Steve_Cornford
Member
- Location
- Brighton, East Sussex
In 233c I notice that the P chairs have taken a holiday, perhaps to get their makeup finalised?
message ref: 3567
TEMPLOT 3D PLUG TRACK - To get up to speed with this experimental project click here. To watch an introductory video click here. See the User Guide at Bexhill West.
@Steve_CornfordThe default sizes are derived from the centres of the base corner radii -- that's not set in stone, but would now require a lot of work to change. Here again is the stuff I posted a few days ago, see item 6.
With the experimental chairing switched on, this is the additional detail which you see on the trackpad when zoomed-in:
@Steve_CornfordDoes this mean that you will treat them as 4 separate chairs on the shove timber window pane?
.
Currently working on the 1PL, 2PL and 1PR, 2PR switch block chairs:
View attachment 3161
These chairs are essentially short slide chairs, the difference from the P chairs being that the stock rail is conventionally keyed instead of bolted, and the switch rail has an outer jaw support.
I have increased the length of the slide table a fraction, to allow for the wider model flangeways and increased switch opening (even P4 flangeways are significantly over scale):
View attachment 3160
The intention for these chairs is that they will be in two parts, separately plugged, so that the rails can be plugged in one at a time. There is a very tiny gap between them, so that the mesh repair tool doesn't merge them into a single chair print (having two plugs).
If that is actually wanted for a more robust chair the gap can be set to zero. That would require horizontal threading of the rails into pre-fixed double chairs of course, rather than vertical plugging of a single chaired rail. Doable for a single turnout, but tricky within more complex formations.
View attachment 3158
There is an issue with these chairs which is not immediately obvious.
Unlike on the prototype the one is not a mirror image of the other. There is a very small difference in the offset between the two rail seats. That's because the switch timbers are square-on instead of being equalized to split the deflection angle. This means that chairs printed for a left-hand switch will not be usable on a right-hand switch, and vice versa. When making plug track it will be important to keep the chair sets carefully labelled for the matching timbering brick and template.
The prototype gets round this by shifting the set in the diverging stock rail forward from its true geometrical position, so that the blade tips are exactly opposite each other. The consequence of this is that the track gauge is fractionally reduced over the diverging part of the switch, although I have never seen this actually marked on a prototype drawing.
Templot puts the set at the true geometrical position (shown as the "set advance" on some Templot diagrams) in order to preserve an accurate gauge through both roads of the switch. I'm not about to change that after 40 years just to make the chairing easier.
View attachment 3159
Now for the jaws and key.
cheers,
Martin.
@HayfieldMartin
Now this is really exciting, one of my biggest bugbears is the total lack of detail in this area. Even some of the best track builders ignore this detail
There may be an issue in both the coarser gauges where the slide chairs need lengthening, this may also occur on the dreaded symmetrical Y turnouts people love and possibly the short 9' switches again in the coarser scales.
Len Newman made available longer slide chairs for EM & P4 gauges, this may go against the grain a bit but is practicable
There seems to be no stopping you at the moment, I am finding it difficult to keep up with all the improvements to the standard Templot usage let alone 3D printing. I do have an FDM printer sitting in the corner but still no time to play with it and now I have to start saving up for a resin printer!
@Terry DownesI tried adding some fill below the key, which seems to be working ok
@Terry DownesView attachment 3206
There is an obvious bug in Templot on the lower face of the part I call the "grip" (ringed red) which explains this strange feature:
Thanks for finding it, I will get it fixed for the next program update.
Hi Martin,.
Sorry there was no update for a while, I've been busy with some electronics work.
But back on Templot today, working on the P chair (slide chair).
I've decided to go with the PJ version of the REA chair:
because it's a bit beefier and stronger on model rail sections. Maybe I could do the older P type later as an option.
View attachment 3035
Outer jaw still to do (you noticed ) but I've got the slide table and stock rail bolt and boss done. The bolt is at 1:20 to match the prototype, even though the model rail will be vertical.
The slide table is 7" wide, which means for REA switches the switch blade tip should align exactly with the edge of the table. Which will be a convenient guide when track building. The length of the chair and slide table is increased from the prototype to suit the model gauge/scale in use where needing an over-scale switch opening (for 00, EM, etc.).
The nut rotation on the stock rail bolt is part-randomised in 15-degree steps (the chair-screw heads are infinitely randomised).
I'm omitting the spring washer under the nut, the screw-thread on the exposed end of the bolt, and the domed end of it -- I have to draw a sensible line somewhere. Otherwise it will take forever and the STL file size will go through the roof.
View attachment 3036
View attachment 3037
Now to get the jaw done.
cheers,
Martin.