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Gradients, Transitions and Curves - Advise


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I want to build a double track roundy-round folded figure of 8 on a 3m x 3m baseboard in OO. I want to keep the gradients to a minimum of 1:50 and an elevation difference of 70mm based on +35mm to -35mm so that I can run at least a four coach rack.

 

At 1:50 this produces a gradient length for a 35mm change of 1750mm plus 300mm each end for transitions gives a total of 2350mm so this means I cant fit it onto the board without going round a curve.

 

I intend to build flat topped baseboards and build risers off this to provide the elevation changes with the station area being at zero. 

 

So advice please on the best methods of building gradients, transitions and gradients on curves to get a smooth track surface.

 

Richard

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I used the Woodland Scenics foam gradients, which are available at your chosen 1:50., which I used. They curve easily as well, and all my 8 locos (Bachman steam and diesel) handle 4 coaches with ease, even on the curves. But I chose not to start the gradient on a curve, where the friction is greatest. Also, as you say, remember to allow for the transition from level to gradient at the start and finish. Some wheelbases and pickups will not like having front wheels on 2% and rear wheels on level. I found I didn’t need much length in this transition, maybe only 6”, but it does help.

I have a double track roundy roundy in about 3.5m x 2m, which is all level, but a branch off it, running virtually parallel to the twin track, which climbs up to the upper surface 150mm above the lower surface. This allows hand access in case I need it. At the 70mm height difference you mention, remember to allow for track height in this, and also any under board structure (battens, point motors) on the upper level.

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Thanks ITG. Does the Woodland Scenics foam allow for a double track? Does it need any track underlay on top before fitting the track. Probably a silly question as without the ballast would drop through! In which case what did you use on top and how was it fixed.

 

How did you build the transitions? Could the last bit of the Woodland foam be sculpted to achieve this?

 

BTW; I made an error in my original post. The station, goods, and engine shed areas will be at -35mm elevation and not zero.

 

Attached is the rough layout of what I'm thinking. The dark grey area will be fixed and the rest removable  to allow the room to be used as a sitting room on the odd occasion when our son comes home.

Train Room.jpg

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The area you have shown as storage tracks appears to be around 1.4m and with turnouts and reverse curves you will lose a big chunk of that, particularly once you get beyond a fan of two or three lines. I would be concerned that they will be too short to hold trains.

 

Are both the storage tracks and outer loop set at +40mm or is one of them -40mm?

 

If the station/goods yard etc are set at -35mm does the over bridge need to be +80mm or could that be reduced to +45mm?

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That storage needs a rethink.  I would suggest my favourite "Hockey Stick" Traverser but may be I'll keep my head down.    You need a long transition from level to up if you use locos like Hornby T9s, the front wheels can only lift about 2mm in 150mm wheelbase.

The key to gradiients is always measure from Horizontal.  Its too easy to have a baseline at 1 in 150 or even 1 in 100.  Check your baseline is level then reverse the spirit level and re check. 1% innaccuracy is 1 in 100.   That makes 1 1 in 50   1 in 33 or  1 in 100.  Then again trains drag round curves and locos grip better on curves, below about 2nd radius un compensated long wheelbase locos run round curves on gradients on 3 wheels.  Its all good fun.  I run absolute minimum clearances under bridges, like under 40mm track top to track top sometimes by soldering rail direct to sheets of PCB which form the bridge deck.  It also makes a nice train going over a bridge roar which can be a bonus.

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Thanks for the input guys. The level numbers on the diagram have changed since I did that sketch. The station area is now at -35mm and the storage tracks opposite are at zero. The track at the back of the station area is at +35mm. this gives a clearance at the bridge crossover of 70mm. 

 

Hi Gordon S, yes the storage area has given me some concern as you say. My thoughts are to make a cassette type loading area on the main board in that area or possibly off the board but there is very little space around. I've also seen a video on a European layout where a point on the main circuit feeds off the board and then allows a cassette to connect at about 45 degrees.

 

Siberian Snooper, Just bought a roll on wall lining paper to do a full size drawing but can't find a large enough area to lay it out on. I don't have use of the room yet as we are still clearing it out to decorate before I can make a start on the baseboards.

 

Richard 

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Be careful of designing the gradients to an average figure and not allowing for the top and bottom vertical plane transition curves.  If you measure from a bottom datum at the point the transition curve starts from level to the the top datum where that transition curve achieves level, and set it to 1 in 50 then, depending on how long the transition curves are, the central portion of the gradient between the 'inner' limits of the top and bottom transitions will be considerably steeper than 1 in 50, and the average will be steeper as well.  Also, don't forget that the 'inside' radius curve on any gradient that has curvature on it will be steeper than the outside one, and this will affect the performance of your trains as well. 

 

Further advice at the risk of teaching granny to such eggs; keep any pointwork or curves as far away as you can from the vertical transition curves, espepially the the convex one at the top of the gradient.  Steam outline locos with long rigid wheelbases will be the most problematical, 8 and 10 coupled types, and bogied diesel or electric outline the least.

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Hi Richard,

 

You must draw your plan to scale using turnout templates to find out whether it will realistically fit in the space. A giant piece of paper is one way of doing it but it’s so much easier in software like Anyrail. You don’t need a full-size room to lay it out and “Rubbing out” can be done many times over and selectively without destroying the whole design or wearing through the paper...

 

I’m afraid your sketch looks very optimistic. The gradient from the crossing @+80 down to storage @+40 (or even @+70 to @+35) will be very steep, for instance. And the curves into the engine shed may use unfeasibly tight radii

 

The folded figure of eight is a nice idea but would it really add much to the operations and the enjoyment of the layout? You might consider keeping a simple main circuit on one level with a "branch line" rising up to the industrial works. That would be much simpler to build, easier gradients, no crossing tracks (unless you particularly wanted them) and would allow longer storage roads.

 

Since parts of the layout would be removable can you use more of the room area? That would help a lot in making the plan work.

 

Edited by Harlequin
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15 hours ago, RichD1 said:

. Does the Woodland Scenics foam allow for a double track? Does it need any track underlay on top before fitting the track. Probably a silly question as without the ballast would drop through! In which case what did you use on top and how was it fixed.

Notwithstanding the potential issues raised by other posters above, if you wanted a double track incline, you would need to lay 2 WS foam inclines side by side. For the transition, I don’t think you could sculpt the foam as the end is already pretty thin - I used thin card in differing numbers of layers to smooth things. I used cork sheet underlay, cut to size/shape, glued onto the foam, and then glued the track to the cork (after painting). I also laid DCC Concepts Powerbase plates on top of the cork, in case I needed extra adhesion, but so far have not found it necessary to fit magnets to locos. So could be a wasted ‘just in case’ investment, but it was fuelled by a problem on the previous layout where I now see I was over ambitious with an incline, at 3% on a 2nd radius curve with inadequate transition. Live and learn.

PS. I echo what others have said about a full size plan. I used Anyrail and found it invaluable. Not just to get track lengths right for gradient calculations, but also for checking space/clearance  at  board edges, along side walls etc.

Edited by ITG
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I'm a Mac user so I've downloaded xtrkcad but not finding it that easy. Did try Railmodeller but I think you need to buy the licence to get the best out of it. I think I will preserve with xtrkcad to get the basic design and then draw out full size on paper.

 

I'm wondering if I move the crossover to the right hand side top corner whether that would give me more length of incline as a solution. I would like to have the figure of 8 so I can run two tail chasers on each line as I plan to use DCC. The circuit length would be approx. 17 metres. The use of Powerbase might be worth considering as a backstop if needed.

 

Can an incline on a curve have a very slight camber?

 

The change to a single loop and and inclined branch line up to a small terminus or industrial in the top left hand corner does have some appeal but I would need to add some bridge/viaduct features to add the extra interest. A tunnel on the main line would be nice but I cant see anywhere that would be long enough so that you wouldn't see the train at each end.

 

Richard

 

 

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On 18/02/2021 at 15:30, RichD1 said:

So advice please on the best methods of building gradients, transitions and gradients on curves to get a smooth track surface.

Richard,

 

To start/end my ramps I cut a U-shaped 'slot' in the baseboard, and then bent the open end up/down to suit. This gives you a nice vertical curve. You can see more, with photos, at:

Ian

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Hi ISW, thanks for your link it's very impressive and given me food for thought. I had thought about doing something similar to your design for transitions but was unsure whether a 6mm ply top would be strong enough to give a smooth raise or just bend mostly at the bottom.

 

Richard

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I used the Woodland Scenics foam inclines and I got around the space limitation by splitting them in two halves. The first run climbs up to a mezzanine section then the next run completes the climb to a proper second level baseboard with tunnels underneath it. I model in N gauge and I the way I created my incline was as follows:

 

* Choose the horizontal length based on final height and preferred gradient (I kept mine at 2%).

* Set aside more space on the board than the horizontal length requires. I went with about two coach's worth of additional space.

* When constructing the incline omit the first and last few sections of incline. Let the track droop down (in my case that's a coach's worth of nominally free hanging track).

 

So for me:

* My mezzanine is at 32mm so the initial horizontal length was 1.5 metres. 32/1500 = ~2%.

* 1.8 metres of the baseboard was made available for the incline.

* Remove the first and last few blocks of the incline.

* Fix enough track to complete the incline and join it to the track at either end.

* Insert supports at the highest end (actually I now have a girder bridge there). The lower end I just ignored. I might have to insert some paper when I get round to ballasting that section but for now it's not going anywhere anyway.

 

I've had almost no problems with any rolling stock. The only problems I had were the result of drooping couplers on one set of wagons which will be the subject of a thread elsewhere at some point.

 

One thing I will add that is probably irrelevant since you're modelling in OO. All my locomotives eat up my 2% curve like it isn't there. They can pull long trains (up to nearly a metre long) from a standing start and can climb the incline faster than is safe because of 2nd radius curves at the top.

 

I would assume that OO gauge locos can pull better than N so if you're not trying to be prototypical (and frankly unless you live in a mansion you can't be with inclines) don't be afraid of exceeding 2%. They do seem to make a difference compared to a flat layout.

Edited by AndrueC
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8 hours ago, RichD1 said:

but was unsure whether a 6mm ply top would be strong enough to give a smooth raise or just bend mostly at the bottom.

Richard,

 

I'd say that 6mm plywood might be not strong enough, and result in vertical curve that was too long. However, if that happens it's easily fixed by screwing a stiffener timber to the underside of the 'open' end of the U-cut to make sure that part is on a single plane (the gradient required).

 

Ian

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Hi Rich

 

Fwiw, I  had a quick play in XTrackCad including some elevation setting and produced the following:

 

622902853_RD1gif.gif.89b8b05c1604f64b20d16f0adf7b729b.gif

 

It's in imperial 'cos that's my default setting, I'm afraid ...... I set the heights shown in black, 3" for the bridge, 2" for each end of the storage space, and zero for the station and yard.  The heights shown in red are intermediate calculations, and the calculated grades are in green, noting XTC does not allow for transitions.  You will see I assumed the outer (green) loop descended over its entire length; if it was levelled out at 0.85" across the bottom the grades either side would be around 1% and 0.9%.

 

If you'd like me to put in any other numbers (and I can do metric) just let me know.  If the XTC file would be any use to you, do PM me your e-mail address (I'm still using version 5.1.2 as the new version (5.2) seems to be having teething problems).

 

Cheers, Chris

 

Edited by Chimer
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Hi Chimer, how did you do that in xtrkcad!! I've been fiddling around for weeks and almost to the point of giving up. Being able to do just lines would be a real step forward before going to put down actual tracks. I'll PM my email and see if I can load the .xtc file. In metric would be great if its no bother.

 

Richard 

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9 hours ago, RichD1 said:

If I use Woodlands incline sections how would they work across baseboard joins?

 

Richard

They are easily cut, either with a sharp knife of a heat cutter. But of course the oft-used method of soldering rail ends to a brass screw to maintain position (and avoid damage by catching a rail end during transit or reassembly) is not possible when mounted on to foam. Unless you replace the end of the foam incline at the baseboard joint with a wooden block. I guess much depends on if baseboard joints only exist  for ease of building layout, or if the layout is portable nd thus regularly assembled/disassembled.

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2 hours ago, RichD1 said:

The layout needs to be removable to allow the room two be used for other purposes but this will only be about 4 or 5 times a year.

 

Richard

Well, you could then use the wood block at the end of the incline, as I said above. Or, if it is a rare occurrence for the boards to be moved, I placed a small linking piece of track, with chairs cut back to allow rail joiners to slide fully back beyond the end of rails. Then dropped the link track into place between the respective tracks on each board (once they are in place) then slide rail joiners out to hold link track in place. I also pre-wired the link track with droppers to ensure better connectivity. The advantage of this method is the slid-back rail joiners allow the link track to be inserted vertically, without having to angle it in as one would normally.
I did this method on about half a dozen joints, but I must say they were all on level joints, not inclined, but the basics would be similar.  I have no plan to move these boards, but just in case I move house (or similar), I at least know I don’t have to cut tracks.

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