I know I could work this out by trial and error but I was just
wondering if anyone has any experience.......
I want to lay the tracks on my new baseboards at the 'correct' scale
6' spacing (as provided by back to back Streamline points) rather
than the overwide spacing used in SetTrack. What will be the minimum
radius I can get away with and still use Mark 3 length stock (scale
75') on adjacent tracks without them fouling each other on the
Back to back streamline points give a spacing (centre line to
centreline) of about 51mm, which equates to a rail to rail spacing
(between the nearest rails of the pair of tracks) of 34mm. At 4mm/foot
(OO) that would be 8.5 feet not 6.
So I'm puzzled at how this "6 foot" spacing is being calculated (Peco's
catalogue does this too, so it isn't just you).
The "6 foot" is actually the minimum. Look at some of the Great
Western main line that was once broad gauge and it's heck of a lot
more than 6 feet.
Also remember that it is going to be bigger in OO because of the
effect of the narrower track gauge.
The more important things are the dis tance between track centres, and
the clearance for any overhang on curves.
With or without a cant under the curves :-)
It will give a different answer.
You've got to adjust the track gauge from under-scale OO.
The prototype 6 foot spacing is from adjacent rail to adjacent rail.
For sidings alongside a mainline, the spacing should be 10ft.
And, if you went to prototype 6ft spacing (suitably increased for the
under-gauge OO to 26.3mm), you'd need to be certain that your vehicles
stayed within a prototype loading gauge (ie. didn't move left-right on the
track within the limits of the back-to-back of the wheels). But, with the
pragmatic wheel geometry of OO, there will always be a risk of movement
outside the pure-scale loading gauge.
However, remember that Peco track is really to a HO design. So, address the
question about spacing in 3.5mm/ft and non UK practise track. It comes out
at 10ft or 3m almost exactly.
3m spacing sounds nice and sensible, I wonder what prototype Bern Gauge
As to the original question, one needs to know the pivot centres of the
coach, then assuming the coach to be rectangular in plan, knowing its
overall length, it should be possible to work out the swept arc of the coach
for any particular radius. Having calculated a theoretical arc, add a bit
for the wheel movement and any other irregularities.
Rob, do not get fixated on ensuring that tracks are exactly 6 feet apart.
This is merely railway terminology and a general minimum.
Take a long hard look at any Network Rail infrastructure and you will see
that "Real Life" tracks rarely display the 6 foot rule.
Has it gone metric yet?
Actually if you do take such a look you will find that the 6ft spacing
is accurately maintained throughout almost all "real life" double
tracks. It gives you a centre to centre spacing of 11ft 2in, just a
tad under 45mm in 4mm scale. Straight track at these centres will be
OK with 00 wheel standards, there's not that much slop in there. With
Mk3 coaches and similar long vehicles you are going to need to start
widening this out to allow for end and centre throw below about 4ft
Make friends in the hobby.
Garratt photos for the big steam lovers.
Yes, track design is metric these days.
The "Standard Track Interval" is now given as 1970 mm.
Note this is now defined between gauge faces of the rails, the '6ft'
was between outside faces of the rail.
So track centre - centre is 1435+1970 = 3405
In 4mm scale is 3405/76.2 = 44.69 mm.
Make friends in the hobby.
Garratt photos for the big steam lovers.
One thing you haven't mentioned is the radius of your curves - this
will very significantly affect whether you can even lay track at 6 foot
spacings. With model curves being significantly tighter than even the
tightest of prototype curves, I would suspect that you will need to
adopt the Peco spacing, afterall, that is why they have created it the
way they have.
I once saw a club religiously try to stick to 6 footways on their 3
foot radius curves. Guess who came along and put some Lima MKIII
coaches and a 4-6-2 pacific on ? They had to relay all of their track.
First, ignore protoype spacing on curves -- our model railway curves are
very, very sharp compared to the prototype. NMRA (nmra.org) has a set of
recommended practices for centre to centre spacing that takes into
account both radius and length of rolling stock. Since I don't know what
"first radius" etc means (and it's a stupid way of describing a radius,
anyhow - why not just use inches or centimetres???), here's a short
table adapted from NMRA practice that should provide the data you need.
For rolling stock up to about 50ft long and six-coupled steam
locomotives, use the following minimum centre to centre spacing.
Interpolate for the missing values. You can measure right rail to right
rail, it's easier than finding the centres first.:-)
15" radius: 3" minimum
18" radius: 2-1/2" minimum.
20-24" radius: 2-1/4" minimum
30-36" radius: 2" minimum
BTW, spacing between track and lineside structures is equally critical.
On straight track, the prototype uses different center to centre spacing
depending on the use of the track. In yards, the minimum in N. America
is 13'6", and it would be a foot or so narrower in the UK. This leaves
about 3ft clearance between cars, so a person working in the yard is OK
standing between trains on adjacent tracks. I use 2" minimum spacing on
straight tracks, which is about 14'6" in HO, and about 12'8" in OO.
On mainlines, the spacing is wider, especially if trains are expected to
pass each other at speed. Eg, on the TGV lines, the spacing is 18ft IIRC.
Since UK OO rolling stock is about the same size as US HO rolling stock,
the numbers above should work for you. If in doubt, make a test car as
Cut a piece of perspex or similar clear plastic as long and wide as your
longest waggon or carriage. Add bolsters and bogies at the proper
spacing. (If you add a coupler at the correct height, you can also test
coupler height on rolling stock.) You can roll this test car around and
see both where the edges come too close to lineside obstructions and
parallel tracks etc, and where the rails are in relation to the car.
It's also useful to have a loading gauge test gauge. Cut a piece of 1"
thick wood to the outline of your scale's loading gauge, or build it up
from pieces of boxboard or other thick cardboard. Make one side a foot
or more wider relative to the centre line (which should be marked), and
mark this side C. This side is the one you use to test clearances on
curves. The other side is marked S, for testing straight track. Leave or
add a tab on the bottom (centered on the centre line as marked) just
wide enough to set between the rails. Set the gauge on the track and use
it to place lineside buildings etc so as to clear the rolling stock.
When I said 6 foot I mactually meant the Peco spacing, not realizing at the
time that the two are not the same. My largest radius will about 55cm and I
am hoping to get 2 tracks inside that.
This is a misunderstanding on my part, when I said '6 feet' I actually meant
the spacing that back to back Peco Streamline points provide. My question
about the radii that I can get Mk3 coaches round at that spacing, without
contact, still holds, though.
55cm (approx 2 foot) radius ? That is _really_ tight. If you are going
to put two tracks inside that, the inner track will be down to
somewhere around 40-45cm. That really is too tight in my opinion. You
definately won't be able to lay a scale 6-foot way with those radii and
you will probably even have to widen the Peco spacing to accomodate
Phil: Well, I don't know how much space YOU have available, but unless
one wants to build a straight line track and spend all ones time with
fiddle yards (as some exhibition layouts do) then in a British home there
is little option than to use 2ft (600mm) radius!
Especially when viewed from INSIDE the circle this is quite acceptable.
It is also about '3 radii' more than 'uk geometry' (as set by Triang
Hornby Series 4 track/system 6 years ago), and much more than the 250mm
radius included in Roco starter sets with an ICE2 train!
I will be having 1 siding on about 17-18inch radius so that it looks
tighter, and I will also be using many Fleischmann points (standard brass
radii) for my main sidings. This provides a contrast to the 600mm
minimimum radius I try to use elsewhere. But how do I then best represent
'Barnstaple Bridge' - a tight curve with check rails over the River Taw
where the original does an S curve from Barnstaple Junction to the Town
station (1 curve over the river)..if not on the minimum radius I can use
for all stock? I am split between 18inch with a straight section between
reverse curves, and 600mm with no gap between the reverses...or since its
Beechingless Barnstaple....building a new bridge that is straighter! 8-(