Railway Track & Structures 12/07

Wheel climb some of the results that are generated by this approach. Existing wheel-climb relationships The most-widely-used relationship for understanding wheel climb was presented in 1896 by Nadal. The Nadal equation for flange-climb derailment was derived based on the simple equilibrium of forces on the inclined plane of contact between wheel and rail (Figure 1) where ∂ is the maximum contact angle and m is the limiting friction coefficient at the contact position. Based on a friction coefficient of 0.5 and a flange angle of 67 degrees, an L/V threshold of 0.8 is commonly quoted in rail safety studies. The Nadal limit is acknowledged to be conservative, primarily because it presumes that slip at the flange contact results in only lateral forces. For many low-floor transit vehicles that use a split axle (which cannot generate longitudinal forces) this is a reasonable approximation. Gilchrist and Brickle2 challenged the limitations of the Nadal formula, noting that in the general case of a wheelset with wheels fixed to a rigid axle, longitudinal forces are usually also present. Subsequent to Gilchrist and Brickle’s work, and with the benefit of additional developments by Kalker in modeling of the wheel/rail contact,3 Weinstock presented a further contribution.4 Through quasi-static modeling he found that the L/V = (tan ∂ - m)/(1 + m tan ∂) [1] Figure 3. Lubrication of the high rail increases the L/V ratio when compared with the same vehicles running on dry rail. These data are from Amtrak’s Northeast Corridor near Baltimore Station for a range of commuter and freight trains. predictive/descsriptive models to provide an improved practical understanding of wheel climb for lay persons. In this article, we will review the basic elements and factors associated with wheel-climb derailments. This analysis includes a discussion of the causal relationships developed by Nadal and Weinstock. We discuss the merits of these relationships, propose a related criterion and examine briefly The Fine Art of M/W Equipment from the Collection Brush Cutter Ballast Undercutter Swing Loader Scrap Crane Tie Crane New 180C Crane The best-engineered, most versatile line of construction and maintenance-of-way equipment available today! With proven reliability, utility and safety. Each unit is designed for maximum efficiency and minimum maintenance using RCEinnovated accessories specially developed for rail and transit operations. BUY • RENT • LEASE Rail Construction Equipment Co. 1400 West Ogden Ave., Naperville, IL 60563 Tel: 866-472-4570 • Fax: 630-355-7173 dennishanke@rcequip.com 38 Railway Track & Structures December 2007 www.rtands.com http://www.rtands.com

Table of Contents Feed for the Digital Edition of Railway Track & Structures 12/07

Railway Track & Structures - December 2007 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Hand-Held Tools Provide the Power to Get Big Jobs Done AREMA C&S Update Striving to Solve the Riddle of Wheel Climb RTA Stages Warm Gathering in Sunny Florida in October Products and Literature People Calendar Website Directory Advertisers Index Sales Representatives Professional Directory Classified Advertising Chicago Perspective

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.