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MartynA

Streamline track spacing minimum radius

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I hope this will be a simple question for the vast, and much appreciated, knowledge pool on the forum! What is the minimum radius that OO streamline track spacing will operate at? I would like to set the outer road at basically 4th radius and therefore the inner would be a little more than 3rd. Would trains of BR Mk1 coaches be able to pass each other without contact or would it be too close? Many thanks as always for all of your incredible assistance! 

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I looked at this as a theoretical exercise a while ago, assuming scale length, width and bogie centres for the Mk1 and doing the appropriate trigonometry to get end and centre overhangs. I can't remember the exact result, but I'm pretty sure I decided it would be too tight for comfort, with zero margin for error in tracklaying. 

 

Hopefully someone who's actually tried it will be along shortly to confirm, or otherwise. 

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I work in H0 so can't help much but there was a thread on OO track centres last year.

https://www.rmweb.co.uk/community/index.php?/topic/131752-oo-gauge-double-track-centres/

Though it got a bit argumentative the actual numbers there should be valid.

 

I think the answer to your question is that, with bogie coaches of this length,  the minimum radius for using Streamline's double track separation without further widening is about 3 feet so for double track with radii of 505 and 572mm (R3 and R4) you would need to increase the separation by a few mm. The big railway also does this of course but with prototypical radii it's not very obvious (they also widen the track gauge by a small amount)  

 

Peco Streamline's geometry gives a 50mm centre-centre separation and this was the BRMSB standard for OO. For EM though the separation was 45mm for plain track and 50mm for sidings. Clearly it's the width of rolling stock not the track gauge that determines this separation but unfortunately the BRMSB standards say nothing about widening for curves.   However the European MOROP's, NEM 103 for clearances does give figures for widening on curves and in H0 a bogie vehicle the same length as a 64ft (BR Mk1) coach in OO falls into their longest "C "category of length for widening. Assuming that the BRMSB 45mm centre to centre separation for straight track gives adequate clearance for British loading gauge stock in 4mm scale then Peco Streamline's 50mm separation should be enough for curves down to 900mm radius (3 ft).  For the much tighter curves  of Radius 4 (572mm) and Radius 3 (505mm) the widening from 45mm would be about 10  mm  so you'd need to increase Peco Streamline's already wider separation by about 5mm.

 

I'd treat these numbers with some caution and allow a bit of wriggle room as the larger European loading gauge that the NEM's are based on is still smaller in H0 scale 1:87 than the smaller British loading gauge is in the larger 1:76.2 scale of  OO.  I don't think that would make a difference to the increase in separation required for the smaller curves but I could have missed something.  In any case it's probably worth making a simple gauge to check the separation and sacrificing a quarter circle of Setrack and a length of Streamline to build a test track before committing to major tracklaying*   

 

*Nobody will forget the fiasco in 2014 when SNCF based their specification for 1860 new trains for local services on the current standard dimensions for station platforms. It wasn't until the first trains were delivered that it was discovered that  1300 of the 8700 station platforms in France were built to a much older standard that the trains were too wide to fit. RFF (the then French equivalent of NR so responsible for the platforms) said that  "It's as if you have bought a Ferrari that you want to park in your garage, and you realise that your garage isn't exactly the right size to fit a Ferrari because you didn't have a Ferrari before. We discovered the problem a little late. " This choice of analogy does suggest that Britain isn't the only country where the pay of senior executives bears very little relationship to their competence. 

Edited by Pacific231G
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Thank you both very much for your help in this question. I really appreciate the time taken to reply and now I an armed with the information I can decide which way I’m going to build things.  All fun in model railways! :)

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On 13/10/2019 at 08:20, MartynA said:

I hope this will be a simple question for the vast, and much appreciated, knowledge pool on the forum! What is the minimum radius that OO streamline track spacing will operate at? I would like to set the outer road at basically 4th radius and therefore the inner would be a little more than 3rd. Would trains of BR Mk1 coaches be able to pass each other without contact or would it be too close? Many thanks as always for all of your incredible assistance! 

 

If you're laying track to set-track radii, then you should be using the set-track spacing (67 mm) rather than the streamline spacing (51 mm), which is effectively designed for layouts that are fairly straight or have relatively generous curves and by that I mean those with a minimum radius of at least three or four feet.

 

Ultimately, the set-track spacing is based on what is required at 1st / 2nd radius, so since your curves are larger that this, there is some scope to move the tracks closer together than 67 mm, but I'd still have thought that you'd be looking at needing something like 60 mm between track centres to provide adequate clearance, but the exact distance required is determined by your worst stock combination.

 

I effectively have the same issue as you, albeit I am trying to work to a minimum radius of 30" (762 mm).  I'd like to lay my double track at the streamline spacing on my curves, but I know that won't be possible with my design vehicles, which I think will be Mark 3 coaches and Cargowaggons.  These are both longer than Mark 1s, but I think I'm going to have to adopt a centre to centre distance of somewhere between 55 mm and 60 mm for my 762 mm radius curves.  The general advice is to pin the track down and then using a pen or pencil held against your design vehicles (outside ends of the vehicle on the inner track and centre of the longest bogie vehicle on your outside track and check that the two plotted envelopes don't overlap.  However, I think there is also an option to do the same thing in Templot, so that's my approach at the moment, since I'm not quite at the track laying stage.

 

I agree that some sort of look up table would be good for those of us at the planning stage.

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On 13/10/2019 at 15:06, Pacific231G said:

I work in H0 so can't help much but there was a thread on OO track centres last year.

https://www.rmweb.co.uk/community/index.php?/topic/131752-oo-gauge-double-track-centres/

Though it got a bit argumentative the actual numbers there should be valid.

 

I think the answer to your question is that, with bogie coaches of this length,  the minimum radius for using Streamline's double track separation without further widening is about 3 feet so for double track with radii of 505 and 572mm (R3 and R4) you would need to increase the separation by a few mm. The big railway also does this of course but with prototypical radii it's not very obvious (they also widen the track gauge by a small amount)  

 

Peco Streamline's geometry gives a 50mm centre-centre separation and this was the BRMSB standard for OO. For EM though the separation was 45mm for plain track and 50mm for sidings. Clearly it's the width of rolling stock not the track gauge that determines this separation but unfortunately the BRMSB standards say nothing about widening for curves.   However the European MOROP's, NEM 103 for clearances does give figures for widening on curves and in H0 a bogie vehicle the same length as a 64ft (BR Mk1) coach in OO falls into their longest "C "category of length for widening. Assuming that the BRMSB 45mm centre to centre separation for straight track gives adequate clearance for British loading gauge stock in 4mm scale then Peco Streamline's 50mm separation should be enough for curves down to 900mm radius (3 ft).  For the much tighter curves  of Radius 4 (572mm) and Radius 3 (505mm) the widening from 45mm would be about 10  mm  so you'd need to increase Peco Streamline's already wider separation by about 5mm.

 

I'd treat these numbers with some caution and allow a bit of wriggle room as the larger European loading gauge that the NEM's are based on is still smaller in H0 scale 1:87 than the smaller British loading gauge is in the larger 1:76.2 scale of  OO.  I don't think that would make a difference to the increase in separation required for the smaller curves but I could have missed something.  In any case it's probably worth making a simple gauge to check the separation and sacrificing a quarter circle of Setrack and a length of Streamline to build a test track before committing to major tracklaying*   

 

*Nobody will forget the fiasco in 2014 when SNCF based their specification for 1860 new trains for local services on the current standard dimensions for station platforms. It wasn't until the first trains were delivered that it was discovered that  1300 of the 8700 station platforms in France were built to a much older standard that the trains were too wide to fit. RFF (the then French equivalent of NR so responsible for the platforms) said that  "It's as if you have bought a Ferrari that you want to park in your garage, and you realise that your garage isn't exactly the right size to fit a Ferrari because you didn't have a Ferrari before. We discovered the problem a little late. " This choice of analogy does suggest that Britain isn't the only country where the pay of senior executives bears very little relationship to their competence. 

 

Out of interest what was the eventual outcome in France with the oversized trains ?  sounds as though DaFT has a branch in Paris !

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A 00 Mk 1 should be 37mm wide, 9ft 2" The widest stock I know of is the Triang 9F at 10 ft 40mm, sadly its cylinder width continued to the 2000s Hornby 9F.

Generally 44mm is fine, for straights, as long as they are straight, Many model tracks weave gently from side to side so 50mm is a bit of insurance. Generally the narrower the better for appearance.    But that is only for adjacent tracks, ideally loops or gaps between pairs of tacks should be an extra 16mm or so,4ft 

I still reckon an old tender drive Hornby King on the inside and a Mk3 on the outside is about worst case scenario for clearance between tracks for 00 curves, but loaded container flats are likely to be the bogy (?) wagons for hitting tunnels and bridges.  At present and for the past 30 years we use the 50mm down to around 2ft radius ,  There is a bit of 3rd radius on the inner radius which has had to be widened and M3 coaches are banned from passing GWR Kings  there (its set 20 years before MK3s were built)   If it was not so much work I would reduce the gap to 44 mm or even 42 on the straights, Downside is it means a lot of trimming points.  Conversely it saves length, lets one use medium points instead of small for the same length.  Set track trimmed to 42 mm and live frogged makes amazing as industrial trackwork where outside cylinder locos and bogie stock is banned.

It is the minimum gap which matters not  nominal, you can get away with less gap with set track as it stays put unlike flexi which does tend to creep out of a precise radius,   If possible I use set track for any constant radius curve I can source it for, even if its means easing it out to a larger radius than it was supplied at.   Of course a derailment will see trains scraping one another and I reckon the Triang spacing now enshrined in set track is designed to as much as to stop derailed trains colliding as to allow long Transcon coaches and long overhang locos like L1 4-4-0s  to pass on 13" radius curves.    If building a BLT I would definitely go for 44 or 42mm track spacing, make the trains almost scrape, just like the real thing, see my pics earlier in the thread.

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The point about locos is relevant - a Dapol western for example has significant nose overhang within its kinetic envelope on curves of this radius, and projecting handrails are another issue - most prominent on D1 -10 peaks. With Mk1 coaches a BSK is the best test vehicle as it has handrails at the mid point which is where clearances will be tightest on smaller radii curves.

 

If in doubt - allow a bit of wiggle room.

 

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The Rapido APT-E has a significant nose overhang, and I imagine the new Hornby APT-P might have a similar one as well. Two Mark 3s (old Lima Sleepers) are what I use to check clearances with. If they can pass without touching, then I know most other stock will be pretty much OK.

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17 minutes ago, Ian J. said:

The Rapido APT-E has a significant nose overhang, and I imagine the new Hornby APT-P might have a similar one as well. Two Mark 3s (old Lima Sleepers) are what I use to check clearances with. If they can pass without touching, then I know most other stock will be pretty much OK.

 

This viedo shows some of the problems, Good thing there was only one of these if two ever met each other on a curve... At speed I suspect the driver would have suffered side to side whiplash damage

 

https://www.youtube.com/watch?v=6Yzd1_3XIbY

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One technique i use to get max number of tracks on the straight is to make outer tracks longer before starting a curve;

also on my layout I further use the difference in straight lengths by

a full quarter circle of 4th radius,

adjoining a quarter circle of 1 4th piece of track followed by 1 3rd radius piece of track 

adjoined a quarter circle of 1 3rd and and 1 2nd

adjoined a quarter circle of 1 2nd and and 1 1st . 

So on the straight trains are protoypically close to each other on adjacent tracks and as they enter a curve the spacing increases. I've got three tracks going under a Hornby footbridge (but tight on the platform edge!!)

All helped by the fact that using Hornby track each track piece covers the same angle. 

When did you see ALL track at the same spacing on the prototype over a significant distance?

 

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13 hours ago, Dungrange said:

However, I think there is also an option to do the same thing in Templot, so that's my approach at the moment, since I'm not quite at the track laying stage.

 

For anyone else's information, I've just been playing around with Templot this morning with the following parameters.

 

Design vehicle length - 920 inches (prototype) - 306 mm (model)

Design vehicle width - 111 inches (prototype) - 37 mm (model)

Design vehicle bogie centres - 666 inches (prototype) - 222 mm (model)

Desired clearance from design vehicle to edge of kinetic envelope - 6 inches (prototype) - 2 mm (model).

 

Inner track centre-line radius = 762 mm (30") - outside track centre-line radius =  818 mm (ie track centre to centre distance = 56 mm). 

 

Templot indicates that these two kinetic envelopes don't overlap, although they are relatively close to touching and in all honesty are about as close as I could reasonably go.  If I reduce the track centre to centre distance by 1 mm, then the envelopes do touch - albeit that just means that the space between non-moving stock is fractionally less than 4 mm (ie twice the specified clearance).  Of course the issue is whether I could lay to a 1 mm tolerance and I think that there is supposed to be 18" (6 mm clearance in real life).

 

Bogie centres is based on the Heljan Cargowaggon, but I have increased the length of the vehicle to that of a Mark 3 to produce a greater end throw (perhaps not by enough though) and left the default width (because I probably won't be running outside cylinder locomotives).  However, if there is a need to accommodate a larger design vehicle, then more than 56 mm is definitely required with a 30" (762 mm) minimum radius.

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17 hours ago, class26 said:

 

Out of interest what was the eventual outcome in France with the oversized trains ?  sounds as though DaFT has a branch in Paris !

DaFT don't need a branch in Paris. France's railways are well able to generate their own absurdities. Reports at the time were that RFF (then the French equivalent of NR but now reabsorbed into SNCF as SNCF Infra) had supplied SNCF with dimensions to current standards but omitted to notice that about 1300 of the 8700 stations in the network were to  an older standard.  At the time when the story came out SNCF (why not RFF was never clear) had reportedly already modified 300 of the affected platforms at a cost of 50M€. There were counter claims that this problem was known about and the need to bring the platforms up to current standards of accessibility etc. had been anticipated but I'm dubious about that.

 

I asssume that, since the story broke in 2014, a programme of upgrades has simply continued but at what cost I don't know. There was a later report in 2015 that the new SNCF trains- used for regional services- were also too tall for Italian tunnels along the Mediterranean coast forcing passengers to change to smaller trains, presumably at Ventimiglia (traditionally. French local trains continued into Italy as far as Ventimiglia while their Italian equivalents ran on to Nice.    

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13 hours ago, Ian J. said:

The Rapido APT-E has a significant nose overhang, and I imagine the new Hornby APT-P might have a similar one as well. Two Mark 3s (old Lima Sleepers) are what I use to check clearances with. If they can pass without touching, then I know most other stock will be pretty much OK.

The APT-E's leading bogie was a log way back from the front. APT-P's bogies are much closer to the end so overhang will be a lot less.

As a result, the real APT-E needed special clearance on where it could run.

 

Lima/Jouef/Oxford & the newer Hornby Mk3s  have a lot of overhang & underhang so are good vehicles for testing clearance if you are ever likely to run them. The LMS 12-wheeled buffet was rather long too, so if your layout is set before the 1970s, you may want to run one of these at some point. I have just compared a Lima Mk3 to a Hornby Mk4. The latter have the same wheelbase but the Mk4 is slightly longer. It has a sightly wedged end so may have slightly better clearance than a Mk3.

An LMS Princess has more overhang than most too. Not much underhang though.

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