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Track Radius Question

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  • jamesc0ldicott
    Hi All, I m finally getting some space for a proper layout instead of my normal shelf style layouts. Am in the early planning stage and looking for some input
    Message 1 of 6 , Sep 8, 2007
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      Hi All,

      I'm finally getting some space for a proper layout instead of my normal shelf style layouts.

      Am in the early planning stage and looking for some input on minimum curve radius.
      Obviously there is no fixed answer except to go for the largest available but thought I'd
      see if anyone has comments on what has or has not worked for them in the past.

      The layout is an industrial scene and will not use loco's above 0-6-0 wheel configuration
      though mainly 0-4-0 types and possibly 0-4-2's.

      Any input appreciated

      James
    • David Woodcock
      Since I haven t seen any other replies to the question about minimum practical track radii, I thought I might throw my hat into the ring. One or two people
      Message 2 of 6 , Sep 11, 2007
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        Since I haven't seen any other replies to the question about minimum
        practical track radii, I thought I might throw my hat into the ring.

        One or two people have built working, exhibitible layouts (eg Arthur
        Budd's The Works) with absolute minimum curves which on the prototype
        would never have been loco worked. These layouts can be fun but never
        look right and my advice is to ignore this approach.

        The minimum I would consider for traction use would be the so-called
        type 2 (36 foot centreline) radius curves which, with careful
        planning, can be used with the smaller i/c locos eg
        RCL Ruston LAT/LBT
        RCL Lister
        Wrightlines 20hp SImplex
        Nonneminstre O&K
        This radius equates to 252mm in 7mm scale - so a plain circle would
        fit within a two foot square.

        The major problem is always end-throw on curves, but these locos have
        a short wheel-base AND short overhangs at each end and will work with
        similarly-sized rolling stock items provided that care is taken to
        always include a straight length between any reverse curves. You
        might get away with larger locos - eg Wrightlines 44/48hp Ruston or
        the erstwhile Chivers Diema - if the couplings are flexible enough.

        Most small steam locos, whether 0-4-0, 0-4-2 or 0-6-0, present a real
        problem because of the length of the overhang at the cab end although
        there are one or two prototypes - eg the smaller "quarry" Hunslet
        0-4-0s or Peckett's Jurassic class 0-6-0s - where the imbalance of
        front and rear overhang is minimal.

        The French Military "Systeme Pechot" defined a number of standard
        curve radii, viz.
        1) 7m63, or about 25 feet, for non-traction use only
        2) 20m, or about 1 chain, mimimum radius for traction use (about 18
        inches in 7mm scale)
        3) 30m, or about 1.5 chains
        4) 50m, or about 2.5 chains
        5) 100m, or about 5 chains - generous for 60cm but tight for standard
        gauge!

        The 20m prototype radius (460mm in 7mm scale) looks OK in model form
        and will allow most small "industrial" locos, whether i/c or steam,
        to operate providing that care is taken to minimise overhang problems
        by providing flexible couplings and avoiding reverse curves. You
        might still wish to experiment to check that a proposed layout is
        workable before committing to final construction.
        A plain circle of this radius will just fit within a metre square.

        David Woodcock
      • John Clutterbuck
        ... curve radius. Further to David s very interesting reply, I have one very tight curve of 35cm radius on the mainline of my common carrier style layout.
        Message 3 of 6 , Sep 12, 2007
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          --- In O-14@yahoogroups.com, "jamesc0ldicott" <james_coldicott@...> wrote:
          >
          > Am in the early planning stage and looking for some input on minimum
          curve radius.

          Further to David's very interesting reply, I have one very tight curve
          of 35cm radius on the mainline of my common carrier style layout.
          According to my fictitious prototype theory this is only meant to be
          traversed by small wheelbase locos and the K1 Garratt, however my
          scratchbuilt L&B 2-6-2 will usually get round it without mishap. I
          used a super elevation of about 1mm, gauge widening of about 0.75mm
          and installed a functional check rail at a distance arrived at through
          trial and error. All my locos are compensated or sprung which I also
          think helps a lot.

          Regards
          John
        • Arthur Budd
          From: David Woodcock ... Can I just clear up a bit of confusion here. My recently retired exhibition layout, which uses Type 1 turnouts and 3.5 inch radius
          Message 4 of 6 , Sep 12, 2007
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            From: "David Woodcock"

            > One or two people have built working, exhibitible layouts (eg Arthur
            > Budd's The Works) with absolute minimum curves which on the prototype
            > would never have been loco worked. These layouts can be fun but never
            > look right and my advice is to ignore this approach.

            Can I just clear up a bit of confusion here. My recently retired exhibition
            layout, which uses Type 1 turnouts and 3.5 inch radius curves (or corners as
            some have refered to them) is called "The Brickworks". I have always
            acknowleged that in reality locos would never have been used on such tight radii
            but modeller's licence applied. Whether it "looks right" I leave to others to
            decide.

            "The Works" is another, much larger, layout superbly built by David Barham and
            featured in issue 44 of NG&IRM Review. As stated in his article this layout uses
            Type 2 turnouts and a minimum radius of 10 inches on curves. Although I have
            never seen this layout in the "flesh", the photos in the Review show that this
            does indeed "look right"!

            Arthur Budd
          • Roy C Link
            My own 0-14 layout NG Sand & Gravel uses Hudson type two (37ft radius) turnouts and curves. This is what I would recommend for internal combustion
            Message 5 of 6 , Sep 12, 2007
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              My own 0-14 layout 'NG Sand & Gravel' uses Hudson 'type two' (37ft
              radius) turnouts and curves. This is what I would recommend for '
              internal combustion industrials', though 'The Brickworks' provided a
              fine example of just how good a layout may be obtained using small
              radii track.

              The reason why the RCL kits run well, even on 'type one curves' (13ft
              3in radius - ) is that the prototypes modelled, have similar wheelbases
              and similar lengths. Thus the problem with regard 'overhang' is largely
              obviated, even on very sharp curves. The curved end frames of the
              'Rugga' pattern chassis (on which all the rolling stock is based)
              assists here, also. Add to this a constant wheel profile and properly
              worked out standards. There should be no surprise, therefore, that it
              works, if properly executed.

              Note that the Hudson 'semi-portable' track system measured the radius
              to the inside face of the outer rail.

              Steam locos, even the small ones, like the Kerr, Stuart & Co., Ltd
              0-4-0ST 'Wren' almost invariably have unequal overhang, that at the
              rear greatly exceeding that at the front. Even on 'type' two curves'
              this moves the coupler centre way out from the track centre line.
              Unless the following vehicle has a similar overhang - it gets dragged
              off the track. The only way to avoid this, is to use wider radii curves
              (say 45cm) or use articulated couplers, like Kadee. Even if you do use
              the latter, they will probably only couple and uncouple properly on
              near straight track.

              For most applications, if you have the room, I would recommend a
              minimum of 45cm and preferably 60cm. Even on the narrow gauge, curves,
              though much sharper than standard gauge lines (which was one of the
              supposed advantages of NG) were still kept as generous as the
              topography allowed. Curves mean friction and friction means wear and
              more fuel consumption. Bogie stock helps - but not too much if the loco
              does not run on bogies as well. The overhang of some of the larger 2ft
              locos in the UK still pose problems on radii under 45cm.

              Ultimately, asking "what is the minimum radius I can use" is a bit like
              asking "how long is a piece of string". Radii depends on so many
              variables - not least what locos and stock are being proposed and what
              space you have to model in.

              Roy C Link

              www.narrowgaugeandindustrial.com

              On 12 Sep 2007, at 10:21, Arthur Budd wrote:

              > From: "David Woodcock"
              >
              > > One or two people have built working, exhibitible layouts (eg Arthur
              > > Budd's The Works) with absolute minimum curves which on the
              > prototype
              > > would never have been loco worked. These layouts can be fun but
              > never
              > > look right and my advice is to ignore this approach.
              >
              > Can I just clear up a bit of confusion here. My recently retired
              > exhibition
              > layout, which uses Type 1 turnouts and 3.5 inch radius curves (or
              > corners as
              > some have refered to them) is called "The Brickworks". I have always
              > acknowleged that in reality locos would never have been used on such
              > tight radii
              > but modeller's licence applied. Whether it "looks right" I leave to
              > others to
              > decide.
              >
              > "The Works" is another, much larger, layout superbly built by David
              > Barham and
              > featured in issue 44 of NG&IRM Review. As stated in his article this
              > layout uses
              > Type 2 turnouts and a minimum radius of 10 inches on curves. Although
              > I have
              > never seen this layout in the "flesh", the photos in the Review show
              > that this
              > does indeed "look right"!
              >
              > Arthur Budd
              >
              >
              >

              [Non-text portions of this message have been removed]
            • Professor Klyzlr
              Dear O-14 crew, While I recognize that it s around 6 too wide in gauge, similar questions are what prompted the creation of the On30 Minimum Radius List.
              Message 6 of 6 , Sep 13, 2007
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                Dear O-14 crew,

                While I recognize that it's around 6" too wide in gauge, similar
                questions are what prompted the creation of the On30 Minimum Radius
                List.

                http://www.geocities.com/loggingloco1/NineMile/On30Loco_n_Car_Radius.P
                DF

                All of Roy's comments RE the actual mechanics and physics of coupled
                stock are very well founded, and the points should be well heeded.
                Maybe a similar list could be collated for the "more common" O-14
                locos and kits?

                Just a thought, from someone who has pondered such things
                previously...

                Happy Modelling,
                Aim to Improve,
                Prof Klyzlr



                --- In O-14@yahoogroups.com, Roy C Link <royclink@...> wrote:
                >
                > My own 0-14 layout 'NG Sand & Gravel' uses Hudson 'type two' (37ft
                > radius) turnouts and curves. This is what I would recommend for '
                > internal combustion industrials', though 'The Brickworks' provided
                a
                > fine example of just how good a layout may be obtained using small
                > radii track.
                >
                > The reason why the RCL kits run well, even on 'type one curves'
                (13ft
                > 3in radius - ) is that the prototypes modelled, have similar
                wheelbases
                > and similar lengths. Thus the problem with regard 'overhang' is
                largely
                > obviated, even on very sharp curves. The curved end frames of the
                > 'Rugga' pattern chassis (on which all the rolling stock is based)
                > assists here, also. Add to this a constant wheel profile and
                properly
                > worked out standards. There should be no surprise, therefore, that
                it
                > works, if properly executed.
                >
                > Note that the Hudson 'semi-portable' track system measured the
                radius
                > to the inside face of the outer rail.
                >
                > Steam locos, even the small ones, like the Kerr, Stuart & Co., Ltd
                > 0-4-0ST 'Wren' almost invariably have unequal overhang, that at
                the
                > rear greatly exceeding that at the front. Even on 'type' two
                curves'
                > this moves the coupler centre way out from the track centre line.
                > Unless the following vehicle has a similar overhang - it gets
                dragged
                > off the track. The only way to avoid this, is to use wider radii
                curves
                > (say 45cm) or use articulated couplers, like Kadee. Even if you do
                use
                > the latter, they will probably only couple and uncouple properly on
                > near straight track.
                >
                > For most applications, if you have the room, I would recommend a
                > minimum of 45cm and preferably 60cm. Even on the narrow gauge,
                curves,
                > though much sharper than standard gauge lines (which was one of the
                > supposed advantages of NG) were still kept as generous as the
                > topography allowed. Curves mean friction and friction means wear
                and
                > more fuel consumption. Bogie stock helps - but not too much if the
                loco
                > does not run on bogies as well. The overhang of some of the larger
                2ft
                > locos in the UK still pose problems on radii under 45cm.
                >
                > Ultimately, asking "what is the minimum radius I can use" is a bit
                like
                > asking "how long is a piece of string". Radii depends on so many
                > variables - not least what locos and stock are being proposed and
                what
                > space you have to model in.
                >
                > Roy C Link
                >
                > www.narrowgaugeandindustrial.com
                >
                > On 12 Sep 2007, at 10:21, Arthur Budd wrote:
                >
                > > From: "David Woodcock"
                > >
                > > > One or two people have built working, exhibitible layouts (eg
                Arthur
                > > > Budd's The Works) with absolute minimum curves which on the
                > > prototype
                > > > would never have been loco worked. These layouts can be fun
                but
                > > never
                > > > look right and my advice is to ignore this approach.
                > >
                > > Can I just clear up a bit of confusion here. My recently retired
                > > exhibition
                > > layout, which uses Type 1 turnouts and 3.5 inch radius curves
                (or
                > > corners as
                > > some have refered to them) is called "The Brickworks". I have
                always
                > > acknowleged that in reality locos would never have been used on
                such
                > > tight radii
                > > but modeller's licence applied. Whether it "looks right" I leave
                to
                > > others to
                > > decide.
                > >
                > > "The Works" is another, much larger, layout superbly built by
                David
                > > Barham and
                > > featured in issue 44 of NG&IRM Review. As stated in his article
                this
                > > layout uses
                > > Type 2 turnouts and a minimum radius of 10 inches on curves.
                Although
                > > I have
                > > never seen this layout in the "flesh", the photos in the Review
                show
                > > that this
                > > does indeed "look right"!
                > >
                > > Arthur Budd
                > >
                > >
                > >
                >
                > [Non-text portions of this message have been removed]
                >
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