Messin' With Resin - 3D printed track

AndyB

Member
Hi Martin,

Many thanks for all the great information.

If I might ask, how are you eliminating the rail inclination? Are you leaving the bottom of the rail in the same position and pushing the top out, pushing the bottom in or rotating the rail so the bottom moves in and the top moves out?

Also, are you leaving the base full size or are you reducing its length at all?

Cheers,
Andy
 
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AndyB

Member
Thank you Martin.

Re. the length question; if you kick the foot inwards you could make a case that says everything on the outer part of the the chair should move inwards too. It's only about a third of an inch so it's probably better not mess with it and leave the base and screw holes as the prototype dimensions.

Thanks for the swift response. You are either up very late or very early :)

Andy
 
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Martin Wynne

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You are either up very late or very early :)

I've no idea. During lockdown life doesn't fall into 24-hour chunks any more. I've just had my main meal of the day. I also like to watch your CNN news these days, so that puts me 5 hours behind the UK.

cheers,

Martin.
 
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AndyB

Member
Pity the poor pattern maker :) Getting there, but it's slow going.


Screenshot (7).png
 
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AndyB

Member
The foundry finally got around to casting a sample for me.

Screenshot (11).png


I'm still not entirely happy with it but I think I now know how to get the best out of the tool. Of course a lot of this is completely academic. Much of this detail is beyond the resolution of the printer at 1:76.2 scale but it's interesting to see what the tool can do. This is built from five quite basic sub-components and the tool does most of the hard work to combine them into something that looks like a casting. (The surface was about as close as I could get to rusty cast iron in an hour or so.)
 
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AndyB

Member
Time flies when you're having fun :)

I thought I was going to have to laboriously produce a whole series of crossing chair models to cover the range of turnouts I need but I think there's a shortcut. It looks like I'll need crossings from 6.5 to 8.25 (eight in all) and that's quite a large number of models to cover the entire range. However, 7.25 is very close to the mid point and the jaws only need to be rotated a maximum of plus or minus 1.1 degrees from there to cover the range that I need.

The plan is to create left and right jaws for a 7.25 crossing and combine them with the appropriate length base-plate as I populate the Templot template in situ. The jaws will be aligned correctly with the rails which means that they could be rotated around a degree from normal to the base-plate. I doubt if that will be noticeable at 1:76.2

As I produce them where required I can also combine them into blocks and save them in a library for future use (assuming I actually remember to do do that).
 
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AndyB

Member
Here's a model that shows the various bits, stylized for 00. The baseplate with riser, screws and buttresses is combined with the jaw piece. The combination is then mirror imaged to produce the complete chair.

Before it is combined with the baseplate the jaw piece is rotated to align precisely with the inner face of the rail on the Templot turnout template.

Screenshot (14).png
 
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AndyB

Member
A crossing.

Screenshot (15).png


I should really have made a slob and briquette slab and bracket but this was a bit simpler :)

It's probably not immediately obvious but this was constructed entirely from four basic elements - "blocks" in Turbocad speak.
There are two jaw blocks. One skewed clockwise and the other anti-clockwise and there are two base blocks similarly skewed. That's all the blocks I need to create a range of turnout crossings from 6.5 to 10 and possibly more if I don't want to be too picky.

It's a bit warm here at the moment. 80F in my workshop at 10:30 PM!

Andy
 
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Martin Wynne

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It's probably not immediately obvious but this was constructed entirely from four basic elements - "blocks" in Turbocad speak.
There are two jaw blocks. One skewed clockwise and the other anti-clockwise and there are two base blocks similarly skewed.
@AndyB

Hi Andy,

Looking very good, but where are the keys?

Are these chairs available as DXF blocks in ASCII format? How could I incorporate them into the Templot DXF output? Are the individual entities readable so that they could be included in the STL output?

It could save me a lot of time to use your good work in Templot, if you are happy about that, but I'm very fuzzy about how to integrate it. :confused:

You can see my current DXF export code in dxf_unit.pas here:

https://85a.uk/templot/club/index.php?threads/t1-files.192/post-1739

It's a text file readable in any text editor, but preferably (free): https://notepad-plus-plus.org/

cheers,

Martin.
 
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AndyB

Member
Hi Martin,

It's way beyond my curfew time so I'll have to reply properly tomorrow. That said the important point here is there is a lot less to this than meets the eye :giggle:

Cheers,
Andy
 
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AndyB

Member
Hi Martin,

Attached is the Turbocad dxf export for one of the blocks. Some of it looks readable but there's a big chunk of code that could be binary.

You'll likely be able to open it with your version of Turbocad so you can at least see the structure.

Cheers,
Andy
 

Attachments

  • VBase.DXF
    1.3 MB · Views: 25
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AndyB

Member
I better explain in a bit more detail what I'm doing here in case I'm creating the impression that it's simpler than it really is.

The Y, X, A, C and D chairs are all made from two blocks. (B is slightly different because it has additional jaws.) However, I have to manipulate them in Turbocad to make each complete chair.

The steps are:

Position a base block on the imported Templot turnout drawing
Rotate the base block to align with the rail/timber
Position a jaw block at the same location
Rotate the jaw block to align with the rail
Explode the base block (blocks are protected - this unlocks them)
Explode the jaw block
3D add the exploded base and jaw to form a single part
Slice off the excess of the part that goes beyond the center-line of the crossing
Copy the part along the slice plane to create the second half of the complete chair (this could be saved as a new block for future turnouts with the same geometry)

It probably sounds a bit more complicated than it really is. In practice it only takes a few mouse clicks but the point is it does rely heavily on the CAD tool (Turbocad in this case).
 
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AndyB

Member
After I wrote my previous post it occurred to me that it might be possible write a script to do all of that. It's pretty mechanical after all. It turns out that some versions of Turbocad support something called "Ruby Scripting" about which I know absolutely nothing :)

What I'm thinking is it might be possible to mechanize the generation of all the crossing chair models required for a whole range of turnout angles. The idea would be to have a script spew out a complete library of models that could either be placed manually on a Templot turnout or automatically substituted for marker references generated by Templot itself.

Obviously I'm "thinking out loud" :D
 
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Martin Wynne

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@AndyB

Hi Andy,

Many thanks for the file and info. But I'm struggling to reconcile all that with what I'm already doing. I can see the model in TurboCAD but I can't make much sense of the actual file contents.

What's puzzling me is why you have generated the screw-top in such fine detail:

andy_screw_top.png



compared with mine:

templot_screw_top.png


Bearing in mind that even in 7mm scale you need a magnifying glass or a close-up lens to see the chair screw details, such fine detail seems completely wasted. It means your file is 1.3MB and a full chair is going to be something like 2.5MB. The STL format is a flat format, it doesn't as far as I know support blocks, so at 2.5MB per chair the file size for a full print is going to be massive. Templot's STL files are already 10 times the size of the corresponding DXF file (which uses blocks).

That's all a bit academic because at present I haven't the faintest idea how to convert your file to an STL in Templot. I could presumably integrate chunks of your DXF into Templot's DXF without understanding it, but I can't do that for the STL. I was hoping your file would be a much simpler DXF (such as can be imported into the background shapes for example).

At present I can see a road forward from where I am now to where I need to be -- plug-in chairs for every common size of switch and crossing, adjustable for rail section and tweakable for gauge, and with corresponding sockets in the timbers. Now that I have implemented the direct STL output, there is no actual technical problem, it is just the long and hard grind of doing it. The switch chairs are fairly straightforward, but for the crossings we have to be able to chair, say, a 1:7.38 V-crossing or 1:4.68 K-crossing. All doable, but I may be gone for some time. :)

cheers,

Martin.
 
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AndyB

Member
Hi Martin,

I believe the large file is created by Turbocad when it generates the DXF from native file format. The native file which also includes a lot of other stored blocks is 660KB. If you can allow file extension .tcw I can post it although it might not be compatible with your version of Turbocad.

Could you perhaps produce an algorithm in Templot that does something similar to what I described above to generate the crossing chairs "on the fly" rather than have them all pre-stored? The tricky bit is producing the rotated jaws but perhaps that might be done by "anding" an overwide jaw with a solid profile that's aligned along the long axis of the chair.

Cheers,
Andy
 
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Martin Wynne

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Could you perhaps produce an algorithm in Templot that does something similar to what I described above to generate the crossing chairs "on the fly" rather than have them all pre-stored?
@AndyB

Hi Andy,

Some confusion there. Everything in Templot is already generated "on the fly" when you do a DXF/STL export, nothing is stored in advance. What is stored is only the actual data (height of a jaw, centres of screw-heads, radius of corners, etc.). That would change if I could find some way to use your pre-drawn blocks.

TCW and DWG now attachable (not all types are shown on the visible list).

cheers,

Martin.
 
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AndyB

Member
Hi Martin,

T'cad file for the crossing chairs attached. They were created using the four blocks also shown in unexploded form - ClBase, ClJaw, VBase and VJaw.

If you can't open it with your version I should be able to produce a compatible file.

Cheers,
Andy
 

Attachments

  • Crossing2a.tcw
    1.7 MB · Views: 32
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Martin Wynne

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@AndyB

Thanks Andy. But my TurboCAD won't open it. I get the message "no matching filter" which seems odd given that TCW is TurboCAD's own native format.

How about trying again with a DXF, with this option:

dxf_r14.png


(Setup button on Save dialog after selecting DXF file type.)

cheers,

Martin.
 
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