I have reviewed several threads here on the subject of maximum grades, and there seems to be a consensus around 2-2.5%, although there are a couple of outliers. What’s almost almost missing from these posts is a reference to what the layout is doing and particularly the length of the trains. Most of the posters seem to be experienced, so I’m guessing trains are usually pretty long.
I am building an around the wall HO layout in a 10/12 x20 basement room with early transition era rolling stock. Because I don’t have a lot of room, I have made an operating decision to limit siding lengths to seven feet or less, and an 8 foot AD track in my main yard. In practice, I expect to be running 5 to 8 foot trains, the latter being about 14 cars plus locomotive and caboose, or six passenger cars plus a baggage/express and the locomotive.
The grade will be on a long spur leading to one staging yard. The rest of the operation will be level, with a second staging yard at the opposing point.
I’m thinking that with these relatively short trains, I ought to be able to cheat a little, perhaps to 3% or so. Am I deluding myself?
Will there be curves? If so, what radius? Moderate curves 24" - 26" will act more like a 4% to 5% grades on the train… I know, 30’ of mainline is currently missing from my layout as I eliminate mine
Steve’s mention of curve radii is certainly a factor. A lot depends also on the motive power. Many HO steamers pull relatively poorly, for example.
Also, the steeper the grade, the longer needs to be the transition from level to grade and back to level, so you’ll need to allow for that. For regular readers, sorry to post this graphic again, but it’s more critical when the grades become steeper.
But luckily for you, your question is easy to mock-up and test. Set up a test track to try it out with your typical cars and engines and see what you think of the performance on straight 3% grades. That may be much more informative than three pages of forum rumination. You could also mock-up a typical curve with a grade and see what happens there.
How long will the spur be and will there be curves?
AN 8 foot long heavy passenger train pulled by one loco? you may be deluding yourself by cheating to 3%. If you toss in curves, {which there are bound to be?} you will have more like 4% or higher, and that will be vey hard on the engine IF it can make it.
Some guys have maybe cheated and have been lucky or run short trains or multi-engines, but “cheating” on a model railroad isn’t like gov’t work: where “close enough is good enough”, Cheating on MRRing inclines can lead todisappointing failure.
I tore up TWO layouts cuz I tried to get away with 4%, then 3% grades with curves. Now I won’t touch more than 1 or 2% including allowances for tight curves, that’s how I know how disappointing it is.
Stick to 2% grade, if you need curves, make it 1 % and with the curves will be more like 2%.
Remember 2% is a 2 inch rise over 100 inches of track {8’ 4" your length of one train there} SO you may have about 14-15 feet of straight track on the 20’ side,. but toss in a wide radius curve at the far end for your passenger cars and…
Although the prototype sometimes has grades of 7% and even more, this won´t work on a normal layout. Anything above 3% means inviting trouble, and it is most advisable to stay under that value.
The grade finally depends on the pulling power of your locos, which, in turn, depends on their weight. A 8 ft. long train is by no means a short train, and there are a lot of locos in the market, which will not pull that train up a 3 % grade.
I can only recommend to build a test track before you finally decide on a grade for your layout. With a test stand, you can check the pulling power of your locos, as well as the wheel sets of your cars. It is nothing but a length of flex track on an incline with varying grades. It is certainly worth the trouble (guess how I came to know this).
How high are you going? Will all of the train be on the grade at one time? If only half the train is on grade you might get by with it.
My self, I am planing a new layout and will have a few sections go to around 6 to 8 inches. I am staying in the 2% range.
If you need some reasonable priced pulling power look at the Proto 2000 E-6’s (guessing the 7’s and 8’s would be the same) I have pulled 60 cars with one and it was not having a problem.
I’m getting the idea that my trains may not be as short as I thought they were.
The uphill spur is intended to be a representation of Sherman Hill west of Cheyenne. My length of climb will be about 360", give or take. There will be two 90 degree turns, one at the minimum 30" and the second a little broader. The final ten feet will be level double decked, and I expect to put a small town there…
The motivation for the initial question is that I’d like to get a bit more than the 7+ inches of vertical separation a 2% grade provides.
FWIW, I’ve modified a good deal of my rolling stock in the direction of free wheeling – the majority will roll without assistance on grades of 1.3%.
Finally, there is a way I could claim another15 feet or so of climb, but it would have really goofy effects on the operation.
It might be nice to get more than that 7 inches, but I tell you again, stick to 2% grades and the height that will afford you and you won’t be sorry. Otherwise you may end up tearing out more than your hair {ask me how I know this}.
FWIW- “free wheeling” can help but it is still the weight the “free wheeling wheels” are carrying that will get you. AND I’ll bet your “free wheelers” will not roll without assistance uphill on a 1.3% grade!
Given the length of the trains your are using, if absolutely necessary, you can go up to 4%, the are commercial gradients available as well as traction tires(such as bullfrog snot) that will reduce wheelslip. Because this is going to a staging yard, a moderately heavily used part of the railroad, I would recommend lees than 4%.
If your bearing journals are 100% frictionless, all that must be overcome is the effect that gravity has on the entire mass of the train. That effect is to want to cause it to accelerate down the grade. The sole contrarily acting force comes from the tractive component, the locomotive. At some point, the adhesion of the working tire surfaces on the locomotive will equal, on average, the effect of gravity attempting to draw the entire consist, engine and tender (if it has one) and all the cars trailing the engine. Add friction in the bearings and you still have the retardant effect of gravity, but also stickiness or resistance in the rolling of the wheels.
It really is necessary to do a mock-up of your worst case. That includes a small engine, by itself, pulling a hefty load that you know is the shortest consist you will accept on your layout. If that lone experiment proves to be too much, what are your options? Change your standards, change locos, add traction, or alter the route. Included in altering the route is the option of reducing the grade and/or curvature.
I have been model railroading for 50 plus years and most model railroaders that I know refer to the NMRA specs. I personally think they are too conservative. I run 5 to seven car trains on a layout that is in a 9 x 24 foot room. 3% will work with the correct easements. I have one grade that goes to my upper deck that is 5%. I have to double head it. Thats what the real railroads did on steep grades. It make for more realistic operating.
If you are in doubt, set up a test grade. Get a board about 8 foot long and put some track on it and then a normal length train. Start elevating it and see if the train will still start on the grade. If it won’t, lessen the grade to the point where the train will start, and call that your maximum grade.
http://www.trainboard.com/railimages/data/500/vert_transition.gif