Saturday, March 16, 2019

Staffs and Staff Boxes - A Model Interpretation

It has been a while since the last post and I did say I was working on something for another post so here it is.

This took a lot longer to do than I anticipated.

I have drawn up and printed some small staff boxes for use on my Bylong layout. These staff boxes had to fit on the layout edge which is made from nominal 2 inch X 1 inch pine framing with 1/2 inch (12/13 mm) chipboard on top. The boxes were designed to fit the nominal 2 inch edge. Nominal means that the pine frame isn't really 2 inches X 1 inch and in fact measures 42 mm X 20 mm.

The idea was to use the small 3D printed staffs available from my Signals Branch shop although I did have to print two more on my FDM (filament) printer which I will come to later in this post.

So the idea was to use the small tabs on the staffs to trigger two micro switches to turn the box into a switch. Now each staff has two tabs in different places just like the prototype does. On the prototype the staff is inserted into a key way in the side of the box and this enables the box lid to be opened so that a book of tickets can be removed and used to allow a train to proceed into the next staff section without the staff. Once the train or trains have left the staff section the following train can proceed with the staff to the next staff section signal box. Of course no train movements can come in the other direction until the staff has arrived at the next section signal box to allow the process to repeat for the other direction. The other aspect of this is that the staff will only open the staff box it is for.

The staff boxes are painted in red, white, blue and green and have a circle, triangle, square and heart respectively.

The name plates on the above staff boxes appear to be a later addition. On the model boxes I chose to used raised lettering to make it easier to paint the signal box/station names.

Here is a photo of the parts I designed and printed on my FDM printer:

Of course, the staff box is too small to contain tickets so the idea is to use the micro switches and the matching staff to say change the opposing Home signal to stop. The switches could be used with a solenoid or servo to unlock another box containing tickets as well. I will be using the staffs and staff boxes to trigger programming in NCE Mini Panels. I set up a Mini Panel with some programming but found that the normal lever (switch) that operates the Home signal would change the signal to clear even if the staff box had put it at stop. So the thought is to use the staff box to disconnect the wiring of the signal lever that goes to the Mini Panel such that the signal can't go to clear while the staff is in the staff box. The staff box would also trigger the Mini Panel to put the Home signal at stop.

A note here about NCE Mini Panel triggering. The Mini Panel uses a wire from the Mini Panel ground to a switch then back to an input on the Mini Panel. The Mini Panel programming reacts to a change of state such as a switch closure but not about the switch already being closed hence the problem above with the Home signal. Also to throw a point or signal the other way it needs a separate input so keep this in mind if using a Mini Panel. The Mini Panel has 5 volts available on the circuit board which could be used with a 5 volt relay or a flip flop transistor circuit if required to feed from a NCE BD20 track detector to the Mini Panel. The Mini Panel will react to the BD20 turning on but does not react to a BD20 or switch turning off so the relay or transistor circuit can be used here to produce the turn off input to the Mini Panel. 

Anyway, that is where I have got to after several weeks of design, printing and painting the staff boxes. Oh yes, I had to make two more staffs with different tabs and matching staff boxes for two extra sections. I painted the circle and heart on the two repeating staff boxes brass along with the area around the circle and heart cutouts on the staffs to indicate that they are different.

While I am sure staff sections on the real railway have a number of stations within them I chose to have staff sections that ran from station to station in model form.

Here is the full set in order including the one already mounted at Bylong. In the way of these things I managed to put the triangle on my white model boxes upside down so It looks like some more printing and painting coming up.

Now I have to get back to finishing and installing the rest of my signals on Bylong, it never ends does it, just as well that it is fun.