Abstract: An exercise device is provided using, for example, handles, connected to cords that increase in tension as the handles are pulled. The tension may be provided using elasticity of the cords or by an actuator, for example powered by an electric motor. Pulleys allow adequate extension while remaining compact enough to fit in a standard height room and allowing accessibility to components. Upper and forward pulleys may be used. The upper pulleys may be displaced from potential obstacles, including the forward pulleys.

Abstract: A hypotrochoid positive-displacement machine includes an inner rotor and an outer rotor with intermeshing projections. During rotation of the rotors, the inward-most tips of the outer rotor trace hypotrochoid paths relative to the inner rotor. A driven rotor, for example the inner rotor, drives a driven rotor, for example the outer rotor, by contact between driving surfaces and driven surfaces of the respective rotors. Improvements are provided, for example in relation to the contact between the rotors. In use of the device contact between the driving surfaces and driven surfaces may move radially outward from a point of initial contact. The driving or driven surfaces or both may be arranged to flex under contact between the rotors. The driving surfaces may be convex. The driven surfaces may be concave.

Abstract: A hypotrochoid positive-displacement machine includes an inner rotor and an outer rotor with intermeshing projections. During rotation of the rotors, the inward-most tips of the outer rotor trace hypotrochoid paths relative to the inner rotor. A driven rotor, for example the inner rotor, drives a driven rotor, for example the outer rotor, by contact between driving surfaces and driven surfaces of the respective rotors. Improvements are provided, for example in relation to the contact between the rotors. In use of the device contact between the driving surfaces and driven surfaces may move radially outward from a point of initial contact. The driving or driven surfaces or both may be arranged to flex under contact between the rotors. The driving surfaces may be convex. The driven surfaces may be concave.

Abstract: A positive displacement gear pump or gear hydraulic motor having at least a first rotor with first rotor teeth and a second rotor with second rotor teeth, the first rotor teeth meshing with the second rotor teeth. First rotor chambers are defined between first rotor teeth and second rotor chambers are defined between the second rotor teeth. As the rotors mesh, the first rotor chambers, second rotor chambers or both become enclosed or substantially enclosed to form what are referred to here as secondary chambers. Pressure variations in a secondary chamber are relieved by internal flow channels in the first rotor, second rotor or both, creating a fluid connection between the first rotor chambers and the second rotor chambers. The first rotor may be an internal gear rotor or both rotors may be external gear rotors.

Abstract: An energy transfer machine includes a piston and cylinder. The piston can have a rocking motion as it enters and exits the cylinder, for example due to one being on a rotor and the other on a stator. The piston and cylinder form a primary chamber, and as they move relative to each other can form a seal separating the primary chamber into first and second sub-chambers which then unseals before the piston exits the cylinder. The first sub-chamber may reach a maximum geometric compression ratio, for example for the purpose of compression ignition, before the unsealing of the sub-chambers.

Abstract: An exercise device is provided using, for example, handles, connected to cords that increase in tension as the handles are pulled. The tension may be provided using elasticity of the cords or by an actuator, for example powered by an electric motor. Pulleys allow adequate extension while remaining compact enough to fit in a standard height room and allowing accessibility to components. Upper and forward pulleys may be used. The upper pulleys may be displaced from potential obstacles, including the forward pulleys.

Abstract: An energy transfer machine includes a piston and cylinder. The piston can have a rocking motion as it enters and exits the cylinder, for example due to one being on a rotor and the other on a stator. The piston and cylinder form a primary chamber, and as they move relative to each other can form a seal separating the primary chamber into first and second sub-chambers which then unseals before the piston exits the cylinder. The first sub-chamber may reach a maximum geometric compression ratio, for example for the purpose of compression ignition, before the unsealing of the sub-chambers.

Abstract: A positive displacement gear pump or gear hydraulic motor having at least a first rotor with first rotor teeth and a second rotor with second rotor teeth, the first rotor teeth meshing with the second rotor teeth. First rotor chambers are defined between first rotor teeth and second rotor chambers are defined between the second rotor teeth. As the rotors mesh, the first rotor chambers, second rotor chambers or both become enclosed or substantially enclosed to form what are referred to here as secondary chambers. Pressure variations in a secondary chamber are relieved by internal flow channels in the first rotor, second rotor or both, creating a fluid connection between the first rotor chambers and the second rotor chambers. The first rotor may be an internal gear rotor or both rotors may be external gear rotors.

Abstract: An energy transfer machine includes a piston and cylinder. The piston can have a rocking motion as it enters and exits the cylinder, for example due to one being on a rotor and the other on a stator. The piston and cylinder form a primary chamber, and as they move relative to each other can form a seal separating the primary chamber into first and second sub-chambers which then unseals before the piston exits the cylinder. The first sub-chamber may reach a maximum geometric compression ratio, for example for the purpose of compression ignition, before the unsealing of the sub-chambers.

Abstract: An energy transfer machine includes a piston and cylinder. The piston can have a rocking motion as it enters and exits the cylinder, for example due to one being on a rotor and the other on a stator. The piston and cylinder form a primary chamber, and as they move relative to each other can form a seal separating the primary chamber into first and second sub-chambers which then unseals before the piston exits the cylinder. The first sub-chamber may reach a maximum geometric compression ratio, for example for the purpose of compression ignition, before the unsealing of the sub-chambers.

Abstract: A displacement device including an inner rotor and an outer rotor with meshing projections. Points on each rotor trace a hypotrochoidal path relative to the other. The tips of the outer rotor projections may contact the inner rotor at Top Dead Center (TDC) and Bottom Dead Center (BDC) to form higher and lower pressure regions. Various elements may shape other elements to form seals.

Abstract: A displacement device including an inner rotor and an outer rotor with meshing projections. Points on each rotor trace a hypotrochoidal path relative to the other. The tips of the outer rotor projections may contact the inner rotor at Top Dead Center (TDC) and Bottom Dead Center (BDC) to form higher and lower pressure regions. Various elements may shape other elements to form seals.