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More tick-boxes!
I'm writing this while I think of it. I shall never remember to mention everything again later.
In 236a there are new options for the
2-part switch block chairs, to permit each half to be included or omitted from a template independently. This is necessary when exporting the chair files for 3D printing, otherwise they would merge in the printing process. Use overlapped partial templates to create a full set of half-chairs at convenient separations for the printer. It all becomes easy and obvious when you do it, it's just something else to explain. I will be making some videos.
The new
extra clearance at open switch blade option needs more explanation:
The REA designs for
A to
D switches (i.e. the sizes most usually modelled) have 2
block slide chairs (lower picture) beyond the normal bolted slide chairs. These have no inner jaw for the moving switch rail, only a rear support jaw for the switch rail when the switch is closed against the stock rail. The switch rail (blade) is free to flex away from the support when the switch is opened.
Beyond those 2 chairs are a number of
block heel chairs (upper picture). In those both the switch rail and the stock rail are keyed conventionally and fixed. It is a single chair (on the prototype) because there is not enough room between the rails for extra chair bases and screws for separate chairs.
All this is fine on the model when the switch is closed. But when the switch blade is open, along comes an over-scale 00, EM, or 0-MF wheel etc., and two things might happen:
1. the back of the wheel might rub against the open switch blade, slowing the vehicle and possibly breaking the chairs.
2. the wheel flange might clonk the inner key jaw on the first block heel chair.
To avoid any such happenings, in those gauges we need to remove the key and jaws on the first block heel chair to clear the wheel flanges, and to allow the switch blade to flex open a bit wider.
Ticking the
extra clearance at open switch blade option does that. The first block heel chair is swapped to a block slide chair instead. So there will now be 3 block slide chairs and one fewer block heel chairs.
I said "might happen" because it depends on the actual wheels and back-to-back settings you are using. In P4, S7, etc., the wheels should run clear, but in 00-SF, EM, etc., you will need to do some trial and error with your models to decide what to do.
For this reason this option isn't ticked by default in 00, EM, etc. Templot has no way of knowing what wheels you are using, and it would be a shame to depart from the prototype if it's not needed.
So it's up to you to remember to tick this box if necessary.
For 00-BF and "Standard 00" and similar in larger scales (i.e. flangeways wider than 3.5" scale), if the box is ticked 2 chairs will be swapped to block slide chairs instead of 1. But I'm not really expecting many users of those gauges to be interested in plug track.
Notice that the stock-rail part of the block chair is identical for both types, and interchangeable for all templates, like the standard chairs. So they can be printed in bulk and used anywhere.
But the switch-rail part of the chair is
not interchangeable on different chair positions or different templates. They are not even interchangeable on the
same timber for the main-side or the turnout side of the switch.
(They are so used on the prototype, but there is a small geometrical discrepancy in the REA designs resulting from that, because the switch timbers are square-on instead of equalized through the switch. Consequently the turnout-side is fractionally tight to gauge when prototype REA switches are first assembled. Soon dealt with by 24 hours running-in under traffic.)
All of which means it will be important to identify carefully which chair is which when 3D printing. It would be a good idea to print out a paper template of your timbering brick and mark it up before 3D-printing it.
cheers,
Martin.