Abstract
This paper describes in detail the design, engineering and testing conducted for 260 self-steering bogies in response to a bid from SNIM (Société Nationale Industrielle et Minière), in Mauritania, Africa.
Severe environmental conditions in Mauritania, caused by the presence of sand, contribute to accelerated wheel tread wear. This in combination with asymmetric wheel wear typically experienced with the standard three-piece bogie, results in poor wheel life. A steering bogie improves wheel life by allowing the axles to self-align, thus reducing asymmetric wheel wear occurrence.
Bogie behavior is explained by comparing the stiffness characteristics of self-steering bogies and standard three-piece bogies. High bogie stiffness keeps a truck square as it travels on the track, thus improving its dynamic response on tangent track. Split type friction wedges are used together with heavy-duty suspension system to obtain high bogie shear stiffness and vertical damping characteristics. An elastic shear pad between the roller bearings and the side frame pedestal roof allows the axles to self-align in curves, giving the truck its self-steering characteristic.
The truck design is unique as the standard AAR unit guide bracket construction point and angle were changed to provide the alignment for the unique combination of axle spacing and wheel diameter. It utilizes 1000 mm diameter wheels and a wheel base of 1800 mm.
The Consolequip steering bogie has been engineered to improve dynamic response on tangent track. This is done by increasing bogie interaxle shear stiffness which increases the threshold of truck hunting. Stability tests with service worn wheels confirmed stability speed to exceed operating speeds used by SNIM network. Preliminary projections have estimated an improvement of up to 50% in wheel life by reducing asymmetric wheel wear and the number of times they are re-profiled.
