Realistic radius curves for a roundy-roundy?

[OnTheBranchline]

Hi everyone,

 

Just out of curiosity, what is the max of radius curves that you could get away with without looking comical or for the locos not to struggle too much?

 

Thanks in advance.

Edited January 13, 2019 by OnTheBranchline

[Dungrange]

I assume that you mean minimum radius, since the maximum is effectively a straight.  Ultimately the answer to that is largely subjective.

 

Most manufacturers design their stock to negotiate 17 1/2" radius curves (2nd radius), but to my eye these are far too tight to be realistic in anything other than a dock or industrial setting.  Ideally the curves for a continuous run should be as large as you can accommodate, but the problem is of course the space that you have available.  Whilst I'd say anything less than 5' is a bit too obviously a model railway curve and begins to lack realism, most people simply cannot accommodate curves of that radius on a continuous run home layout, so you need to find a compromise that fits the space you have available.  I've started contemplating a similar scenario to you and I definitely don't want any curves less than 24" and if I can manage it, I'd like to keep the minimum to 36".  However 30" might be a reasonable target.

 

I suspect you'll get a wide range of opinions.

[davknigh]

I suspect by your concerns you actually mean minimum radius. As far as maximum radius goes the bigger the better, remember that the prototype would put check rails and a 10 mph speed limit on most model railway curves.

 

Cheers,

 

David

[Colin_McLeod]

Basically as large a radius that you have room for, but if it is to have any semblance of realism I would suggest 2ft minimum radius.

 

On my own layout I work to 3ft minimum radius or more where it fits. I will go down to 2f radius in tunnels if that gives more space for larger radius visible curves.

 

Note that the radius of some prototype curves are measured in miles but unless your layout is in a large car park you have no room for that.

 

Colin

[JST]

For reference here is a pic of a corner of my layout under construction. The inner track on the bank is the branch line which is Peco Setrack 4th radius (22.5 inches I think!). As it still looks a bit tight I have done the tunnel trick as Colin has suggested. Be aware that some locos don't like tight turns.

 

[Mike Storey]

Just as the real railways do, restrict the locos that don't like the tight curves to the larger radii tracks.

 

Your pic shows that you have hidden the tighter radius well, and maintained a good flowing curve on the outer tracks. Looks good to me!

[Andy Hayter]

My H0 layout (the only roundy roundy I have) had a ruling 3ft minimum radius - most of which is actually off-stage - and at times the on-stage bits look obviously train-set - even if it is far from it.    TGVs ( short coaches) do not create a problem but long length "modern" coaching stock makes the curve look tight due to the overhangs.

 

If you are running pre-grouping with say maximum 8 inch coaches and relatively compact locos, you will get away with a lot more than if you are running 32cm coaches and long modern diesel locos.   So in a sense, there is no right answer since what you run on a piece of track will visually alter how it looks.  

[TheSignalEngineer]

My roundy is just over 8' square. The visible end has a section about 8' x 4' where the lines are on a continuously changing curve, the outer main line varying between 30" and 60". The loop on the inside comes down to 24" in places. The some of the hidden running loops at the other end come down to a minimum of approximately 22" radius but they are restricted to smaller locos. The 'Industrial' branch in front of the hidden loops sets off at 18" but the largest loco using that is an LNWR Coal Tank.

[Teabag]

Also critical is the transition from the straight to the curve,if you make this nice and gentle - as per JST's photo above, the tightness of the final curve is a little less obvious.

 

Teabag

[Colin_McLeod]

And the trains will run more smoothly into the curve without the very sudden change of direction.

Edited April 11, 2020 by Colin_McLeod
typos

[JohnR]

Also, the place you are viewing the layout from will have an impact on how the curves look. If the normal viewing is from within (ie, the operating well, or it is around the walls of the room) then sharper curves will be more acceptable than if you are viewing the layout from 'outside' the curve. 

[DCB]

Generally as big as you can squeeze in.   I find 2000s  RP 25 flanged RTR are dodgy and derailment prone on less than 2nd Radius, some simply can't get round 2nd Radius. Most bang and crash their way over set track points which are around 16" radius at the tight bit but not really reliably.   For reliable RTR running I would stick with 3rd radius or larger and 2ft minimum radius points. Older Wrenn and Triang stock is happy on 1st radius, they have bigger flanges no centre wheel flanges and loads of sideplay on bogies.

As said above curves look better viewed from inside, however there is a trade off between length of straight and curve radius on solid table Roundy Roundy layouts.   Bekra models Newton Abbott have a fantastic 00 2ft wide roundy roundy with a very realistic station and impossibly sharp curves, except it works very reliably with locos grinding endlessly around, admittedly they have been specially modified but its a very impressive bit of kit and it works.

I plan something similar on an old N gauge board 5ft X 2ft 3ft approx where my collection of 0-4-0 tanks and diesels can play .

[Crewlisle]

OnTheBranchline,

 

I am the owner of the 00 gauge DCC exhibition layout 'Crewlisle'.  I operate a three level 2.6M x 2.3M 'roundy-roundy' layout with the high level having a 4 platform terminus for 6 coach expresses, diesel shed, steam shed with tiurntable & goods yard; the middle level is the WCML with OLE; the lower level is the reversing loop which goes under the main baseboards. 

 

I use 2ft or 5ft radius Peco Code 100 points.  All my second radius curves are in the mid level tunnels with a 7ft radius curve on the visible section.  All other visible track radii are plus 20 inches.  If you want a lot of railway in a relatively small area, you have to be prepared to compromise against your ideal layout.  Select 'Crewlisle' in Google & you will see what I mean.  I have 50 locos, 65 parcel/carriages & over 100 wagons stored on cassettes which are 'slotted' in as required in the cassette exchange system on the reversing loop in the operating well.

 

Peter

Edited February 3, 2019 by Crewlisle
spelling mistake

[The Stationmaster]

8 hours ago, Crewlisle said:

OnTheBranchline,

 

I am the owner of the 00 gauge DCC exhibition layout 'Crewlisle'.  I operate a three level 2.6M x 2.3M 'roundy-roundy' layout with the high level having a 4 platform terminus for 6 coach expresses, diesel shed, steam shed with tiurntable & goods yard; the middle level is the WCML with OLE; the lower level is the reversing loop which goes under the main baseboards. 

 

I use 2ft or 5ft radius Peco Code 100 points.  All my second radius curves are in the mid level tunnels with a 7ft radius curve on the visible section.  All other visible track radii are plus 20 inches.  If you want a lot of railway in a relatively small area, you have to be prepared to compromise against your ideal layout.  Select 'Crewlisle' in Google & you will see what I mean.  I have 50 locos, 65 parcel/carriages & over 100 wagons stored on cassettes which are 'slotted' in as required in the cassette exchange system on the reversing loop in the operating well.

 

Peter

And it is a most impressive layout, and a great example of compression, to see in action.

[Butler Henderson]

If the curves are in the Setrack radii I always find it best to use Setrack than flex for them and if you remove the moulded sleepers from the end part of the curve that joins the straight track and replace them with sleepers from some flex the rails will try to straighten out giving a transition curve.

[DCB]

2 hours ago, Butler Henderson said:

If the curves are in the Setrack radii I always find it best to use Setrack than flex for them and if you remove the moulded sleepers from the end part of the curve that joins the straight track and replace them with sleepers from some flex the rails will try to straighten out giving a transition curve.

 

I go a bit further and treat rails and sleeper bases as separate items,   Threading flexi sleepers onto set track rails keeps a continuity of sleeper styles.   I always buy second hand track.  You can also bend set track by cutting the webs between sleepers a la flexi and it stays bent, unlike flexi which has an uncontrollable desire to straighten if bent and an uncontrollable desire to snake from side to side if laid straight.   My track is a mix of Streamline points and flexi track with bits of set track on tight curves and also set track on the straight bits which need to be straight.

 

i developed this cavallier approach as I have a garden railway find damaged sleepers in some places and damaged rails in others so quite often and I  make up one good piece from two damaged ones by threading replacement sleepers on. Recently I have also threaded new N/S sleeper bases on to Steel track as steel seems to have been discontinued. 

[The Johnster]

I agree; if you're going below 2' (Peco Streamline 'small') radius you are much better off with set track.  Flexi will distort and pull out of gauge at these sorts of radii.

[The Johnster]

On 03/02/2019 at 15:47, DavidCBroad said:

 

I go a bit further and treat rails and sleeper bases as separate items,   Threading flexi sleepers onto set track rails keeps a continuity of sleeper styles.   I always buy second hand track.  You can also bend set track by cutting the webs between sleepers a la flexi and it stays bent, unlike flexi which has an uncontrollable desire to straighten if bent and an uncontrollable desire to snake from side to side if laid straight.   My track is a mix of Streamline points and flexi track with bits of set track on tight curves and also set track on the straight bits which need to be straight.

 

i developed this cavallier approach as I have a garden railway find damaged sleepers in some places and damaged rails in others so quite often and I  make up one good piece from two damaged ones by threading replacement sleepers on. Recently I have also threaded new N/S sleeper bases on to Steel track as steel seems to have been discontinued. 

Surprised to hear you are using steel track on a garden layout; how do you deal with the rust?

[DCB]

1 hour ago, The Johnster said:

Surprised to hear you are using steel track on a garden layout; how do you deal with the rust?

Ha Ha Ha Rust is a serious issue, I did use some steel track in the garden and it disintegrated within about ten years,  It was in sidings but I guess if its lon the main line and you run enough trains it might be OK especially as my trains are battery powered.

Actually the steel rail is for the indoor layout, we still have two or three Triang Locos with Magnadhesion and reprofiled wheel tyres and they pull about three times as many coaches up gradients on Steel as on N/S, so when the sleepers get damaged I replace them with new ones taken  from N/S  track.

 

[The Johnster]

Ah.  Now it makes sense, especially if you still have anything with Magnadhesion.  To be honest, I'm surprised you managed 10 years outdoors, though; I managed less than that back in the day in a garage!

[Junctionmad]

My own experience in OO convinces me to set minimum radios at 32 inches with most curves not going below 36” 

[TheQ]

Looking up real railways 4ft8.5in not tramways or underground or sidings, industrial yards, it's seems the minimum radius was an incredible 3chains Or 1048mm in 4mm scale.  This was of course with check rails and a very slow speed limit. 

For main line without check rails But with speed limits, I know the MSWJR was refused opening with a radius minimum below 12chains,  or about  3.168mm/ or just over 10ft in 4mm scale.

 

Even in my huge shed I've not managed to acheive this, so it's down to hiding curves, I've seen many times,  tight curves before entering the tunnel mouths,  I prefer to bring the tunnel mouth forward to hide the curve entirely.  Other methods I'm using rebuilding my n gauge railway min radius 2ft are buildings and cuttings,  blocking the view of tight curves. 

[Sir TophamHatt]

Is there a list of what 2nd radius curves means in Hornby's "R" number system?

I think my roundy layout has the largest curves Hornby make.

But then there's one curve that's nearly a right angle!  I'll take a photo later.

[JohnR]

This pdf shows all the Hornby geometry including radii and R numbers.

 

https://www.Hornby.com/media/pdf/Track-Geometry-PDF.pdf

[Dungrange]

1 hour ago, Sir TophamHatt said:

Is there a list of what 2nd radius curves means in Hornby's "R" number system?

 

Yes - see https://www.Hornby.com/media/pdf/Track-Geometry-PDF.pdf - basically R606 (22.5 Deg) and R607 (45 Deg)