The design of the engine that transforms fluid pressure differences throughout the height of the transmission mechanism (in this case), the supposed name: "pressure difference engine".

## Design of the pressure difference hydraulic engine:

The proposed engine is shown in Fig. 3 (side view) and Fig. 4 (end view). It includes the transmission mechanism and the following elements shown by arrows:

1. cylinder fairing
2. bypass manifold
3. fairing plug
4. fastening plug
5. rack reducer

included in the design of the transmission mechanism but requires the following clarification: all the reducers must have two automatic gears that must ensure forward and reverse stroke of the piston when the transmission mechanism is moving circumferentially. Moreover, all the reducers should include a differential gear for matching speeds of pistons in cylinders with the rotation speed of the transmission mechanism.

Two solutions are possible for engine application: in the first case, the engine is submerged into the fluid, the bypass manifold contains air at atmospheric pressure or the engine works using air and the bypass manifold contains fluid. At that, the engine design does not change, and in this case we examine the first option, i.e. the engine works submerged into the fluid.

The engine design is described below: the bypass manifold (2) that is immovably fixed at the transmission mechanism shaft provides a pressure-tight connection between cylinders of the transmission mechanism. The number of cylinders should be maximum possible, the best way is to use cylinders with the section shape close to truncated from the segment fastening side. In this case, cylinders will act as fairing themselves. The joining fairing (1) is required when using cylinder of round or other shape. It is a hollow cylinder joining internal and external circumferences of transmission mechanism cylinders surfaces. The plug (3) and the fastening plug (4) are located inside the fairing on the shaft. They create an air block inside the fairing. The purpose of the air block and the fairing is given in the end of the text.

## The proposed engine operates in the following way:

The example of engine operation is a motion of a single piston in a cylinder of the transmission mechanism. The motion starts from the point (of a circle) located at the half-height of the transmission mechanism. At this time, the piston must be in the extreme left position inside the cylinder in accordance with Fig. 3. In this position the cylinder is filled with air. Under pressure the piston is set in motion and displaces the air block from the cylinder, and the transmission mechanism starts rotating. The cylinder length should correspond to a 180° rotation of the transmission mechanism taking account of gear ratios, but the first half-revolution in this engine is done only through the lower part of the rotation circumference. After the mechanism makes a half-revolution, the rack reducer (5) switches the piston to the reverse motion. When this happens, the transmission mechanism continues to rotate in the same direction, and the piston moves backward under the action of transmission mechanism gears thus displacing the fluid out of the cylinder. Rotation of the transmission mechanism during the piston backward movement in the cylinder is caused by work of the opposite piston inside the opposite cylinder. After the transmission mechanism performs a complete revolution, the piston returns to the home position and one more switching happens in the rack reducer (5), but from reverse motion to forward one, and the motion cycle is repeated. The power of the proposed engine is proportional to the difference of pressures acting on the piston in the lower and upper rotation half-circles of the transmission mechanism. But the cylinders will be subjected to buoyancy forces due to presence of air blocks. The linear calculation of active torques action created by fluid pressure acting on pistons in cylinders and reactive moments created by action of air blocks in pistons yields that they are almost equal. It is necessary to make unequal the torques of cylinder fairing and air block at the transmission mechanism shaft because that is required to move the transmission mechanism. The cylinder fairing combines actions of individual air blocks into the single force, and an air block changes the radius length of the action vector of this force. Use of the air block with length equal to 0.62 length of the piston for the engine with pistons having shape of truncated segments located at a distance equal to a half of the transmission mechanism radius and having the same height increases the buoyancy force value by 1/8 and shortens the action vector radius length of this force by two times. Thus, the inequality of torques required for motion of the transmission mechanism is achieved. In this case the cylinder fairing is not necessary. An additional purpose of the fairing: it smooths the fluid resistance if cylinders are round or have other shapes. The essential requirement for the fairing design: its density should be equal to or higher than the density of the fluid used, i.e. the fairing must not create an additional buoyancy force. The air block length is calculated individually for each design depending on the cylinder shape.

The operating parameters of this engine can be estimated on the example of the above-mentioned engine with truncated segment cylinders. As it was said, the use of the air block increases the buoyancy force value by 1/8 and shortens the radius length of the action vector of this force by two times. This yields that the action of active torques will exceed the action of reactive moments approximately by 45%. The design losses in the engine structure will be somewhat lower compared to the external pressure engine. Assuming that these losses are about 15% of the total power, we obtain that efficiency of this engine will be about 30% of the difference between actions of fluid pressures on pistons in lower and upper half-circles of the transmission mechanism. Despite the fact that these calculations are approximate, this engine can be the basis for free-standing sources of mechanical and, correspondingly, electric energy.