I am looking build tracks to rise up to 3 to 4 inch need know how long you build your tracks to meet 3 or 4 inch. Thinking 1/4 every 10 inch rise.
Do yourself a favor and go out and buy a Woodlands Scenic riser set. They come in 1,2,3 and 4 percent versions. On the box, it will let you know what run is needed for your rise. They all go up to 4 inches.
It is a great product…and no guessing.
David B
Approximately 12 to16 feet in length.
This will depend on if you want a 2% grade or a 3% grade
2% will be about 16 feet in length from lowest portion to your 3 or 4 inch rise.
3% will be approximately 12 feet in length.
I am basing this on a Woodland Scenics incline sets which are about the same.
See davidrmbedards posting above, good advice
TheK4Kid
.25:10 = 1:40 = 2.5%.; 3" ÷ 2.5% = 120"; 4" ÷ 2.5% = 160"; 3 X 40 = 120"; 4 X 40 = 160".
Now wasn’t that easy?
Perhaps R.T. made it TOO easy!
Going back to the original 1/4 inch rise in 10 inches of run, you are looking at a 2 1/2% grade (which, coincidentally, is the ruling grade on my mainline, and that of the prototype I’m modeling.) Ten feet of run will raise your track three inches, BUT, an abrupt change of grade would be impossible to operate over. There has to be a vertical easement between the grade and the level at both ends. Optimum length of such an easement is L x %G, where L is the length of your longest piece of rolling stock, and %G is the grade expressed in percent. If you run full-length passenger cars, the easements will be thirty inches long and will add 15 inches to the length of the grade at the bottom and an equal amount at the top. (Half of the easement comes out of the grade, half out of the level.) So that 3 inch rise at 2 1/2% will actually be 12 feet 6 inches long.
If you are using a cookie-cut subroadbed, the easement will form automatically. Using the WS grade formers requires a little creative shaping, with drywall mud (or some other filler material) at the bottom and a surform rasp at the top.
Chuck (Modeling Central Japan in September, 1964 - with horizontal and vertical easements)
Chuck said it all.
Thanks Chuck! [tup]
I’ve never seen a formula for transition before.
One other thing no-one ever seems to mention… If you’re making that 3" rise to get over another track you need to think about how you’re crossing the other track.
Now I could be wrong but this is how I’ve always figured it…
If it is with a slim decked truss bridge you need the 3" plus the thickness of the deck (and track). If the raised baseboard is continuing over the lower track you need 3" plus the baseboard thickness (and track)…
This is based on reading the clearance required as lower track top of railhead to underside of structure. The upper track top of railhead is going to be the thickness of the baseboard (or bridge deck) plus any roadbed material plus the thickness of the track above that.
So, if you want the RR 20’ clearance under the bridge for the lower track and you have 1/4" thick baseboard and 1/8" thick roadbed/track the rise [of upper track top of railhead] you will need will be 3 3/8". Not a lot extra but if you miss it out you may find that you can’t get double stacks through the lower route… well, not without peeling the top deck… [:O]
Chuck, would I be right in thinking that with 89’ TOFCs and Superliners we nhave to watch the outer car ends for grounding as we start the climb and the bottom of mid car when we get to the top? Is there any issue with Kadees hooking up their bars at the bottom or coming apart at the top?
So I have now shown up that everything I have done so far has been flat as a pancake! [:-^]
Algebra:
PercentGrade = Rise / Run. (definition of grade)
You know your rise (3 inches) you want to find the run. Percent grade can be 2% (0.02) a stiff but climbable grade, or 3% (0.03) which is really stiff and requires big power and short trains. Some people have built 4% grades but I don’t recommend them, too steep for locomotives to climb.
Solve equation for run.
Run = Rise / PercentGrade.
Be sure to make allowances for the thickness of the bridge deck on the up and over track.
Depends on what is being modeled. A long 4% on a mainline operation with full-length freights would be a bear. 4% on a timber or mineral hauler in rough country, short trains and LOTS of tractive effort, just duplicates what the prototype sometimes has to do to get the product from where it is to where it’s needed.
My own coal hauler has a 4% ruling grade and 400mm radius curves, deliberately engineered to require either bigger power than ever ran in Japan or several teakettles on a very modest train - one that will fit comfortably into a passing siding a meter long, even with three locomotives. The big power gets used on my unit coal trains, which are equivalent to ten ore jimmies plus brake vans - and WON’T fit into those short sidings.
If one track has to clear another track, it might be possible to engineer a dip in the lower track to get the requisite clearance. In my work, the minimum railhead-to-railhead clearance is about 3.25 inches - the ‘bridge deck’ on my hidden helices is a steel stud positioned rain gutter fashion, to which I caulk a track template (thin card stock) and Atlas Code 100 flex. Unfortunately, visible crossings can’t get away with anything quite that minimalist while retaining prototype believability.
Chuck (Modeling Central Japan in September, 1964)
There are some very good answers here. With a hint of smartalic, but still true I was going to say, “As long as possible”.
I will be using 2 or 3 SD75M run together on my lay out. They are a Genesis.
If you are running HO scale with modern double stack intermodals, 3" will not be enough clearance. I’d suggest at least 3.5" . I’ve got some that come in exactly at 3" or just a hair over in height. Check the hight of your truss bridge also. I had to modify a Walthers double truss to get double stacks through it. Dave The Train has it right above.
If you are intimidated by the math and are okay with dealing with 10" increments, then figuring the grade is pretty easy. A .1" rise every 10" is a 1%, a .2 is 2% and so on. If you are running into a situation where you are running out of room to get the track high enough without massive grades, try looking and see if you can lower the bottom track as well. If it is going to take 120" to get the height you need, you can split that between the two. For example, you could have the upper track rise for 80" and the lower track dropping for 40" to get that 120". That is if you are using the same grade for both. If you alter one of them then a bit of math is in order. The biggest downside to this is it will take an additional 40" to get that lower track back up to grade, plus transitions.
Grade percentage is the rise in track in feet / 100 feet or the rise in track in inches / 100 inches.
.25 inch in 10, that’s a 2.5% grade. Very reasonable for a model, not so much for a real railroad. for three inches that’s a run of 120 inches or 10 feet. For four inches, that’s a run of 160 inches or 13’ 4". You might want to look at a steeper grade if you don’t have room. 3 or even 4% are reasonable for a model with a short train.
|
% Grade |
in/10in |
Run for 3" |
Run for 4" |
|
2 |
0.2 |
150.0 |
200.0 |
|
2.5 |
0.25 |
120.0 |
160.0 |
|
3 |