Experimental Plug Track - file exports for 3D printing

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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Martin Wynne

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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
@Steve_Cornford

Hi Steve,

The colour of the rectangle doesn't matter. Any rectangle shape found in the background shapes is treated as a raft when exporting for 3D printing the chairs. Likewise any line shapes found in the background shapes are treated as splints when exporting for 3D printing a timbering brick.

It would be possible to put a hole in the raft (anything is possible :) ), but not very easily with the current code. I would need to write something new for creating the support rafts.

But I don't think a hole is needed -- certainly it didn't occur to me that one was needed when I made the chairs. If you are using the Elegoo wash/cure station, the rafts remain on the build plate while being washed. A bracket is supplied to suspend the build plate in the wash tub.

Likewise when brush washing the fine detail over a suitable container, the rafts can remain on the build plate:

index.php


After washing and blasting dry with an air gun/hairdryer, the rafts are peeled from the build plate ready for curing. Yes, because the chair rafts are so small in relation to the size of the wash/cure station, I placed them on an upturned glass jar on the turntable for curing. That puts them more central within the UV beam, but whether it made the slightest difference I have no way of knowing. I gave them a couple of minutes each way up on the jar. Different coloured resins take different times to cure because the UV needs to penetrate the translucent resin. But the chairs are so small that they seem to need only a couple of minutes. It is being translucent which makes them so difficult to photograph.

Curing continues in UV light until they eventually crumble to dust 5 years later. So keep them in the dark until you need them, paint them as soon as you have used them, and draw the curtains in the railway room when the sun is shining. :)

cheers,

Martin.
 
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Phil O

Member
Location
Plymouth.
@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.


Hi Martin,

My experience of the 2 sizes of fishplates on the ESR is that they fit ok against the fishing surfaces of 95lbs bullhead rail, I don't recall any problems with a direct replacement of broken fishplates with the wrong pitch of holes with the 2 centre bolts, only the inability to fit one or other of the outers.

I don't think that a lot of time or resources were expended by BR on the branch in its final goods only days and the Extension from Merrifield Lane to Mendip Vale was done with recovered materials from various sites and was just cobbled together, sufficiently for the inspecting officer from whatever department it was at the time.

There's an ongoing replacement with bullhead rail and concrete sleepers from the loco shed access crossover towards Merrifield Lane, which includes replacing some very old 85lbs rail, the only 60ft lengths on the original part of the line.

I realise that this may have opened a can of worms, but can heritage be termed as being prototypical? We only used what materials we had available to us.
 
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Hayfield

Member
Location
Essex
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:-
View attachment 2087
View attachment 2088
printed on a phrozen sonic mini 4K. Aqua 4K resin, XY 0.037mm Z 0.030mm.

Excellent piece of work, very impressive

Just out of interest what are the printing costs please
 
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Martin Wynne

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As a further thought to the above, the 85lbs rail has/had two bolt fishplates.
@Phil O

Hi Phil,

Short 2-bolt fishplates were quite common at one time, for both BS-95R and BS-85R rails. They were 9" long (or 11.1/2" long on the Southern). It was thought that by allowing the joint sleepers to be moved closer to the rail ends, the performance of rail joints would be improved. In practice the improved support was undone by the failure of the short fishplates to hold the rail ends properly in line. So the practice of using them died out in favour of the traditional 4-bolt fishplate.

They are worth bearing in mind when Templot timber shoving, because it means the usual 24" timber spacing at rail joints can be reduced to 15" centres if it helps with the timbering layout. But bear in mind that to use them on plain track the standard sleeper spacings need to be replaced with a custom setting. 9" needs to be added to the total spacings, usually divided among the middle spacings. So for example on the 25 sleepers/60ft spacings there are 18 middle spacings of 2ft-5.1/2in centres, which would each be increased to 2ft-6in when used with short fishplates.

The 85lb BS-85R rail was intended for branch lines and sidings. In practice very little was used because such lines were usually relaid with reclaimed serviceable 95lb rail from main-line renewals. I have (so far) completely ignored it in Templot, along with the model trade -- in 4mm where is the code 72 rail or S2 and L2 chairs?

The BS-85R section is 5.15/32" high (1/4" lower than BS-95R). In 7mm/ft that scales to code 125. I'm wondering if that explains the mystery of the frequent use of code 125 bullhead by 7mm modellers, even including the S7 Society? Someone measured a bit of 85lb rail by mistake? To their credit C&L have just replaced their code 125 supplies with a proper code 131 95lb rail, but there have been complaints that it's "non-standard". Modellers are funny sometimes. :)

cheers,

Martin.
 
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timbersgalore

Member
Location
England
Martin

I did mean undersize compared to the nominal values for the C&L track. I estimate that my rail is between 10 to 20% undersize. I think I could have fixed the problem using the presets you have already build in. I don't think the taper on the key was causing the sloppy fit.

After adjusting my CAD to describe the rail profile it terms of fish, I have done a lot of experiments to get the rail grip right. I started of with daylight under the key and adjust the prints to get a good grip of the web. The rail was still sloppy in the sense it was easy to roll the rail from vertical. Rather than fill completely below the key I have tried only filling below the key at the centre of the key, shown purple below.

a_sect.jpg


a0.JPG


a2.JPG


a1.JPG


The is still a bit of roll. I printed this with FootWidth set to 1mm, My rail is 0.9mm.

I think this demonstrates the benefit of customising the 3d print to the actual profile of the rail to hand. The other option is to deliberately make the rail a tight fit but I that is not an option if using a brittle resin.

I think it will take a least another iteration to get something I am happy with.

Steve: my sub layer already has the sockets cut in it.
 
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I have saved the Phrozen details on my wish list, just an aside , I can't remember if have mentioned here that in 7mm scale I do cosmetic etched (by PPD) brass fishplates, mainly because C&L stopped doing them mainly as a result of Phil not being able to get any more because the artwork had gone AWOL. I know he does alternatives now but there are times when etched is best (and cheaper).

EMGS and Brassmasters do them in 4mm scale.
 

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Hi Timbers,
Can you confirm that the concept of sockets in the sub layer works ok for you, and that it is practical to do away with any timber sprues?
If it does we can bunch the timbers up and get the most economical cuts of timbers.
Steve
 
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Martin Wynne

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I did mean undersize compared to the nominal values for the C&L track.
@timbersgalore

Hi Timbers,

Those are not "nominal" values for C&L rail. They are just random test data. Please ignore any dimensions you find in the current program release. It is all just dummy data used to test the programming and the process. I grabbed just any data that I had to hand. It is almost certainly wrong. My big fear in releasing unfinished stuff is always that someone will regard it as definitive info and start using it for real. Or worse still post it elsewhere on the web. :(

It is all utterly experimental at this stage. I will let everyone know when Plug Track has reached a stage where it can be used for actual models, but it won't be for some time yet.

I think you have your key too small and your outer jaw too low, which probably explains why the rail is not being firmly held upright. The key should completely fill the space between the rail head and foot, and the top of the jaw should be level or fractionally below the outer face of the key:

timbersgalore_chair.jpg


Also the rail seat/platform should extend across to the jaw, so that the rail can be dropped into the chair before being keyed across into place.

s1_bs95r_vertical.png


Making the rail vertical does affect the dimensioning to some extent. But check rails are always vertical, so the jaw dimensions from the inside of check rail chairs can be a reference. For REA chairs all outer jaws are 5.11/16" above the underside of the chair (except 2-level chairs and thick-base chairs).

Here is an actual GWR / BR(W) 2-bolt S1 chair. The top of the outer jaw is 5.5/8" above the underside of the chair. The jaws are 4" wide at the top:

gwr_s1_casting2.jpg


gwr_s1_casting1.jpg


cheers,

Martin.
 
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timbersgalore

Member
Location
England
Martin
Don't worry I am taking very little form the templot chairs. My height comes from measurements of the plastic chairs from the 4mm Soc. The only reason I looked at the stl from templot was to provide you with feedback.

On the other hand the pictures of the fullsize chairs are gold dust to me. Plus your written feedback has been most helpful. Are the close up of the chair casting from your own private collection or are the available on the internet?
 
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Martin Wynne

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Are the close up of the chair casting from your own private collection or are the available on the internet?
@timbersgalore

Hi Timbers,

That chair has been in my garden for about 40 years. :)

I dragged it into the sunshine and took the pictures this afternoon.

cheers,

Martin.
 
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Martin Wynne

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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,

Here you go, green and blue outlines adjusted for the width of the cutter kerf. No need to remove the timber extension marks:

kerf_2d_layers.png


kerf_2d_help.png


kerf_2d.png


tc_kerf_layers.png


Apologies if I have posted all this before, I'm getting in a bit of a muddle again. :(

I'm going to try to post an update soon, so that you can play with this stuff and report any problems.

cheers,

Martin.
 
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Martin Wynne

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Just out of interest what are the printing costs please
@Hayfield

Hi John,

Do you mean the cost of getting them printed commercially? Sorry, no idea.

If you mean the cost of making the chairs yourself, the actual resin cost is about 3 chairs for 1p (4mm scale).

But at a bare minimum you will also need:

A well-ventilated workshop area away from your living space. A bathroom + extractor fan or openable window might be suitable.

3D resin printer, around £200. The one I'm using (Elegoo Mars 2P) is currently on Amazon at £230, but there are cheaper models, offers and bundles.

A bottle of "ABS-like" liquid resin, around £35 per kg bottle. (Bundles will likely include the cheaper more brittle resin.)

A bottle of 99% isopropanol (IPA) solvent for washing the chairs. Price varies, the stuff I'm using costs £3.80 per litre.

A sunny day.

The amount of resin needed to make a chair is negligible, more resin will be wasted in the support sprues and washing than ends up in the actual chair. For the last batch of 144 chairs which I made, the software says the total cost of resin including supports was 26p. Say about 48p including washing, IPA and clean-up, which makes the chairs cost 0.33p each or 3 for a penny.

How you factor in the cost of the printer is up to you, but once you have one you will be able to make all sorts of other models and parts, not just chairs. But note that a resin printer is no good for making the filing jigs, for that you need a FDM filament printer (which is no good for making chairs below about Gauge 3).

If you don't have any sunny days in stock you can use a UV lamp instead. Cost is the same as a length of string. Or a dedicated UV curing and washing machine to match the printer costs around £100.

cheers,

Martin.
 
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Hayfield

Member
Location
Essex
Martin

Thank you, I think the biggest problem is not having am outside workshop, secondly my inability of being able to use said machine. like injection moulding it seems the costs of materials are quite inexpensive. So I assume it will not be long until someone like Wayne comes along and offers a service at a reasonable cost

I may have misunderstood a previous post but the longevity of the resin seems questionable if unpainted and left in sunlight
 
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timbersgalore

Member
Location
England
Martin

Laser cutters are capable of understanding shapes. What it means is that when presented with a nested set of rectangles they work out what is inside and outside. The result is that the cut planner can works out which bits to cut first. It also means that the laser can provide the Kerf offset. It would be worth checking whether a cutting service is automatically applying it own kerf offset to closed figures. That said it would be usefully to have the timber outline and chair socket layers on there own layers.


Here is a screen shot showing the cut layer from my recent test:-

cut layer.jpg


A little shape manipulation is required to join the spruces to the timbers.


Timbers
 
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