Absolute smallest practical radius in 00 curves

[GreenDiesel]

A few years ago, I saw two HO layouts at a train show that used curves that were tighter than the usual minimum of 14.7 to 15".   One layout was long and narrow and used scenery & buildings to cover up the extremely tight curves. The operator was running 1-2 North American diesels on this layout which seemed to work quite well.

 

The other was a larger, tail-chaser layout that had even tighter curves. The owner was running some IHC / Mehanno locos on it, which can handle tight curves better than most new locos.

 

Using a piece of Peco code 100 flex-track last week, I measured out 2-3 different radii so I could try to see the tightest radius would be. I'm thinking of creating a new but very basic tail-chaser so I can run my Hornby Dublo and Triang locos on it.  Using my Dublo 4MT, I tested out a few of the radii. I know for sure that Dublo locos will handle 14.7" radius curves but, on my tests, I could only go as tight as 14" before the loco started to bind. I think it really started to bind on the 13.5" size (which is the size I was hoping to use).

 

So, based on your experience, what is the absolute smallest practical radius that one can use?  Again, I'm thinking of using only Dublo and Triang, which should be the easiest to run on extra tight curves.

 

Thanks in advance,

 

Rob

[YK 50A]

Hi,

 

I've experimented with code 100 flexi myself and the best I could get to be reliable with contemporary Hornby and Bachmann Co-Co and 1-Co-Co-1 diesels was about 18" and even then there was a bit of trial and error.  Obviously, Bo-Bo and short wheel based 0-4-0 shunters were more forgiving.  Unsurprisingly, older Tri-ang Hornby and Airfix locomotives were also less prone to binding.  The problem, I believe, is that flexi will go out of gauge if you bend it too tightly (I think Peco say that you shouldn't try and make anything shorter than 18" or 19" - I can't remember off the top of my head).  Setrack is designed to keep the gauge, even down to Hornby and Peco 1st radius (14 5/8"), but I haven't used 1st radius curves in a long while.  Some of the locomotives I have in my collection are advertised as not being suitable for anything tighter than 2nd radius (17 1/4").

 

Hope that's of interest.

 

Alun

[GreenDiesel]

Thanks, Alun. So maybe I should stick with First Radius track then. One thing I did notice when experimenting with the flex track was that it was tricky getting the curve to remain consistent, when making very tight curves. So maybe that's part of the gauge problem you were referring to. Rob

[YK 50A]

Thanks, Alun. So maybe I should stick with First Radius track then. One thing I did notice when experimenting with the flex track was that it was tricky getting the curve to remain consistent, when making very tight curves. So maybe that's part of the gauge problem you were referring to. Rob

 

Hi Rob,

 

That the track tries to spring back is an added complication.  Running would be perfect, then a couple of days later certain stock would have problems, that's what I meant by "trial and error".  A tiny alteration would make the track reliable or unreliable.  Code 75 is more flexible, but regarding the distance between the tracks, it can or will still go out of gauge.  Quite simply, setrack is manufactured taking the variances of the gauge into account.

 

From what you have described, yes, I would stick to setrack.  I wanted concrete sleepers and also to ladder some curved points in a confined area.  I had to redesign!

 

Alun

[PatB]

Do any of the continental H0 track systems have sharper curves than UK R1? I know some of the N gauge ones do. If they did you could get the accuracy of set track which might let you get away with the tighter radius.

[GreenDiesel]

Do any of the continental H0 track systems have sharper curves than UK R1? I know some of the N gauge ones do. If they did you could get the accuracy of set track which might let you get away with the tighter radius.

Funny you should ask! I just found some very tight Roco curved track that I knew I had stored away somewhere. These curves are ultra sharp as the box says that the radius is 250mm (or 9.8"!

 

My son & I just put together a small loop of track and my Dublo R1 0-6-0 steam loco the class 08 diesel switcher run through this tight circle with no problems. The Dublo 4MT barely does -- you can really hear it binding  and see it wobbling (so I'm going to stop as I don't want to break it).

 

I'll search online then. Maybe one of the similar continental brands makes something more reasonable, in the 13-14" range.

 

Cheers, Rob

[PatB]

Wonder what Roco 2nd radius is? Based on a 1st radius of 9.8" I doubt if it would be more than 13" or so.

 

Others on here are better qualified than me to confirm it but my memory is telling me that early Dublo 1st radius was between 12" and 13" or so. If correct I'd expect an accurate curve in this region to work ok.

Wonder what Roco 2nd radius is? Based on a 1st radius of 9.8" I doubt if it would be more than 13" or so.

 

Others on here are better qualified than me to confirm it but my memory is telling me that early Dublo 1st radius was between 12" and 13" or so. If correct I'd expect an accurate curve in this region to work ok.

[Ian Kirk]

Hi,

 

Two rail Hornby Dublo was 15" radius. Triang was 13.5".  Remember though that they had flangeless driving wheels on the centre axle so were really all 0-4-0 (bogies etc were really like a separate vehicle).

 

Builders of real life industrial locos and 4 wheel wagons specified one chain radius (66ft) which works out about 9" but remember that real trains would creak around these at less than walking pace. When John Cameron had the A4 Union of South Africa on his farm I was one of the local enthusiasts that helped out.  The point leading into it's loco shed (ex colliery track) was far too tight but 160 tons of loco and tender just re-gauged the track to suit. The sounds of this being done had to be heard to be believed. Model locos just can't do that.

 

best wishes,

 

Ian

[shortliner]

You also need to remember that the ROCO Radius 0 curves were intended for very short wheelbase 0-4-0 locos, or slightly longer USA Bogie vehicles and trams/freight motors/interurbans - if you are using longer fully flanged locos, even fitting guard rails through the curve is almost certainly going to prove unworkable

[GreenDiesel]

You also need to remember that the ROCO Radius 0 curves were intended for very short wheelbase 0-4-0 locos, or slightly longer USA Bogie vehicles and trams/freight motors/interurbans - if you are using longer fully flanged locos, even fitting guard rails through the curve is almost certainly going to prove unworkable

Thanks. So these 250mm radius curves are called Radius 0 by Roco? I also found some 350mm radius set-track curves for sale on Roco's website...

 

At any rate, while most of my Dublo locos won't run through these curves, my son & I have been able to get most of our Triang locos (Princess Elizabeth, B12, Winston Churchhill, etc.) to run through them.  :-)  I was really happy about this and wish I had taken the time to discover this earlier.

 

Rob

[shortliner]

Yes - but I think you may only be able to pick them up second hand - possibly from ebay - maybe the French, German, or Austrian versions of the site - I think Roco themselves stopped making them some time ago - I had some but passed them on to a member who was looking for them some while ago. You should also be aware that some of the early Setrack from PECO was a much tighter radius than currently - I have some curved points that are considerably tighter (and shorter!) than the current ones - again found on ebay

[Il Grifone]

This has been asked before, but basically Dublo needs every bit of its 15", the Duchess in particular*. Tri-ang (and Trix) will stand sharper curves (probably thanks to their 'steamroller' wheels). Most makes seemed to settle on something around 360mm (roughly 1st radius). I have some sharp radius Rivarossi track, but since it came in a set with their B&O 0-4-0ST, two 40' freight cars and a bobber caboose, it isn't typical (standard Rivarossi radius is 400mm ).

 

Sharper curves really require gauge widening, which rules out any flexible track.

 

* The awful 1950s 3 rail wheel profile (all square - the earlier mazak and later nylon wheels are better in this respect) does not help either - the Dublo rounded railhead mitigates its effects to a certain extent, but binding is likely on track with a normal square head.

[corneliuslundie]

I was going to mention gauge widening. It is done on the prototype on sharp curves, I believe. When I build EM track using a triangular gauge it gives gauge widening automatically, the sharper the curve the greater the widening. Had you thought of building your own track for just the sharp curves? With suitable gauges it's not hard, but just roller gauges won't give you the gauge widening.

 

The other thing if you want to get stock round sharp curves is to have some kind of transition curve between the straight and the sharpest curve. It will make it much more likely that things will stay on the track. But again this means building your own track. But of course it takes more room.

 

If you really want to see what is possible look at some tram layouts. Corners rather than curves!

[34theletterbetweenB&D]

It's a good many years ago I did this, but there was no real difficulty getting a Bachmann WD 2-8-0 around carefully laid Hornby R1 set track. The old Bachmann split chassis Jubilee was still 'loose' on this radius - very narrow chassis block deriving from its Mainline origins - so it had plenty of sideplay on the driven wheels.

 

Selected locos will run on far smaller radii, bo-bo types a real winner here; the Bachmann class 20 I tried was quite happy just below 12" radius. The gauge was about 17mm, made the track by dividing some Gem TT flexi, and laying each half on drawn curves. Far easier to form true sections of a circle with just one coninuous rail to bend at a time, and a single 36" length connected to the Peco Y point defined the outer rail radius.

[GreenDiesel]

It's a good many years ago I did this, but there was no real difficulty getting a Bachmann WD 2-8-0 around carefully laid Hornby R1 set track. The old Bachmann split chassis Jubilee was still 'loose' on this radius - very narrow chassis block deriving from its Mainline origins - so it had plenty of sideplay on the driven wheels.

 

Selected locos will run on far smaller radii, bo-bo types a real winner here; the Bachmann class 20 I tried was quite happy just below 12" radius. The gauge was about 17mm, made the track by dividing some Gem TT flexi, and laying each half on drawn curves. Far easier to form true sections of a circle with just one coninuous rail to bend at a time, and a single 36" length connected to the Peco Y point defined the outer rail radius.

Yes, I've noticed similar things. So far, most of my Bachmann and Hornby pacifics and 4-6-0's run very well on my 14"R track (not sure if I'm damaging them though!). And my new Bachmann 08 Diesel runs smoothly on the 10"R curves.

[stewartingram]

Probably completely off topic, but I'll relate a story of a layout built by a friend of mine quite some time ago.

 

He obtained (in one of his infamous "deals" a large handful of the old Wren fibre based track. Now not being one to waste anything, he built a layout with it, on which he could run some of his Continental" stock. Some of this was stud contact Marklin AC; I converted those (quite simple to do) to be standard 12v DC, so the layout became 3-rail by adding a 3rd rail soldered to brass pins. (At a later date we converted it back to 2-rail for an English layout using Hornby-Dublo locos, but that is another story).

At least one of his locos was an eight coupled tank (may have been an 0-8-0T or 2-8-2T), fully flanged, rigid wheelbase. That loco went everywhere on the layout

Smallest radius curve we measured at 8" radius!

 

Stewart