The next job in the fiddle yard rebuild was to create a latching mechanism that aligns the traverser tracks to the entry track, and provides power to the aligned track. This uses the same sprung notch and pin arrangement as proven on Loctern Quay and the home fiddle yard for Hexworthy.
- A spring taken from a soap dispenser as shown
- A length of aluminium - in this case T-profile - with a pivot hole at one end, and a curve cut and filed at the other, with a V-notch at its centre. There are also 3 holes through the vertical web
- A long screw which passes through a hole in the aluminium, through the spring, and into the block of wood which is fixed to the board.
The extra depth of the rebuilt fiddle yard allowed the pivot bolt to be inserted with the nuts below (Awngate had a very shallow baseboard), this meant only the shallow mushroom head of the bolt protruded. This meant I could make the centre track a through road rather than having two dead-ends, both making it more useful and making the electricals easier, so a short length of track was cut to fit the gap between the existing PCB strips. However, the bolt head caused a hump in the track, and cutting away the sleepers meant the rails touched the bolt head. I carved away the lower part of the rail with the dremel so they sit neatly over the bolt head, and the red insulating tape should prevent any shorts. There seems to be adequate clearance for wheel flanges.
An overview of the assembled fiddle yard. It can be seen how the two "handles" lock the rotating upper deck to the traversing lower deck, they are unlocked when the handles are folded down to act as end-stops preventing stock runaways when rotating. Rotation is free and smooth, the latching seems to work well, and sliding the traverser forwards is smooth. However... when pushing the traverser back the latch is difficult to overcome and movement can start with a jolt, which is likely to derail trains.
I realised that the previous latching fiddle yards I have built were sector plates, the curvature of which allows the latching arm to be pivoted at a point in line with the track join, and so the arc of the movement of the arm is perpendicular to the movement of the pin - that is, the v-notch moves directly away from the pin and resistance is equal in either direction (see here). In this case the arms have had to be pivoted some way back from the track join, and despite making the arms as long as possible they must be at about 20 degrees to the line of travel of the traverser. Pulling the traverser forward the pin has an easy job to slide out of the v-notch, but when pushing the angle of movement of the arm effectively steepens the "slope" the pin has to push against to free itself.