Templot Club Archive 2007-2020                             

topic: 1129Creating a Custom Switch
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posted: 23 May 2010 14:35

from:

philchudley
 
 

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Hi All

Sorry if this is a basic question, but I am attempting to create a custom swicth in P4/S4 to represent a LSWR Type 2 switch using 1908 geometry.

I have the necessary data and drawings from the South Western Circle but am having some difficulty transferring the data to Templot.

Upon creation Templot requests various bits of info, and it is the first set of data that I need help on. the data requested (and the values presented by Templot are)

Lead length to heel (inc planing) : (Default 144")

Offset at the heel : (Default 4.5")

Stock rail joint to toe : (Default 65")

Length of switch rail (blade) : (Default 174")

Length of stock rail from joint : (Default 360")

----------------------------------------------------------------

The data on the drawing is:

Length of lead to switch blade tips : 8' 0"

Planing : 7' 8 3/8"

To first fixed chair : 19' 11"

Switch rails : 30' 0"

Stock rails : 45' 0"

------------------------------------------------------------------

I am assuming that the first entry in Templot would be (using the data above) 8' 0" + 7' 8 3/8"

The offset is left at 4.5"

But the others? I could guess "Stock rail joint to toe" is 19' 11"

Length of switch rail 30' 0" (this would much greater than the default)

Length of stock rail from joint 45' 0"

Is this assumption correct? If not any advice as to what to enter into Templot? Alternatively what is meant by

"Stock rail joint to toe"

"Length of stock rail from joint"

I have tried the help and Templot Companion, but cannot find what these measurements mean.

Cheers and thanks

Phil

posted: 23 May 2010 16:35

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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philchudley wrote:
what is meant by

"Stock rail joint to toe"

"Length of stock rail from joint"

I have tried the help and Templot Companion, but cannot find what these measurements mean.
Hi Phil,

All the dimensions are explained if you click the ? help F2 button below each line, or press the F2 key:


2_231031_140000000.png2_231031_140000000.png

An overview of the dimensioning is available if you click the more general information button.
  
The "joint" being referred to is the rail joint where the turnout "starts". The "toe" is the location of the tips of the point blades. The end of planing (blade machining) and other rail joints are marked on the templates:


2_231113_100000000.png2_231113_100000000.png


"Stock rail joint to toe" means the dimension a in the above drawing. It is often called the "switch front". Dimension b is the length of planing.

The heel position may coincide with the end of the switch rail, or for dimensioning purposes a virtual heel may be defined as shown in red. The "offset at heel" is the distance between the rail gauge faces at the heel.

Not all of this information may be available. If you have no heel dimensions, you can assume the heel is at the end of the switch rail. If you have no offset for that position, it can be calculated (assuming a straight switch) from the deflection angle, which in turn can be calculated knowing the length of planing and the width of the rail top.

If you post a scan of your drawing, we can help determine all these dimensions. :)

regards,

Martin.

posted: 23 May 2010 19:01

from:

philchudley
 
 

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Thanks Martin for the very prompt and informative reply. The drawing I have is too large for my scanner at home, but I'll have a go when I am in the office on Friday.

Meanwhile I will use your reply to correct my assumptions, with the correct values. There is an offset dimension on the drawing, marked at the end of the stock rail. It is 1'-5.1/2"

No specific heel position is shown, so I will try the heel at the end of the stock rail. These switches were Straight switches.

Thanks again

Best regards

Phil

posted: 23 May 2010 19:21

from:

philchudley
 
 

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philchudley wrote:
Thanks Martin for the very prompt and informative reply. The drawing I have is too large for my scanner at home, but I'll have a go when I am in the office on Friday.
Hi Again

I did manage to get a scan at home and it is attached. The switch I am trying to create is the one at the top.

Cheers

Phil
Attachment: attach_798_1129_LSWR_Type_2_Switch_1908.JPG 491

posted: 24 May 2010 01:08

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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philchudley wrote:
There is an offset dimension on the drawing, marked at the end of the stock rail. It is 1'-5.1/2"

No specific heel position is shown, so I will try the heel at the end of the stock rail. These switches were Straight switches.
Hi Phil,

Thanks for uploading the scan.

In fact it's a semi-curved switch, not a straight switch -- otherwise the size of the heel offset doesn't make sense: :)

semcu_sw.gifsemcu_sw.gif

Also the length of the switch rails and reference to the "first fixed chair" firmly suggest that it is a flexible switch, even though the drawn arrangement for the open switch rail appears to indicate a loose-heel switch. You would need to check photographic evidence for this.

Here it is matched to a 1:7CLM generic V-crossing in P4 (.box file attached below): 

2_231927_370000000.png2_231927_370000000.png

As often with pre-group drawings the dimensions don't quite add up -- the quoted 470ft radius appears to mean the internal geometrical radius of a full turnout, rather than the actual switch radius in the rail. I had to set the switch radius to 441ft-6in (5298") in order to get the quoted heel offset.

The timber spacings all worked out to round number inches, with 26" spacings at the rail joints.

Here's the full custom switch info printout:

Dimensions  for  LSWR Type 2 Switch:
--------------------------------
 
Dimensions are in FULL-SIZE prototype INCHES, with model conversions at 4.0 mm/ft. Unit angles are RAM.
 
This switch is a SEMI-CURVED pattern switch:
 
straight planing length (along blade) = 92.38 ( 30.79 model mm )
straight planing unit angle 1 : 33.59
lead length to heel (incl. planing) = 360.0 ( 120.0 model mm )
 
switch radius = 5298.0 ( 1766.0 model mm )
 
stock-rail joint to toe = 96.0 ( 32.0 model mm )
length of switch-rail (blade) = 360.0 ( 120.0 model mm )
length of stock-rail from joint = 540.0 ( 180.0 model mm )
 
deflection angle at blade tip = 1 : 33.59
planing length (along stock-rail) = 92.41 ( 30.8 model mm )
heel angle 1 : 12.42
heel offset = 17.5 ( 5.83 model mm )
-------------------

Timber spacings (to timber centres) :
 
switch-front is sleepered:
spacing back from toe (blade tips) to first front sleeper (J1) = 26.0 ( 8.67 model mm )
spacing back to next front sleeper (J2) = 29.0 ( 9.67 model mm )
spacing back to next front sleeper (J3) = 29.0 ( 9.67 model mm )
spacing back to next front sleeper (J4) = 0 ( 0 model mm )
spacing back to next front sleeper (J5) = 0 ( 0 model mm )
 
spacing forward from toe (blade tips) to first timber (S1) = 3.0 ( 1.0 model mm )
 
spacing forward to next timber (S2) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S3) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S4) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S5) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S6) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S7) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S8) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S9) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S10) = 28.0 ( 9.33 model mm )
spacing forward to next timber (S11) = 27.0 ( 9.0 model mm )
spacing forward to next timber (S12) = 27.0 ( 9.0 model mm )
spacing forward to next timber (S13) = 27.0 ( 9.0 model mm )
spacing forward to next timber (S14) = 27.0 ( 9.0 model mm )
spacing forward to next timber (S15) = 26.0 ( 8.67 model mm )
spacing forward to next timber (S16) = 29.0 ( 9.67 model mm )
spacing forward to next timber (S17) = 29.0 ( 9.67 model mm )
spacing forward to next timber (T1) = 26.0 ( 8.67 model mm )
____________
v: 0.91.c   ©   

regards,

Martin.
Attachment: attach_799_1129_lswr_type_2_switch_7clm_p4.box 371

posted: 24 May 2010 11:26

from:

donald peters
 
United Kingdom

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Hi Martin,

I like the diagram giving a clear explanation of terminology. A successor to my 'crib sheet' of yore except that that has all your terminological abbreviations installed on the face of the diagram as well. However, it is always on the wall above my pc. (necessities of a fading memory I regret to realise)

May I make an appeal on behalf of an optically challenged ( another failing personal service) regarding colours. To one of normal vision I am certain you can see no problem but to those of us with 'normal' colour indequacy in the most common red/green area (and I am nothing if not common) the red cones are feeble or insuficient, and lines and other finer detail in red that occur in diagrams (as in the present case) can be rendered barely discernable. I can just make out the wording to the lower dimension line for example but scarcely see the top line of letters. (my daughter comes to my aid at such an impass) 

I do not wish to give the impression that this is 'complaint' in any sense but hope that this thought may give pause before choosing red to be superimposed (i.e. on other than a white or grey/black background) as fine detail and print.   

Kind Regards,

Donald

 

posted: 24 May 2010 11:41

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Donald,

Just copy the image and convert to grey-scale. Here you go:

2_240640_330000000.png2_240640_330000000.png

regards,

Martin.

posted: 24 May 2010 11:57

from:

donald peters
 
United Kingdom

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Hi Martin,

Perfect. Something for me to learn every day. (because every other day I have forgotten it, but not in this case i hope)

Thanks for such quick service (again)

Kind Regards

Donald

posted: 24 May 2010 13:08

from:

philchudley
 
 

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Thanks Martin! Your effort and help is most appreciated, I would never have twigged that the switch was a sem-curved and not a straight switch. I can now update my plan with the correct turnouts, and start building.

Thanks again

Best regards

Phil

posted: 25 May 2010 11:32

from:

Brian Lewis
 
United Kingdom

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Hi Phil.

The Timber Tracks range includes some LSWR trackwork in P4, which I cut for Eddie and Bob Bourne.  A 1:7 turnout is included.

Regards

Brian Lewis

philchudley wrote:
Thanks Martin! Your effort and help is most appreciated, I would never have twigged that the switch was a sem-curved and not a straight switch. I can now update my plan with the correct turnouts, and start building.

Thanks again

Best regards

Phil


posted: 25 May 2010 12:58

from:

philchudley
 
 

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Thanks for the info Brian, will certainly have a look at the products on offer.

Best regards

 

Phil

 



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