Performance in Service, Technology of Fabrication, and Future Promise

the manufacture of such ties has grown into a major forest products industry. Today, over a billion wood ties support the 350,000 miles of railroad tracks in the United States. The success of these ties in service-particularly under the stress of World War II traffic-is a testament to the utility of wood crossties. Abstract It is generally agreed that railroads of the United States must substantially increase their rate of tie renewals, if roadbeds are to be maintained in acceptable condition. To accommodate faster trains and heavier loads, future mainline ties may average larger than the 7by 9-inch size now in common use; fewer 6by 8-inch ties will be utilized. A logical source of wood for these ties is the enormous inventory of underutilized small hardwoods in the South, East, and Midwest. The process of dowel-lamination can permit manufacture of wane-free 7by 9-inch mainline ties from logs with small-end diameters of only 8.3 inches-a size plentiful in this inventory. Bigger ties can easily be fabricated from logs only slightly larger. Through use of a new type of conversion machine the shaping-lathe headrig-lumber recovery can approach 10 bd. ft./ft.) of log input, with six half-ties produced per minute. Mainline ties dowel-laminated from two half-ties (interface vertical when in place) have suffered no failures in extensive service tests extending over 15 years, and their service life should be at least as long as that usual for one-piece ties. Laboratory tests indicate that dowels withdrawn from dry wood have greater withdrawal resistance if they are inserted in green (rather than dry) wood. When 1/2-inch fluted-steel dowels were inserted in green wood and withdrawn from dry wood of four species, withdrawal forces were highest in hickory and blackgum (average 1,935 Ib./in. of penetration) and least in southern red oak and sweetgum (average 1,468 lb./in. of penetration). These findings are useful, because handling costs can be reduced if half-ties are doweled green rather than dry, as is the present practice. Six half.inch fluted-steel dowels per tie should be adequate. The Problem After nearly 15 decades of usage of wood crossties by railroads, two problems have lately emerged.