Acceptable gradients

[index2020]

Hi,

Are there any general rules for incline gradients that I should keep in mind as I think about my layout? I read somewhere that it should not exceed 6%...? I think in prototype the gradient is much less?

Cheers,

[ACY]

For HO scale do not exceed 4%, but if at all possible try to keep it at 3% or lower, the only exception would be if you are modeling a railroad that operated on large inclines that only carry 1 or 2 cars at a time. Then you can go up to about 6%, but pulling power will decrease exponentially, I think 3% is best because it still allows for somewhat longer trains.

[index2020]

Thanks - this is useful advice. Is there a standard look-up table which defines which describes how pulling power declines with gradient? Does the power of the loco (2 motor vs. 1 motor) help at all?

Cheers,

[ACY]

The more locos you have in the consist, the more you can pull, but the locos have to have the same gearing and speed for best results.

[jward]

the following table is taken from the book "Atlas HO layouts for every space"......


grade    percent of pulling power (level track)
1%               57%
2%               38%
2.8%            25%
4%               17%
5.6%             8%

[JerryB]

jward:

Thanks for researching & posting that excellent information!!

To put the data into reality, consider a theoretical engine that can pull a train of 10 freight cars plus a caboose. Assume the engine is capable of pulling the total of 11 cars on the flat without slipping or exceeding its tractive force rating.

With a grade of only 1%, that consist must be reduced to 5 freight cars plus the caboose. Otherwise, the tractive force of the engine is exceeded with the strong possibility of slippage.

Go up to a gradient of 2%, and the maximum train is limited to 3 cars plus the caboose. At 3%, only one or possibly two cars plus the caboose.

All the solutions for gradients steeper than 3% indicate that the crew should leave the hack at the bottom of the grade while they deliver at most one car at a time. If it's a through train, they would need to double, triple, or quadruple the hill. Better, they should suggest to the foreman of engines that they be provided more capable head end power.

Gradients are a serious impediment to the transportation system, and definitely need special consideration, even in modeling!

Now where is that Shay that is required to move these ore cars up the 6+% gradient to the pit?

Happy RRing,

Jerry

[Terry Toenges]

Another exception is if the loco had traction tires. In model railroading, of course. Not in the real world. With traction tires, you can pull a whole s**t load of cars.

[Terry Toenges]

A Bachmann HO old time 4-4-0 (with traction tire) pulling 29 cars up a 2% grade.