Templot Club forums powered for Martin Wynne by XenForo :

TEMPLOT 3D PLUG TRACK - To get up to speed with this experimental project click here.   To watch an introductory video click here.   See the User Guide at Bexhill West.

  • 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 Some of the earlier pages of this topic are now out-of-date.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 topic.   For some practical modelling aspects of using Plug Track see Building 3D Track.

    The assumption is that you have your own machines on which to experiment, or helpful friends with machines. Please do not send Templot files to commercial laser cutting or 3D printing firms while this project is still experimental, because the results are unpredictable and possibly wasteful.

    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. All files derived from Templot are © Martin Wynne.
  • The Plug Track functions are experimental and still being developed.

    For an updated overview of this project see this topic.   For some practical modelling aspects of using Plug Track see Building 3D Track.

    The assumption is that you have your own machines on which to experiment, or helpful friends with machines. Please do not send Templot files to commercial laser cutting or 3D printing firms while this project is still experimental, because the results are unpredictable and possibly wasteful.

    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. All files derived from Templot are © Martin Wynne.

Loose Heel Switches in 4mm

Quick reply >

LittleWestern

Member
Location
Slovakia
Hi all,
So I'm currently in final preparations to construct my layout. However, there is one snag I have hit and was hoping the good folk here could point me in the right direction.
I want to attempt to model accurate representations of GWR Loose Heel Switches on my layout (currently GWR Old Type 10ft) and have been reading various articles around the subject namely these 2:
- https://85a.uk/templot/archive/topics/topic_2776.php#p19351
- https://www.scalefour.org/forum/viewtopic.php?t=6257

They have been eye opening and concur with a lot of my other research however, there is one thing that still gets me.... flangeway clearences...
I have my pointwork templates directly placed from templot prefab 10ft Old Type and trackwork set to 00-SF as that will be my standard. But when measuring the flangeway clearences they show as >1mm "In 00-SF and EM you must extend the length of the switch rails to the position where the heel offset provides at least 1mm flangeway clearance." (I believe @Martin Wynne this is from you on the S4 Forum post).

I wondered if someone could proof my work? I've taken the standard 10ft Old Type and set everything to the same bar the "offset at the heel" to 6.5 rather than 4.5 this seems to allow a 1.2mm clearence and not sure If I have done the right thing.


(Ignore the timbering on crossover and other turnouts, I'm yet to figure out how to get it looking correct)
 

Attachments

  • Brickworks 1.box
    131.4 KB · Views: 78
_______________
message ref: 5587
I want to attempt to model accurate representations of GWR Loose Heel Switches on my layout
@LittleWestern

Hi James,

I'm afraid the bad news is that you can't do that in 00. Or in EM, 0-MF, etc. In fact you can't even do it in P4. :(

To model prototype track accurately to scale you must use an exact scale track gauge and a scale flangeway gap. As in S7, S4-X, etc.

In other gauges, you can use the prototype track components to scale, but you have to re-arrange them to make the geometry match the modified track gauge and flangeway gaps. I think you have discovered that.

But you have rather overdone it. There was no need to change the lead-to-heel or heel offset. By doing that you have changed the turnout geometry -- the heel angle and turnout radius. Which means it can hardly still be called a GWR 10ft switch.

All you needed to do was to change the position of the heel joint by one timber space, i.e. lengthen the switch rail that much. Leaving everything else unchanged:

gwr_10ft_for_00sf_1.png


The spacing of S6 and S7 timbers at the existing rail joint is 25". Next spacing of S7 and S8 timbers is 29.5". So to be central between S7and S8 the rail joint needs to move by the average of these spacings:

(25 + 29.5) / 2 = 27.25"

I therefore lengthened the switch rail by 27.25" from 144" to 171.25":

gwr_10ft_for_00sf_3.png


Which preserves all the turnout geometry and timber spacings unchanged. You could reasonably still call this a model of a GWR 10ft switch.

However, it doesn't look quite right -- the closer timber spacing should be at the rail joint. So you ought really to move timber S7 4.5 inches to the right to make the 25" spacing from S8. That would mean adding a further 2.25" to the switch rail length to keep the joint central between timbers S7 and S8, making the switch rail length 173.5".

Over you to decide about that -- moving timbers means it is no longer a scale model of a GWR 10ft switch. Are you wearing your scale modeller's hat or your permanent-way engineer's hat today? :)

The timber centres can be changed in the custom switch settings, or you could simply shove the S7 timber on the templates. Either way, save the result as a library template for future use.

Also for 00-SF and EM you need to increase the switch opening from the scale 4.25" to 1.75mm.* As you can see I used the ruler tool to set that after rotating the switch rail at the new joint position:

gwr_10ft_for_00sf_5.png



With the result that there was just enough clearance at the closest behind the open switch blade (minimum 1.0mm for 00-SF and EM):

gwr_10ft_for_00sf_4.png


*thickness of a UK 20p coin, which can be used as a spacer when building it. Leave as much rail foot as possible when filing the switch blade -- to ensure the clearance it needs to open as a rigid piece or rail rather than flexing.

cheers,

Martin.
 
_______________
message ref: 5590
Hi @Martin Wynne

Thank you for that fantastic explanation, I had sort of come to that conclusion. I honestly had no idea it would be as was as moving the her joint position.

I think I have my "scale modellers" hat on for now considering this is my first project. I think I'll stick to the standard Templot provided GWR 10ft Old Type switch and just focus on producing constantly good trackwork ahead of more complicated turnouts.

But as much as I would like to fully model a loose heel switch (brass fishplates as a pivot point and all) I will save this article and perhaps experiment with these settings in future layout extensions.

Thanks again,

James
 
_______________
message ref: 5591
Back
Top