What would the minimum distance be to go from 5mm roadbed to 3mm roadbed. I am thinking 36 inches but I'm not sure thats enough.
What are you trying to do with the roadbed?
Ray:
A one percent grade will produce a change of 2mm in 200 mm, or just less than eight inches.
Anything over this distance is either acceptable, or perhaps excessive. IMO
Dave
Unless you're modeling the New York Central's Hudson River routes, where any deviation from dead level was considered a serious grade (they needed a push to climb a 0.59% grade from a standing stop!) your suggested grade is approximately 0.2%. (Our Japanese friends would label it 2/1000 on a trackside grade sign.) Any model loco that can't pull ten times that is seriously underpowered and/or underweight.
I'd go for a one foot transition, and round it out top and bottom to avoid hangups with couplers. On the prototype and on most model railroads, such a modest increase in elevation would be treated as a momentum grade - no need for heavy throttle or brakes. After all, even if you run transition era cars, there won't be more than two of them on the grade at one time.
I have similar 'grades' at the ladder end of my yard tracks, to keep my needle-bearing cars from making unauthorized excursions on the more important tracks connected to the other end of the ladder. My yard switcher (either a 2-6-0 or a DD13 class B-B diesel-hydraulic) doesn't even notice them.
Chuck (Modeling Central Japan in September, 1964)
It isn't the grade of the transition, it's the sudden change. 2mm doesn't sound like much, but it is about the height of the rail, or maybe about half the cork height. I dunno. I model N scale.
The issue isn't pulling cars up, it's de-coupling at the ski bump.
I'd make the transition (including the 'transition' at the ends of whatever shim the OP decides to use) as much as I had room for. And then go a little more. I'd try to start the transition a car length on the upper level and a car length on the lower level and a car length on the slope; about 12" in N scale. Maybe 18" in HO.
Robert
LINK to SNSR Blog
If my converter is correct, that is about 0.10 inch of change. Am I missing something?
SouthPenn If my converter is correct, that is about 0.10 inch of change. Am I missing something?
RayG8 What would the minimum distance be to go from 5mm roadbed to 3mm roadbed. I am thinking 36 inches but I'm not sure thats enough.
I took one of my HO sidings to a 3-track tank car area, from typical mainline cork roadbed (I'm guessing around 1/4") mainline down to the plywood. I just laid the cork well into the yard area and then used a belt sander to establish the top and bottom transitions and intermediate grade, I'd say over about 18". You can pretty well see what is reasonable. And you can just use a 3' piece of flextrack to see what will work reasonably.
As some above have pointed out, you need a smooth vertical transition at the top, an intermediate gentle grade, and a smooth vertical transition at the bottom. Take note that any grade involved will not be a good spot for solo cars (or uncouplers) if they are free rolling. I found that they indeed like to move downhill.
Paul
Modeling HO with a transition era UP bent
I think we all think that you don't need more than 36".
And if you have it, use it.
My "guess" is an 18" minimum. Maybe 24".
Ed
In the photo below, the distance between the near end of the turnout in front of the cars in the distance is about 16" to the turnout on the same track in the foreground...
The foreground track and turnout are on standard 3/16" thick cork, while the turnout near the distant cars is directly on the plywood top of the layout. While this is industrial track, there's absolutely no issues with coupler height disparities on this grade, and it sees car lengths varying from 50 ton USRA hoppers to 80' coaches.
Wayne
Cascade Rail Supply makes transitions as part of their Homosote roadbed collection. They go from .2" to 0" in a 14" run. I have these installed and they work fine.
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Thanks to all who responded. Ithink this will be a matter or sanding the 5mm roadben down 2mm over a distance of about 18 in. Appreciate the input.
RayG8What would the minimum distance be to go from 5mm roadbed to 3mm roadbed.
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What am I missing here? You are talking a difference of 2mm? That is 0.079". In 36" at 2% grade you can raise (or lower) almost 3/4 of an inch, or 8-10 times that much.
For any transition of 0.125" or less, just get a 9" piece of track and use it to straddle the transition spiked loosely only at the ends. Ballast and glue will hold it in place, and you will have a reliable transition, especially if you use Kadee #5 size coupler heads.
-Kevin
Living the dream.