Messin' With Resin - 3D printed track

Martin Wynne

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Hi Jim,

Here you go. Sleepers deleted from the DXF in TurboCAD. Saved as STL. Fixed solid in the online tool. 4mm scale (to fit Exactoscale rail):

chairs_only_for_jim.png


You will need to rescale the STL for S. I don't know how you are going to support them and keep the base dead flat for use?

cheers,

Martin.
 

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  • exacto_chairs_only_mm_fixed.stl
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I don't think scaling the CTB will work, will it? The layers were already sliced at 0.05mm, so by scaling you have increased them. I think you would do better to scale this STL, and then re-slice it.
Martin,

I'll have another go with the .STL file.

I had another look at importing your Chitubox project file and now that I look closely at it, I see the extreme layering on the image on Chitubox after scaling - I didn't look closely the first time. :) I think Chitubox has developed quite a bit over the years and I dug up some of my project files from two years ago when I was working with a very early number version - probably around V1.2 or V1.3. I could load them and re-scale them with no problems. So it looks as though the current project files are storing the sliced .stl including sliced support stl information whereas the early versions were just storing the stl files of the part with supports. When I rescaled these early files, Chitubox removed the supports (after a warning).

Jim.
 
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richard_t

Member
Location
nr Spalding
Jim,

I'd be happy to send you some of my STL files for 7mm chairs, as per the images earlier in this thread. The files are on the large side though.

Martin used WeTransfer which seem to work quite well.

The offer is there.

Richard.
 
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Martin Wynne

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Hi Jim,

Just to explain, Richard's STL files are incredibly detailed CAD renderings of prototype chairs:

richard_chairs.png


With separate keys and even including the code letters on the screw heads. I'm going to have a go at printing them when I've got a bit more time.

My chairs are simple geometrical approximations which can be generated on the fly in Templot. There is no CAD program involved:

templot_chairs.png


Two different things.

I fear I shall have my work cut out trying to get this difference across to 3D printing users when/if I finally get a Templot update released. :(

cheers,

Martin.
 
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Charles Orr

Member
Location
Leicester UK
Hi Martin,
This is excellent news.
For some reason I've been holding back building the bulk of the the track on my magnum opus layout.
(I've just got a small terminus built at the moment using copper clad).
Now I know why :) .
Perfect, I can print the sleepers on my Prusa I3 Mk 3S and now the chairs on the Elegoo Mars.
I can't wait. :):)

Charles
 
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I printed the chairs stl last evening and printed them directly on to the plate and they all stuck using the standard settings for the Phrozen printer and the Phrozen resin.

TemplotChairs-04.jpg


Not the best of shots but I had to fiddle around to stop too much light reflecting off the plate and still get a reasonable image of the chairs.

They have come out quite well but are a bit of a handful when working with them during the washing and curing phase - three have disappeared already. :)

TemplotChairs-05.jpg


For the same reason, they have not had the aerosol spray treatment so they have that slightly off focus look of cured 3D resin. They also don't appear to have acquired a noticeable elephant's foot after printing on the plate.

TemplotChairs-06.jpg


...and just a check that they fit the S scale rail.

I think if I was going to print a large number of them, I would print them on the plate but add a sprue between them to keep everything together during the post-printing handling. If the sprue made contact with the chair base under the rail then you wouldn't need to be too fussy about cleaning up sprue pips when you break the chairs off.

Richard

I would be interested to experiment with one of your chair files to see what I can do. I'm up to my eyes with getting an N scale layout (actually FS160) ready for an exhibition in November and that's taking up most of my time at the moment. Optimism reigns down in the West Country. :):) So I don't want to get too involved in chair making - I've just been following Martin's adventures over the past year or so and thought I might have a try at printing some of his output, mainly to try out my new mono printer to see what it can do.

Jim.

Jim.
 
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Martin Wynne

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AndyB

Member
Hi Tom,

For me the big change was the realization that I could at last afford to buy a resin printer for the cost of a few Shapeways prints :D

Cheers,
Andy

PS Anyone want a mark one plywood and string (no kidding) FDM printer?
 
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AndyB

Member
I rediscovered the attached track panel(s). I think I was going to have Shapeways print them but my forgetory is such that I don't know if I ever did or not :giggle: The S1 chairs are quite good but IIRC they are designed for SMP rail which is a bit narrow.

The edge filleting on the chairs was done in TurboCad Pro which is a bit spendy but I'm tempted to buy the latest version because of the detail that the resin printer can produce.

The attached file is a DXF which you might be able to edit.

Andy

RATS! The file is too large. Where should I put it?

But here's a screenshot.

Screenshot (1).png
 
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Paratom

Member
Location
Cardiff
Interesting reading all these threads on 3d printing chairs. I have been 3D printing printing for a number of years now and acquired my second printer a few months ago. The printer was a fraction of the price I paid for the first printer and can print down to 10 micron layer thickness. I model in EM and planning on building a Midland Railway layout. I have noticed that nobody makes some of the chairs that are required to make a prototypical point and they have to be made up from sliced up chairs. Exactoscale do a check rail chair but only for P4 with a .8mm flangway gap. In EM it should be 1mm so I decided to make a MR one. I haven’t printed it out yet but looking forward to seeing what the results will be like. I was planning on making some of the other chairs for various crossing angles but if anyone have already done these and would like to share their results in return for printing them I would be interested. Below is an example of some coach parts I have printed and my 3D MR check rail chair. These coach parts were printed straight onto the build plate and did not require supports under them contrary to what some modellers do.

MRCCR.JPG


Coach fittings 2.jpg


Thomas
 
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Martin Wynne

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I've been mucking around with TurboCAD (Platinum unfortunately) and I was able to create this in less than an hour.
Hi Andy,

Very good -- so far. :)

Chair screws have a tapered square head. Below that is a pan flange, which is larger than the tapered oak ferrule which locates in the tapered hole in the casting:
chair_screw_400x742.png

The ferrule provides a precise location on the timber without needing a close tolerance hole in the casting. The ferrule stands proud of the casting to be effective. If frequent tightening cause the screw to contact the casting, the ferrule must be replaced. Different sizes of ferrule are available for maintenance purposes. Modern ferrules are no longer oak, but a tough plastic polymer.

This is Templot's generated geometrical version of that, I think the flange could be beefed up a bit.:

dxf_screw_head_860x646.png


cheers,

Martin.
 
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AndyB

Member
Thank you for that Martin.

I guessed the square heads were 1.125" so I was not too far off. I can easily taper them and fillet the corners too. Probably a waste of time for 1:76.2 but I'm drawing it actual size so it can be scaled.

My base plate might be a bit too thick. It's currently 5/8" but looking at some photos I think it should be a bit thinner.

How high are the tops of the screws relative to the timbers typically? (There's not too much bullhead track in North Idaho for me to measure :D)

This started off as a bit of an exercise to see how well TurboCAD produces fillets. So far I'm quite impressed. BTW, this is a solid model rather than a surface. I only applied the fillets after all the basic geometric shapes had been added together. It will be interesting to see if there are any holes in the STL. This version also has some 3D print tools but I have not investigated them yet.

The big snag is it is not cheap but it's nowhere near as expensive as the likes of Autocad. I decided it wasn't too bad if I amortized the cost over the number of years I'm likely to be able to use it. There are also annual subscription versions but I don't care for that approach. The 2020 download actually includes the code for all the versions including Platinum. You buy license keys that unlock the various features.

Like all things "you pays your money and you gets what you pays for" (in theory) and I concluded the resolution of the resin printer justified some decent CAD software. I suppose I could even defray some of the cost by producing highly detailed STL files and I'd at least be able to validate them by printing test pieces here.

Cheers,
Andy
 
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Martin Wynne

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Hi Andy,

Answering for REA chairs (other chairs are available):

My base plate might be a bit too thick. It's currently 5/8" but looking at some photos I think it should be a bit thinner.

Chair base is 1/4" thick at edge.

Seat for rail is 1.3/4" thick.

How high are the tops of the screws relative to the timbers typically? (There's not too much bullhead track in North Idaho for me to measure :D)

Before tightening: about 3". After fully tightening: 2.3/4" min, say 2.7/8" in new track.


The standard REA chair drawings are available here:

http://www.lmssociety.org.uk/assets/pdfs/permanentWay1928.pdf

Unfortunately the scan quality is rather poor and some dimensions are difficult to read. Chair screws and ferrules are on page 1.
The ordinary S1 chair is on page 4.

Extracting some dimensions from more readable scans:

Screw head top. 1.1/16" sq.

Screw head at flange: 1.1/8" sq.

Screw head height above flange: 7/8" at side, 15/16" at corner.

Flange thickness: 3/8" at side of head.

Overall height of screw head and flange: 1.1/4"

Flange diameter 1.7/8"

Ferrule diameter at top (before compression): 1.35/64"


Boss on casting: overall height: 1.1/2"

Boss on casting: top diameter: 2"

Pictures of some chairs. Notice how prominent the screws can be. The screws are galvanised, the chair castings are raw, which is why the screws stand out in photos, especially when new:

bullhead_crossing_detail1.jpg


long_check3.jpg


pw_heap.png


p.s. I have copied the above into the Resources section, to keep the info easier to find, and allow it to be tagged.

cheers,

Martin.
 
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Martin Wynne

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The big snag is it is not cheap but it's nowhere near as expensive as the likes of Autocad.

Hi Andy,

TurboCAD pricing is impossible to pin down, at least here in the UK. My version is TurboCAD Deluxe 2D/3D which cost me all of £9.99 as a special offer only a few years ago. I assumed others would be able to find it at a similar price. But searching comes up with £179.99 as the current price. The disparity between these two costs is difficult to fathom.

Autodesk's Fusion 360 is free for personal use. I believe it is popular with modellers for 3D printing. But it's online only, and involves jumping through several registration and login hoops to get there. I assumed that being from Autodesk it would support 3D DXFs from Templot -- it is after all their file format. But sadly no. :(

But I have now implemented a direct export in STL from Templot, so no-one now needs an expensive 3D CAD just to convert Templot's DXF output to STL for 3D printing.

cheers,

Martin.
 
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Trevor

Member
Location
Morecambe
This afternoon's entertainment was to get the chair plugs into the 2D:

View attachment 716

I have put a 1/2" break across the plug corners for a clear fit in the sockets. For the bridge chairs I have increased the base overlap, so that the sockets do not get too close to the edge of the timber.

The plugs and screw centres aren't really needed in 2D, but the only way to check that the code is putting every one in the right place is to draw them on the screen.

One more tiny step on what is going to be a long journey.

Martin.
Hello Martin,
Is there a particular reason why you are using square/rectangular sockets for chair location? Would a round socket allowing them to rotate not enable one to adjust a chairs position indefinitely without restriction? Or am I missing something really obvious?
Trevor :)
 
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