• The Plug Track functions are experimental and still being developed. Some of the earlier pages of this topic are now out-of-date.

    For an updated overview of this project see this post.   For some practical modelling aspects of using Plug Track see The Book of Plug Track.

    Some pages of this and other topics include contributions from members who are creating and posting their own CAD designs for 3D printing and laser-cutting. Do not confuse them with Templot's own exported CAD files.

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

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Hi Martin,

example of increased label text height, I doubled it

20221031_140937.jpg


Meaning: 4mm, S1, plug width adj. 0_00
Ie default plug width.

I am using this convention as I try various negative adjustments to suit my experimental ply timbers, easier to keep track of them if labelled!

Thank you for pointing out the text depth parameter.
Steve
 
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Meaning: 4mm, S1, plug width adj. 0_00
@Steve_Cornford

Hi Steve,

In the next update, a separate setting for text on rafts:

raft_text_height.png


It has to be kept low for the bricks so that it gets hidden under the ballast.

You are being far more methodical than me -- all I'm doing is to felt-tip the date and time on the back of the raft. :) Which I can then cross-reference to the relevant files.

cheers,

Martin.
 
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I'm now in something of a quandary.

Whether to continue with the work I have done so far (not much) on split chairs for the check rails, like the switch block chairs. Or to swap to using the loose jaws for the check rails? For P4 I think it will have to be loose jaws, but for 00 and EM it could be either. But it would be a lot of work to have two different systems for both the chairs and the timbering bricks.

When it comes to the V-crossing, splitting the chairs involves 3 chair parts for the A and B timbers. Whereas loose outer jaws would be much simpler with a single chair and more chance of replicating the spacer blocks properly. And be more amenable to complex formations such as tandems. I haven't given much thought yet to K-crossings and slips, but I suspect loose jaws will be easier there too -- it is after all replicating prototype practice in principle.

Forming rail bends and trimming to length can be a trial and error process -- the rail can be tried and placed against the inner jaws as many times as you like before finally fixing it. Blu-Tack is handy for holding it in place for testing -- the inner jaws set the gauge.

What's making me hesitate is the thought that many folks might regard it as far too fiddly, and might have trouble printing the parts successfully. I thought myself that it was a silly idea and too fiddly for words. Until I tried it. It is actually working well and quite satisfying to do. Put the rail in place, and push in a loose jaw to lock it into the chair. You can feel a slight click as the key snaps into place below the rail head.

Decisions, decisions. But in the final analysis it is my hobby...

cheers,

Martin.
 
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Hi Martin,
Just to clarify. For loose jaw check rail chairs would the process be:

1 Slide the stock rail part of the chair (with plug containing the slot for peg) onto the stock rail, together with other chairs required for stock rail.

2 Plug the stock rail into the timber bases, bash fit as before

3 Place the check rail into position on the check rail chairs

4 Plug in the loose jaw pegs so that they click in place below the check rail head.

or have I misunderstood the process?
 
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Hi Martin,
Just to clarify. For loose jaw check rail chairs would the process be:

1 Slide the stock rail part of the chair (with plug containing the slot for peg) onto the stock rail, together with other chairs required for stock rail.

2 Plug the stock rail into the timber bases, bash fit as before

3 Place the check rail into position on the check rail chairs

4 Plug in the loose jaw pegs so that they click in place below the check rail head.

or have I misunderstood the process?
@Steve_Cornford

Hi Steve,

Yes, that's it. The check rail chair would be in one piece on one plug, entirely prototypical except for a vertical slot on the inside where the opposite jaw should be. Into which the missing jaw+key is inserted later, after dropping the pre-formed check rail in place.


inner_check.png


The check rail chairs would be threaded on the stock rail along with the S1 chairs and all bash-fitted into the base at the same time.

The check gauge is the most critical dimension in pointwork. So it will be important that the check rail is firmly secured against the middle part of the chair to set the check gauge. That might mean a drop of superglue is used behind the rail, or we might print a selection of loose jaws with keys of different thicknesses, so that you could choose ones that fit tight against the rail. Model rail sections do vary at times.

A point to bear in mind is that for any individual piece of rail it has to be all one or all the other. It won't be possible, or it would be very tricky, to combine bash-fit chairs and loose jaws on the same physical piece of rail*. Which means it will be necessary to have rail breaks in the prototype positions. So for example the closure rails would be bash-fit as far as the wing-rail front rail-joint. A separate wing rail with the knuckle bend would then be loose-jawed all the way to the end of the rail. I don't see that as a problem, just something to bear in mind.

*edit: but see: https://85a.uk/templot/club/index.p...3d-printed-cnc-milled-laser-cut.229/post-5225

Once we've got the print settings sorted, it would be possible to print a thousand loose jaws in one go on the build plate -- because they are all identical and Templot can create an STL with them all bunched up. At a cost of about 10p per thousand, so there's no need to go looking for the one which pinged out of the tweezers. :)

All this stuff is still waiting to be learned on the job. I'm sure there will be lots of tricks and tips to talk about once we get going.

I just need to make progress a bit more rapidly -- for example James is still waiting for some rail locators on the timbering brick to create a full track assembly jig for rivetted plywood or copper-clad.

cheers,

Martin.
 
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Hi Martin,
I like the idea of a "standard" loose jaw part for multi-rail chairs.

You mentioned manually dipping the loose jaw raft vertically as an aid to cleaning uncured resin out of the slots.
To help this process along, would it be possible to design in a hole leading from the bottom of the slot out to the end or side of the plug as a drain hole to assist in this process?
After machine rinsing a gentle blast of air from a blower should see the slot clear of liquid before curing?

I assume there would be two classes of chai:
single rail chairs which have fixed jaws (S1, S1J, L1, M1 etc)
multiple rail chairs that would have loose jaws (CCL, CC, CCR, etc)

My intuition tells me that after one more boiled egg your quandary will be solved.

Steve
 
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You mentioned manually dipping the loose jaw raft vertically as an aid to cleaning uncured resin out of the slots.
To help this process along, would it be possible to design in a hole leading from the bottom of the slot out to the end or side of the plug as a drain hole to assist in this process?
After machine rinsing a gentle blast of air from a blower should see the slot clear of liquid before curing?
@Steve_Cornford

Hi Steve,

From the start I had thought of a small release hole somewhere near the bottom of the slot. Originally because I thought trapped air might prevent the jaw sitting down flush. When there seemed to be a problem I even tried holding the jaw down for several seconds for any air to escape, but it made no difference. (There is a reasonable clearance on the pin at the sides of the slot, because the position of the jaw in the sideways direction is not critical. So air should be able to escape.)

I thought about a release hole again when washing the print. I was thinking it would have to be a hole in the side of the plug, because it would be blocked by the support pyramid at the bottom. But simply taking the slot right through the plug is by far the easiest to program, so maybe the support pyramids could have a groove across the top to clear the slot?

In the event, all the chairs I have tried seem fine, and the loose jaws sit fully home now that I have modified them. So maybe it's a solution to a problem which doesn't exist. On the other hand, it only takes one clogged slot in 50 to bring track assembly to a halt, so it is possibly worth looking at it anyway. Only a short halt, because it would be possible to shorten the pin and if necessary glue the loose jaw in place, in the event of finding a clogged slot.

Sometimes I think my problem is too much thinking and not enough getting on with it. :)

My intuition tells me that after one more boiled egg your quandary will be solved.

Hmm. It would be easier if I could be sure everyone will be able to print loose jaws and slots which fit together cleanly. I'm going to post the STL files here shortly so that everyone can if they want try them and report back. But if I'm going to add the through hole clearance as above, obviously I should do that first. And before then, a boiled egg awaits... :)

p.s. How did your 2.2 seconds trial work out?

cheers,

Martin.
 
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Hi Martin,
I first changed the exposure time down from 2.5 seconds (the default when setting printer to Mars 2 Pro in Chitubox) to 2.2 seconds, but this made no discernable difference.
I then read the article you linked to, and then amended the Chitubox "advanced" settings from:-
1667393813606.png


by unticking [Image Blur} tickbox and setting Grey Level to 0 giving this:-
1667393900387.png


Now when printing a raft of 20 S1 Locators, I get most printed as 2.02mm with a few 2.01mm and 2.03mm, so this change which is consistent with your parameters now appears to give me similar results as yours, so for now I will stick with settings that match yours.

However it was an interesting article, and also the video that you linked to was also informative, but he does talk quickly and non-stop! A bit like one of my sister in-laws!


I would be happy to try out one of your loose jaw example .STL's when you are happy to release it into the wild.
Regards Steve
 
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Now when printing a raft of 20 S1 Locators, I get most printed as 2.02mm with a few 2.01mm and 2.03mm, so this change which is consistent with your parameters now appears to give me similar results as yours, so for now I will stick with settings that match yours.
@Steve_Cornford

Hi Steve,

Thanks for reporting your results and confirming that the Image Blur function upsets the dimensions. It's a bit of a mystery why it is on by default if it does that.

If you are getting 2.02mm consistently for the 2.0mm plugs, you could correct that by reducing the shrinkage allowance. If you are still using the default 1.5% shrinkage for resin-printing exports, try changing it to 0.5%.

Your result has prompted me to check mine again. They are fiddly things to measure, but using my trusty Mitutoyo micrometer instead of a digital caliper I'm also now seeing 2.02mm (0.0795"). I'm going to change the shrinkage default in the program to 0.5%.

2.5 seconds (the default when setting printer to Mars 2 Pro in Chitubox)

I'm still using the version of Chitubox which came bundled with the printer, and the default in there is 2.0 seconds. This is also shown in the printer instruction book as the recommended setting. Is yours the same? I increased it by 10% to 2.2 seconds following some discussion on one of the web forums, although I can't remember which one.

I don't know why it was changed to 2.5 seconds, but it is probably a trade-off between accuracy and stronger prints with a longer exposure.

p.s. We now have a through slot in the plug:

slotted_plug_underside.png

So now to design a support pyramid which clears that.

Newsflash: curing the rafts on the build plate appears to have stopped them curling up so much.

cheers,

Martin.
 
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Hi Martin,
As the printed manual had illegible LCD screen images so, i downloaded a PDF copy. The PDF copy has chitubox screen image showing 0.05mm layer height with 2 second exposure, but on first running Chitubox I opted to upgrade to the latest version & when I then selected Elegoo Mars 2 Pro as the printer the resin setting defaulted to 2.5 seconds. Later on I uninstalled the latest version, installed v1.8.1 then selected Elegoo Mars 2 Pro and the exposure was still defaulted to 2.5 seconds.
I have since amended that to 2.2 seconds to match your setting.

Blur
Dont know either but will review the homework you set me. I might understand it if I read it a second time!

Steve
 
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@Steve_Cornford

Hi Steve,

Does your instruction book have this page:

elegoo_mars_ins.png


I agree the images are barely legible. For some reason the whole thing appears to have been printed at half of A5 size when it should have been A4.

It's probably time I upgraded Chitubox and the firmware to the later versions. But it is all working so well I'm loath to mess with it while I'm in the middle of Templot design changes.

The video seemed to suggest that 2.0 seconds gave better results, but having done all my testing at 2.2 seconds I'm going to stick with it for the present.

cheers,

Martin.
 
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Martin Wynne

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So now to design a support pyramid which clears that.

Looking something like this:

slotted_pyramid3.png


slotted_pyramid2.png


slotted_pyramid1.png


Which hopefully should allow a free flow of wash through the slot.

The top of the small pyramid section is very narrow, only 0.25mm (10 thou) wide in 4mm/ft scale, but it's necessary to prevent an "island" and ensure the plug prints properly.

I will do a trial print later and see how it looks.

cheers,

Martin.
 
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It won't be possible, or it would be very tricky, to combine bash-fit chairs and loose jaws on the same physical piece of rail.

Which is nonsense of course -- it depends on the situation.

For example, it would be advantageous to have the P slide chairs with a loose jaw. The plain slide bases could then be bash-fitted in advance. The stock rails then being bash-fitted over the top of them without any fiddling about. The loose P bolted jaws could then be added one at a time, making it much easier to add a drop of superglue to each one if desired.

So that's next, a loose P jaw. :)

Martin.
 
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Loose P jaw:

loose_p_jaw.png


Test print done and looking good (4mm/ft):

loose_p_jaws3.jpg


cheers,

Martin.
 
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@Steve_Cornford

Hi Steve,

The improved washing of the pin slots has made a noticeable difference, so it was worth making the change. The pins were previously a bit tight in some cases, and now they are a loose fit in the slots -- a bit too loose in fact. I shall need to tweak the clearance settings.

A loose fit may not be a bad thing for the P slide chairs, leaving scope to add a drop of cyano superglue when fixing them, and fixing to the rail. On slide chairs there is no inner jaw to clip the rail against, so the loose jaws could pull out.

I'm now more confident that others will be able to replicate my results, so I've decided to proceed on the basis of loose jaws for the crossing chairs for all gauges. It's not really an option for the switch block chairs for which I have used split chairs, because in those the loose jaw would be between the rails, and too small and fiddly to fix. But maybe worth a try one day.

Before I make a final decision I have ordered some fresh resin for some more test prints. My existing resin is now 12 months past its labelled shelf life, but the results are fine. I have noticed some changes though -- instead of pouring out like smooth cream, it is more gloopy like lumpy custard. :) It is also taking longer to cure, the latest test prints were still quite soft after the first cure and needed to be done again.

cheers,

Martin.
 
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I would be happy to try out one of your loose jaw example .STL's when you are happy to release it into the wild.
@Steve_Cornford

Hi Steve and all,

Below are the STL files from my latest test prints (4mm/ft scale).

These are for slotted S1 ordinary chairs and loose S1 jaws, and for slotted P slide chairs and loose P jaws. Don't get them muddled up -- the S1 jaws (the ones with a key) won't fit the P chairs.

S1 ordinary chairs won't normally need to be loose jawed, I'm just using them as a test of the process. But it will be handy to have a few loose-jawed S1 around the V-crossings.

I'm very interested to receive reports from anyone who would like to try printing the files. On the Mars2 Pro printer I recommend putting the rafts north-south across the build plate. Perhaps other printers will be similarly direction-sensitive for best results.

test_slots_ctb.png


If your printer has a choice of pre-set print qualities, choose the finest setting available. If your slicer software has anti-aliasing Image Blur functions, you will probably need to turn them off for the loose jaw pins to fit in the slots, like this:

index.php

All testing so far has been done with Elegoo ABS-like grey resin. Results from other resins would be interesting. (The standard resins may not be flexible enough for the loose jaw pins.)

When you first try using the loose jaws, you will think that here lies madness. :) But it is no more difficult than other fiddly tasks in 4mm scale, such as fitting locomotive handrail knobs, or applying wagon strapping. And remember the trade-off -- you don't have to thread the chairs on the rail. Which also means you don't need to chamfer the rail ends. The secret is to have the right tools, and you can soon get into the swing of it. It's quite satisfying when the jaw key snaps into place and locks the rail.

loose_p_jaws2.jpg


First-off you need good light, and close-up reading glasses or magnifying lamp or headband or whatever.

For bash-fiting the chairs you need wooden cocktail sticks. Lots of 'em. Snip off one end entirely, and trim back the other end to a suitable size for different jobs. Locate the slotted chair in the base, and then use the cocktail stick as a punch with a pin hammer to seat it home. It won't damage the chair.

For the loose jaws you need some fine-tipped tweezers, but not too fine. You need to grip the the loose jaw pin close to the end of the tweezers, otherwise the tweezers will catch on the rail. So slightly blunt-tipped tweezers are preferably, about 1/2mm (20 thou) wide at the tip. If you have cheap plastic tweezers you can trim or file the tip to whatever you want.

In practice I prefer cross-over locking tweezers (not the ones in the pic) which clamp the part. You then have both hands free to position it. I have found some on Amazon which have removable screw-on plastic tips -- which we could 3D print to be the exact profile needed to handle the loose jaws. They should be here tomorrow, I will report.

Break off the loose jaws from the raft with fingers and put them in a tin lid. Some will be facing the right way up for the tweezers. Use those first. Then shake the lid and repeat. Note that for the S1 jaws, each row on the raft is keyed in the opposite direction*.

For pushing the loose jaw down into position, I have made a pusher-downer tool out of a bent paper-clip. Or a cocktail stick would do. Or even a thumbnail.

index.php


Here are the STL files. Mesh repaired ready to slice:

https://85a.uk/templot/plug_track/test_s1_slots_fixed.stl

https://85a.uk/templot/plug_track/test_s1_jaws_fixed.stl

https://85a.uk/templot/plug_track/test_p_slots_fixed.stl

https://85a.uk/templot/plug_track/test_p_jaws_fixed.stl

p.s. the rafts for the loose jaws are just for testing the experimental process. For production they will be better bunched up to save wasting resin and get more on the build plate. When washing the prints, plunge the build plate up and down in the wash a few times, to ensure a good flow of wash through the vertical slots.

*Using loose jaws makes it much easier to correct any keying mistakes than when using the solid chairs. :) Just pull out the loose jaw and replace it. For example, at rail joints the adjacent keys should be driven towards the fishplate.

cheers,

Martin.
 
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Hi Martin,
My 2nd bottle of abs like grey resin arrived today. I gave not used all the 1st bottle but thought best to get some more before price goes up!
Atip I read online was to shake the bottle well (your tip actually) then warm the resin up whilst still in bottle by placing in a basin of warm water before another gentle shake & then pouring into the tank.
Thanks for providing the sample files.
I assume the P slide chairs are for EM and OO-SF rather than P4 as so far your tests have all been EM?
Cheers Steve
 
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