Flex Track 00

[End2end]

Avoid laying flexible track to be closer then the sectional track at the corners to reduce the spacing (Six foot) as your locos and especially the coaches need to have this wider gap or they will collide with trains coming the other way. This has nothing to do with using sectional or flexible track. It is more the gap has been set with sectional track so trains done get too close and collide!

So are you saying that the second diagram wouldn't work ?
Thanks
End2end

[Mountain]

The space between second radius and third radius curves needs to be wide enough to allow your longest coaches which under hang and overhang to pass without touching. (It is usually the coaches which collide if the space is too narrow). With straight track or with gentler curves it is less of an issue, hence why it is possible to reduce the gap between the two tracks.
It is always a good idea (If not essential) to widen the gap between the two tracks where you get sharp corners, hence why sectional track has a wider gap. Mind you, with the third radius curves, you can move to using flexible track instead as the issues where the rails push outwards are less intensified.
An idea here is to lay the second radius curves and get your longest pair of coaches and hold flexible track on the third radius curve to see if you have space to slightly reduce the gap at the ends of the semicircle so your track can smoothly flow into the reduced width that streamline points have. You maybe OK to do this depending on what stock you are using, though I tend to prefer to be generous with such a gap where tight radius curves are concerned. It only takes a long modern DMU to run on the line and you soon find how much room you need!

[End2end]

Hmm yes the Intercity coaches I have been upgrading are the longer ones and I have a 2 car DMU.
Oh well it was worth going through the idea.
Thanks
End2end

[End2end]

I came up with another theory. Not sure if it will work though.
Instead of the curves meeting at the same point, by using 2 of the smallest available straights on the 3rd outer radius staggering the curve this would possibly give more room for coaches on the curves.
I'm not really explaining myself very well so here's another shoddy diagram.

TrackEdit2.jpg (51.33 KiB) Viewed 1287 times

The 2 green parts represent the 2 added small bits of straight track before the actual straight running lines.
So with these straights added would I be able to bend the inner 2nd radius flexitrack peice closer to the 3rd radius at the top of the diagram without coaches hitting each other? And thus be able to use narrower track spacing and electrofrog points at the back of the layout / top of the diagram?
Thanks
End2end

[MickleoverTestTrack]

Using the short straights will increase the clearance but I'm afraid it is again down to experimentation, you can use maths to work out the loading gauge on a given curve radius and therefore the required structure gauge but it gets complex at the transitions.

What is your longest bit of stock? Is it 20m (e.g. Mk1 and 2 coach or 1st gen DMU length), 23m (Mk3 or 4 coach or modern DMU like 156/158) or longer (26m Class 800)?

Mixing steam locos and modern 23m stock can reduce clearance a bit as long steam locos can overhang more at the outside of the curve with modern coaches overhanging more to the inside but if it is all modern there is less to worry about.

[Mountain]

I came up with another theory. Not sure if it will work though.
Instead of the curves meeting at the same point, by using 2 of the smallest available straights on the 3rd outer radius staggering the curve this would possibly give more room for coaches on the curves.
I'm not really explaining myself very well so here's another shoddy diagram.
TrackEdit2.jpg
The 2 green parts represent the 2 added small bits of straight track before the actual straight running lines.
So with these straights added would I be able to bend the inner 2nd radius flexitrack peice closer to the 3rd radius at the top of the diagram without coaches hitting each other? And thus be able to use narrower track spacing and electrofrog points at the back of the layout / top of the diagram?
Thanks
End2end

You can do that. One of the older "Bodges" when it comes to sectional track where with some systems there may only be a first radius curve available, is to lay the track as you have shown by bringing the outer curves further out and adding a short straight at the 90° position. When I first came into model railways for a number of years there was only first or second radius curves. It wasn't until the early part of the mid 1980's (If I remember correctly) that the third radius was introduced.

[End2end]

I think the longest single loco I have is a bachamnn Collet goods with tender (this may change once I have a HST power and dummy car though) or my Bachmann twin car DMU.
The longest rolling stock is the longer Hornby intercity coaches in what I think is called JAM SANDWICH livery?
I think they are 50ft MK4s but definatly the longer of the 2 available intercity coaches.

I grabbed this pic off the net. It's not my exact coaches but rather, an example of the 2 different lengths of intercity coaches available.

s-l225.jpg (8.45 KiB) Viewed 1277 times

As to trying this out phsyically, unfortunatly I cannot do that as I've not bolted the baseboards together yet.
Neither do I have any electrofrog points nor know which ones I would need.
I think theres more than one option but please do correct me if I'm wrong.
Not sure how you'd do the maths either.

It's becoming glaringly obvious no doubt to everyone why I haven't strayed from setrack for my track plan before.
Thanks
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[MickleoverTestTrack]

The pivot point of a steam loco tends to be the front and rear main driving wheel, problem locos will be those with a long overhang infront or behind the driving wheels (like a Pacific). The collet is an 0-6-0 so won't be anywhere near the overhangs on your longest coach or DMU which will be 23m.

The inner and outer overhangs are called the "swept envelope" I believe. I did do some calculations of the swept envelope for my own Hornby Mk3 and Mk4 stock for the various standard OO radii. If I can find them over the weekend I will post them up and also draw some diagrams of how I worked them out and the tolerances I allowed for.

I actually intend to write a guide on using streamline in smaller spaces and mixing sectional and streamline geometry. It seems to be a subject that comes up a lot on forums but without any decent reference material on the internet.