The specialists from Stehr in the central hessian town of Schwalmtal, together with Hessen-Forst-Technik (Mr. Kessler and Mr. Tolle), developed a system to restore streets and roads with water-bound surfaces as rapidly as possible and with a minimum of expense and effort. Since worldwide only about 75 % of roads are paved and farm tractors can be found everywhere, this new Stehr system will make a major contribution to greatly improving the transportation infrastructure in many developing countries and in a way that is also economical. Called the gravel road finisher, this system is mounted on the front and back of tractors, wheeled loaders, Unimogs and similar carriers.

 

The rear-mounted system consists of a mixing apparatus with an attached shaping device or built-in screed. As the vehicle moves in its normal direction of travel, the roadway material is loosened, mixed and shaped. The built-in screed is designed so that every familiar roadway cross-section or profile can be formed in only one pass of the system. The remarkable thing is that all this happens at a speed of 15 - 20 km/h.

 

We know of no machine on the market that comes even close to this kind of performance. The mixing effect is accomplished purely statically and requires no additional drive or power: tools stir the material up using the energy generated by the material itself moving through the system. A scraper blade is also mounted on the sides, which can be extended beyond the system's normal operating width, and is used to push humus and other vegetation outward on to the embankment to allow rainwater to drain off. It is also possible to mix previously applied binding agents such as lime or cement, or gravel and blends of minerals that were spread earlier into the existing surface material. The dimensions of the Stehr gravel road finisher have been engineered to allow a road with a water-bonded surface of 3 meters in width to be built and restored in three steps: push organic material (vegetation, humus etc.) from the center of the road outward on to the embankments; loosen, mix and camber; then compact. The latter is accomplished using plate compactors mounted on the front.