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.
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On 11/03/2011 10:37, John Nuttall wrote:
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
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On Fri, 11 Mar 2011 18:25:02 +0000, "Just zis Guy, you know?"
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:
Curves definitely increase the drag very substantially.
- --
Guy Chapman, http://www.chapmancentral.co.uk
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On Fri, 11 Mar 2011 19:32:33 +0000, "Just zis Guy, you know?"
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:
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
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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.
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
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:
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.
- --
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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.
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
???????
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!
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.... ;-)
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
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!
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