Pneumatic-Hydraulic Engines. Build your own models powered by air and water pressure to learn about the laws of physics. This unique kit allows you to build two different air-and-water-powered systems: water-jet propelled cars and hydro-pneumo (which simply means air pressure and water pressure) powered engines. The hydro-pneumo system uses a self-contained air-and-water turbine system as a motor. Construct 15 models including a truck, excavator, radar car, tank, antique car, helicopter, motorbike, backhoe, rocket car, forklift, roadster, propeller plane, grinder, and cutting machine. The water-jet propelled cars are a fun outdoor activity, while the self-contained hydro-pneumo powered models are fun both indoors and out. The 48-page color instruction book included in this kit illustrates the step-by-step assembly of each model and related principles so that children learn through playing. The 165 building pieces included in this set are compatible with those in all Thames & Kosmos Construction Series kits, Physics Series kits, Wind Power, and Hydropower kits.