Experimental Plug Track: 3D-printed, CNC-milled, laser-cut

Martin Wynne

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We now have some REA S1J joint chairs:

joint_chairs_3d2.png


joint_chairs_3d1.png


These joint chairs appear adjacent to rail joints in pointwork.

And also at each end of plain track panels if you set the option for wider sleepers adjacent to the rail joints:

joint_chairs_3d3.png


S1J chairs have the same jaws and screw patterns as ordinary S1 chairs, but on a wider 10" base to support the rail closer to the joint:

joint_chairs_3d4.png


There are lots of prototype ifs and buts relating to the use of joint chairs, so expect a fresh sprinkling of tickboxes. :)

cheers,

Martin.
 
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Phil O

Member
Location
Plymouth.
Hi Martin,

Don't forget that keys are driven in the same direction on each sleeper, yours appear to be in opposing directions, as shown in the middle shot.
 
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Martin Wynne

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Two more tick-boxes: :)

flip_key_dir.png


Flip the driven direction of the keys on chairs 1 and 4, and/or on chairs 2 and 3.

No room for proper labels at present. Those boxes may move elsewhere eventually.

They will mainly be needed for rail joints on partial templates -- I'm hoping to get the key direction automatic on the normal joints in turnouts (and also joint chairs).

Also for the keying on bonus timbers -- there is no practical way to automate the keying on those, it will be random and likely need the above options. I'm writing this now while I'm working on it, because the chances of remembering to mention it later are nil. :(

cheers,

Martin.
 
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Martin Wynne

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I have added some blue markers to the 2D trackpad view:

key_offset_indicator.png


These marks on the rail gauge-face are intended only to indicate the direction of chair key offset (the direction from which the key has been driven into the chair). For use when making changes to the chair key settings.

The actual 3D key will be a different length, and on the opposite side of the rail. The centre of the key will be opposite the centre of this blue mark. The amount by which the mark is offset from the centre of the chair is randomised -- only the direction of the offset is significant.

On the control template only, not shown on background templates (or anywhere else).

cheers,

Martin.
 
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Martin Wynne

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@Phil O

It's been a battle of wits but we now have the keying direction under control:

keying_options.png



The default setting is for single track branch lines on level track, with the keys swapping direction in the middle of each track panel, driven towards the nearer of the two rail joints:

s1j_keying.png

For gradients and double-track running lines the other options can be set. These settings are template-specific, i.e. each template has its own setting.

But regardless of any other setting, the keys adjacent to a rail joint are always driven towards the fishplate. This applies for both S1J joint chairs on widened joint sleepers, or ordinary S1 chairs on standard sleepers.

Both keys on a timber are always driven in the same direction, but by random amounts.

All this is a bit academic and really applies only to CAD renderings such as above. In practice the chairs are likely to be resin-printed separately from the timbering base, and can therefore be mixed and matched at assembly time to suit any desired keying practice.

cheers,

Martin.
 
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Martin Wynne

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The 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:

index.php
@Steve_Cornford

Hi Steve,

Just an update on my previous reply to you. It's been another battle of wits -- but I have now undone the silly mistake I made months ago, linking the socket rectangles to the centres of the chair corner radii. That was causing headaches for the special switch and crossing chairs. The socket rectangles are now spaced from the chair outline independently of the chair corner radii:

socket_corners_mod.png


This makes no practical difference to the chairs already done, although it would now be easier to change them if necessary.

1. timber outline.

2. black lines -- cutter kerf line for laser cutters. Outside the timbers, inside the sockets.

3. extent of the timber flanges.

4. chair base outline.

5. chair base corner radius.

6. socket outline.

7. chair plug outline at the top. There is a small clearance from the socket on the sides, and a smaller clearance at the ends.

8. outline of the chair plug at the bottom inset section.

9. plug corner relief angles. Small for FDM and laser-cut sockets. Larger for CNC milled sockets.

10. outline of the top of the support pyramid below the plug.

11. outline of the bottom of the support pyramid.

12. chair screw/bolt centres.

All the above can be adjusted via the buttons on the DXF export dialog (except 4, 5, 12). They are shown on the trackpad so that you can see the effect of any changes (after rebuilding the templates). The chair dimensions 4, 5, 12, are set in the custom chairs dialog (not yet done).

More evidence of progress -- another line on the info panel: :)

chairs_in_info.png


In due course I will add a breakdown of that to show the number of each chair type.

I'm posting this stuff as I go along now because I just know I will forget to mention it later. It's mainly for my own benefit to refer back to. I hope no-one minds. Just keep in mind that everything in this topic is experimental and might change or never be seen again.

cheers,

Martin.
 
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Martin Wynne

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It's all too easy in Templot to create inadvertently duplicated identical templates. For the most part that doesn't matter for the 2D paper templates.

For the 3D chaired exports however, there will be problems. Where the chair is identical the mesh repair tool will discard the duplicated elements. But where features are randomised the duplicated elements will get combined with strange results:


duplicated_chair.png


See the strange spanner which will be needed for the chair screws! Also the key has grown to almost the full width of the chair.

I'm hoping duplicated templates will be easily noticed when extracting the timbering bricks from the plan. But if you see such strange results in your 3D prints you now know the likely answer -- which might not always be immediately obvious. :)

Sometimes when using partial templates in complex formations the templates are duplicated intentionally, or left overlapping. If it's intended to export them in 3D, it will be necessary to switch off the duplicated chairs, or make sure overlapping rails do not extend across a timber.

cheers,

Martin.
 
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Martin Wynne

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Currently working on the 1PL, 2PL and 1PR, 2PR switch block chairs:

pl_pr_chairs.jpg


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):

plr_seats.png

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.
plr_seats2.png

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. :)
plr_seats3.png

Now for the jaws and key.

cheers,

Martin.
 
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Martin Wynne

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Does this mean that you will treat them as 4 separate chairs on the shove timber window pane?
@Steve_Cornford

Hi Steve,

At present no. It's one chair which is printed as two half-chairs. I haven't made any plans to export one half without the other. The S1O and S1N half-bolted chairs will be separate designs.

But everything is still very experimental -- I haven't made a grand master plan. I'm just seeing what works best as I progress each part. I may go back and change things later if I get better ideas. I may also want to improve the detail rendering of some of the chairs once the basic process is up and running.

I am keen to stress the vertical plug-in assembly of chaired rails, rather than fitting the chairs into the base and then sliding the rails into the chairs. Only vertical plugging allows the creation of complex track formations, although hybrid methods will be possible in some situations. But plugging one rail at a time does require that the special double chairs are treated as two halves. For example the check rail chairs, especially where the check rails merge together or run into parallel-wing crossings or check lumps.

In the smaller scales the half-chairs might be quite fragile, but I have to bear in mind how it will work in the larger scales too.

For "threading" chairs onto the rail which don't have an inner jaw, my thought is to use a tiny dab of Blu-Tack or similar as a temporary inner jaw. I've been looking for something like Blu-Tack in a tube which can be extruded as a thin bead. I feel sure the electronics industry must have something of the kind, but so far I haven't found it. Anyone?

cheers,

Martin.
 
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Hayfield

Member
Location
Essex
.
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.

Martin

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
 
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Martin Wynne

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Martin

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
@Hayfield

Thanks John.

At present I am doing only the REA switches, i.e. "A" rather than 9ft.

I want to get as far as a fully chaired REA turnout with flexible switches as the initial goal. With matching rail filing jigs for the vee rails. When I've got there I can go back and add all the other options such as the straight switches and loose-heel options, GWR and custom chair designs, etc.

At present the P slide chairs lengthen automatically in the coarser gauges. I haven't yet done that for the block chairs, I'm waiting to see how it works out in practice. It may be necessary to remove, or loosen, the inner jaws on the 3P and 4P chairs to achieve sufficient opening. In any event I think the joint in the switch rail will need to be a dummy joint in all except S4-X and S7 to ensure the flexing rail is adequately secured.

cheers,

Martin.
 
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ThatMKTGuy

Member
Location
Kansas
(I'm not well-acquainted with how these older-style web forums operate so I apologize in advance for any inconvenience. I also have no idea whether what I've asked has been answered previously, but this thread is pretty long to go looking through.)

I was referred here by someone online and considering I have a laptop and a resin printer, it looks like a prospect I want to get into! I couldn't tell what software this was all being done with outside of slicing for printers, so if someone could do me a huge favor and direct me to a comprehensive "getting started" thing I would be grateful. I'd also be glad to help out in any other way should you find something.
 
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Martin Wynne

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@ThatMKTGuy

Hi,

Welcome to Templot Club. :)

This is a support forum for my Templot software, which creates designs for hand-built model railway track and layouts using such track. It is very strongly biased towards UK prototypes using bullhead rail, but can be fully customised for other prototypes if you have the relevant data.

More info about Templot is at:

https://85a.uk/templot/companion/templot_explained.php

https://85a.uk/templot/companion/

You can download Templot (free) from:

https://85a.uk/templot/companion/installation.php

If you have any questions about Templot, just ask away here, there's lots of friendly help.

Templot has been my hobby project for over 40 years now, and has been available to other modellers for over 20 years.



This particular topic is about an experimental project which I am working on to create 3D-printed track parts directly from Templot designs. There is still a long way to go before it is finished, or even much usable, although we have got as far as creating 3D-printed plain track in UK-bullhead pattern, in any scale or gauge.

If you read through the topics at:

https://85a.uk/templot/club/index.php?forums/plug-track.34/

you will get a better idea of what we are doing and where we have got to. :)

cheers,

Martin.
 
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Martin Wynne

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We now have some outer jaws for the switch block chairs:
sc_outer_jaws.png





switch_block_chairs.jpg


These 2-screw outers are common to several of the special crossing chairs, and also the check rail chairs.

(They might also be used with the REA 2-screw S1 inners to provide a generic 4-screw plain chair design for those who want that for their prototype.)

cheers,

Martin.
 
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Hi Martin, you are making excellent progress in your experiments.
I wonder if in the smaller scales using ply timbers it is practical to have two sockets so close together, it might need to be one socket but with the two plugs shaped to meet at their adjoining faces so that when you insert the 2nd plug it presses against the first plug?
Just a thought.
That is an interesting photo. What is the name of the strap between the switch rail and the stock rail?
Is it for electrical bonding or for minimising the longditudinal movement of the switch blade?
Like the soleplate rarely modelled in 4mm scale apart from a wire soldered underneath the rails that is for electricl continuity.
 
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