OO Gauge double track centres

[DCB]

On 12/03/2018 at 19:27, martin_wynne said:

 

In 4mm/ft scale (00, EM or P4) the centre-to-centre distance for UK standard-gauge models should be not less than 44.67mm, and wider on sharp curves. For 00 and EM that is commonly rounded to 45mm.

To measure centre-to-centre, measure from the edge of the left-hand rail on one track to the same edge on the left-hand rail on the other track.

Posting misinformation about using narrower spacings is not fair to beginners. If you want to do it that way on your own railway, fine.

Martin.

Contradicting people who have spent a great deal of time explaining about track centres is plain disrespectful
I don't know which arm chair you model from but it is complete nonsense to say "To measure centre-to-centre, measure from the edge of the left-hand rail on one track to the same edge on the left-hand rail on the other track."  when you are laying track. It can't be done in the real world. There is a rail in the way.  You need a template or spacer to fit between the tracks spanning the 6 foot or 10 foot way, may father in law used a steel ruler between one rail and the sleeper ends for Peco streamline spacing, but that didn't work on curves.. 
There is no standard centre to centre figure  Peco used 2" for 00 Streamline from the 1950s which looks and is too wide on the straight and probably works down to 20" in the worst case scenario I know of which is  Hornby tender drive King on the inner and a full length Lima  Mk 3 coach on the outer, those are my test vehicles.  Set track dates back to around 1961 I believe with Trang Super 4 which carried its 22.5/45 degree curves and 14.65 " 1st Radius  geometry over into system 6 and Peco set track, Its cruder than Hornby Dublo from the 1930s but used 2nd radius points instead of 1st.   Earlier Triang track used 33 degree points, and 13.5" min radius  H/D always was 22.5 /45 degree and 15" min radius.  A lot depends on whether you need to get pudgy fingers between the trains which are only about 4 or 6mm apart to scale to re rail them.
Poor track spacing has ruined an awful lot of otherwise good layouts because people blindly follow standard advice which is almost always wrong because it does not differentiate between 6 foot way between a pair of tracks and 10 foot between the pairs.  We are all tight for space, don't waste it.

[Wheatley]

Six years has to be something of a record for re-opening an argument, surely ?

[5BarVT]

4 hours ago, DCB said:

"To measure centre-to-centre, measure from the edge of the left-hand rail on one track to the same edge on the left-hand rail on the other track."  when you are laying track. It can't be done in the real world. There is a rail in the way.

Unfortunately, that is exactly what I do, successfully, for straight track, so to state categorically that it can’t be done is rather disingenuous.  I use a steel rule (6” usually) place the 0” end against the inside of the rail over the intervening rail and move the second track until it is at my required distance.  To the accuracy that I need (I’m an engineer, not a mathematician) it works.

Paul.