switch and crossing angles

[johnp]

I have been trying to work out what the equivalent ratio is for a 12 degree crossing. I presume there is a simple formula somewhere but my naive searches have not so far turned up anything. Would you experts out there kindly help a novice track maker and layer.

Thank you.

Regards,

John

[Russ Elliott]

tan.png

If theta is 12 degrees, tan theta is 0.212

X is therefore 4.7

[Chris Mitton]

According to Martin Wynne on the Templot forum, it depends on how you measure the angle. Most modellers, and apparently European railways, use Right Angle Measurement, as set out in Russ's diagram. UK and US railways (and seriously masochistic modellers) use Centre Line Measurement, whereby you describe the angle by offsets from an imaginary line bisecting the angle. Two minutes with a spreadsheet (preceded by some de-rusting of the brain, as it's thirty years since I last taught A level Hard Sums!) comes up with these numbers:

AngleCalculator.pdf

As you can see, for most sensible common crossings (up to about 1 in 6), they are pretty well the same up to the first decimal place, but for sharper crossings the way you set them out will make a difference.

Hope this helps,
Regards
Chris

[grovenor-2685]

Most modellers, and apparently European railways

Which means that Martin chose to make the default on Templot Right Angle Measure when most users model railways that use Centre Line Measure, and therefore need to remember to change the default every time.
Regards
Keith

[johnp]

Thank you all for your lucid replies.

Regards,

John

[Martin Wynne]

Which means that Martin chose to make the default on Templot Right Angle Measure when most users model railways that use Centre Line Measure, and therefore need to remember to change the default every time.

At the time when I made this decision, 30 years ago in the early 80s, Templot was in its infancy and used only by me, for EM gauge. The template discrepancy introduced by the reduced EM track gauge far exceeds that from the difference between RAM and CLM angles, so I chose the most convenient angle method. At that time I was using Templot as an adjunct to track layouts marked out by hand on the baseboard, for which the engineer's method of setting out angles (RAM) is about 100 times easier. The RAM method makes all measurements along the rail or at right-angles to it, and can be easily set out with dividers. The CLM method doesn't and can't.

But it is only one click to convert a template from RAM to CLM, or if you prefer to enter an angle in degrees, prefix it with a letter k. i.e. to create a 12 degree crossing, set the crossing angle to k12. real > V-crossing options > V-crossing angle... menu item.

The majority of Templot users are not modelling in P4/S7, etc., so I still think it was the right decision to use the more intuitive RAM method. Those in P4 etc. for whom exact prototype equivalence is important can easily convert to CLM if they wish. Remember also in most cases to change to the non-default generic-type V-crossing.

regards,

Martin.

[kipford]

I always use RAM, you cannot see the difference when the track is built. Also its worth noting that the Crossing Vee filing tools are drawn and machined in RAM.
Regards
Dave