The Effects of the Lateral Instability of High Center of Gravity Freight Cars

1968 ◽  
Vol 90 (4) ◽  
pp. 727-735
Author(s):  
D. Wiebe
Keyword(s):  
Lateral Force ◽  
Center Of Gravity ◽  
Body Motion ◽  
Lateral Instability ◽  
Vertical Side ◽  
Track Maintenance ◽  
Car Body ◽  
Lift Off ◽  
Lateral Resonance ◽  
High Center

High center of gravity freight cars experience extreme weight shift from side to side as a result of lateral resonance on track with cross-level differences from alternately staggered joints, as well as soft or other local variations in either rail. Dynamic measurements from tests made on test track with controlled 3/4-in. cross-level difference changes illustrate the force and motion magnitudes resulting from resonant and near resonant operating speeds; side bearing loads of 138,000 lb and spring group loads of 100,000 lb, accompanied by center plates separating and wheels lifting. The rotational energy input to the car body can be approximated for a given motion cycle and is proportional to the product of the amplitudes of the track profile and the car body motion. The high lateral (horizontal) forces on the truck at the side bearing and center plate make the truck unstable and cause wheels to lift off the rail on one side. This lateral force at a given end of the car is proportional to the corresponding vertical side bearing load. Freight cars traveling at resonant speed are especially prone to derail on curved track under high wheel-rail friction conditions. Forces and motion generated between the car body, truck, and the track, cause high cyclical stresses and severe wear between components that can shorten equipment life and cause severe track maintenance problems.

Design, Simulation, and Test of Variable Damped Suspensions for M-965 High CG Cars

2001 ◽  
Author(s):  
Armand P. Taillon ◽  
Peter E. Klauser
Keyword(s):  
Vehicle Dynamics ◽  
Center Of Gravity ◽  
Performance Criteria ◽  
Vehicle Performance ◽  
Car Body ◽  
Test Input ◽  
Analysis Methods ◽  
Body Roll ◽  
Dynamics Simulations ◽  
High Center

Abstract This paper reviews design and analysis methods applied in developing a three-piece Coulomb-damped truck arrangement to meet the requirements of specification M-965. This section of the AAR standards specifies performance criteria for high center of gravity cars over twist and roll inputs. The test input is a track section with a series of staggered low joints. These act to excite car body roll. The review demonstrates that properly designed suspension and damping components, in combination with side bearings, will achieve the required performance through the life of the truck. It also demonstrates the effectiveness of accurate vehicle dynamics simulations as a conservative predictor of actual vehicle performance on perturbed track. The design and analysis methods are described in detail. Guidelines are provided to help determine appropriate suspension arrangements for high CG car applications.

Analysis of coupler jackknifing and its effect on locomotives on a tangent track

2017 ◽  
Vol 232 (5) ◽  
pp. 1559-1573 ◽  
Author(s):  
Lirong Guo ◽  
Kaiyun Wang
Keyword(s):  
Dynamic Performance ◽  
Compressive Force ◽  
Lateral Force ◽  
Lateral Instability ◽  
Lateral Deviation ◽  
Running Safety ◽  
Car Body ◽  
The Stability ◽  
Yaw Angle ◽  
Active Measure

Coupler jackknifing has caused a number of derailments, and it is a significant topic that needs in-depth studies. This paper aims to investigate the characteristics of coupler jackknifing and its effects on the dynamic performance of locomotives during braking. A field braking experiment using three eight-axle locomotives was conducted on a tangent track. The experimental results indicated that in-service couplers with a friction arc surface are prone to coupler jackknifing once the compressive force of the coupler exceeds 400 kN. After coupler jackknifing, the coupler angle has a significant positive correlation with the yaw angle of the car body; both coupler jackknifing and coupler angle increase rapidly to maximum values. The contact between the car body and the bogie seriously affects the dynamic performance of the locomotive and causes lateral instability of the locomotive. In particular, the lateral deviation of the coupling couplers generates an eccentric wear on the tail of the coupler. A numerical simulation model is developed to investigate the effect of coupler jackknifing on the running safety of the locomotive. Simulation results show that coupler jackknifing induces an excessive lateral force on the wheelset and increases the risk of derailments and gauge widening. Compared with the existing measures against coupler jackknifing, in this study, an effectively active measure is proposed to improve the stability of the coupler and to prevent possible derailments caused by coupler jackknifing during braking.

Posture stable control of a high center-of-gravity move robot

2004 ◽  
Vol 2004 (0) ◽  
pp. 37-38
Author(s):  
Takashi SATO ◽  
Hideyasu SUMIYA ◽  
Shinichi AOSHIMA ◽  
Masatake SHIRAISHI
Keyword(s):  
Center Of Gravity ◽  
Stable Control ◽  
High Center

scholarly journals Analytical Model of Wave Loads and Motion Responses for a Floating Breakwater System with Attached Dual Porous Side Walls

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Weiliang Qiao ◽  
Keh-Han Wang ◽  
Wenqi Duan ◽  
Yuqing Sun
Keyword(s):  
Analytical Model ◽  
Dynamic Responses ◽  
Body Motion ◽  
Linear Wave ◽  
Wave Loads ◽  
Vertical Side ◽  
Damping Coefficients ◽  
Floating Breakwater ◽  
Exciting Forces ◽  
Porous Walls

A set of two-dimensional analytical solutions considering the effects of diffraction and radiation are presented in this study to investigate the hydrodynamic interaction between an incident linear wave and a proposed floating breakwater system consisting of a rectangular-shaped body and two attached vertical side porous walls in an infinite fluid domain with finite water depth. The Matched Eigenfunction Expansion Method (MEEM) for multiple fluid domains is applied to derive theoretically the velocity potentials and associated unknown coefficients for wave diffraction and body motion induced radiation in each subdomain. Also, the exciting forces, as well as the added mass and damping coefficients for the floating breakwater system under the surge, heave, and pitching motions, are formulated. The displacements of breakwater motions are determined by solving the equation of motion. As a verification of the analytical model, the present solutions of the limiting cases in terms of exciting forces, moments, added masses, and damping coefficients are found to be well matched with other published numerical results. Additionally, the hydrodynamic performances and the dynamic responses in terms of Response Amplitude Operators (RAOs) of the proposed floating breakwater system are evaluated versus various dimensionless variables, such as wavelength and porous-effect parameter. The results show that the attached porous walls with selected porous properties are observed to have the advantages of reducing wave impacts on the floating breakwater system and at the same time its dynamic responses are also noticeably improved.

The effect of the secondary lateral stopper on the compressed stability of the couplers and running safety of the locomotives

2017 ◽  
Vol 232 (3) ◽  
pp. 851-862 ◽  
Author(s):  
Kaikai Lv ◽  
Kaiyun Wang ◽  
Zaigang Chen ◽  
Lirong Guo ◽  
Zhiyong Shi ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Lateral Force ◽  
Tangent Line ◽  
Running Safety ◽  
Car Body ◽  
Influence Mechanism ◽  
Heavy Haul ◽  
Multi Body ◽  
Positive Effect ◽  
Body Dynamic

This paper aims to study the effect of the secondary lateral stopper on the compressed stability of the couplers in order to improve the running safety of the heavy-haul locomotives. The influence mechanism of the secondary lateral stopper on the compressed stability of the couplers is theoretically analyzed. To verify the effect of the secondary lateral stopper, both the simulation and the field braking tests are conducted. The multi-body dynamic model consists of two eight-axle locomotives, one dummy of freight vehicle and four detailed connected couplers. The field braking tests are conducted on the tangent line using three eight-axle locomotives. The results indicate that decreasing the free clearance and increasing the stiffness of the secondary lateral stopper both have a positive effect. However, when the free clearance decreases from 20 mm to 10 mm, there is no remarkable decrease in the yaw angles of the coupler and the car body, and the maximum lateral force of the wheelset is still out of the standard in the simulation. When the stiffness of the secondary lateral stopper increases by five times, the yaw angles of the coupler and the car body are reduced significantly and the running safety of the locomotives is also enhanced.

scholarly journals Numerical analysis of the effective stiffness of elastomeric bearing pads under precast beams for the limit load of lateral instability

2020 ◽  
Vol 13 (1) ◽  
pp. 95-119
Author(s):  
L. C. REIS ◽  
P. A. KRAHL ◽  
M. C. V. LIMA
Keyword(s):  
Numerical Models ◽  
Precast Concrete ◽  
Limit Load ◽  
Span Length ◽  
Lateral Instability ◽  
Technical Literature ◽  
Initial Imperfections ◽  
Elastomeric Bearing ◽  
Concrete Girders ◽  
Lift Off

Abstract Precast concrete girders on bearing pads are subjected to instability depending on several variables such as span length, initial imperfections and bearing pads behavior. On this paper, numerical models are developed in order to assess the instability limit loads and the rotational stiffnesses of the pads in many combinations of span length, cross section of the girder and lateral sweep. The lift off phenomenon is considered in each analysis by a bearing pad model composed by springs with compression only behavior, with good results in comparison with the experimental values of the technical literature. The increase in spans and initial imperfections causes a decrease in the rollover limit load. The lift off effect is aggravated as the lateral eccentricities increase. In the analyzed combinations, the reduction of the rotational stiffness is about 37% for the critical situation, which span length about 40 m and lateral sweep of L/300, with loss of contact between 50% and 60%.

Accuracy Analysis of Car Body-Mounted Doppler LIDAR Technology Used to Measure Track Speed and Curvature

2015 ◽  
Author(s):  
Joshua Muñoz ◽  
Masood Taheri Andani ◽  
Mehdi Ahmadian
Keyword(s):  
Research Team ◽  
Ground Truth ◽  
High Accuracy ◽  
Dynamic Responses ◽  
Body Motion ◽  
Laboratory Research ◽  
Doppler Lidar ◽  
Lidar System ◽  
Track Geometry ◽  
Car Body

Modern track inspection technologies contribute to more efficient and reliable identification of track conditions including track geometry and sections requiring maintenance. Records of car body motion and rail conditions are also vital for derailment or track failure investigations. Doppler LIDAR technology is a tool with a vast array of utility in measuring speed of a moving target with a high degree of accuracy and precision, and has been proven by a Virginia Tech (VT) research team to record body motion and track curvature through car body speed characteristics. In the context of track maintenance, high sensitivity to rail surface deviations and signal fidelity at high speeds make LIDAR a desirable tool for collecting information on local curvature deviations and car body dynamic responses to such irregularities. Virginia Tech’s Railway Technologies Laboratory research team has completed extensive analysis on its Doppler LIDAR system’s ability to obtain train speed and track curvature profiles in terms of the system’s accuracy and dependency on car body motion during curve navigation. Due to the LIDAR system’s capability of providing curvature data from the speed profile, it follows that the LIDAR system also serves as a high-accuracy alternative to the geometry car’s IMU which also provides curvature data. Results show the LIDAR system records curves with a high correlation with ground truth measurements. The signal processing techniques used to reveal track curve and car body motion are reviewed to show that, indeed, the LIDAR system detects car body motion in addition to the track’s curvature profile. Results strongly suggest Doppler LIDAR serves as a high-accuracy alternative to multiple rail inspection instruments and provides useful data for the improvement of rail condition localization and mapping.

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