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

[Martin Wynne]

Apologies if I have missed something on this topic - I have to confess to not really paying attention to all the posts but is there a major reason to have holes in the sleepers rather than using the Exactoscale "NewTrack" method ( circa 2004 ) method of round dimples on the sleepers and a matching recess in the base of the chairs ? Would it not make the sleepers/timbers stronger.....and the alignment of the chairs would be set by the rail to chair jaw interface.

@Guinea_Pig_Tester

Hi Rob,

I tried that 3 years ago, see:

https://85a.uk/templot/archive/topics/topic_3307.php#p26312

Of course with "exactopips" on the timbers we don't need to make our own chairs and can use the Exactoscale chairs. In the Exactoscale system the chairs have an easy clearance on the pips, it is intended to use gauges in the usual way for assembly.

The downside is that you are restricted to the chair prototypes provided by Exactoscale and their continuing availability. But the main reason I threw them out of the window is because the rail is canted in the chairs (an utter no-no in my book below about Gauge 1) and the extremely poor fit on the currently available rail sections -- see various topics on the Scalefour forum.

If you then decide to make your own chairs for the exactopips system, you have the difficulty of supporting them with a flat base for printing, and without the plug base in 4mm scale they are much more fragile and difficult to handle. The plug base solves all that. Also of finding a suitable adhesive -- ideally the Plug Track chairs are a press fit and any adhesive is only a backup.

But no doubt I will add an option to add exactopips to the DXF export -- I want to add all possible options that anyone might want.

cheers,

Martin.

 

[Steve_Cornford]

Having produced a straight B7 and a curved B7 turnout in templot, I exported to 2D .DXF file, opend the resultant file in Inkscape, then grouped all the components of timber 1.X9(straight turnout) together as one object, changed stroke to black ink, 0.076mm wide, then took a copy and overlayed the copy onto the green timber 2.x9 of the curved (2400mm radius) turnout.

This was in order to check the corelation of the sockets, and whether it will be practical to just produce "standard" laser cut sheets of straight turnouts of a given size/angle (advantage being all timbers can have grain alighned with long edge of timbers) and use these to assemble curved turnouts.

The corelation is pretty good in my opinion, at least for a B7 curved to 2400mm.
The laser cutting service recomended closing up or perhaps concatenating is a better description of the timbers for a most economical cut. Cost is dependent on sum of the lengths of all cut lines, so by sharing timber outlines we can reduce the total cost, see their .pdf attached example.
So could have a "bespoke" trackbed layer cut in cork just with sockets to suit the track layout.
Then for the sleeper/timber layer cut in ply, use some standard "plain" sleeper sheets, and standard straight turnout sheets. Then just produce a "bespoke" extended timber sheet of ply for all the non-standard timbers relationg to the track layout.

If you have time to print some S1 chairs with longer narrower pegs to try them out that would be great.
Steve



Steve

 

[AndyB]

Hi Martin,
Apologies if I have missed something on this thread - I have to confess to not really paying attention to all the posts but is there a major reason to have holes in the sleepers rather than using the Exactoscale "NewTrack" method ( circa 2004 ) method of round dimples on the sleepers and a matching recess in the base of the chairs ? Would it not make the sleepers/timbers stronger.....and the alignment of the chairs would be set by the rail to chair jaw interface.

Rob

I had a similar thought. Why not just put circular holes in the sleepers to accept a cylindrical pip on the bottom of the chair and let the rail align the direction of the chair?

I'm pretty sure Martin will have considered this and abandoned it for several good reasons

(Crossing chairs would probably need two pips)

Andy

(Personally I think it would be a much better idea to print timbers, chairs and rails all at the same time and simply stick a conductive cap on the rails but I'm a well-known heretic )

 

[Martin Wynne]

The correlation is pretty good in my opinion, at least for a B7 curved to 2400mm.

@Steve_Cornford

Hi Steve,

Yes, a timber in a curved template is identical to the same timber in a straight turnout. That is how Templot draws curved templates.

I already have a function to bunch template timbers together side-by-side. I haven't had any use for it since the 1990s when I was experimenting CNC milling timbers from copper-clad laminate sheets. It will be commented out in one of the earlier files -- I just need to find it again, or re-write it. It is needed to allow a set of template timbers to be resin-printed on the small build plate. If you set the timber separation to zero the outlines would coincide, but it needs some careful thought on setting the cutter kerf width.

Thanks for the feedback.

Martin.

 

[Martin Wynne]

I had a similar thought. Why not just put circular holes in the sleepers to accept a cylindrical pip on the bottom of the chair and let the rail align the direction of the chair?
I'm pretty sure Martin will have considered this and abandoned it for several good reasons
(Crossing chairs would probably need two pips)

@AndyB

Hi Andy,

I've been asked this several times, but no-one has explained what benefit accrues by discarding information which Templot already knows (the angle of the chair on the timber) and leaving it to be determined by the rail? And if you then say two pips that argument is destroyed anyway.

The intention is that the plug chairs are a firm press fit in the sockets, in most cases not requiring any adhesive, and setting the gauge in the process. Once pressed home it wouldn't be possible for the rail to rotate the chair into alignment. So with a cylindrical plug you would be relying on the chair being aligned by means of the ungauged loose rail before pressing it home. The chances of getting some misaligned chairs strikes me as very high.

Having a rectangular plug makes it much easier to adjust the tolerances for a good press fit. In comparison two cylindrical plugs would be very difficult to tolerance.

As far as I can see the only advantage to a cylindrical plug is that you could drill the holes in home-made timbers. But because they also set the gauge, it would be necessary to do the drilling on a CNC miller or jig borer for sufficient accuracy.

The edge of the chair base is very thin and fragile, so adding a rectangular plug provides support as close the the edge as possible.

cheers,

Martin.

 

[Steve_Cornford]

Hi Martin,
I might have known that you have not only chosen the most apposite word, but have written the code in the dim distant past!

So a "Bunch Timbers" option in the 2D .DXF dialogue would be very convenient.

Steve

 

[Martin Wynne]

They recommend cutting the sockets first then the timbers, in particular this service cuts blue lines first, then green, so it would be really useful as you suggested to have a SOCKOUTL layer as well as a TIMBOUTL layer, with colour choice.

@Steve_Cornford

Hi Steve,

I have added 6 new layers for the 2-D DXF so that colours can be changed or elements omitted:

Also a 3-D option to create tall headless locator plugs for the trackbed. These are a looser fit in the timbers so that the timbers can be dropped over them, and then removed. Presumably you would make the sockets in the trackbed a fraction smaller so they are a firmish fit in the trackbed.

As you can see the dialog is getting too large and crowded. I need to move stuff to a set of separate tabs.

Does anyone want the template > symbols... included in the 2-D DXF? It might be useful to have pre-drilled holes in the trackbed below the rails for the dropper wires and/or the dropper ID text marked?

cheers,

Martin.

 

[Steve_Cornford]

Hi Martin,
Looking good. Have you tried any locator pegs yet?

I got a bit distracted playing with some of Wayne's OO-SF B7 kits.

Oh, and then I started reading about Free Pascal!

Does anyone want the template > symbols... included in the 2-D DXF?

Could be useful, but not if it delays the rest of your 3D chair design

Steve

 

[Martin Wynne]

With several additional combo drop-downs the list has got a lot longer.

To make setting the colours a bit easier I have added some buttons below the list to use as a precursor to making the required settings:

I have changed the omit layer option from "none" to blank, to make it more obvious in the list.

Note that the radial centres option always defaults to omit. Otherwise the fit extents function in CAD programs will zoom out to include all the radial centres, potentially making the actual track plan a tiny smudge on the screen. If the radial centres are needed in the file, they must be explicitly turned on.

This stuff has remained virtually unchanged for over 20 years, it feels strange to be returning to it now and making changes.

No doubt if I was starting from scratch I would do things very differently.

Martin.

 

[Steve_Cornford]

20 years!
How many boiled eggs?

Plug Track
Chairs are produced as separate components from the timbers.
You have illlustrated how to produce a "raft" of S1 chairs by manipulating sleeper spacing and gauge and adding a background shape.
By "raft" I mean the small group of chairs that are able to fit as a module onto your build plate, that you then "cloned" 5 times

How about adding this as a separate function so that one could produce a raft of one particular chair type or a "set" of related chairs.
For Example
S1 chairs
L1 Chairs
Set of Check Rail Chairs (CCL,CC,CCR)
Slide chairs / Switch chairs
1:5 Crossing Chairs.
1:6 Crossing Chairs
etc
A bit like the plastic sprues we are used to at the moment

But as usual I expect your are 2 steps ahead of me already

Steve

 

[Martin Wynne]

How many boiled eggs?

How about adding this as a separate function so that one could produce a raft of one particular chair type or a "set" of related chairs.

@Steve_Cornford

Hi Steve,

You can do most of that now. Here's a raft of mostly L1 bridge chairs -- or it would be when I get the L1 chairs finished:

which could be cloned on the printer (with timbers omitted of course).

That's part of an E-16 template in EM with the gauge reduced to 10mm, and the timber fill spacing changed to 14":

Blank off and shorten the template in the usual way to get what you want.

In the same way you could get rafts of other special chairs.

I intend to do everything you are asking for -- but not just yet. I sense that you are getting impatient for the special chairs?

Me too, but I dare not leave off the timbering bricks and DXF interface until I have got all I want to do done. At present there are dozens of loose ends and if I leave off now I shall be in the same boat I was in with 227a -- powerless to release an update because I had left unfinished and forgotten about too many loose ends. It took 4 program updates to sort all that out, and there is still the silly diamond-crossing mistake not yet fixed.

As soon as I can FDM print a defined timbering brick from within a track plan, with all the on-off options working, I will have somewhere to put the special chairs and will be able to test them as I create them.

p.s. boiled eggs total = +1 half an hour ago.

cheers,

Martin.

 

[Steve_Cornford]

Hi Martin,
No not impatient, just excited!

As a retired programmer (54 years of coding behind me) I really appreciate the lifetime of effort you have put into Templot, and the way you are evolving the software to take advantage of modern technology.

The chips from the lasercut plywood sockets are strangely reminiscent of the "chads" from punched cards that I remember from my early days of 1900 PLAN programming!

Thanks for the E-16 EM illustration.

Steve

 

[John Lewis]

According to my calculator about 7, 301 boiled eggs.

 

[Martin Wynne]

Posting this now in case I forget to mention it later.

There was some confusion between the tickboxes for 3-D DXF layer options, and the previous method of setting the DXF colour to "none" to omit 2-D layers.

To avoid re-writing all the 2-D stuff, I have removed the duplicated tickboxes and reverted to the drop-down method for all except stuff which can only be in 3-D files (chair jaws, keys, etc.).

To make it easier to omit a layer with a single click, you can now do that by right-clicking on the drop-down combo.

I've added a note at the top of the dialog, and to the mouse-hover hint:

Omitted layers now show with the colour showing blank, to make it more obvious in the column.

The layers and colours have no meaning in STL files, but elements are omitted from the file by the same means. Set any colour to include an element.

Martin.

 

[Martin Wynne]

@Steve_Cornford

Hi Steve,

Two more layers for the 2-D DXF:

These modify the outlines to allow for the kerf width of the laser cutter (or any other cutter), i.e. outside the finished timber outline, inside the finished socket size. Also the timber extension marks are ignored, so don't need to be rebuilt in the generator.

It's intended that you would switch one or other layer off for any given file, but can have both outlines in the file if you wish (and is the default).

I didn't want to do this with a zero-able offset, so that both outlines can be on by default, as a reminder of the setting option. You wrote:

the laser burns a 0.2mm line

so I have set this as the default, i.e. 0.1mm offset (independent of model scale).

• n.b. This is not intended to be used for socket tolerancing (otherwise the timber outline size might be wrong). After setting the kerf width to give the required timber size, adjust the plug/socket fit using the settings on the chair/socket fit... button.

The kerf layers are ignored in 3-D files.

cheers,

Martin.

 

[Martin Wynne]

How far to go on detail when it is hard to see with the naked eye? If I can successfully print it I will have a go at modelling it.

@timbersgalore

Hi Timbers,

Are you referring to my note about the nuts on GWR chair bolts?

That was partly in jest, at least for 4mm scale.

But -- the bolts are 1" diameter and might typically protrude above the tightened nuts by say 1/2". That scales to 0.17mm in 4mm/ft scale.

Your Phrozen 4K printer claims a resolution of 0.035mm, so that would correspond to 5 layers in your sliced model. Even on my Elegoo printer with 0.05mm resolution it would be 3 or 4 layers. So it should be doable.

However I will let you off modelling the bolt thread.

In 7mm scale and above it would definitely be doable, so I must include it in the Templot export. The nuts will be generated at a random angle, and 1/2" of bolt will optionally protrude above them on the GWR S1 chairs.

You may have noticed that the screw-heads on the REA S1 and L1 chairs are also generated at a random angle:

(L1 chairs unfinished)

Notice how much more prominent the REA chair fixings are, compared to GWR.

GWR L1 bridge chairs have only 2 screws on diagonally opposed corners (right-hand side when looking towards the rail). Here's 4 of them:

They always look as if they have a screw missing!

Not used on plain sleepers, so they are always screws not bolts. Having written the dreaded word "always" I now have to leave some space for someone to post a photo showing GWR L1 chairs fixed with through-bolts.






cheers,

Martin.

 

[AndyB]

They always look as if they have a screw missing!

And it looks like someone swiped two fishplate bolts

 

[Phil O]

That may be due to the wrong fishplates, there are rails drilled to 4 1/2 inch centres and rails drilled to 5 inch centres, there are fishplates for both, but if there's a mismatch then only the 2 centre bolts fit. More commonly is one rail has been replaced and you end up with 3 bolts.

 

[Martin Wynne]

I print some chairs from the templot files. I first had to fix and unsupported island formed at the bottom of the rail clip.

@timbersgalore

Hi Timbers,

Looking good.

Can you clarify which part you mean by the rail clip?

In Templot terminology, the part of the inner jaw shown green is called the "stand". As far as possible allowing for model wheel flanges it follows prototype dimensions.

The part coloured blue is called the "grip" and has to match the model rail section, with no regard to the prototype.

I'm aware of a bug in the area circled, and it's on my list to be fixed.

Looking at your print, you seem to have lost the angled fillet between the jaw and the rail seat:

edit: see later posts.

This what Templot generates in that area:

which is also in the generated STL:

So it's a bit of a mystery where it has gone, or appears to have gone, in your print? Maybe it is an optical illusion.

I'm aware that those side fillets on the jaws are a poor representation of the radiused fillets on the prototype, and they are also on my list to do something about. When I did the design originally I was thinking in terms of FDM printing. The resin printers can create higher resolution results, so need rather more work on the design.

cheers,

Martin.

 

[Martin Wynne]

That may be due to the wrong fishplates, there are rails drilled to 4 1/2 inch centres and rails drilled to 5 inch centres, there are fishplates for both, but if there's a mismatch then only the 2 centre bolts fit. More commonly is one rail has been replaced and you end up with 3 bolts.

@Phil O

Hi Phil,

Fishplates with bolt holes at 5" centres are intended for flat-bottom rail. Do they fit ok on bullhead? They are 20" long (as opposed to 18" for bullhead) so wouldn't easily fit between the chairs at a bullhead rail joint. Flat-bottom rail fixings do not obstruct the fishplates to the same extent, and the fishplates can be longer. If an 18" fishplate is drilled at 5" centres, the end holes would be very close to the end of the fishplate.

We need the full info on this because Plug Track will need it's own 3D printed fishplates. The standard H-section locking fishplates from the trade won't work because the rail needs to slide into them. Whereas Plug Track rails are pressed home vertically. The fishplates will need to be attached to the side of the rail rather than inserted from the end. The insulator lug on the back of the fishplate will occupy only half the rail height (and can be cut off where the fishplate is on a dummy joint).

cheers,

Martin.