Author: Mark Lester: MDOT Southwest Region Fleet Manager
The snow & ice control guidelines issued by Maintenance Division of the Michigan Department of Transportation specify that granular deicing agents be applied in a concentrated band along the crown of the pavement. It is the experience of MDOT that "windrow" application of granular deicing agents reduces material usage significanly over broadcast applications. In fact, all of Michigan DOT snow plow trucks are equipped with ground speed systems which are programmed for a maximum application rate of 500lbs. per mile in salt mode.
Obviously applying salt in a windrow cannot be accomplished by use of a spinner. The Department uses both slip-in and chassis mount salt hoppers. The dump truck mounted slip-in hoppers are equipped with a Y-chute attachment for windrow application. The side delivery system design discussed in this article is used predominately in the Southwest Region, a nine county area in southwest corner of the state. In this region are located twelve MDOT maintenance garages responsible for maintenance of state trunkline.
The side delivery systm is a transverse mounted box, approximately 13" by 8' long, bolted underneath the discharge of the chassis mount hopper. This unit is of steel construction with a UHMW bed.There are several variations in use. Most are equipped with either a 1" X 1" or 1/2" X 1" flat stainless chain (lime spreader type chain) which is hydraulically driven by a single hydraulic motor. There are some unts with a pintle chain with slats or externally cogged snowmobile belt. These units are bi-directional providing material application capabilities from either the left or right side of the truck. Bi-directional capability is provided by a Vickers cartridge type directional valve utilizing 12v. solenoids and controlled by a cab mount electric toggle switch. This feature provides the operator with the capability of switching material discharge from one side to the other instantly, in the event they must change lanes or apply material to the high side of a ramp.
The unique feature of this particula side delivery systm is that it also offers a spinner assembly mounted in the center of the unit. This spinner features a 24" polyurethane spinner plate with adjustable deflector doors. There is a hinged door which directs material from the hopper chain into the spinner housing or side delivery chain. This door is activated by a tailgate air cylinder which is cab controlled by a cab mounted air toggle switch. This feature provides the operator the ability to windrow material on the roadway and broadcast material at intersecions and on bridge decks. And, if a failure occurs with side delivery chain or bearings, the spinner assembly is fully functional and can be utilized until repairs can be made keeping the salt truck in service.
The side delivery system can be plumbed into exhaust oil from hopper chain, providing synchronization between hopper and side delivery or plumbed on separate hydraulic circuit with it's own control.
This system was the "brainchild" of Barry Hall, MDOT Grand Region Fleet Manager and was built and perfected by Mark Lester at the Fennville MDOT Maintenance Garage in 1986. This unt is now manufactured by Monroe Truck/Snow & Ice Division and can be purchased through Truck & Trailer Specialties in Dutton, MI. (616)-698-8215.
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