The 13/2 is interesting for a couple of reasons.
Firstly, the overall layout, with the crankshaft, cylinder, boiler and burner all in line longitudinally, on a long thin wooden base.
Secondly, and the most interesting aspect, is the semi-rotative valve gear (see below).

The meths burner has three short wick tubes set into a cylindrical fuel tank.
In working position, half of the tank sits under the boiler and the other half protrudes outside.

Steam feed is taken from the bottom of the boiler and directly to the valve chest housing the semi-rotative valve.
This consists of a brass rod, cross drilled with two holes at right angles to each other, a small distance apart.
The outside end of the rod has a crank, linked to a crank on the engine crankshaft, so that it rocks back and forth by about 90 degrees.
This causes the two holes to alternately line up with the steam and exhaust passages.

The cylinder is a substantial brass casting.
It is single acting but the open end is small in comparison with the overall diameter, giving it the appearance of a double acting type.
The cylinder is fixed (not oscillating) but it contains a long piston, as found in oscillating cylinders, so that it does not require a cross-head guide.

The end of the piston rod is connected to a built-up crank at the centre of the crankshaft.
The crankshaft has the valve return crank at one end and a flywheel at the other.
The 13/2 is interesting for a couple of reasons. Firstly, the overall layout, with the crankshaft, cylinder, boiler and burner all in line longitudinally, on a long thin wooden base. Secondly, and the most interesting aspect, is the semi-rotative valve gear (see below).
The meths burner has three short wick tubes set into a cylindrical fuel tank. In working position, half of the tank sits under the boiler and the other half protrudes outside.
Steam feed is taken from the bottom of the boiler and directly to the valve chest housing the semi-rotative valve. This consists of a brass rod, cross drilled with two holes at right angles to each other, a small distance apart. The outside end of the rod has a crank, linked to a crank on the engine crankshaft, so that it rocks back and forth by about 90 degrees. This causes the two holes to alternately line up with the steam and exhaust passages.
The cylinder is a substantial brass casting. It is single acting but the open end is small in comparison with the overall diameter, giving it the appearance of a double acting type. The cylinder is fixed (not oscillating) but it contains a long piston, as found in oscillating cylinders, so that it does not require a cross-head guide.
The end of the piston rod is connected to a built-up crank at the centre of the crankshaft. The crankshaft has the valve return crank at one end and a flywheel at the other.
Cyldon