This mechanism adjusts the position of the valve mechanism so that the valves move in a slightly different pattern with respect to the wheels and thereby control the direction of travel. We opted for a "screw reverser" rather than a "pole reverser". This means the mechanism is controlled by turning a wheel so that a nut travels along a screw thread, rather than a lever which moves forwards or backwards. Why? Well this is because of the other name for this control: the cutoff. The cutoff changes the proportion of the stroke during which steam is admitted to the cylinder. The Polly pole reverser has five positions: full ahead, mid-ahead, neutral, mid-reverse and full reverse. The screw reverser gives analogue control - more fiddly, but our home track has some gradients and we hope the screw reverser will give us better control in the long run.
The screw reverser came ready assembled, but bolting it on to the frame took longer than expected as the screws had to be trimmed to the right length. If they are too long the boiler won't fit!
After an exchange of photographs with Andy, we dropped and rotated the central, driving, axle and tried again. This worked better, but not as well as we thought it should.
An email then arrived from Andy pointing out that we had two brackets inside the valve gear the wrong way round. So we fixed them and, to our dismay, the left-hand valve developed the original symptom again.
Eventually, Andy sent us a diagram showing the correct alignment of the eccentrics with respect to the key-ways. We checked several times, because dropping the axle was very tedious, but there was no doubt that the left most eccentric had slipped 60°.
Once this was fixed setting the left valve was easy (we had had some practice by this point) and the lids could go on the steam chests.
A delay that took all September to resolve!
The distinctive feature of the kit must be the long thin metal strip which travels attached to some wood. This runs from beneath the cab right to the front of the locomotive, where it connects to the draincocks of kit 6 at the bottom of the cylinders. A second lever brings the linkage up into the cab area where a simple knob becomes is the second of the cab controls to appear.
