Slope & Grade

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JeffShultz

Stay off the tracks!
I'll be moving (yeah!) to a house within the next month and getting a 14x24 garage that I'll share with some shelving and the inevitable lawn mower (I'm trying to negotiate a garden shed).

Anyway, this means that my 2x8 layout will soon have a great deal more room to live in. It's obvious that I'm going to expand off both ends of it, but I've got a problem of some interchanges that really need to go somewhere.

So I decided that my layout needs a basement. It will be pure track - no scenery - just a bunch of staging yards essentially.

The scale is HO.

I now have a number of questions:

1. What is a recommended height difference between levels? The normal width of the layout is 2 feet wide - it will be up to 4 feet wide at the ends, where on one end there will be an oval helix (more later) and on the other a horseshoe curve. I think that as long as the basement is at a comfortable level off the floor, 1 1/2 to 2 feet should work.

2. Slope... what is the run/rise for a 2.5% slope? I figure I can get away with that on both the UP interchange track, which will decend from the back of the layout near the middle to one end of the layout, and on the oval helix.

3. The oval helix - my idea is that I'd like to see if 24" radius curves would work if instead of a pure circle the sloped sections are straight and the curves are level. I think I can fit a 4x6 section (possibly longer) in for this. I can't quite see dedicating a 5ft square to this in order to get a wider radius curve. I may have to of course... am I nuts, has anyone ever tried an oval helix?
 

grumpybob

Lake Shore Lines
Jeff,

Last helix i put together for someone was a 6' x 9' with a 2.5% grade. the curves were 30" as he runs mostly 6 wheel trucks. There were 4 complete revolutions for a total height of approx 24". the straight sections were somewhat flat and therefore became a braking section, that way if a train broke apart it didn't come out of the bottom at warp speed.

So, you aren't nuts.

Bob A.
 

ncng

Member
You might have a little problem with your plan but it is workable with restrictions.

A circle of 24" radius track is 150.792" long. A grade of 2.5% will climb 3.7698" per loop. Your sub-roadbed (plywood?) and roadbed (cork?) plus track height will affect your climb requirement. If you are using 1/2" plywood and 1/4" cork plus about another 1/4" for the track ties and rail, you are looking at a clearance of only 2.7698". That is less than the NMRA standard for clearance.

If you make the loop an oval with straight sections of approximately 5" on each side, you would gain about 1/4" in elevation per loop. That would give you 3" of clearance.

Don't forget to use transition curves and transitions to slope changes. You will want to be at your 2.5% slope before you enter the helix.

David
 




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