Copyright Goodheart-Willcox Co., Inc. Chapter 3 Tools and Equipment 47 gasoline engine. The purpose of troweling is to give the surface a smooth, dense finish. When large concrete projects are to be troweled, a riding trowel can be used. Figure 3‑55 displays a riding towel that has two powered rotating blade systems with a diameter of 46″ each. The panning path width of the machine unit is 101.5″, or 8′-5 1/2″. The trowel is controlled by a hydraulic system that runs on a diesel engine. Safety Note A power masonry trowel can be dangerous. Fuel- powered engines give off carbon monoxide fumes during the running process. The hazardous fumes can cause serious health conditions or death. Carbon monoxide sickness can occur when gas-powered equipment is operated inside buildings or in confined spaces where fresh air is limited. Allen Engineering Corporation Figure 3‑55. This riding trowel is operated by hydraulic steering, which aids the operator in maneuvering the machine across the concrete surface.