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

Hayfield

Member
Location
Essex
Martin

Certainly from a track builders point of view this is the correct way, I have found though when using the Exactoscale parts which are designed for P4 timber spacing, they also work well for both EM and 00 spacing, however in the case of separate chairs the next few standard chairs have their position altered (if only for a few thou), but are we talking about amounts that within normal build tolerance ?

Or am I misunderstanding what you are saying

Another thought does the gauge alter the slide rail lengths, if so would you have to increase them up to PL2 position ?
 
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Paul Boyd

Member
Location
Loughborough, UK
.
Now that I'm looking at the switch and crossing chairs, I have had to make a decision about something I've been pondering for ages. Should the chairing be prototypical or programmatic? I've settled on programmatic.

What do I mean by that? Suppose you have created an irregular diamond-crossing which fits your track plan nicely, and one of the V-crossings is showing as 1:7.38 angle. Now obviously no such size of V-crossing exists on the prototype -- the nearest size, 1:7.5, would be used instead. And the big 'ammer would be brought into play to make it fit. That is also what you do if building with C&L or Exactoscale chairs, because they don't make 1:7.38 crossing chairs either.

To be strictly prototypical therefore, Templot should do the same, and I should implement a corresponding big 'ammer function.

Well I'm not going to -- it's just too much of a minefield of conflicting dimensions and prototype variations. I am hoping to finish this project within my lifetime!

Instead, Templot will programmatically create 1:7.38 crossing chairs for a perfect fit. Only you and I will ever know the difference, no-one else will notice. If that's not something you can live with, -- using Templot isn't compulsory. :)

Another example of programmatic chairing will be for the switch block chairs. Suppose you shove one of the switch timbers along a bit, like this:

View attachment 2675

You know and I know that you should never do that. The block chairs support angled rails, and will fit the rails in one position only. You can't shove switch timbers more than an inch or so under the chairs, and the chairs need to stay put while you do it.

But Templot doesn't know that, and will happily shorten or lengthen the block chair, and adjust the rail angle, as you shove the timber along. Whereas the prototype has only a few fixed sizes of block chair, not an infinite range of sizes.

But in a cramped model design, you may need to shove switch timbers more than a bit, so this unprototypical result might be useful.

Again, I'm creating these chairs programmatically in order to have some hope of chairing the whole range of switches in my lifetime.

But this decision does have consequences. It means the 3D chairs file and timbering brick file will be a matched pair and need to be created at the same time and kept together, and not interchanged with the files for other templates or bricks, even if the templates are nominally the same size.

I'm intending that it will be possible to bunch together all the chairs from a brick for resin-printing, and print a paper chart showing which chair goes where on the templates.

cheers,

Martin.
Hi Martin

That all sounds an eminently sensible and pragmatic solution to me!

Cheers,
Paul
 
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Martin Wynne

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West of the Severn UK
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but are we talking about amounts that within normal build tolerance ?

Or am I misunderstanding what you are saying
@Hayfield

Hi John,

Providing you use the chairs from the corresponding STL file, and not some you had left over from a previous file, they should fit the corresponding timbering base perfectly, and there should be no need to rely on build tolerances to make things fit.

I say "should" because I haven't actually written the code yet. :)

Also, it is necessary to set the shrinkage rates correctly. At present there is a single allowance on the dialog which is used for all 3-D files, and ignored for all 2-D files. The default I have on there at present is 1.5% which is about right I think for the resin-printing, but maybe a bit too much for FDM filament printing. Indeed with the wide footprint of a typical timbering brick on the build plate, there may be very little shrinkage of the timbering brick at all, unlike when printing more bulky items having a smaller footprint. My test prints tend to confirm this. But like most plastics, some age-shrinkage may take place afterwards over time.

In addition, all machines 2-D and 3-D may need scaling adjustments to cover for any mechanical errors in the pitch of lead screws, pitch of toothed belts, diameter of pulleys, rollers, etc., on individual machines.

All this is still very much in the air and subject to trial and error when we are in a position to start making Plug Track in anger.

Another thought does the gauge alter the slide rail lengths, if so would you have to increase them up to PL2 position ?

The P slide chairs are all a single size along the rail, like the S1 and L1 chairs, but will be adjusted in length to suit the current scale/gauge setting -- see my previous reply. They should therefore be interchangeable in different templates, provided you don't mix up the P4 ones with the EM ones, etc. Beyond the P chairs are the block chairs. These will be programmatically generated to match the switch, as I mentioned, so they won't necessarily be interchangeable with any other template and will need to be kept for the corresponding timbering base if you want a perfect fit.

At some stage all this stuff will need to be written up, with all the ifs and buts, and I'm not looking forward to it. But that's jumping a long way ahead, because I'm still at the more fundamental stage of making stuff work.

cheers,

Martin.
 
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Martin Wynne

Admin
Location
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Enjoy using Templot?
Thanks.

Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add
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@Hayfield

p.s. John, apologies if my previous post appeared in bits, I think I've found a bug in this forum editor related to the Tab key.

I have posted a bug report on the XenForo site.

cheers,

Martin.
 
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Trevor

Member
Location
Morecambe
Hello Martin,
With regard to the switch blade over hanging chair bolts.
Could one not simply file a couple of slight hollows in the bottom of the switch blade to clear the bolt heads?
Trevor.:)
 
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Hats off to Martin.
By providing four more radio buttons, Martin is allowing you (the builder) to choose which solution best suits you.
Having used the 301A Exactoscale slide chairs for OO-SF turnouts I don't think you really notice that they are longer once laid.
ps time to get my eyes tested again then!
pps must save a 20p piece before they go out of circulation in this cashless society!
 
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I'm intending that it will be possible to bunch together all the chairs from a brick for resin-printing, and print a paper chart showing which chair goes where on the templates.
In the far off future, please can we have a template timber bunch facility for the 2D export for use when Laser Cutting but in this case with the timbers adjacent. ie sharing a cutting line. This makes the laser cutting more economical when outsourcing.
Obviously when 3D printing the timbers need to be discrete and the bunching is just to maximise the use of the print bed area.
Steve
ps but don't let this request distract from chair production ;)
 
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Martin Wynne

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Location
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Enjoy using Templot?
Thanks.

Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add
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In the far off future, please can we have a template timber bunch facility for the 2D export for use when Laser Cutting but in this case with the timbers adjacent. ie sharing a cutting line. This makes the laser cutting more economical when outsourcing.
Obviously when 3D printing the timbers need to be discrete and the bunching is just to maximise the use of the print bed area.
@Steve_Cornford

Hi Steve,

The timber separation will be adjustable to whatever you set. If you want them to share a common cutter line it will be up to you to set the separation accordingly, allowing for the laser kerf width.

If the timber kerf lines end up coincident I will find some way to omit one of them, so that the cutter lines are not duplicated in the DXF file.

If you don't have any waste between the timbers, how do you hold it all together while cutting?

cheers,

Martin.
 
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If you don't have any waste between the timbers, how do you hold it all together while cutting?
Don't know.
They cut the sockets first, then the timbers.
LaserCutSleepers.jpg

This is what I got back. There is what appears to be masking tape on the back.
I can only assume that it is gravity.
They do offer a "taping" service as an option, but this is to alleviate the burn marks on the surface.
I did not opt for the "taping" service, as I was not too worried about burn marks, as sleepers(or timbers) will be stained with indian ink etc
Most of the sockets that are missing have fallen out with my handling.
Just like punched cards chad from my early programming days.
Miniature bricks anyone?
The cost depended in part upon the total length of lines cut, hence request for "bunch".
The sample I sent you of the turnouts etc was just as output by Templot, the above was as a result of the cutting service editing one of the files I had output from Templot.
I will ask the cutting service about duplicate lines. They might have some utility that removes them.
Steve
 
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