To ensure a clean sweep, all mechanical broom street sweepers use some type of drag dirt shoes. These shoes are positioned to the right and left of the main sweeping broom and the elevator/conveyor. They act as a moving barrier to ensure debris does not escape before it can be swept by the main broom onto/into the conveyor or elevator system. Without effectively functioning drag dirt shoes, debris could easily dribble out the sides of the main broom resulting in poor sweeping performance.
The thickness and quality of the dirt shoe materials also determine their long term performance. Quicker wearing varieties are often made of thinner, mild steel. Longer wearing varieties are made of thicker, higher quality materials. Stewart-Amos dirt shoes are 2” wide at the base and made of carbide steel.
Drag dirt shoes are highly effective on streets and highways. Their solid steel walls are perfect for preventing fine debris and even light quantities of water from escaping the sweeping process. However there is one sweeping application where they can pose a huge problem – milling sweeping.
During the milling process, a cross section of an existing asphalt surface is ground or milled away to be replaced with a fresh top coat at a later date. Milling machines employ revolving drums equipped with cutting teeth which can remove 6+ inches of asphalt in one pass. Mechanical broom sweepers follow behind the milling machines to clean sweep the remaining loose millings.
This requires the sweeper operator to drive the unit down into the milled “cut” which can often run 3 to 6 inches below the surrounding road surface. If the sweeper operator isn’t careful the rear of the sweeper could swing wide resulting in the rear broom assembly’s steel dirt shoes striking the sunken edges of the milled cut. Once a dirt shoe is bent, sweeping performance is greatly diminished. There is little recourse but to take the unit out of service and perform a costly and time consuming repair. This is unacceptable to milling contractors and something to be avoided at all costs.
This is why brush bristle is replacing steel as the dirt shoe material of choice for many milling sweeping companies. Instead of using a material like steel that does not yield to impacts, softer, impact friendly materials like brush bristle are being used with great success. A brush bristle dirt shoe consists of a thick row of brush bristle similar to that of a rear sweeping broom. It is mounted where the steel dirt shoes normally are and serve the same purpose, that of keeping millings between the main broom and elevator.
Brush bristle dirt shoes are highly flexible. This and their long length provides excellent protection against impacts. They are perfect for milling applications because of their impact resistance. They can save a contractor a lot of time, money and downtime over the course of a summer.
If your street sweeper is used for more than one purpose you may want to quickly modify your unit to match your sweeping application. This is why Stewart-Amos sweepers come equipped with the mounting hardware to accept both style dirt shoes. When milling, quickly mount the brush bristle dirt shoes. When sweeping streets and highways, quickly mount the 2” wide, carbide steel dirt shoes which will provide maximum performance sweeping fine debris, sand, and other common highway debris.
