[:)] Evening folks; 2newbies here. My neighbor and my self are building a layout which includes an incline Is there a formula for tractive effort for HO as to deg or percent ?? We get much info from the ( Mag) , but have not found this yet . I found this site from a pipeline . We have read the threads and found them very interesting. [:)]
Respectfully, Barney & 75mm Cannonball
No more than a 4% grade. Thats the general rule.
For whatever it’s worth, in the first edition of John Armstrong’s Track Planning for Realistic Operation there is a table of grades showing effect on train length. The table was based on O-scale models, so the scale will affect results. (A 1:1 scale will be more affected by grades, and smaller scales such as 1:48 will be less and 1:87 even lesser.) According to the table, for a 3% grade in O, a train might pull only 45% as many cars on a 2% grade it could on level, 31% as many on 3%, for 23% as many on a 4%, etc.
Curves also decrease what locomotives can pull, and the sharper the curve, the greater the resistance. For instance, a train completely on a 32" radius curve in HO scale will experience something like a 1% grade. So, if a train is on a helix with a 32" radius curve on a grade of 2%, the result will be something like a 3% grade on the straight.
Mark
The prototype Horseshoe Curve is an apx. 1.75% grade – not even 2%.
After all, the Appalachians are just a bunch of hills.
No, these are not the Appalachian Mts; these are mountains, not hills:
Mark
Not really. In railroading circles (model and prototype) the phrase “tractive effort” means how hard the locomotive can pull, and is measured on the flat. That sort of tractive effort doesn’t change on grades. The cars behind a locomotive constitute a drag, and when the drag exceeds the tractive effort, the train stops moving. The drag of the cars increases on a grade. The tractive effort stays the same.
If you have grades on your layout, you will have to run shorter trains than you could run on the flat. HO locomotives can pull decent sized trains up a 1% grade, and perhaps 15 cars up a 2% grade, and just a few cars up a 3% grade. A 4% grade is so steep that the locomotive will struggle pulling just itself up the grade.
Was it me, I would make every effort to keep the grade under 3%. Anything more than that will be more of a roadblock than a scenic haul up into the hills. Also take care to “ease” into and out of the grade. You need a transition section where the grade increases gradually from zero to 3% over a distance of a foot or so. Without this transition, locomotive pilots can touch the rails and couplers will uncouple as the train encounters the grade.
There is a discussion of this on Model Railroad Hobbyist
I had forgotten I’d written so much on the topic. Well, it was an entire year ago.
Mark (an old guy)
That is an exaggeration. Most model locomotives can pull several cars up a 4% grade. A probable exception would be something like a 4-4-0 trying to pull a heavy brass-built, full length passenger car.
Mark
Hey, Barney. Welcome!
For any given engine, each 1% of grade halves the towing capacity as a general rule. A very general rule. Fact is, even among engines in the same production run, variances in assembly can mean one pulls like a tractor while its next off the assembly line might pull as much as 50%. And, as you would gather from the responses, some engines were meant to pull hard on hilly terrain while others were meant for speed. In our model world, some engines pull better than others, no matter what prototype they were designed to emulate in scale. My PCM Y6b is a monster puller, and so is the BLI Pennsy J1 2-10-4. My Hybrid TTT-6 from BLI is also a strong puller. So is BLI’s Duplex T1, considering it has two axles with blind drivers!!! In the real world history, the Duplex was famously spinny, and designed to move modest tonnages quickly. It had large 80" drivers, like the model does, meaning its tractive effort was reduced from that of what it could have been with 69" drivers.
Anyway, it is one of those things where the proof is far better coming from your own trials. Mock up some test tracks with the grades and curves you would like to build permanently, and test an engine or two. Remember, though, you can double head and work a grade the same way the prototypes did/do.
-Crandell
[:)] TO all who answered my post, our thanks to you one and all. This has been most informative. We will look up ( model RR Hobbyist ) . Must build a temp. incline trial & error . ~~~ THANK YOU IVRW-Mark-tgindy-David- Doc and Crandell
Respectfully, Jim & Barney