Grades ?!?

[Anonymous]

I’m working on my dream layout. But it requires a helix and some grades. What is a good rule of thumb for an average grade in G scale. As in how much rise per foot is expectable? I have been working with a ¼ “ per foot. Looks good on paper, but -- .. Here is what I’m looking at. I have a 25’ run of track. 25’ x 12” = 300” total inches. A grade of 1/8” or .125 x 300” = 37.5” of rise over the 300” or 37 and ½ “ of rise over 25’ of run. Any ideas ? [?]

[Curmudgeon]

That's a 1:48 rise (4x 1/4"=1", 4x 12"= 48").
a 2 in 100 rise is a common standard gauge gradient. 4% is what I use on my narrow gauge.
At 4%, a 12' diameter circle will clear with room to spare in an over/under.
TOC

[Rastun]

Just a suggestion recheck your math, the formula you have going there is a rise of 1/8 inch in every inch. The 1/4 inch per foot at 25 feet should give you about 6 1/4 inches of rise in the 25 feet 3 inches of rise in the 25 feet would be 1% and 9 inches of rise in the 25 feet would be 3% so at 1/4 inch per foot it looks like you're a little over a 2% grade.

Now if we could get it to work the 1/8th inch of rise in every inch would be right around a 12.5% grade which I think you might need to help the engines along on.

What I've heard is stay in the 1 to 3% range for grades.

Later,
Jack

[Anonymous]

Hi Phantom,

A helix in G is a big animal. To calculate circumference from diameter multiply by 3.14, so an 8' diameter gives a circumference of 25.12', 10' = 31.4' etc. So if you are using 8' diameter and expect to rise by 1/4" every foot then a circle would give you a rise of just over 6", a foot in 1/2" per foot rise. Put your track out and expirement with grades and your loco's, they all aint born equal. If your loco is having to struggle then it's too steep, you don't want to strip gearboxes!
Enjoy,
Kim
[tup]

[markperr]

You could also backwards calculate based on the tallest piece of rolling stock you own or anticipate owning. If it's, say, 9" tall from the railheads, add an inch for safety, making it 10" and calculate backwards from there. For example, a 2% grade is 2" in 100" or 10" in 500". Divide this number by twelve to get feet (41.66 ft). This becomes the circumference of your helix. Then divide that number by pi, which is 3.14 (diameter = circumference divided by pi) to determine the diameter of the helix, which in this case would be a 13.25' diameter.

3% grade
3" in 100"
10" in 333"
divide by 12= 27.75 ft
divide by 3.14= 8.83 ft diameter helix

further measuring from top to bottom of the helix will determine how many coils you need to make your entire climb. Bear in mind the additional strain on the couplers on the front cars of the train as you increase the grade of you helix and the length of your train. If the couplers don't give way, there is a good possibility that the cars immediately behind the engine will be pulled off the track if the load is too great as the train will want to straighten out causing the car to literally "hop" off the rails.

Good luck
Mark

[whiterab]

Grades and curves are a nasty combination as both effect the resistance seen by your engine. You can take a lot more grade on a straight section than you can on a curve.

While I haven't scientifically measured it, I get more drag on my 11' diameter curves than I do on a 2% straight. section. As the drag is additive, don't expect to make as much grade with a helix as you would be able to do with an equivalent length of straight.

If you use really tight curves and your flanges and couplers strart binding, your drag is going to go up exponentially. Also the tighter the curves, the more rise you have to have to get clearance for the engine to clear the track above in the helix..

One solution to the clearance problem is to use a spiral (only one crossing of the track below). However, this creates a problem in that the curves have to get progressively tighter as you go up. This means you had better plan on keeping your hand on the throttle each time the train goes up the spiral.

It's hard to predict how much grade you can take because of the other factors such as steel/plastic wheels, weight of cars pulled, truck vs body mount couplers, length of each car, engine manufacturer..... Better plan on some experimentation before commiting to a plan.

[Anonymous]

QUOTE: Originally posted by whiterab

Grades and curves are a nasty combination as both effect the resistance seen by your engine. You can take a lot more grade on a straight section than you can on a curve.

While I haven't scientifically measured it, I get more drag on my 11' diameter curves than I do on a 2% straight. section. As the drag is additive, don't expect to make as much grade with a helix as you would be able to do with an equivalent length of straight.

[#ditto]

Glen.