Abstract: A hot gas water heater has a housing, and at least a pair of concentric coils in the housing through which liquid to be heated is sequentially passed. Each coil has a helical tube with adjacent turns connected by a web member such that the tube and web member form an imperforate coil wall. Hot gas passes sequentially between the coils in co-current flow with liquid flow in one adjacent coil and counter-current flow with liquid flow in another adjacent coil.

Abstract: A hot gas water heater has a housing, and at least a pair of concentric coils in the housing through which liquid to be heated is sequentially passed. Each coil has a helical tube with adjacent turns connected by a web member such that the tube and web member form an imperforate coil wall. Hot gas passes sequentially between the coils in co-current flow with liquid flow in one adjacent coil and counter-current flow with liquid flow in another adjacent coil.

Abstract: A motorcycle has a motor mounted on a frame, a drive shaft extending from the motor transversely to the direction of travel, a rear wheel axle and a shaft drive mechanism extending longitudinally from the drive shaft to the rear wheel axle for transmitting power from the drive shaft to the rear wheel axle. The drive mechanism has an elongate housing with a first end portion pivotably mounted about the drive shaft and a second end portion pivotably mounted about the rear wheel axle. A drive gear is located on the drive shaft for rotation thereby, and an axle gear is located on the rear axle for driving the rear axle. A pinion shaft is supported by the housing so as to be rotatable about its own longitudinal axis.