Gradients

Hey you lot Rebuilding a new layout at last. Woodland scenics have a 2 or 4 % incline kit. I will be running 6 coach trains. Do you think 4% is too steep, given Im only in a garage? Ta much Rob

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Rob -
Yes. You will have enormous difficulty getting 6 coach trains up such a grade even on straight track. You should aim for 2% max on straight, and less on curves. If you can't fit this in you will probably have to settle for shorter trains.

wrote:
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Or redesign so that one track goes down and one up, giving twice the height difference in the same length.
MBQ

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On 11/03/2011 10:37, John Nuttall wrote:
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The Hornby A3 will pull 13 coaches up 2% even with a slight curve. The 9F will pull 50 trucks up 2% with ease. It will depend largely on the mass of the engine, I reckon. I would not use the Woodland inclines, though, I'd make the inclines with the baseboard because the track fixes more securely that way. My experience with Woodland inclines has not left me with any conviction that they beat the other methods. Even carving the inclines from insulation board is better, IMO, because the result will be less geometrically precise.
It's very easy to make inclines from insulation board carved to shape with a sharp pallette knife and a Surform.
- -- Guy Chapman, http://www.chapmancentral.co.uk The usenet price promise: all opinions are guaranteed to be worth at least what you paid for them. PGP public key at http://www.chapmancentral.co.uk/pgp-public.key -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org /
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On Fri, 11 Mar 2011 18:25:02 +0000, "Just zis Guy, you know?"
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Also the train's weight and friction
A friend and I were privileged to visit the late Colonel Hare's famous 7mm scale Bromford and High Peak railway, with its American-style helix between the higher and lower levels. His heavy prize-winning B1 with a large Pittman motor had difficulty pulling a train that it took with ease on the rest of the layout.
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On 11/03/2011 19:04, Christopher A. Lee wrote:
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Curves definitely increase the drag very substantially.
- -- Guy Chapman, http://www.chapmancentral.co.uk The usenet price promise: all opinions are guaranteed to be worth at least what you paid for them. PGP public key at http://www.chapmancentral.co.uk/pgp-public.key -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org /
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On Fri, 11 Mar 2011 19:32:33 +0000, "Just zis Guy, you know?"
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Yes.
This engine was properly weighted, had a huge, powerful motor and had just won a trophy at Telford a week earlier.
One solution would be to use a banking engine (helper on the left side of the Atlantic) just like the real thing.
Another friend has an O-scale Lickey banker 0-10-0 built from an Eric Underhill (now JLRT) kit for this purpose but he ended up with a single level layout.
In OO you could use an engine with the front coupler removed.
The train engine stops on a short isolated section, the banker stops at the back of the train, power is restored to the isolated section and they both set off. Not having any load the banker will want to go faster than the train engine.
Similarly the train stops with the train engine just in front of a longer isolated section. Power is removed from this and the train sets off leaving the banker behind.
With DCC it's even easier.
Or you could double-head trains.

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On 11/03/2011 20:11, Christopher A. Lee wrote:
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Or use DCC :-)
I have tried banking, it is amusing. The working arrangements add a bit of interest too. There's scope there for one of those bleak hilltop settings.
- -- Guy Chapman, http://www.chapmancentral.co.uk The usenet price promise: all opinions are guaranteed to be worth at least what you paid for them. PGP public key at http://www.chapmancentral.co.uk/pgp-public.key -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org /
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John Nuttall wrote:
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I've seen a couple of compact HO layouts at Canadian shows with a triple helix climbing up a circular mountain. The train disappears into a tunnel at the top, descends a (presumably steeper) helix inside the mountain, and re-emerges at the bottom level. The grade and curvature are quite sharp, but the train is a short one with a few freight cars, usually hauled by a Bo-Bo diesel loco.

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Wasn't there one where the whole mountain rotated while the train climbed against the gradient? The result being you could observe the train climbing vertically but it stayed in front of the viewer until it finally went into a tunnel near the top. I saw it in the UK but have a feeling that it came from across Pond and has since gone back.
G.Harman

snipped-for-privacy@yahoo.co.uk wrote:
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Yes, I think I remember seeing that one in Ottawa some years ago. The one I saw just last week at a local show had a stationary mountain.

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Can someone please remind me how you convert ratios into percentages and vice versa (and I'll refrain from commenting on the sillyness of using "percentage" as a measure of gradient).

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On 13/03/2011 11:48, Chris Wilson wrote:
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2% is 2:100 or 1:50. No silliness at all, or at least no sillier than posting a gradient of 9:37 would be.
- -- Guy Chapman, http://www.chapmancentral.co.uk The usenet price promise: all opinions are guaranteed to be worth at least what you paid for them. PGP public key at http://www.chapmancentral.co.uk/pgp-public.key -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org /
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On 13/03/2011 7:48 AM, Chris Wilson wrote:
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A percentage is a ratio. ;-) It's the ratio "per hundred". It (or the more precise permille) is the standard engineering spec everywhere except in the UK, where "percent" is for some reason a shibboleth.
OK, example:
3% means 3 foot rise/fall in 100 feet. Could be written as "3%, 3 in a hundred, 3:100, 3/100," etc.
The UK gradient specification is given as "1 foot in X feet", so 3% is 1 foot in 33-1/3rd feet, or 1 in 33, rounded off.
You can avoid all this by making a gradient tool. Materials: a 55cm piece of 1x2 lumber, a 1/4" bolt, a 9 inch level. Drill a hole for the bolt exactly 50cm from end. Thread the bolt in from below.
On piece of paper, make a table of gradients, using the fact that you have a 500mm run. Eg, 1 "1 in 250" is equivalent to "2 in 500". IOW, divide the run into 500, and that will give you the rise (in mm) of the trackboard over 500mm. Thus:
1 in 250: 2mm 1 in 200: 2.5mm 1 in 150: 3.3mm 1 in 100: 5mm 1 in 50: 10mm
and so on. Glue this table to the tool for ready reference.
Now measure the exposure of the bolt below the tool, set it on the track board with the bolt down hill, place the level on it, and raise and lower the track board until the tool is level. The track board will now be at the set gradient.
HTH Wolf K.

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What Wolf has not stated is that gradients on road and rail are measured as unit rise over linear distance travelled. The mathematical equivilent is unit rise per horizontal distance travelled (Tan theta). The difference is significant at the steeper values. Mathematically 1:1 is a slope of 45° but in road/rail terms it is vertical! Clearly this is a non linear function such that % should not be applicable but expressing rise per 100 units travelled is convenient if expressed as percentage and makes the smaller figure into the shallowest rise (but the biggest fraction). Peter A Montarlot

On 13/03/2011 2:13 PM, Sailor wrote:
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???????
I don't think 100% grade means "vertical" at all. It just means what it says: 100 foot rise in 100 foot run. It's possible (but feasible only on roller coasters or in material delivery systems) to have grades in excess of 100%.
IOW, "3% grade" does not mean "3/100 of the vertical slope". It's possible that some (many?) people have a vague fuzzy notion that is what it means, but that's likely just because they haven't thought much beyond "How do I calcuate how much space I need to run my track back and over itself?"
"Vertical" would be zero run over any (=indeterminate) rise, IOW an infinite grade.... Again, think roller coaster. Normally, we don't give "grade" a direction or dimension, but on a roller coaster we could say you can go from zero to positive to infinite to imaginary to infinite to negative and finally to zero grade again. And you get to pay for the privilege!
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Again, I think you've missed the point. Of course it's a non-linear function. So why should that prevent us from expressing it as a percent? I don't follow your thinking here. The tangent (Rise/run) is a ratio, which can be expressed in any way convenient to the user. The fact that it's a non-linear function is neither here nor there.
Some background:
In N. America, by the mid-1800s the surveyors had adopted the 100-ft "chain", and laid out the railway line in "stations" of one chain. Elevations were calculated for each station, so it was handy to plot grade (change in elevation) as so many feet per station = so many feet per 100 ft. So a grade of "X feet per hundred" became " X percent grade".
In Europe, the metric system encouraged a superficially more precise measure of gradient, the "pro mille". What in N. America is designated as, say, 2.5% is Europe is designated 25,0 "pro mille" (sorry,I don't have a character for that.)
No matter how it's designated, a grade/gradient is a ratio. The conventions are historically explicable, and interesting as clues to how our ancestors discovered/invented/adapted the new technologies to their needs.
Cheers, Wolf K.
PS: and let us now start a side bar on frog angles and turnout numbers.... ;-)

On Monday, March 14, 2011 5:47:58 AM UTC+11, Wolf K wrote:
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Along with the incomprehensible "degrees of curvature", as opposed to using radius.
John

On 14/03/2011 2:10 AM, John Dennis wrote:
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Degree of curvature makes sense in the field, because it is a direct measure of the angular offset of each successive station when laying out the line on the ground: you swing the transit through the degree of curvature, measure to the next station, and so on. Specifying a curve radius as, say, 1,000 ft is singularly unhelpful for laying out the line. You have to convert the radius to degree of curvature first.
On the typical layout, radius makes sense, because the curves are small enough that a reasonably sized template can be drawn on a piece of cardboard taped to the floor (or dining room table, if you think you can get away with that. ;-))
Either way, curvature curvature imposes constraints on the operation of the railroad.
HTH Wolf K.

Yes, I know that it makes sense in the field. I just find it very difficult to visualise.
Interesting that here in Australia the various railway authorities have always quoted curves as a radius, typically (in pre-metric days) expressed in chains. I wonder how the line was surveyed and laid out?
John

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I had this problem recently when laying out a 4'6" radius curve in the garden, where the theoretical centre of the circles was (and still is!) in the middle of the pond.
A few minutes' doodling***** reveals that one can very quickly lay off way-points from the two intersecting tangents that come off the straight section.
***** It helps to have to hand a school geometry book from the 19th Century!
We might muse today at how the standard of mathematics teaching has fallen in this country (Hardly surprising when you see who is doing the teaching?), but even in the 1960s, what we had to learn in geometry was trivial compared to what the Victorians had to do ... not only to reproduce Euclids' proofs, but having to use exactly the same letters to annotate the proofs!