drive gear teeth mesh with and drive a gear on the pump shaft or may be belt driven from the engine or gear shaft the pump used on the prototype installation is a propeller type pump mounted on the radio battery cover of the car chassis and gear driven from the drive gear alternate pump drives may be a pulley from the engine output shaft gear or drive shaft or electric drive powered by the radio control battery the liquid to air heat exchanger is of metal or metal and plastic construction to provide good heat transfer both aluminum based alloys or copper alloys are satisfactory although other metals may also be used the size and configuration of the heat exchanger is dependant on the space available in a given car chassis some chassis may use more than one physical heat exchangers piped in series the heat exchanger must be in a location that has good airflow when the car is in motion the heat exchanger design may be but is not limited to finned tubes or plates through which the hot liquid flows as heat is transferred to the air through the extended heat transfer area provided by the fins the size of the heat exchanger which can be accommodated in a.