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Starting a grade -- what's the best method to smooth the transition?

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  • Member since
    February 2021
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Starting a grade -- what's the best method to smooth the transition?
Posted by crossthedog on Tuesday, April 27, 2021 12:34 AM

Another related but separate issue. The branch line will start out parallel to and at the same level as the main, but then will begin to rise. I'm trying to envision how to soften the transition that the wheels of both the locos and rolling stock will feel going from flat to suddenly a kink upwards. Even with cork roadbed, and no matter how gentle the grade, there will still be a point of change and I'm worried the wheels will be unforgiving if they sense it.

How do you make sure the grade starts as smoothly as possible?
Do you shim it in fine steps with layers of some fantastically thin Elven pastry?
How do you support that first 12 inches or so before you can get the track onto the piece of angled subroadbed?

Grateful for any ideas/experience/warnings, etc.

Thanks,

-Matt

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

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Posted by doctorwayne on Tuesday, April 27, 2021 2:23 AM

On the main part of my layout, where there are grades, the layout is open grid 1"x4" on 16" centres, with the track on cut-out 3/4" plywood roadbed.  The roadbed is, in almost all locations, on risers, even if it's level track.

For grades, the level portion is fixed in-place at the top and bottom of the grade (this applies for grades on both straight and/or curved track).

I then determine the mid-point of the grade (most are multiple curves and straight areas, too) then add a riser at that point and raise it to exactly one-half of the total rise, temporarily clamping the riser to an open grid member.

Next, I calculate the 1/4 and 3/4 points on the grade, and add (and clamp) risers at those points.

By that stage of the process, the 3/4" roadbed at both the bottom and top of the grade has very smoothly transitioned from flat, then into the grade, and at the top from the grade, and smoothly into the level track.  

The next step is to add all of the intermediate risers, simply affixing the top ends to the underside of the plywood roadbed, and the bottoms to appropriate benchwork crossmembers, as, by this step, the heavy plywood is fairly stiff and unlikely to sag.

This photo shows the beginning of the longest grade on my layout, at left, just this side of the tall black water tower, and, at upper right, in the distance, the track approaching the partial upper level, 45' from the beginning, and 15" higher...

Here are some views of the risers, all 1"x2"s with suitable pieces of scrap wood affixed, using screws, to the tops of the risers and to the roadbed...

If you're using thinner plywood, you may need to measure appropriately for more of  the intermediate risers (1/8, 3/8, 5/8, etc. points of the grade).

Using risers also allows the layout builder to easily add superelevation to the curved sections of track, whether on level track or on grades.

Wayne

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Posted by selector on Tuesday, April 27, 2021 3:20 AM

Yes, screw down, but at grade as closely as possible, a thickness of plywood or birch, or spruce, that can withstand bending. Then lift the far end of the wood item to get the 'middle portion' to climb at the rate you need.  When you have this supported near the far end, the portion nearest the screwed down end will have bent upwards.  This is what you want, that vertical curve.  Place a riser somewhere close to the bend to secure the bend when you release the pressure on the part you're lifting.

Near the middle, another riser to keep the grade constant to the extent possible.

Then, reverse what you did previously at the lifted free end.  You're going to screw it level again, at grade, but you'll place a riser just prior to, or partly under, the curve back to level.  It might help to cut the top surface of the risers in each case at a bit of an angle to match the grade where the riser is placed up against the nether surface of the wood strip.

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Posted by riogrande5761 on Tuesday, April 27, 2021 6:55 AM

How do you make sure the grade starts as smoothly as possible?
Do you shim it in fine steps with layers of some fantastically thin Elven pastry?
How do you support that first 12 inches or so before you can get the track onto the piece of angled subroadbed?

If you use open grid framing, you can simply mount the surface of the subroadbed flush so that there is no need for a "transition".  No shimming.  No muss, no fuss.

Perhaps this is one of the disadvantages of foam, as you have one large flat surface.  But if you go old school, and use risers and plywood or OSB, you can easily match the top of the surface to avoid annoying things like ramps.

Bottom of this photo illustrates on example of using risers to match surface that track is on - no ramp:

Similar example here:

Rio Grande.  The Action Road  - Focus 1977-1983

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Posted by Lastspikemike on Tuesday, April 27, 2021 9:08 AM

You can't eliminate the transition point but you can create a number of transition points, each with a different %grade change.

Vertical grade changes present the same problem as easements for curves. From zero to say 2% you create a curve of infinitely variable radius. A hyperbolic curve, technically, except we do eventually touch the axis at each end, because we really build it.

Wood tends to bend in this way naturally but so do foam sheets.  Unless you pre-bend wood it sits there under tension. So does foam but the forces trying to straighten out the foam are tiny compared to the screwed down wood.

The simplest easement for vertical grade changes is use a filler on foam. Woodland Scenics makes a product that works: Foam Putty. At the top of a grade simply grind down the foam progressively to create the easement you want. 

You can create a 1% grade using WS incline starters. Placing a 2% reversed onto a 3% reduces the grade to 1%. This only works starting from a riser. Obviously you cannot reach zero elevation with this method.

Or simply ignore the change from zero to 1% or 2% as your trains actually won't be affected. It just looks better if the grade change is eased as it does firvessed curves. Bear in mind that eased curves look much better the sharper the final radius. Same for grade changes. If your straight curved into a bend only by 2% I bet you'd not bother trying to create an easement for  that curve. 

Alyth Yard

Canada

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Posted by rrebell on Tuesday, April 27, 2021 9:24 AM

Best way with cork is to caulk it down with extra caulk uner the transition area. Pin one end and then pin the other letting the cork to provide the transition by being pulled tight. Also lets you choose length of transition.

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Posted by SeeYou190 on Tuesday, April 27, 2021 10:26 AM

crossthedog
How do you make sure the grade starts as smoothly as possible?

This is a subject I have interest in as well.

I have always had issues with grades, and my next layout will have a 5% grade.

Surprise

I hope we can get helpful responses from people that have successfully built layouts with grades and not just a lot of noise.

There are a few good responses already.

My 5% grade will be to a branch line staging area, and will only have 50 foot freight cars maximum and very short train lengths. It needs to run smoothly.

-Kevin

Happily modeling in HO scale. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by BATMAN on Tuesday, April 27, 2021 10:26 AM

I butted spline up against the foam for my climb through the Rockies. You can't tell where it starts to go up only that it does. I love spline and will use it again.

Brent

It's not the age honey, it's the mileage.

https://www.youtube.com/user/BATTRAIN1/videos 


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Posted by dknelson on Tuesday, April 27, 2021 10:34 AM

I think one take away from the advice given above is to try to make use of the natural vertical easement curve that is created when "bending" otherise fairly stiff subroadbed or other base materials.  Stated another way, do what you can to avoid having two pieces of wood or foam meet each other at the point of origin of the upward slope.

Similarly, even at the cost of cutting up a perfectly usable piece of flex track, I'd suggest doing whatever is needed to have a single piece of flex track straddle both sides of the start of the upward slope, and avoid having two pieces of track meet right at that point.  Let the track itself resist too abrupt a change in elevation.

Dave Nelson

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Posted by josephbw on Tuesday, April 27, 2021 10:41 AM

Shimming shingles will work for that and also for transition from ground level to high iron.

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Posted by Lastspikemike on Tuesday, April 27, 2021 2:10 PM

It's very easy to measure the rate of grade change with a ruler. I use a stationers stainless steel ruler because it bends and also makes a handy scraper on filler material.  High spots get you a rocker effect and low spots let the center of the ruler bend sideways. Eyeballing the gap(s) under the ruler automatically gets you the percent grade change over 12". You can use a second ruler to actually measure the gap if that's important. 

In my experience the transition from zero (horizontal) to 2% really needs no transition length but a very small amount of filler will ease the transition if you wish.  A 5% grade is too abrupt to use only filler easily, although you could.

Were it my layout I'd start at 2% and create a transition length up to the 5% maximum. Same at the top to transition back down to flat.

Wooden splines don't bend vertically. They are used to create eased curves.  If curved splines are used for vertical grades there will be an abrupt transition of some kind from horizontal to a rise. There has to be. The secret to creating grades splines is to keep the percent slope very low. The transition from horizontal to slope will be imperceptible to the eye and the couplers.  

Wood only bends naturally in the one dimension at a time. Usually it bends first across the shorter dimension. To try to bend wood in two directions at once twists the wood, as in boatbuilding. To induce two directions of bend without twist steaming is the most common technique. That's a real bother for roadbed use. You also end up crushing some wood fibre when bending in this way.

Classic cookie cutter benchwork relied on plywood sheet bending naturally into eased grades by jig sawing the roadbed width and mounting the cut strip on wooden risers screwed at appropriate heights. Plywood naturally creates the transition vertically. Splines work in the same fashion horizontally in eased curves. Splines can be made from ripped plywood in fact. 

Alyth Yard

Canada

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Posted by crossthedog on Tuesday, April 27, 2021 6:24 PM

Thanks all. As usual I've gotten useful feedback here.  :)

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

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