Hidden trackage Grad percentage

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Active Member
My floor square footage does not have the area for a decent helix. What would be the sharpest grade for hidden trackage to drop from the upper deck to hidden staging on the lower level? The trains would be a single unit Athearn Blue Box GP7s and the trains lengths would be 6-7 Hortner Aggragate cars. I do not anticipate uphill traffic on this hidden track, but.....

D&J RailRoad

Professor of HO
How long will the grade be?
You locos ability to pull a grade also depends on the weight of the cars and if there are any curves in the track.


Active Member
How long will the grade be?
You locos ability to pull a grade also depends on the weight of the cars and if there are any curves in the track.

The grade will be 17 feet, plus transitions for an additional 1-2 feet at each end. I calculated that would be close to 9%. The current plan is for the railroad to climb around three walls of a 10'x7' room point to point with a shofly behind the scenery back down along the walls.

Cars will be weighted to NMRA standards. I think that is one ounce plus an additional ounce per 10 scale feet of car? That would be 4 ounces.

The more I kick around this idea the worse it seems.

D&J RailRoad

Professor of HO
That's quite a grade. Looks like your bench height difference is about 19 or 20". Can you crunch that down a bit to lesson the grade? I think your GP will have a bit of trouble with 9%


BN Modeller
For going downhill one loco should be enough, if the weight of the cars aren’t real heavy.
I had a thirty six car weighted coal train actually push two locos down a steep hill on a club layout, even when I tried reversing to stop it!
I think you’d definitely need at least two locos if you decide to ascend tho.
Could you work in a switchback? That would cut the grade down significantly.


Well-Known Member
It's difficult to answer your question without knowing more:

Weights of cars;
Rolling resistance (it matters, no matter if rising on a grade or descending);
Heft of the locomotive, or if there is to be more than one locomotive, the heft of each of them;
The types of couplers (this matters because mixed 'n matched couplers don't do well 'shoved', which is what happens on descent); and
The grade, and if there are curves during the descent or ascent.

All these factors have a bearing on how successful any one track arrangement will be, and only for the consists tested. Make up a different train and all bets are off!

In the real world, only heavy tank rodded steamers would be able to climb 5-12% grades, and then only with very limited trailing tonnage. Or, it would have been a geared locomotive such as a Heisler, Climax, or a Shay. Diesels are like those latter three for the same reason: the weight is all on driven/geared axles, providing maximum braking and tractive efforts.

Helices require great skill and care in design and construction unless you don't mind getting into one several times each session to fix something, like a derailment. The shorter the radius, the less high the coils are overhead, the steeper the ramps/coils, the worse it will be. Unfortunately, the more separation you want overhead, the steeper the ramps have to be, defeating yourself and your trains.

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