Minimum Curve Radii?

Here's something using O-54 ScaleTrax and O-54 turnouts. I'm not a big fan of "island" layouts as the larger ones have a reach problem. What kind of room are you looking at using? You may be able to put in an around-the-walls layout with larger curves and better viewing.

Regardless of the minimum radius that your engine will handle, most here would say "go with the widest curve that will fit.  It will always look better."  I'm not really up on who makes what curves.

It'll be in a room thats 8 feet wide by probably 10' deep.  I wasn't planning on doing an "around the wall" layout, but.. I'm not opposed to it.  I thought about only using the 8' wide by 6' deep space, but if that doesn't accommodate a good curve, other suggestions work.  I definitely do not want any tight curves, but I also dont want just a simple oval

That's the real trick. Confined space is the challenge in our chosen scale. It can be difficult, but not impossible to overcome.

Believe it or not, you can have a simple oval, but in an "around the walls" configuration, you can only view one sector of the layout at a time which by itself makes the layout appear larger. Operating at reduced speeds enhances that appearance. This is further enhanced by "hiding" the train in some areas using buildings, trees, or tunnels (even further if you can set up a "two-lap" oval.) If you can provide a drawing of the room indicating where the door(s) is/are I might be able to give you some ideas on around-the walls. As TrainsRMe said, when it comes to curves on a layout, go with the widest curve that will [reasonably] fit.

Wide curves, limited space and O-gauge are a challenging combination!

Ace,

Understood, I was planning on waiting until I had more room, but I dont think that will happen for years, so I have to make-do with what is there!

Matt,

Here is a layout and dimensions of the room.

Mike

Here's the first crack at a continuous run. While it's small, you still can't view the entire layout. There's a storage yard/industry at the lower left, run-around capability, and a second industry in the interior. It's all O-72 with a #4 turnout in the lower left. As you can see from the 3D rendering, there's an elevation change which separates the main line from the passing/run-around. Grades are roughly 3%. This is the smallest continuous layout with O-72 I've ever taken a crack at. I've used MTH ScaleTrax in both examples.

There's the other option -- point-to-point/switching. Here's a basic one that allows for run-around and switching of two industries. In Britain, they do switching decks (called shunting layouts) that are very small because space is at a premium. They benefit from shorter locomotives and rolling stock, so a freight "wagon" is typically only 20 feet long (5" in O scale.) As above, the minimum is O-72, but the outer curves are O-80 with a 1/2" extension of the straights to give more clearance.

I just realized I screwed up on the dimensions. I have the height at 9'4" as opposed to 9'10", so an additional 6" can be added to the height of each design.

That's nice work, Matt. A U-shaped layout allows wide curves in a limited space, and an optional bridge would give a continuous-run option.

When I started out in HO decades ago, I accepted that I would have to use an 18" minimum radius standard to have a continuous-run layout in a reasonable space, especially because this was before I had a permanent residence. I simply gave up the idea of running scale passenger trains because they needed much wider curves to look right. I initially limited my trains to 40 foot cars and 4-axle diesel power, although I eventually stretched my rules to include 50 foot cars and six-axle diesel power, after learning that they would operate OK and not look too bad on curves with easements.

I would suggest to Mike that you consider using O31 or O36 curves in your limited space, and use smaller equipment to suit. The U-shaped space could then accomodate a big bent dogbone track plan. Your SD70 and larger cars could stay on the sections with the wider curves and avoid the end loops, if necessary.

You could put the O31 or O36 end curves in tunnels so you wouldn't see them, and the visible track would have wider curves. Some of the larger trains will still manage the sharp curves, even though they may look silly doing it.

If you are OK with a switching layout instead of continuous-run, you could have switchbacks with tracks at different elevations to fit in more track and operating variety. But it sounds like you want mainline operations with intermodal cars.

Thanks Matt, I'm liking the first layout example.  I've never thought of that.  I guess I could also build some type of bridge the opening of a U type layout.  I'm thinking I'd be better suited with a continuous-run layout.  Ace, so are you saying put the smaller radius curves in tunnels?  Also, that is correct, I'm aiming for "mainline" operations with both intermodal on one train and TTUX on another.  Hopefully I can fit 2 on one layout.

That's just a possibility for you to consider. Not necessarily in tunnels, but hidden from direct view and preferably still easy to access.

Let me ask the question, what is the minimum radius that your trains will actually run on reliably? As opposed to, what is the minimum radius you want for an 'acceptable' appearance?

I have an HO layout with a long double-ended yard on a shelf, originally dead-ended. I decided it would expedite my train operations if I could turn trains around on a turn-back loop instead of having to always switch locos and cabooses from end to end. My minimum radius standard on the visible mainline was 18", but I didn't want to make the end of my yard shelf that wide. I already had a mostly hidden reverse loop with 15" minimum radius and most of my trains handled that without problems. Anyhow, I ended up making a turn-back loop at the end of my yard with a 13" minimum radius, and nearly all of my HO equipment can handle it reliably. I've gone against the "conventional wisdom" of "acceptable" curve standards, but it works for me. I've disguised the sharp-radius turn-back loop with scenery. I can turn trains around easily in a limited space.

Many of the O-gauge trains will actually take relatively sharp curves like O31 or O36, they just don't look doing it. If sharp curves are just a minor portion of the total trackage and are hidden from view, and they give you a continuous run option in a limited space, then it's something to consider.

Ace,

I actually do not know what the minimum radius they will run on is.  That is sort of where I was going with this thread.  Appearance to me, because of the limited space, is second to, what is the minimum they will run on.  The 3 older Lionel I have are a Chessie System GP-20 #8463, Steam Locomotive 2035, SW-1 Switcher #8154, and this weekend will be buying the MTH SD70ACE.  Freight cars will be traditional Lionel and MTH RK.  I like the idea you have with your HO, do you think that'd be possible with O?

Thanks,
Mike 

The Lionel locomotives you described will run on O-31 track, but the appearance won't be that good. Your Rail King SD70ACe will also run on O-31 track as well. If you stay within the Rail King line (including Imperial) and "traditional" Lionel you can safely run the equipment on O-54 curves. All of the manufacturers list the minimum curve size required for a particular piece of equipment, so there's little risk of getting anything new that won't run on your layout. My recommendation of O-72 is because every piece of 3-rail equipment produced to date can run on O-72 curves, including very large scale-proportioned equipment.

A secondary advantage to an "around the walls" style of layout is that trains are viewed from the inside of curves which is aesthetically better than seeing the outside of the curve where the sharpness and equipment overhang are much more evident.

I'll take another look at my initial design using O-54 and see what I can come up with that you can use as a starting point.

Matt, I never thought of that inside the curve" view advantage.  You are right.  I just have to do an around-the-wall next time.

I agree.  Matt, I like that idea.  Also, thank you, your information on the curve diameter helps a bunch.  Maybe I'll end up sticking with something like that.  My only thing with the "horseshoe" is that I'm not sure how I'd turn the locos around.  With that in mind, I'm thinking of a bridge or something like you have on the design above to cross over the gap

In a practical sense, you don't have to turn diesels, especially road and yard switchers. A prototype example of this was SP's Torrance Branch run as they ran North cab-forward and South hood-forward, but your larger diesels modernly run cab forward, with the last unit in the locomotive consist running hood-forward. At the end of the run, they just run the consist from the other end. Any arrangement to turn locomotives consumes a lot of space, whether a turntable or wye. A wye can sometimes be stuck in a corner of a layout with the "tail" sticking into the corner space of the room. Tricky, but not impossible; the tail limits the size of the locomotive you can turn.

In an ideal world, the most efficient (space wise) wye is an equilateral triangle. With sectional track, sometimes the turnouts to do this (wye turnouts) aren't readily available in smaller sizes. Ross makes two -- an O-72 curve-replacement wye, plus an 11-degree wye (+/- 5.5 degrees); Atlas, MTH, and Lionel make an O-72 wye (+/- 11.25.) To the best of my knowledge, no one makes one in O-54. So you have to improvise and make a "pinwheel" wye that roughly duplicates the geometry. So you use a left (or right) hand turnout, add curves to extend the angle of divergence out to 60 degrees, then duplicate it. Put a tail on one end and integrate the other sides into your layout. Great on paper, but still takes up quite a bit of space. In trying to fit an O-54 pinwheel wye into the layout space, I ended up turning the layout into a two-lap with the wye at the lower level and crossed by a larger curve above. The bridge section across the entry would have to be a lift-out since the straight tracks are on grades. The construction actually wouldn't be that difficult since straight pieces are involved. Grades are pretty steep with one being at 4%, but since the trains are shorter, this isn't as much of an issue. Viewing is from the inside, so overhang isn't really visible.

Matt's design above is real good for wide curves in limited space. Some possible modifications would be to use a more compact turntable instead of a wye, add a long siding to hold a second train, and make it all flat instead of 4% grades.

The plan below illustrates my dogbone idea for a similar space (rough draft in 10'x 10'). It uses O36 turnback curves for equipment that can handle the sharper curves, while wider curves are used for better appearance on the main part of the layout. The advantages to this are:

* easy layout access with no moveable bridge required

* trains look good on sweeping wide-radius S-curves

* trains go back and forth across the main part of the layout, breaking the circular pattern

I've used this idea on some of my own layouts in HO and O. I previously explained how I make a distinction between minimum radius requirements for operation vs. appearance. 

Both of these are great ideas, thanks guys.  I'm still a fan of the "continuous run" though.    

Matt, would it be possible to have 2 sets of freight on that type of layout?

Ace, I like this idea.  I may actually look into this a little bit.  I agree, especially with the freight that I'll be running, it would look good on the long s curves.

The run is long enough to support two trains if you're running under command control. That design is preliminary and I'm sure a siding could be cut in there somewhere. Ace's design actually works better on a couple of fronts. While the curves are sharper, you don't have to contend with a lift-out/duck-under. Atlas and FasTrack are available in O-36 while the MTH ScaleTrax is only available in O-31, O-54, and O-72. Also, his design actually provides better operation as opposed to mine which is more of a "let's watch the trains run through scenery" type layout.

If you decide on a simple oval design to start, I used smaller diameter curves on the back side, and then wider curves on the viewing side if you will.  That way the two curves up front will look much better and you can't see the far away curves as well or they may be hidden by buildings.  So you could use for example O-96 up front and O-72 in back.

This is a rough draft for a flat oval with yard and a diverging line up a long 4.5% grade to an overhead reverse loop. The lower level has room for more spurs. The long grade gives an operating challenge and a substantial mainline with relatively wide curves in a small room. Curves are O54 minimum. There are two single-track moveable bridges across the room entrance. The upper reverse loop can hold two trains.  

Here out west I've been inspired by some of the railroads with long mountain grades.

The grade down from the reverse loop could be reduced by almost half if the entire loop along with all elevated trackage was on the same sub 3%% flat grade. 

A digital inclineometer like Norms choochoo stuff sells can be very helpful on a winding  right of way.

For clairity: Level is flat but flat does not have to be level it just has to be flat. 

Any perfectly consistent grade is flat.

When working with a room of this size I have found it imperative to reduce or eliminate level or reduced grade upper return loops.  Even the five foot long section of upper track in the lower left corner that runs from over/under to over/under can best be installed flat without vertical curves in a non level fashion. 

A perfect grade will make operation much more enjoyable.

Like Matt I am no fan of Island layouts although I dismantled a 12 year old 15x23 Island operation in October 2009 that I enjoyed, it had several access pop ups and a Drop Section entry to a central Yard and Wye. With advancing age and health issues it had become a chore to access,run and maintain.

Anyway the Domestic CEO was running me out of the layout space [upstairs in our Condo]in favor of her TV and Excercise Room. I had recently also dismantled a 5-track, 14x32, twin shelf operation at our mountain cottage when we moved back to the City for more specialized Med facilities.

Moving down the hall to a 9x19 attic room over the Condo Garage I built a round-the-wall 9x16 layout and following my "Druthers" it has double track mains with wide 072/084 and 084/096 end-curve arcs, a Service Yard on one side and hopefully [sometime] a Village on the other. Originally the two far corners were left open as access triangles because of long reach but now are build-sites of a Denim Mill and and a Sawmill/Lumber Yard[unreachable now except from a temp raised work platform]. My track is all recycled Gargraves Flex with Ross, Tortoise operated, turnouts.

A year ago I scratch-built a Lumber Shed but bascially hand tremors have limited my fabrication work and I am increasingly relying on folks such as Joe Fauty of Model Structures, Harry Heike's great work and structures such as the Ash and Cinder Lift Tower and a Curved Depot from David Duhmel. 

I enter the layout interior via a long ago Jim Barrett designed Drop Section that I recycled and rebuilt as a fake plate girder bridge. "Ducking Under" in my '80s is not now as efortless as in the past. The Service Yard with its Enginehouse and 6 Towers is 40" wide and the Village side is 36". I can reach them.

In the same sense that Matt noted I hope to use structures, fronts, etc, and landscaping to distract from the "track loop effect" plus running shorter trains and comparatively slow. I can now only turn trains via my 0-5-0 "switcher"and it is not feasible to build an elevated  second level due to the roof pitch begining at 54" high[layout @ 42"h.].

The layout work has been on hold for quite awhile now due to some health problems but will soon resume as I complete rail side rust painting and ballasting a short section on the Village side.

Photos provide a glimpse of the initial raw benchwork, Service Yard side and the far corners.

Ace,

So at the "summit of grade" is that switch on the 4.5% grade?  I kind of like this idea.  I'd probably go with less of a yard, only because that would give me more room for buildings, roads, etc.  What would you do at the entrance of the room, some sort of gate?  The elevated reverse loop, would you just use trestles?

Matt,

That's ok if I have a layout that is "just watch the trains run through scenery."  I dont mind that idea at all.  

 Dewey,

I like your layout, looks good! 

Dewey, my thoughts about this plan were to have two moveable bridges across the room entrance, with the uppermost level of track high enough to walk under. If the lowest track level was made about 54" high with thin roadbed across the doorway, you could easily roll under it while seated on a wheeled desk chair so you wouldn't always have to move the bridges. High benchwork gives good train viewing while standing and also leaves more room under the layout for workbench, bookcases, computer desk, etc. High benchwork makes it possibile to multitask the room. Of course, choice of benchwork height depends on your personal preference. Moveable bridges for the track across the door would allow easier access to the room when you aren't running trains.

The 4.5% grade on my first plan gets the track from the main level to the overhead reverse loop with only one additional bridge across the room entrance. The overhead reverse loop is relatively flat for easier construction AND safer operation of trains through the sharper O54 curves with 180° + curves; I didn't want to create additional risk for "bowline" derailments overhead. Where the entire train is on the 4.5% grade it has wider O72 curves of 90° arc. Trains headed uphill would take the straight path through the switch into the reverse loop. The reverse loop is big enough to hold two trains, so the switch end looks ike a passing siding.

I know that a lot of guys will criticize the steep grade, but for your size of room a steep grade gives more vertical separation between the levels of track in the course of one lap around the room, and minimizes the additional bridges across the room entrance. A dramatic grade gives some visual interest and operating challenge. I have similar grades on an HO layout.

If you like to run trains in the modern style, you could use "distributed power" with locos on the head and tail end of each train. It would eliminate the possibility of uncoupled cars running away down the grade. Locos on each end of a train would also make it easy to return trains without the overhead reverse loop. The uphill end of the track could simply be two tracks on a shelf to represent one end of a siding, with one train waiting to head downhill while another train heads uphill. Or the uphill end of track could be a double-ended siding to allow the head-end power to be run around the train. The minimum radius for the layout could be larger without the reverse loop.

I'll work up a modified and simplified plan for you to think about ...

A simplified plan without the overhead reverse loop as discussed above. The grade is reduced to 3.6% and the upper "terminal" is about eye level. The upper terminal is intended to represent one end of a passing siding, and provides staging track for another "distributed power" train. The upper "terminal" could have another switch (or transfer table) at the end for running locos around the train, although that would reduce siding capacity. The minimum radius is still O54 but most of the curves are wider.

The purpose of this plan is to provide relatively wide-radius mainline running in a small room, beyond a basic oval, without overly complex construction.

Ace,

Wow.... you've put a lot of time into helping me, it is truly appreciated.  I like these designs a lot.  I think the one with the steeper grade is nice, simply for the fact that I wouldn't have to worry about turning anything around.  I don't know if I'd be comfortable with the distributed power idea either.  With the one that has the reverse loop, when the train is on the main level, how would it turn to go back up the grade to the second level?  Or am I missing something?

Thanks!

Mike 

You'll have to run the power around the train to run them back up the hill. Unless you want to spiral another track down into the basement for a reverse loop under the floor ... LOL 

If you want easier continuous running with wide curves in that space, it brings you back to an oval or double-oval arrangement?

A double-track oval in an 8'4" x 9'10" room with O60 minimum curves. By using the underpass track and the crossover, two trains can cruise around in the same direction on a three-lap configuration. Or two trains can run independently on the single-lap flat ovals. The grade on the underpass track is 3.3% with a railhead-to-railhead clearance of 6 inches. The room entrance is by the bridges. Drawn with SCARM free track-planning software using Lionel FasTrack.

Grade on underpass track is 3.3%, other tracks are level.

Thanks Ace,

I couldnt go any lower with a spiral into the basement....as this is in the basement and it'd be hard going through the concrete 

I'm liking the idea above, but I also like the layout of the bottom level on your post from yesterday (3 pictures up).  I thought maybe one less loop, unless that was a yard-type area.  Are you designing these in SCARM?

Thanks,
Mike 

Yes Mike, the 3-D images are drawn with SCARM.

Here is another idea for you: If the layout is shortened, you could walk into the room far enought to operate the layout without having to duck under or move the bridges.

Grade on underpass track is 3.5%, other tracks are level.

The "underpass track" could be built as an overcrossing instead, which would be easier to construct on top of an otherwise flat table. However, operationally an underpass is somewhat easier to operate because the train will speed itself up going downgrade and that helps carry it uphill beyond the underpass. Also, when the rear part of the train is still going downhill it helps push the front part of the train uphill. Whether you choose an underpass or overpass also depends on what visual effect you might prefer. In this case, a curved overbridge on a shallow skew angle wouldn't look so good IMO.

Ace,

I forgot all about you posting another layout...
I just looked at it again and I'm pretty sure it was playing with my eyes!  I like the tunnel concept and now I see why there are the two tracks that end, so that one train can sit while the other makes its rounds.  I dont know why I didnt realize that before.  Anyway, the grade... how do you figure out the % grade compared to the angle?

Thanks,
Mike 

Mike, I added some info about the grades and etc in the previous posts.

Here is an idea for a layout with no duckunder, except for access to the far side of the layout. Figure-8 mainline is level with O54 curves, with a 5% grade down to a hidden reverse loop with O48 curves. The lower and upper tracks have 6" clearance, railhead-to-railhead. Grey areas are open floorspace.

Ace:

Nice design. You can reduce the grade a little by starting the grade at the crossing on the upper level. Or you can continue the grade through the turnout on the lower level. The trick will be setting things up so the turnouts aren't twisted.

Thanks Matt. Yeah, the grade could be reduced considerably if it was split with the mainline circuit, it just depends how a guy might want to build it. I thought it might be handier to have the figure-8 mainline all flat. Trying to maintain that wide radius in a small room really limits the track plan options. My personal preference in that size of room would be the U-shape shown previously, with tighter curves. When space is this limited I think it makes sense to scale back to smaller equipment and tighter curves - personal preference.

So then, I'm assuming a 4.5% grade is too steep?  Does that mean the loco would have a difficult time pulling the train up the incline?  Also, from what Matt said, is it ok for the turnouts to be on the grade?

Mike, it's really a personal preference thing. I run some long HO trains on 5% grades reliably. Abrupt vertical curves in the track should be avoided; they can cause coupler separation and possibly loss of traction with loco wheels. Some guys here are opposed to grades over 2% or so, but I say the real test is, with what standards can you achieve reliable performance AND achieve other goals with your train operations and track plan ambitions in a limited space?

Before you commit to building any layout plan, I suggest that you set up at least a trial oval with the minimum-radius curves that you expect to use, and run your full-length trains on that to see how it looks to you. From what you've said previously, I'm not sure that you've acquired all the cars for the trains that you are thinking about running. With the size of room that you have available, I would caution you not to acquire a bunch of equipment that needs wide-radius curves for good appearance and reliable operation, especially if you want to fit a continuous-run track plan into that space.

For a starter layout you may want to build it all flat, then you can experiment with building temporary track on grades to see how well it works for you. These are my suggestions, and hopefully others will offer you additional ideas to consider.

Mike,

Basement. So can you cut a "window" into one of the walls for viewing?