The "Ultimate" fiddle yard - refinements and finishing

So, here's where I think the problem is. With the sector plate of the home fiddle yard (left-hand diagram) the latch arm is pivoted in line with the movement of the pin, so it's movement is perpendicular to the pin movement. However, with the traverser (right-hand diagram) the pivot must be set back, causing the arm to be at an angle, and more importantly the movement of the notch is not perpendicular to that of the pin. When the traverser is pulled forward (down in the diagram) the pin pushes the notch away easily, but when pushed back (up) as the arm moves the slope out of the notch is effectively steepened, requiring much more force to move it. 

It had become clear that no amount of adjustment of the shape of the notch was going to allow the traverser to release forwards smoothly while latching positively, and I couldn't move the location of the pivot for the latch arm. Therefore if the traverser was to move smoothly and not jolt so that trains were derailed, a latch-release mechanism would also be required. I gave this some thought since the objective of the latching mechanism was to make fiddle yard operation easy and requiring minimal intervention from the operator, the latch release would therefore need to be easy and instinctive to use one-handed so that the traverser could be moved with the other. That meant it had to disengage the latches at both ends of the traverser, and return to self-latching mode once released. 

This view of the underside shows the solution I came up with. 

• At the top left of this view is a wooden lever on the front fascia of the board, pressing this down rotates a dowel "shaft" which runs across the board (top to bottom on the left of this view). 
• The shaft rotates a wooden arm, the top of which pushes the aluminium latch lever back (left) away from the pins, releasing the latch. 
• The lower end of the arm is linked to another dowel that runs along under the board (left to right in this picture), such that the rotation of the first shaft causes this dowel to push to the right
• At the end of this second dowel another wooden arm is pushed against the aluminium latch at the far end of the traverser, releasing that end too

With the traverser deck removed the two dowels can be seen, with the wooden arms that bear on the latch levers. Pressing the lever on the front left of the board thus pushes both latches back and releasing the traverser to move smoothly. Releasing the lever allows the latches to spring back into place, and so the traverser will then slide into the next latch position.

This view also shows a wooden arm fixed to the deck on the left, this is a "gate" that swings out to prevent runaways from the traverser when it is pulled forward. Held with a single screw it simply pushes back parallel to the board as shown for transport. There is a similar gate at the right-hand end.   

Another refinement is this old bathroom door draw-bolt. The lower part is fixed to the supporting cross member and the upper part is on the front of traverser, engaging the bolt locks the traverser in place for transport. 

As seen in the photos above the fiddle yard board got a coat of the standard grey paint used on my recent layouts, to match with Hexworthy. The smaller home fiddle yard also got a coat of paint. I use grey wood primer from Wilkinsons (although a primer it has a nice finish), I guess I'll need to find another source when this runs out. Mind you, it's oil based, smelly, takes ages to dry, and is a paint to clean out of brushes, so next time perhaps I'd choose a water-based paint!

The paint really smartens the fiddle yard, although I have not painted the deck or moving parts. Here the latch release lever can be seen, as can the two gates that protect the ends of the traverser when pulled forwards. 

So the exhibition fiddle yard is now complete. It seems to work well in the brief tests so far, but will spend most of its life in the garage, I guess the real test will be when it gets used in anger. 

Of course, life might have been much easier if I'd gone for a simpler turntable or traverser, rather than combining the two. The original intention was to have the benefits of a turntable (fast turnaround with no stock handling) while able to turn it when used against a wall at home, hence the need to pull it clear of the wall. Now I can't erect this fiddle yard against the wall at home anyway and as rebuilt it can only turn when pushed back, but decided I might as well continue to use the sliding/rotating arrangement as:

1. I'd already got the sliding/rotating assembly which seemed to work so might as well reuse it
2. The traverser arrangement allows parallel tracks so I can fit more in - a turntable needs space for the tracks to curve at the ends, so less tracks in a given width
3. It actually proved handy. Being able to slide it away from you and rotating it without having to get off a stool and move out the way is quite useful!
4. The double-ended latching arrangement works with a traverser but wouldn't with a turntable. (I expect it could work with a turntable using a common return rail powered through the pivot bolt and a changeover switch for the polarity when turning, perhaps as microswitches set up to automatically switch)

Finally, here's the home fiddle yard in place with Hexworthy. The grey paint looks much neater, again the moving deck is unpainted. The pillar on the right is the reason for the L-shape fiddle yard and why the larger exhibition fiddle yard can't be used here.