Gradients for layouts

S

Spongemike

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May 5, 2006
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Kia Ora

What is a generally recommended gradient for small HO layouts? The train lengths won't be very long (like a max of about 10 50'ers).

I'm in the throes of design (i.e. mucking around with various ideas and plans) and kinda like the idea of having one of the tracks cross over. It won't be any bigger than 1220 x 2440 (that's 4' x 8' for those still using such measurements! :) )

Also, what is the 'usual' clearance recommended for such things? I seem to recall a figure of about 75mm (3") but of courseI could well be wrong!

Cheers from NZ

Mike
 
If your train lengths won't exceed 10 cars, the maximum grade I'd go up to would be in the 2.5%-3% range. Most quality HO diesel locos (P2Ks, Atlas, Athearns, Katos) should be able to handle 10 cars up a 3% grade.

Good luck!
 
a simple rule of thumb and one i try and follow when doing grades, 1/4" rise per foot of track, on a 4x8 layout you will have to do a bigger grade, mayve 3/8" to 1/2" per foot of track
 
Mike:
For calculations: a n% grade does up n inches in 100 inches (8' 4").
A 3% grade will take the whole length of your layout to rise above the other track or probably one side plus half the curves at each end. A gentler grade will take even farther; at 1.5% it might take all the way around.
Sometimes you can shorten the grade by having the other track go down, but that means cutting into the layout.
 
Unless you're running really tall cars, there's plenty of room on a 4'x8' for an elevated track to cross over other tracks. My first layout was that size, and while I'm unable to post a track plan, the grade started, on the outside of the oval that encircled the layout, about mid-way on one 8' side. It continued to climb around the curve at the first 4' end and as it entered, still curving, the opposite 8' side, it crossed over the lower main line. It continued, on a diagonal, across the layout, again crossing the main line at a point just before where the elevated line had first diverged from the main, then curved around the other 4' end, dropping in elevation until it rejoined the main at a point roughly under the first bridge. This was effectively a reverse loop, so another reverse loop was incorporated inside the oval, so that trains could, if desired, run continuously in a forward direction. The gain in elevation was enough to clear the cupola on a Silver Streak or Athearn caboose. When I later acquired an Athearn 200 ton wreck crane, I had to cut a bit off the top of the stack in order for it to clear the overhead bridges.

Wayne
 
On a 4x8, I've seen some track plans that uses a figure-8 loop of track with 22-inch curves which looks workable.

The 22-inch curves (3/4 of a full circle) has a horizontal run of 103 inches, which will allow a vertical rise of 3 inches for a 3% grade (though the effective grade would actually be steeper due to the curvature), and the straight sections will give another inch or so of vertical rise.

That means where the figure-8 crosses over itself, the clearance can be around 4 inches.
 
Just for general principals, for those who think ridiculous grades are not prototypical, I once got a book from the library titled "Railroads Of The Coeur D'Lanes" (spelling?) about railroads in mining country of Idaho. I've probably totally mutilated the spelling, but there was discussion in the book about how steep some of the grades were. There was one picture in the book of a 2-6-6-2 mallet very similar to the Mantua mallet with tender. It was pulling lees than 10 cars with a cabboose, and the caption described that as a the maximum it would pull without a helper! The picture was taken around 1900-1910, so the cars would have been 36 foot wood sheathed cars!
 
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