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

timbersgalore

Member
Location
England
I am amazed at the level of detail acheivable by the Sonic mini 4K. I think it is helpful to model the detail as it helps to get the big stuff right. Martin thankyou for the chair pictures. Mine arn't as good as the old track near me is still part of network rail. I have the drawings for the chair plan views but I am having to work out the cross section.

I have refined my ordinary char and made a stab at the SS chair:-
chair_OC.JPG

chair_SS.JPG

printed on a phrozen sonic mini 4K. Aqua 4K resin, XY 0.037mm Z 0.030mm.
 
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timbersgalore

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

templot_chairs.JPG


A you can see I droped them on the floor!

Timbers
 
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Martin Wynne

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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?

s1_inner_detail.png


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.

s1_inner_fillet1.jpg


This what Templot generates in that area:
s1_inner_fillet2.png

which is also in the generated STL:
s1_inner_fillet3.png


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.
 
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Martin Wynne

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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.
 
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Hi Martin,

This is what I get displayed in a 32-bit version of Chitubox after uploading to the "fix" service linked on the .DXF export window.
1630876748175.png

No fillet, but as you can see I generated some deep plugs to go through to the trackbed layer.
This was before uploading to the "fix" service
1630877115767.png

Fillet appears to be there before fixing.
Hope this helps
Steve
 

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  • OO-SF-S1-Chair_fixed.stl
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Last edited:

Martin Wynne

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@Steve_Cornford

Hi Steve,

Thanks for that. This is what I get back from the repair service:

s1_inner_fillet_fixed.png


So clearly that bug in the file is throwing the repair. I need to get the bug fixed.

And apologies to Timbers for suggesting he might have a problem there. I should have noticed it in my own prints, see earlier in this topic:

https://85a.uk/templot/club/index.php?threads/229/post-838

cheers,

Martin.
 
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timbersgalore

Member
Location
England
Martin
island.JPG


The problem it shown by the Red arrow. When the chair is printed from the bottom up the pyramid tip is not supported for several layers. The easiest fix is to introduce a horozontal slab from the tip to the chair.

templot_fixed.jpg



On my version I decided it was better to go for more fill to better support the rail.
rail support.jpg




I have been trying to work out the nominal dimensions of the rail (bull head from the 4mm society). I tried looking at the " 3-D custom rail section" dialogue in templot. Most of it makes sense but could not work out fish angle. Are the initial values shown based on anything? eg the last used non custom option.


Reflecting on how much work is going to be required to get Templot to reliably generate all the chairs types needed for a complete turnout I wonder if it would be better to produce the chairs separately. Placing the sockets on the template is a tremendous step forward even if only for the ordinary chairs.

Timbers
 
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Martin Wynne

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@timbersgalore

Hi Timbers,

Many thanks for finding that. The angle on the underside of the key is from the prototype -- the key is tapered end-to-end so that it can function as a wedge, but is symmetrical front to back so that it can be used either way up. The model key gets distorted in two ways -- I added a rail-side taper at both ends to ease rail threading, and the rail-side is further modified to match the thicker model rail web and fishing angle. There is an option to fill below the key, but as it's not prototypical I left the default to off:

fill_below_key.png


I will modify the bottom of the unfilled key so that it is horizontal, or angled a fraction the other way.

The fishing angles shown for the model rail sections are my best estimate from the samples available. It is obviously better to err towards a steeper angle, rather than risk fracturing the chair if the angle is too low. Likewise the height of the rail foot. If you have access to better info please do share it. Bearing in mind that model rail batches do vary, so it would be wise to leave a bit of leeway in the settings. I have added a rail-fit tweak (see above) which allows for small changes in the rail web thickness.

Reflecting on how much work is going to be required to get Templot to reliably generate all the chairs types needed for a complete turnout I wonder if it would be better to produce the chairs separately. Placing the sockets on the template is a tremendous step forward even if only for the ordinary chairs.

My aim is that Plug Track should be available to any Templot user who wants it, without needing CAD design skills. 3D printers can be purchased or accessed via friends, but the skills to design a chair from prototype dimensions are not so easily acquired. Anyone who wants to source or create their own chairs is obviously free to do so, but I want Plug Track from Templot to be usable as a self-contained system available to anyone.

It also needs to work in any chosen scale -- so that for example the handful of folks using 5.5mm/ft can also have chaired bullhead if they want it (and can find some suitable rail). And likewise at any desired crossing angle, and any desired flangeway gap -- crossing chairs and check rail chairs for say P4 wouldn't be usable in EM. Finding crossing chairs for a 1:7.63 or 1:9.5 crossing in S scale anywhere else seems extremely unlikely, but that might be the only angle which fits the site. On a model we can't use the prototype big 'ammer to make stuff fit, the chairs are in fragile resin, not cast iron. :)

cheers,

Martin.
 
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timbersgalore

Member
Location
England
HI Martin
Regarding the rail and grip on it. I found the templot chairs quite a sloppy fit on the 4mm society rail. I would say you have overdone the allowance for rail side taper. It would be helpful the know what are the profile numbers for "C&L / EMGS/ S4Soc code 75" rail. What is "Fish centre" How is the fish angle measured (between what).

The accuracy I am achieving with the sonic mini 4K is amazing so far what I draw is what I get.

I have kept the grip parallel to the rail and find my chairs easier to thread than the plastic chairs form the 4mm society. I am using a web thickness of 0.4mm

I am in the throws of making a "test of method" track sample. It consists of a GWR 12ft heel V7 with return curve. Rather than post detail here it is probably better I start another topic elsewhere. I will be using a laser to cut the sleeper base as I get far superior results compared to the FDM printers I have (I have three!).

Timbers
 
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Hi Timbers,
As you have a laser, have you thought of cutting a cork(or ply) trackbed layer just with sockets, then make the chair pegs deeper. That way you dont need to have sprues on your timbers, and you can cut the timbers with the long edge parallel to the grain. Then the longer pegs locate the timbers onto the trackbed layer.
Good luck with your "test of method"
Steve
 
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Martin Wynne

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What is "Fish centre" How is the fish angle measured (between what).
@timbersgalore

Hi Timbers,

Tightening the fishbolts wedges the fishplate between the angled fishing faces, putting the rail web in tension. Ideally sufficient to ensure that it doesn't become unloaded under the traffic load. Otherwise the bolts would work loose:

fish_angles.png

Note that there is a space between the back of the fishplate and the rail web, otherwise the system doesn't work. The same applies to the fishwashers and spacer blocks which are used on bolted crossings.

The fish angle on all UK REA bullhead and jointed flat-bottom track is 1:2.75. Here is the way the rail is dimensioned:

2_120508_000000000.png


BS-95R prototype dimensions in red. The dimensions in black relate to a sample of C&L rail from AndyB at the time that drawing was made, and taken from this old 2016 topic:

https://85a.uk/templot/archive/topics/topic_2734.php#p29639

You can see that the all-important fishing faces are dimensioned from their intersect on the rail section centre-line. The head and foot depths can then be derived if needed.

n.b. the dimensions in black are NOT metric equivalents of the dimensions in red.

Here is a bit of Exactoscale steel rail, and you can see why I estimated the model fish angles to be much steeper than the prototype:

2_111752_390000000.jpg


I found the Templot chairs quite a sloppy fit on the 4mm society rail. I would say you have overdone the allowance for rail side taper. It would be helpful the know what are the profile numbers for "C&L / EMGS/ S4Soc code 75" rail.

Thanks for the feedback. The chairs which I printed here are a nice close fit on the Exactoscale steel rail and maybe a fraction loose on the C&L nickel-silver rail which I have here. But in both cases the rails are from old stock which I have had for many years, so feedback about current production rail is valuable.

I want to emphasize again that everything related to 3D track which I have released so far is utterly experimental. There is no guarantee that any of it is correct, or workable, or will remain unchanged in a final release. I released it only so that folks could see my direction of travel, maybe join in with some experiments, and provide valuable feedback. There was no intention that it should be used for any actual modelling, because almost certainly it is wrong. The object is to first prove the concept of Plug Track, and if successful only then go back and make it an accurate model of anything. :)

If/when the whole thing works, I will then make fresh drawings as above showing how everything is dimensioned and provide some recommended settings. The settings in the program at present are not a recommendation of anything.

cheers,

Martin.
 
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Derek

Member
Location
UK, Midlands
Hello Martin

I'm sorry to ask this slightly o/t question, but regarding the fishplates- why does it need the gap behind to work properly? I accept what you are saying and that it does, I'm just trying to understand from an engineering point of view why that is. I can understand the web being put under tension as an aid to locking the tapered edges together, it's just the space at the back that puzzles.

Many thanks
Derek
 
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timbersgalore

Member
Location
England
Thankyou Martin
Than helps me a great deal. I can now see that the sample in fornt of me is undersize. My web is 0.40mm (measured by filling off the head/bottom then micrometer).
Timbers
 
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Martin Wynne

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Hello Martin

I'm sorry to ask this slightly o/t question, but regarding the fishplates- why does it need the gap behind to work properly? I accept what you are saying and that it does, I'm just trying to understand from an engineering point of view why that is. I can understand the web being put under tension as an aid to locking the tapered edges together, it's just the space at the back that puzzles.
@Derek

Hi Derek,

No need to be sorry about asking questions. :)

The space behind the fishplate allows for routine maintenance -- the fishplates need to be tightened up (move inwards) as the fishing faces become worn. Which they will do under heavy traffic -- it is interesting to stand close to a fishplated rail joint and watch what happens as traffic rolls over it.

If the fishplate were to bottom against the rail web, there would be no means to tighten it further, and no way of knowing that the correct tension force had been applied to the rail.

cheers,

Martin.
 
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Martin Wynne

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Than helps me a great deal. I can now see that the sample in fornt of me is undersize. My web is 0.40mm (measured by filling off the head/bottom then micrometer).
@timbersgalore

Hi Timbers,

I think you mean oversize? The prototype rail web is 3/4" thick, which scales to 0.25mm in 4mm scale.

All model rail tends to be oversize in web thickness -- although C&L have recently introduced a new code 131 bullhead rail for 7mm scale which has a commendably thin web.

cheers,

Martin.
 
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Trevor

Member
Location
Morecambe
Hello Martin and you other geniuses,
Just a thought from a lay person.
With various crossing angles varying by such small amounts would a suitable solvent make it possible to soften chair jaws and enable fitting of fewer angle variations using fewer printed alternatives? Or am I suggesting something that would wreck things?
Regards to you all
Trevor. :)
 
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AndyB

Member
Hello Martin and you other geniuses,
Just a thought from a lay person.
With various crossing angles varying by such small amounts would a suitable solvent make it possible to soften chair jaws and enable fitting of fewer angle variations using fewer printed alternatives? Or am I suggesting something that would wreck things?
Regards to you all
Trevor. :)

No need to apologize Trevor. I think we are all lay persons here. This is all new and still quite experimental.

As you point out the variation in angle over a fairly wide range of crossings is really quite small and it may not be strictly necessary to model the angles perfectly, particularly in the smaller scales. However, the distances between the chair jaws at the crossings change significantly with the crossing angle so the chairs that incorporate two of more jaws do have to be modeled accurately.

I'm using a slightly different method from Martin. I assemble jaws and baseplates in a CAD program as separate models superimposed on the 2-D Templot template and that does allow me to take advantage of small angle variation. Martin could be doing something similar as he constructs the chair models.

Cheers,
Andy
 
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Martin Wynne

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With various crossing angles varying by such small amounts would a suitable solvent make it possible to soften chair jaws and enable fitting of fewer angle variations using fewer printed alternatives? Or am I suggesting something that would wreck things?
@Trevor

Hi Trevor,

Thanks for your kind words.

But I'm obviously missing something. If you set out to build, say, a C-9 crossover from your Templot track plan, you would export the files for it from Templot in the same way you might print the construction templates for it. Then you would use the exported files to 3D print the required chairs for it.

I don't see what advantage would arise from printing instead the wrong chairs from some other template, and hoping to modify them to fit? The work involved in making the 3D print is exactly the same either way.

Are you looking for a solution to a problem which doesn't exist? :)

The more likely problem, as I develop Plug Track in stages, is that you can have an 'X' chair for any crossing angle you like, and any flangeway gap. But not yet a 'Y' chair for any size at all. Which no doubt will be extremely frustrating, but that's just the way it goes.

Flooding a component with solvent is not a very good way of softening it. It tends to make a sticky mess of the surface, destroying detail in the process, while having little effect on the core of the component. For FDM (filament) printed components, a better way to soften them would be with gentle heat. But that won't work, as far as I know, with cured resin-printed components.

In any event, again as far as I know, we don't have any readily available solvents for the cured resin, or for PLA polymer for FDM. That's why modellers building resin kits tend to use cyano superglue or epoxy adhesive. It is possible to use ABS polymer for FDM printing, in which case butanone solvent could be used. But FDM printing ABS makes unpleasant fumes, and I don't believe it would work very well for chairs in 4mm scale, any more than PLA did when I tried it.

cheers,

Martin.
 
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AndyB

Member
Hello Martin

I'm sorry to ask this slightly o/t question, but regarding the fishplates- why does it need the gap behind to work properly? I accept what you are saying and that it does, I'm just trying to understand from an engineering point of view why that is. I can understand the web being put under tension as an aid to locking the tapered edges together, it's just the space at the back that puzzles.

Many thanks
Derek
Hi Derek,

As Martin says the plates have to be able to move further. It's like any wedging action. The wedge has to be able to "keep going" to be effective. If it didn't it would just become a sort of spacer and it could not maintain a tight connection between the surfaces.

The Victorian engineers who came up with the system were very clever!

Cheers,
Andy
 
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HI Martin,
When outputting a string or raft of say S1 chairs, you recomend craeting a rectanglular shape in purple or mauve (cant remember which) that will act as a printing base on the build plate.
Would it be possible to have a whole in either end of the raft, to act as a suspension point for use in a washing and or curing station?
I dont have an elegoo mercury yet but hope to get one the next time there is an offer.
I believe you have mentioned propping the strip on a glass beaker inside the mercury for curing?
Steve
 
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