Route Selection

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Archie

Route Selection

Post by Archie »

Browsing through the guest lounge I came across references to route selection.

The only cases I know of with route selection in real life involve power switching partly because route selection was generally used in order to allow a smaller signal box rather than operator convenience and power switching drastically reduces the size. Secondly route selection generally requires the operation of several points at the same time and would therefore require superhuman effort.

It seems to me that each route is designated by the release of a signal. Moreover distant signals merely reflect the position of the stop signals, ahead or on the same post. Thus a route selection frame should be able to eliminate all the yellow and black levers. I'm not sure about the locking levers or the, presumably in real life point locking would be part of the automatic sequence which involves about three positions of the lever Select/Actuate/Lock.

Operation with a miniature frame would involve two parts. The interlocking of the routes to avoid conflicts and the operation of the points and signals.

The operation of the points and distant signals is basically a case of slotting. When a route is set it sets the stop signal directly but the points have to be slotted as do the distant signals.

Selection of a route will pull the points into the designated position but will not reposition them on deselection. Deselection must allow the point to take either position. This can be done by either arranging for some levers to push the point back or to use a lever to convert the pull from the lever into a push. The existence of holes above and below the spindle on a MODRATEC lever makes it natural to use pushing rather than having to introduce another lever.

Point slotting could be done with SlotWITs but as there is no requirement to return the point to the original position on deslection it could be done by pieces of string (pulls but doesn't push) or, more sanely, by putting elongated loops on the ends of the piano wire pullers (pushers), which operate a lever, which in turn is connected to the pointWIT. The active end of the loop would be adjusted to operate the lever through a sufficient distance. The pointWIT eliminates the need for great accuracy.

The distant signals do require proper slotting, which is most easily achieved with SlotWIT. They provide the mechanical logic which releases the signal only when the home, the starter and the signal on the same post are all released.

Interlocking may involve more locking bars than with the normal system but could be modelled with SigScribe4 by adding dummy point levers in order to set the points even though the only important interlocking is between the signal levers. I leave that to any that wish to try it.

Archie
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