measurement Sites 1 and 2. CW running 

results in the train passing this lubricator in advance of Measurement Sites 3 and 4. 
12 

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13 

5.0 Data Collection 

As stated above, both RDG and lateral/vertical force (TPD) measurements were collected during 

testing at FAST. In addition, push-tribometer measurements of low rail TOR, high rail TOR, 

and high rail GF friction levels in (approximate) five-lap intervals were collected at the 

measurement sites to monitor the lubricated state of the rail as the lubrication strategy was 

adjusted to produce a range of lateral forces. The following paragraphs give a brief description 

of these measurements. 

5.1 RDG Measurements 

The prototype RDG (shown in Figure 2) collects rail deflection measurements through linear 

variable differential transformer (LVDT) based displacement probes, mounted such that the 

probe makes contact at the center of the vertical railhead surface on the field side. In addition, 

the signal from an active magnetic wheel sensor is used to trigger the system and track passing 

axles. Once triggered, the system collects data for a fixed period of time (corresponding to the 

maximum expected length of a single train), and then goes into a sleep mode until the subsequent 

train is detected. 

All signals are collected by the RDG digital data acquisition system at a sampling frequency of 

100 Hz, after passing through high order analog anti-aliasing filters with break frequencies tuned 

to 50 Hz.1

 Figure 5 shows a sample set of signals. The data shown was obtained at 

Measurement Site 2 (stiffest track). As shown, the stiff track structure results in clearly 

identifiable peaks in the rail deflection signal and a relatively stable zero point for each signal. 

 

1 As seen in Figures 9 through 12, spectral analysis of rail deflection signals at typical freight speeds has shown that the 

meaningful characteristic frequencies are typically less than 10 Hz. 
14 

Measurement Site 2 (Section 25, Tie 1319)

7 June 2005, 03:50

12

12.5

13

13.5

14

14.5

15

15.5

16

0 10 20 30 40 50 60 70 80 90 100

Time (sec)

Deflection (mm)

0

1

2

3

4

5

6

7

8

9

10

Sensor (Volts)

Low Rail Wheel Sensor

Measurement Site 2 (Section 25, Tie 1319)

7 June 2005, 03:50

12

12.5

13

13.5

14

14.5

15

15.5

16

0 10 20 30 40 50 60 70 80 90 100

Time (sec)

Deflection (mm)

0

1

2

3

4

5

6

7

8

9

10

Sensor (Volts)

High Rail Wheel Sensor

Figure 5. Sample (Raw) RDG Data showing Wheel Sensor (Blue), Low Rail (Red) and 

High Rail (Green) Signals—Wheel Sensor Values are in Volts, 

and Rail Deflection Signals are in Millimeters 

5.2 TPD Measurements 

Throughout testing, lateral/vertical force measurements were obtained via TPD sites. 

Measurement cribs 1/2 (Section 7), 3/4 (Section 9), and 5/6 (Section 25) were used to monitor 

and record lateral force levels. With data from RDG installations at Measurement Sites 1 and 3, 

a direct correlation with TPD signals is possible. For Measurement Sites 2 and 4, TPD data can 

be used to assess typical relative force levels for directional comparisons. 

During testing, TPD data was plotted in quasi-real time (approximate two-lap lag) to assess intrack force levels and determine when each lubrication condition had reached steady state. 

5.3 Tribometer Measurements/Event Log 

Tables 2 and 3 detail tribometer measurements obtained during testing, as well as events and 

observations, such as changes in lubrication conditions and RDG re-location activities. 

Tribometer measurements were used to monitor the friction of each rail surface and provide 

further confirmation that changes in lubrication conditions were manifesting themselves in 

measured values of friction. 
15 

Table 2. Tribometer Measurements and Event Log for Night 1 (6/6/2005-6/7/2005) 

Lap Location High Rail Low Rail Gage Face 

1 Sec 25 Tie 199 46 48 

1 Lube on NORMAL 

5 Sec 25 Tie 199 36 37 25 

10 Sec 25 Tie 199 37 33 21 

12 Low Rail Oil OFF 

15 Sec 25 Tie 199 42 52 24 

17 Low Rail Oil ON 

20 Sec 25 Tie 199 40 39 26 

25 Sec 25 Tie 199 36 30 28 

28 Low Rail Oil FLOOD 

30 Sec 25 Tie 199 34 28 18 

35 Sec 25 Tie 199 43 26 40 

38 Low Rail Oil OFF 

39 Low Rail Oil ON 

40 Sec 25 Tie 199 40 40 24 

43-50 RDG Relocated to Sec 25, Tie 1319 

57 Sec 25 Tie 1319 

58 Low Rail Oil OFF 

65 Sec 25 Tie 1319 45 36 15 

65 Low Rail Oil ON 

70 Sec 25 Tie 1319 43 42 17 

72 LOW RAIL FLOOD 

75 Sec 25 Tie 1319 40 26 17 

80 Sec 25 Tie 199 44 25 17 

85 Sec 25 Tie 1319 29 32 18 

86 Low Rail Oil NORMAL 

90 Sec 25 Tie 1319 32 33 17 

96 Sec 25 Tie 199 35 30 12 

96-102 RDG Relocated to Sec 7, Tie 306 

104 Sec 7 Tie 306 39 38 26 

109 Sec 7 Tie 306 45 45 13 
16 

Table 3. Tribometer Measurements and Event Log for Night 2 (6/7/2005-6/8/2005) 

Lap Location High Rail Low Rail Gage Face 

1 Lube on NORMAL 

5 Sec 7 Tie 306 35 31 6 

10 Sec 7 Tie 306 33 31 22 

11 Track Lubrication at Steady State 

15 Sec 7 Tie 306 36 32 20 

20 Sec 7 Tie 306 41 31 21 

24 Low Rail Oil OFF 

26 Sec 7 Tie 306 35 33 29 

29 Sec 26 Low Rail Oil ON 

30 Sec 7 Tie 306 40 33 29 

32 Sanding Section 7 

33 Sanding Section 7 

35 Sec 7 Tie 306 35 49 33 

40 Sec 7 Tie 306 37 39 25 

42 Low Rail Oil ON 

45 Sec 7 Tie 306 47 28 30 

49 Low Rail Oil FLOOD 

50 Sec 7 Tie 306 23 43 21 

55 High Rail Grease FLOOD 

55 Sec 7 Tie 306 21 43 23 

60 Sec 7 Tie 306 18 34 28 

63 Sec 7 Tie 306 17 34 29 

65 Low Rail Oil NORMAL 

67 High Rail Grease NORMAL 

70 Sec 7 Tie 306 20 36 20 

74-82 RDG Relocated to Sec 3, Tie 522 

85 Sec 3 Tie 522 48 39 12 

90 Sec 3 Tie 522 48 30 13 

91 Low Rail Oil OFF 

95 Sec 3 Tie 522 48 38 11 

97 Low Rail Oil ON 

100 Sec 3 Tie 522 39 32 12 

105 Sec 3 Tie 522 44 32 9 

108 Low rail oil FLOOD 

110 Sec 3 Tie 522 40 24 13 

113 Low Rail Oil NORMAL, High Rail Grease OFF (Begin Dry-Down) 

115 Sec 3 Tie 522 29 22 12 

117 Low Rail Oil OFF 

119 Sec 3 Tie 522 28 20 16 

120 Sanding 

121 Sanding 

125 Sanding 

126 Sanding 

127 Sanding 50 47 29 
17 

6.0 Test Sequence 

Four measurement sites were established for RDG testing on the HTL. Sites 1 (Section 25, tie 

199) and 2 (Section 25, tie 1319) were monitored on Night 1 (6/6/2005-6/7/2005). Sites 3 

(Section 7, tie 306) and 4 (Section 3, tie 522) were monitored on Night 2 (6/7/2005-6/8/2005). 

For each installation, the following general sequence was followed: 

1. Normal Forces: Establish steady-state running with normal lubrication conditions 

(HR grease and LR oil applied at typical levels to balance forces) and collect at least 

five laps of data. 

2. High Forces: Turn off LR oil, allowing the LR to dry-down and lateral forces to 

increase. This condition was maintained until maximum-deflection monitors (fishscales) installed at key locations showed peak deflections approaching 0.5 inch. 

Following this, typical LR oil application was resumed. 

3. Normal Forces: After returning to typical application levels, steady-state running 

was re-established (approximately five laps).

4. Low Forces: Over apply LR oil, flooding the rail and producing minimal lateral 

forces. At least five laps were collected before returning to normal conditions.

5. Normal Forces: After the low-force condition, LR oil was typically turned off for 

one to two laps and then turned on at normal levels to facilitate a rapid return to 

baseline conditions.

Deviations from the test sequence above occurred at Measurement Site 3 (Section 7, tie 306). As 

mentioned above, this is a reverse curve in which the lubrication strategy results in GF grease 

applied to the LR and TOR oil applied to the HR. As such, producing the desired range of forces 

was not straightforward. Combinations of reduced inside (high) rail oil application and overapplication of outside (low) rail grease were attempted. While a range of lateral forces was 

produced, it was not as wide as the range seen at other sites. 

In addition to the sequence above, a total dry-down was done in the final laps of Night 2 in 

anticipation of rail-flaw detector use on the following day. This provided additional data at 

Measurement Site 4 (Section 3, tie 522). As detailed in the observations listed above, outside 

rail GF grease was shut down at lap 113. Subsequently, inside rail oil was shut down at lap 117. 

Locomotive sanders were used on laps 120, 121, 125, and 126 to facilitate accelerated dry-down 

and provide extra data points. 
18 

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19 

7.0 Data Analysis 

7.1 Rail Deflection and Lateral Force Signal Characteristics 

As mentioned above, the purpose of this work is to assess the suitability of RDGs in assessing 

TOR friction modifier effectiveness. In particular, the aim is to examine the relationship 

between rail deflection and lateral force measurements to determine whether reductions in lateral 

forces can be correctly inferred from rail deflection data. For reference, Figure 6 shows a sample 

lateral force signal collected from a strain-gage based L/V measurement site installed in a 6.5-

degree curve. As shown, distinct peaks in lateral force (corresponding to the passage of each 

axle) are seen, with a stable zero point continuing throughout the series of measurements. 

-6

-4

-2

0

2

4

6

8

10

12

14

0 10 20 30 40 50 60 70

Time (sec)

Force (kips)

Figure 6. Low Rail Lateral Force Signal from 6.5-degree Curve with 

Standard Cut-Tie Fasteners 

7.1.1 Dependence of Rail Deflection on Track Structure and Condition 

As seen in Figure 5, rail deflection signals collected in stiff track structures have characteristics 

that are similar to those seen in lateral force measurements (Figure 6). Distinct peaks and a 

relatively stable zero point are seen in both signals. 

In contrast, Figure 7 shows typical rail deflection signals collected at RDG Measurement Site 1 

(Section 25, tie 199). As shown, gross shifts in the deflection signals are produced by quasistatic rail movements in this softer cut-spike track structure. These motions are accommodated 

by relative movement between the rail base and tie plate, and/or tie plate and tie. The presence 

of these gross shifts produces a wandering zero point, which makes analysis of dynamic rail 

deflection difficult. 
20 

Measurement Site 1 (Section 25, Tie 199)

6 June 2005, 22:18

12

13

14

15

16

17

18

0 10 20 30 40 50 60 70 80 90 100

Time (sec)

Deflection (mm)

0

1

2

3

4

5

6

7

8

9

10

Sensor (Volts)

Low Rail Wheel Sensor

Measurement Site 1 (Section 25, Tie 199)

7 June 2005, 22:18

14

15

16

17

18

19

20

0 10 20 30 40 50 60 70 80 90 100

Time (sec)

Deflection (mm)

0

1

2

3

4

5

6

7

8

9

10

Sensor (Volts)

High Rail Wheel Sensor

Figure 7. Example (Raw) RDG Signals from Site 1, showing Wandering Baseline 

due to Gross (Quasi-Steady State) Lateral Shifts 

7.1.2 Dynamic Model of Rail Deflection 

Figure 8 illustrates the external forces that are applied to the rail section with a passing wheel in 

a simplified way. In addition, the degrees of freedom and reaction forces occurring at both the 

rail base and tie plate are indicated. The internal bending of the rail is indicated by θ, and the net 

deflection measured by the LVDT probe is denoted by D. 
21 

FVERT

FLAT

f1

f2

x1

x2

θ

FR

D

FVERT

FLAT

f1

f2

x1

x2

θ

FR

FVERT

FLAT

f1

f2

x1

x2

θ

FR

D

Figure 8. Simplified Diagram Indicating External Forces Applied to the Rail Section, 

as well as the Internal Bending and Net Deflection Measured by the LVDT Probe 

FVERT and FLAT, the forces applied to the rail by the passing wheel, are dynamic forces that 

presumably reach a maximum value as the wheel is directly over the rail section. The lateral 

reaction force, f1, between the rail and tie plate will normally be a friction force that is linearly 

related to FVERT through the nominal coefficient of friction at this interface and nonlinearly 

related to the relative velocity between the rail and tie plate ( 1 2 x& − x& ). The magnitude of f1 will 

also be governed by the dynamic stiffness of the rail cross section. When the relative 

displacement between the rail and tie plate reaches the end of the available travel, f1 will become 

a reaction force between the vertical surfaces of the rail and tie plate at the point of contact. 

While the lateral reaction force f2 is not applied to the rail, it is indicated in the figure because of 

its relation to relative motion between the tie plate and tie, which also appears in the net 

deflection signal, D. This reaction force is similar to f1 in its relation to vertical load and the 

frictional characteristics between the tie plate and tie. 

The vertical reaction force, FR, at the bottom surface of the rail produces the required vertical 

force to balance the system based on the net moment created by the applied vertical and lateral 

forces, augmented by the lateral reaction force and dynamic stiffness effects. 

Given the discussion above, a general dynamic model for the deflection of the railhead at the 

point of LVDT probe contact can be written (in the Laplace Domain) as: 

( ) ( ) ( ) ( ) 1 2 D s d d G s F s LAT ≈ + + ⋅

Where d1 and d2 are nonlinear, quasi-random gross shifts of the rail occurring at the rail/tie plate 

and tie plate/tie interfaces. The transfer function G(s) maps the applied lateral force to a 

deflection term through the overall dynamic stiffness of the linear portion of the system. The 

typical form that would be expected for G(s) is: 
22 

eff eff eff m s c s k

G s

+ + = 2

1 ( )

where meff, ceff, and keff are the effective mass, damping, and stiffness terms for the system, 

respectively. 

Assuming that the data can be processed in a way that effectively removes the nonlinear gross 

rail movements, the resulting relationship between deflection and lateral force would be the 

given by the (approximately) linear: 

D(s) G(s) F (s) LAT ≈ ⋅

If this is the case, then assuming that the underlying lateral force signals between measurement 

conditions are similar in frequency content on a bulk basis, a reduction in the average value of 

peak lateral force over a large number of axles will be accurately reflected in the reduction of the 

average value of the peak of the linear component of deflection. 

7.2 Spectral-Analysis of Raw RDG and L/V Signals 

In order to examine the relationship between RDG and L/V data empirically, a frequency domain 

(i.e., Fast-Fourier Transform (FFT) analysis) was performed on raw, time-series data from the 

TPD and RDG measurement sites. 

7.2.1 FFT Comparison 

Figure 9 shows the frequency spectra from TPD and RDG signals recorded at Measurement Site 

3 (stiff track–direct fixation, wood ties). Lateral force and rail deflection signals are shown on 

the left and right of the figure, respectively. 

Figure 9. FFT Magnitude Plots for Raw TPD (Left) and RDG (Right) Signals Taken at 

Measurement Site 3 (Stiff Track – Direct Fixation, Wood Ties) 
23 

The fundamental frequency of ~1.2 Hz in both cases corresponds to the car-passing frequency 

(i.e., the basic periodicity of the train). As seen in the frequency spectra, both the L/V and RDG 

signals contain peaks at the same fundamental and harmonic frequencies. Higher frequency 

peaks in the RDG data are attenuated, as can be expected from the transfer function that maps 

lateral force to deflection. 

Figure 10. FFT Magnitude Plots for Raw TPD (Left) and RDG (Right) Signals Taken at 

Measurement Site 1 (Soft Track–Cut Spikes, Wood Ties) 

Figure 10 shows the frequency spectra from TPD and RDG signals recorded at Measurement 

Site 1 (soft track–cut spikes, wood ties). In this case, the RDG spectra contain additional content 

at frequencies near and below the car-passing frequency. This corresponds to the nonlinear gross 

lateral shifts of the rail, as Figure 7 shows. The noise introduced by these shifts overlaps with 

the deflection data in the frequency domain. This further highlights the challenge in analysis of 

RDG data to produce meaningful results, particularly in soft track structures. 

Figure 11. FFT Magnitude Plot for Raw and RDG Signal Taken at Measurement Site 2 

(Stiff Track–Direct Fixation, Wood Ties) 
24 

Figures 11 and 12 show the RDG frequency spectra from Measurement Sites 2 and 4, 

respectively (recall that no TPDs are located at these sites). These plots further demonstrate 

signal content at the car passing frequency and harmonics, as well as low frequency noise that is 

more prevalent in softer track structures. 

Figure 12. FFT Magnitude Plot for Raw and RDG Signal Taken at Measurement Site 4 

(Soft Track–Cut Spikes, Wood Ties) 
25 

8.0 Correlation of Peak L/V and RDG Signals 

8.1 RDG Analysis Software 

Kelsan Technologies has developed a custom RDG signal analysis program. The RDG analysis 

software detects the peak deflection caused by each wheel and determines the corresponding axle 

type (leading/trailing truck, leading/trailing axle). 

As mentioned above, one of the key requirements in analysis of rail deflection data is that the 

nonlinear portion of the signal be removed. Basic algorithms using the static rail position 

(obtained before/after each train) as a zero point have shown significant errors in estimation of 

dynamic deflection. With this in mind, Kelsan has developed an algorithm that estimates and 

updates the relaxed position of the rail with each passing car. The estimate is then used as the 

zero point when calculating peak deflections. This algorithm was used to generate the peak 

deflection data presented here. 

8.2 RDG Measurement Site 1 (Soft Track, Co-Located TPD) 

Figures 13 and 14 show the average values of peak lateral force and deflection calculated per lap 

at RDG Measurement Site 1. Each data point is the average value of force or deflection 

calculated for the 82-vehicle consist. Peak lateral forces were generated by TTCI and 

transmitted to Kelsan, while peak deflections were calculated using the algorithm described in 

the previous section. 

Recalling that the LVDT probe was installed adjacent to TPD crib 5, the trend in average 

deflection can be seen to follow the trend in average lateral force closely, particularly following a 

break-in period associated with (approximately) the first 10 laps. It is possible that the rail 

response in the relatively soft cut-spike track structure adjusted as the rail temperature and 

lubrication conditions reached a stable running state. 

Site 1, Leading Axles, Low Rail

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50

Lap

Average Lateral 

Force (kips)

0

0.5

1

1.5

2

2.5

Average Rail 

Deflection (mm)

Crib 5 Crib 6 RDG

Figure 13. Average Lateral Forces and 

Deflections Calculated Per Lap 

Site 1, Leading Axles, High Rail

0

2

4

6

8

10

12

14

16

18

0 10 20 30 40 50

Lap

Average Lateral 

Force (kips)

-0.5

0

0.5

1

1.5

2

Average Rail 

Deflection (mm)

Crib 5 Crib 6 RDG

Figure 14. Average Lateral Forces and 

Deflections Calculated Per Lap 

Figures 15 and 16 show the correlation between average values of peak lateral force and peak 

deflection, with the first 10 laps excluded. As shown, the correlation is strong with R2

 values of 
26 

0.93 and 0.89 for the low and high rails, respectively. The y-axis intercepts of 0.34 mm and 

0.51 mm will result in an inexact correspondence between percent reductions in lateral force and 

deflection. The directional differences, however, will be highly consistent (suggesting that rail 

deflection may be considered a valid means to assess TOR friction modifier 

coverage/performance). In addition, analysis of loaded cars will minimize the impact of nonzero intercepts via higher lateral forces and deflections in relation to the intercept values. 

Further improvements in the rail deflection analysis algorithms may drive the intercept values 

closer to zero, improving the correspondence in estimates of percent change. The large data set 

created during this testing will aid in the validation of future algorithm enhancements. 

Site 1, Leading Axles, Low Rail

(First 10 Laps Excluded)

y = 0.1843x - 0.3391

R2

 = 0.9258

0

0.5

1

1.5

2

2.5

0 5 10 15

Crib 5 Average Lateral Force (kips)

Average Rail Deflection

(mm)

Figure 15. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

Site 1, Leading Axles, High Rail

(First 10 Laps Excluded)

y = 0.119x - 0.5067

R2

 = 0.893

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 5 10 15 20

Crib 5 Average Lateral Force (kips)

Average Rail Deflection 

(mm)

Figure 16. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

Figures 17 and 18 show scatter plots of peak lateral deflection versus force on a per-axle basis, 

calculated for both leading and trailing axles. While there is some scatter due to both the 

nonlinear components of rail deflection and variations in frequency content, the clear pattern 

reinforces the validity of the correlation between measurements. 
27 

Site 1, Trailing Axles, Low Rail

-1

0

1

2

3

4

5

0 10 20 30 40 50

Lap

Average Lateral 

Force (kips)

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

Average Rail 

Deflection (mm)

Crib 5 Crib 6 RDG

Figure 19. Average Lateral Forces and 

Deflections Calculated Per Lap 

Site 1, Trailing Axles, High Rail

-1

0

1

2

3

4

5

6

0 10 20 30 40 50

Lap

Average Lateral 

Force (kips)

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Average Rail 

Deflection (mm)

Crib 5 Crib 6 RDG

Figure 20. Average Lateral Forces and 

Deflections) Calculated Per Lap 

Figures 19, 20, 21, and 22 show the average values and correlations of peak lateral force and 

deflection collected at Measurement Site 1 for trailing axles. As shown, the correspondence 

between lateral force and deflection is much weaker than seen for leading axles. This is due to 

significantly lower lateral forces generated at the trailing wheelsets, reinforcing the focus on 

leading axles of loaded vehicles when interpreting rail deflection data. 

Peak Deflection vs. Peak Lateral Force

Site 1, Low Rail, All Axles

-10

-8

-6

-4

-2

0

2

4

6

8

-10 -5 0 5 10 15 20 25

Crib 5 Peak Lateral Force (kips)

Peak Deflection (mm)

Figure 17. Scatter Plot of Peak Lateral Forces 

and Deflections Calculated Per Axle 

Peak Deflection vs. Peak Lateral Force

Site 1, High Rail, All Axles

-1

-0.5

0

0.5

1

1.5

2

2.5

-5 0 5 10 15 20 25

Crib 5 Peak Lateral Force (kips)

Peak Deflection (mm)

Figure 18. Scatter Plot of Peak Lateral Forces 

and Deflections Calculated Per Axle 
28 

Site 1, Trailing Axles, Low Rail

(First 10 Laps Excluded)

y = 0.0135x + 0.1015

R2

 = 0.0046

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-0.5 0 0.5 1 1.5 2

Crib 5 Average Lateral Force (kips)

Average Rail Deflection 

(mm)

Figure 21. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

Site 1, Trailing Axles, High Rail

(First 10 Laps Excluded)

y = 0.2896x - 0.878

R2 = 0.4899

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0123456

Crib 5 Average Lateral Force (kips)

Average Rail Deflection 

(mm)

Figure 22. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

8.3 RDG Measurement Site 2 (Stiffest Track, No TPD) 

Figures 23 and 24 show the average values of peak lateral forces at cribs 5/6 and peak deflection 

at RDG Measurement Site 2, calculated on a per lap (i.e., per-train) basis. Because the RDG and 

TPD measurement sites are not co-located in this case, lateral forces are not identical at both 

locations. Rather, lateral forces at cribs 5/6 can be seen as an indication of the directional trend 

in forces at the RDG measurement site. Despite the difference in physical location, the trend in 

average deflection can be seen to follow the trend in average lateral force closely. This is further 

supported by the correlations in Figures 25 and 26. 

Site 2, Leading Axles, Low Rail

0

2

4

6

8

10

12

14

46 56 66 76 86 96

Lap

Average Lateral 

Force (kips)

0.5

0.7

0.9

1.1

1.3

1.5

1.7

1.9

2.1

Average Rail 

Deflection (mm)

Crib 5 Crib 6 RDG

Figure 23. Average Lateral Forces and 

Deflections Calculated Per Lap 

Site 2, Leading Axles, High Rail

0

2

4

6

8

10

12

14

16

18

46 56 66 76 86 96

Lap

Average Lateral 

Force (kips)

0.2

0.4

0.6

0.8

1

1.2

Average Rail 

Deflection (mm)

Crib 5 Crib 6 RDG

Figure 24. Average Lateral Forces and 

Deflections Calculated Per Lap 

The range of peak deflections measured at this site (0.4–2.0 mm) is more than adequate for good 

signal resolution to be achieved via the RDG instrumentation. This indicates that RDG 

measurements are suitable in very stiff track structures. In addition, the clean signals shown in 

Figure 5 suggest that stiff track structures are more conducive for RDG measurements. 
29 

Site 2, Leading Axles, Low Rail

y = 0.1162x + 0.5089

R2

 = 0.9255

0

0.5

1

1.5

2

2.5

0 2 4 6 8 10 12 14

Crib 5 Average Lateral Force (kips)

Average Rail Deflection (mm)

Figure 25. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

Site 2, Leading Axles, High Rail

y = 0.0753x + 0.0594

R2

 = 0.9154

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 5 10 15 20

Crib 5 Average Lateral Force (kips)

Average Rail Deflection (mm)

Figure 26. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

8.4 RDG Measurement Site 3 (Stiff Track, Co-Located TPD) 

Figures 27 and 28 show the average values of peak lateral force and deflection calculated per lap 

at RDG Measurement Site 3. 

Recalling that the LVDT probe was installed adjacent to TPD crib 2, the trend in average 

deflection can be seen to follow the trend in average lateral force closely. While a small 

separation does exist in the high rail signals, it must be reiterated that the range of lateral forces 

that was achieved at this site is small in comparison with Measurement Sites 1, 2, and 4 due to 

the impact of the reverse curve on the effectiveness of the lubrication strategy. 

Site 3, Leading Axles, Low Rail

0

2

4

6

8

10

0 20 40 60 80

Lap

Average Lateral 

Force (kips)

0.2

0.4

0.6

0.8

1

1.2

Average Rail 

Deflection (mm)

Crib 1 Crib 2 RDG

Figure 27. Average Lateral Forces and 

Deflections Calculated Per Lap 

Site 3, Leading Axles, High Rail

0

1

2

3

4

5

6

7

8

9

0 20 40 60 80

Lap

Average Lateral 

Force (kips)

1

1.2

1.4

1.6

1.8

2

2.2

2.4

Average Rail 

Deflection (mm)

Crib 1 Crib 2 RDG

Figure 28. Average Lateral Forces and 

Deflections Calculated Per Lap 

Figures 29 and 30 show the correlation between average values of peak lateral force and peak 

deflection. As shown, the correlation is strong with R2

 values of 0.99 and 0.83 for the low and 

high rails, respectively. The substantial high rail y-axis intercept is likely due to the limited 

range of lateral forces that was generated at this site. 
30 

Site 3, Leading Axles, Low Rail

(First 10 Laps Excluded)

y = 0.0916x + 0.2795

R2 = 0.9896

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0123456

Crib 2 Average Lateral Force (kips)

Average Rail Deflection

(mm)

Figure 29. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

Site 3, Leading Axles, High Rail

(First 10 Laps Excluded)

y = 0.0993x + 1.2795

R2

 = 0.8349

0

0.5

1

1.5

2

2.5

0 2 4 6 8 10

Crib 2 Average Lateral Force (kips)

Average Rail Deflection 

(mm)

Figure 30. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

8.5 RDG Measurement Site 4 (Softest Track, No TPD) 

Figures 31 and 32 show the average values of peak lateral forces at cribs 5/6 and peak deflection 

at RDG Measurement Site 4, calculated on a per lap (i.e., per-train) basis. In this case, the RDG 

and TPD measurement sites are located at a significant distance from each other (see Figure 1). 

As such, lateral forces at cribs 5/6 can be seen at best as an indication of the directional trend in 

forces at the RDG measurement site. Despite the difference in physical location and the very 

soft (i.e., highly nonlinear) track structure, the trend in average deflection can be seen to follow 

directional trend in average lateral force. 

Site 4, Leading Axles, Low Rail

0

2

4

6

8

10

12

14

70 80 90 100 110 120 130

Lap

Average Lateral 

Force (kips)

1.5

2

2.5

3

3.5

4

4.5

5

5.5

6

Average Rail 

Deflection (mm)

Crib 5 Crib 6 RDG

Figure 31. Average Lateral Forces and 

Deflections Calculated Per Lap 

Site 4, Leading Axles, High Rail

0

5

10

15

20

70 80 90 100 110 120 130

Lap

Average Lateral 

Force (kips)

-1

-0.5

0

0.5

1

1.5

2

2.5

Average Rail 

Deflection (mm)

Crib 5 Crib 6 RDG

Figure 32. Average Lateral Forces and 

Deflections Calculated Per Lap 
31 

In addition to the basic directional agreement, the range of average rail deflections exhibited 

(1-5 mm) is reflective of the soft track structure. Raw data from this location shows substantial 

quasi-static shifts in rail location, which is in agreement with heavy plate cutting seen at the site. 

Site 4, Leading Axles, Low Rail

y = 0.3055x + 1.6614

R2

 = 0.6954

0

1

2

3

4

5

6

0 2 4 6 8 10 12

Crib 5 Average Lateral Force (kips)

Average Rail Deflection (mm)

Figure 33. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 

Site 4, Leading Axles, High Rail

y = 0.126x - 0.3674

R2 = 0.5845

0

0.5

1

1.5

2

2.5

0 5 10 15 20

Crib 5 Average Lateral Force (kips)

Average Rail Deflection (mm)

Figure 34. Correlation Between Average 

Lateral Forces and Deflections 

Calculated Per Lap 
32 

(blank page) 
33 

9.0 Suggested Equipment Improvements 

After inspecting and installing the RDG prototype, field test personnel made a number of 

suggestions for equipment improvements, including: 

• LVDT and wheel sensor cable-ends and connectors should be color-coded to ensure that 

incorrect connections are not made to the RDG instrumentation box. 

• A set of magnetized calibration shims could be used to verify in-situ verification of 

displacement probe accuracy. 

• LVDT cable lengths should be extended to allow RDG instrumentation box to be locked 

in an enclosure some distance from the track when using in areas where theft/vandalism 

is a risk. 

In addition to these suggestions, Kelsan has identified several improvements that should be made 

as the prototype matures to a (potentially) commercial product, including: 

• Revised internal layout (i.e., minor adjustments to top-plate machining) to enhance speed 

of assembly and ease of fit. 

• Reduced internal hook-up wire diameter (gage) for enhanced compatibility with custom 

interface board terminal blocks. 

• Adhesive application to any connectors without positive latching mechanisms to enhance 

resistance to vibrations. 

As a follow up, a field demonstration on a revenue railroad with a variety of traffic will be 

conducted. This will allow data from a variety of trains operating over the same site to be 

evaluated. The site selected will be part of an existing heavy axle load monitoring site and is 

equipped with load detection equipment and wayside based TOR equipment. By varying the 

settings of the wayside TOR system, the effect on curving forces can be determined, along with 

the associated changes in RDG performance. 

Provided acceptable results are obtained from the field test, a commercialization plan is planned 

to transition the RDG through the stage-gate process used at Kelsan and address any outstanding 

design issues. This will provide the railroad industry with an additional tool for use in assessing 

and adjusting TOR application systems in the field. 
34 

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35 

ACRONYMS 

CW clockwise 

CCW counterclockwise 

FAST Facility for Accelerated Service Testing 

FFT Fast Fourier Transform 

FRA Federal Railroad Administration 

GF gage face 

HR high rail 

HTL High Tonnage Loop 

LR low rail 

LVDT linear variable differential transformer 

NS Norfolk Southern 

RDG dynamic rail deflection 

TOR top of rail 

TTCI Transportation Technology Center, Inc. (the Company) 

TTC Transportation Technology Center (the Site) 

TPD truck performance detector 
36 

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