Templot Plug Track Developments

[martin_wynne]

@adrian

Hi Adrian,

Oh sorry! That's a bug in the works. The loose jaws are 7mm scale on width and 4mm scale on height! I forgot to test the option of printing chairs and loose jaws at the same time. Usually the loose jaws are printed on a separate raft to save space, for which the new option should be unticked.

I will get this fixed and release 244e as soon as possible.

Martin.

@adrian

Hi Adrian,

Templot version 244e is now available with a fix for the above.

Your copy of Templot should update automatically if you restart it and follow the instructions. There is no need to uninstall your existing copy of Templot.

I have tested it as much as I can. Please let me know if you spot anything wrong.

Martin.

 

[martin_wynne]

@adrian @Hayfield1

Hi Adrian,

Returning to the 7mm/ft timbering base, here is a comparison of the normal thickness base (6mm), and the thin-base (3.5mm) option and matching chairs:




This is now working as intended in 244e if this box is ticked:





The advantage of the thin base is obviously that it is faster to print and uses less filament. Or thinner plywood. Also that in FDM it matches up with Peco 0 gauge flexible bullhead track. And it works fine with solid-jaw chairs -- the plug depths and tangs are the same size as for the 4mm/ft chairs and they plug nicely into place.

The BIG disadvantage is that in order to work with loose jaws, the jaw pin needs to be longer than the depth of the timbers, and protrudes below the underside of the track after assembly:







So some means has to be found to get round that:

1. the track is raised up on battens or packing between the chair positions, or

2. a hole or recess is created in the trackbed below each chair, or

3. the track is built on the bench in such a way that there is a clearance for the pins, and track can be turned over after assembly to have the protruding pins trimmed flush.

The latter option needs some thinking about. My best guess so far is to build the track on a slice of stale bread. The pins would push through into it easily. Answers on a postcard for something more practical. I have tried expanded polystyrene, but the surface is too resilient for the pins to penetrate.

It would be fairly simple to FDM-print or laser-cut a disposable spacer base to use below the track during assembly, but in that case you may just as well use the thick base option instead.

or

4. if you want to use the loose jaws, stick with the thick timbering base.

More about this at: 3D plug track - version 244c and beyond

Martin.

 

[simond]

Whilst Martin was busy adding features and fixing track spikes, I got this far. WR 2-bolt 95R ordinary chair. 7mm scale.









Pls see post 20, top left, and the two photos that Martin added to page 1

I'll get round to adding keys (left and right) and nuts at some point, and will also have a go at adding Templot clip-plugs on the bottom as I quite fancy plywood sleepers. I need to add the cast-in lettering too.

I'll put various versions on WT Resources when I get there.

Martin, I can share STEP, IGES, STL or SW-native 3D with you if it would help. Please let me know.

atb
Simon

 

[simond]

needs a little more work.





too "fat" where the flange will pass. should not be too difficult to fix

 

[martin_wynne]

Martin, I can share STEP, IGES, STL or SW-native 3D with you if it would help. Please let me know.

@simond

Hi Simon,

Thanks for the offer, but I'm not using such CAD-type files in Templot. The chairs are generated programmatically to match their position on the template, the model rail section, model flangeway gap, etc.

It will all be open-source eventually. Here's a small snippet of code to explain what I mean by programmatically generated:

                             ///////////////////////////////////////////////////

                             procedure do_rib_rad(pcentre:Tpex; rad,startk:extended; nmod:integer; make_horz_faces:boolean; z:extended);

                                            // do 90 degs convex rad
                             var
                               n:integer;
                               nk:extended;

                             begin

                               for n:=0 to 6 do begin

                                 nk:=startk+n*Pi/12;     // 15 deg steps clockwise

                                 p[n+nmod].x:=pcentre.x+rad*COS(nk);
                                 p[n+nmod].y:=pcentre.y-rad*SIN(nk);     // y negative from gauge-face on outer jaw

                                 if (make_horz_faces=True) and (n>0)
                                    then begin
                                           debug_code:=115;

                                           s:=s+dxf_3dface_pex(p[n+nmod],z, pcentre,z, p[n+nmod-1],z, p[n+nmod-1],z, 21,0);
                                         end;

                               end;//next
                             end;
                             ///////////////////////////////////////////////////

Martin.

 

[simond]

I sort-of see what you're doing in much the same way as I see what Elton John does when he plays the piano...

 

[J_F_S]

Here's a small snippet of code

Looks worryingly like Pascal to me ... only just got my head round C ...

You will have to keep on for while yet I fear Martin!

Best Wishes,
Howard

 

[simond]

I reckon that's more like it

Decent clearance under the flange too...

 

[ChrisBr]

Looks good

No inclination inwards?

 

[simond]

Similar form if different modelling approach to Martin's software-generated plug. I'll print some, and laser some sleepers over the weekend all being well.

 

[simond]

Looks good

No inclination inwards?

Hi Chris, thanks.

no, following Martin's lead here. Clearly it is possible to put the 1/20 inclination into the CAD very easily, but I have not applied it.

I'd have to go looking for the reasons and it's a few weeks since I read the history of plug track (great way of passing a very pleasant TGV journey home from the Alps) on the Templot forum, but I recall the rails are mounted vertically. Maybe Martin can advise his reasoning.

cheers
Simon

 

[adrian]

Thanks for the update - another print run under way now.

The advantage of the thin base is obviously that it is faster to print and uses less filament. Or thinner plywood.

I'm using plywood - with the quantity I'll be cutting thinner also means lighter, not just the sleepers but the reduced volume of ballast as well, and lighter is important to me.

 

[Hayfield1]

Hi Chris, thanks.

no, following Martin's lead here. Clearly it is possible to put the 1/20 inclination into the CAD very easily, but I have not applied it.

I'd have to go looking for the reasons and it's a few weeks since I read the history of plug track (great way of passing a very pleasant TGV journey home from the Alps) on the Templot forum, but I recall the rails are mounted vertically. Maybe Martin can advise his reasoning.

cheers
Simon

Simon

excellent piece of modelling

 

[martin_wynne]

Hi Chris, thanks.

no, following Martin's lead here. Clearly it is possible to put the 1/20 inclination into the CAD very easily, but I have not applied it.

I'd have to go looking for the reasons and it's a few weeks since I read the history of plug track (great way of passing a very pleasant TGV journey home from the Alps) on the Templot forum, but I recall the rails are mounted vertically. Maybe Martin can advise his reasoning.

cheers
Simon

@simond @ChrisBr

Hi Simon, Chris,

All rail in the plug track design is vertical. If you want inclined rail, Templot plug track is not for you.

If an inclined rail is curved, the radius in the head of the rail differs from the radius in the foot of the rail. Which means that to turn through a specified angle the head must be a longer or shorter in length than the foot. Not by much, but in order to deform rail to such a condition requires strong forces, such as being held in heavy cast iron chairs. The idea that such forces can be applied by flimsy little plastic chairs is crazy.

I do not believe it is possible to build small-scale model track with inclined rail without special equipment. Such as pre-curving rail by passing it through heavy tapered rollers, or making knuckle bends in a press tool with strong clamps and a conical mandrel. Likewise for putting the twists in vee rails while maintaining the running edge straight. Few modellers have access to such equipment.

Which is why I think trying to use inclined rails in the smaller scales is just plain daft. It causes many problems including with gauging, and is impossible to see anyway. The one place where it might be noticed would be at the exposed ends of check rails-- but prototype check rails are vertical in all post-grouping designs.

Which means that for the Templot plug track project all rails will be vertical throughout. Consequently the plug track chairs will not be directly compatible with inclined chairs from other sources -- although in practice I suspect that for plastic chairs it will be possible to fudge it, if not with lost-wax cast chairs.

Martin.

 

[Pencarrow]

@simond @ChrisBr

Hi Simon, Chris,

All rail in the plug track design is vertical. If you want inclined rail, Templot plug track is not for you.

If an inclined rail is curved, the radius in the head of the rail differs from the radius in the foot of the rail. Which means that to turn through a specified angle the head must be a longer or shorter in length than the foot. Not by much, but in order to deform rail to such a condition requires strong forces, such as being held in heavy cast iron chairs. The idea that such forces can be applied by flimsy little plastic chairs is crazy.

I do not believe it is possible to build small-scale model track with inclined rail without special equipment. Such as pre-curving rail by passing it through heavy tapered rollers, or making knuckle bends in a press tool with strong clamps and a conical mandrel. Likewise for putting the twists in vee rails while maintaining the running edge straight. Few modellers have access to such equipment.

Which is why I think trying to use inclined rails in the smaller scales is just plain daft. It causes many problems including with gauging, and is impossible to see anyway. The one place where it might be noticed would be at the exposed ends of check rails-- but prototype check rails are vertical in all post-grouping designs.

Which means that for the Templot plug track project all rails will be vertical throughout. Consequently the plug track chairs will not be directly compatible with inclined chairs from other sources -- although in practice I suspect that for plastic chairs it will be possible to fudge it, if not with lost-wax cast chairs.

Martin.

And generally we modellers make matters far worse by using radii that can be significantly smaller than the real thing, certainly on plain track.

 

[simond]

Martin

thanks, makes perfect sense.

I very much doubt that the inclination difference would be a problem at the interface between Plug Track and anything else - in my experience, the transition from 0MF to Peco (0.25mm per rail) is pretty much invisible and easily accommodated in one or two sleeper lengths of plain track, and I'd guess the vertical to 1-in-20 would be the same.

OTOH I suppose I could always design a special (and extremely expensive) fishplate to accommodate it...

cheers

Simon

 

[simond]

I figure this is a yee-haar moment

I didn’t have any 3mm ply but after a brief fight with the laser, persuaded it to cut me some sleepers from 2mm mdf. This is far from an ideal material as the holes take out too much of the strength of the material, ply would be so much better.

Anyway this is just a look-see, so they’ll do just fine.

I printed five dozen chairs with the Templot plug - 12 fit nicely on a sprue that goes across the build plate - I could probably print 18 or 20 such sprues per run.



They fit the rail



Which is something of a benefit

And they fit my “not terribly good” sleepers



And they can be assembled into 60’ panels, though it’s a job for Ann Octopus, at least getting the first few sleepers on and not breaking anything.

Of course, if the material is used was the right thickness it would have been much easier, and I guess you’d normally have the sleepers fixed down to the template and then just bang the rail-with-chairs into place.

My jig was not a great help!



I need to adjust the fit of the chairs to the rail - some of them were just too tight, and they broke as I pushed the rail in - about 8 out of the 48 I did, and all but one were one hand. No idea why.

Costs - I’ll get back on that but the chairs were cheap and the MDF is less than 30p for an A4 sheet that could do 170 sleepers. Ply will be more expensive of course, but compared to commercial prices, it’s a no-brainer

And it’s very satisfying!

 

[simond]

And it’s very cheap.

I can get 24 sprues onto my build plate, ie 288 chairs, and allowing the costs I calculated last Sunday, I make the cost of a chair to be £0.01119444444444. That’s £5.60 for 500.

I also checked the gauge of the track I made - it seems to be 31.76 to 31.92. Given I build my pointwork to 0MF, I guess this is not an issue but it would be a trivial adjustment to the sleeper DXF to sort that.

I should also note that Martin recommends a water washable resin to improve cleaning. I used Fast Navy Grey which is IPA wash. Water wash would save on the alcohol cost, and might also mitigate against some chairs being too tight on the rail, if that is because, for whatever reason, the tight chairs had not washed well.

it occurs to me that by jigging the chair spacing on the rails, it might be possible to spray the rails and chairs with a suitable rust colour before plugging them in, if the sleepers were pre-stained, the freshly laid track would be ready coloured, just weather to taste! Might be brave but perhaps it’s also possible to ballast before fitting the rails.

and did I mention how cheap it is?

 

[John_B]

Checking the current price of rail, I think I should be planning to use radio control for my O gauge layout, so I can use 3D printed rail too!

 

[martin_wynne]

I should also note that Martin recommends a water washable resin to improve cleaning.

@simond

Hi Simon,

That's mainly for the loose-jaw chairs, to ensure the pin slots are clear. Not so important for one-piece solid-jaw chairs.

Looking good.

p.s. this looks suspiciously like a hexagon nut:

GWR chair bolts have square nuts. 7/8" dia bolt, 9 tpi, nut 1.1/4" sq.



Martin.