Port belt arrangement

A port belt arrangement for use in a two-stroke internal combustion engine containing a pair of adjacent cylinders, the arrangement including:

• a first hollow annulus having an outer wall and an inner wall and defining a first annular channel between the outer and inner walls, the first annular channel tapering in a radial direction, with increasing circumferential distance from a first port, the first hollow annulus defining a first central aperture configured to receive a first cylinder;
• and
• a second hollow annulus having an outer wall and an inner wall and defining a second annular channel between the outer and inner walls, the second annular channel tapering in a radial direction, with increasing circumferential distance from a third port, the second hollow annulus defining a second central aperture configured to receive a second cylinder;
• wherein:
• a second port is located in the inner wall of the first hollow annulus;
• a fourth port is located in the inner wall of the second hollow annulus;
• the first hollow annulus and the second hollow annulus are joined together at a joining point located on each of their circumferences;
• the cross-sectional area of the first annular channel at the joining point is less than the cross-sectional area of the first annular channel at the point on the circumference of the first hollow annulus which is furthest from the joining point;
• the first port and the third port are inlet ports for the annular channels;
• the second port and the fourth port are cylinder inlet ports through which gas can flow from the annular channels toward the central apertures;
• a first gas flowpath is defined, in the first annular channel, between the first port and the second port;
• and
• a second gas flowpath is defined, in the second annular channel, between the third port and the fourth port.