# Parabolic curves

Discussion in 'HO Scale Model Trains' started by NBS2005, Feb 9, 2007.

1. ### NBS2005New Member

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Does anyone use these for their layout? The idea is that the transition from increasingly tighter radius curve to a minimum at apex, then opening back up again gives better operation and is more prototypical. Any one doing this?

Also, how many HO loco's can the PowerCab run in stock form (without the booster)? Figure newer Atlas loco's.

Thanks,
2. ### Santa Fe JackMember

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They're not mathematically parabolas, but I have transitional curves on my layout. I am doing the gradual curve transtition "by eye" with flex track.
3. ### TorpedoMember

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They are called transition curves or spiral easements, more commonly just easements. I have an old track engineering manual. I think it has the formula for calculating one in it.

As mentioned, they are not parabolas, but in some cases are something called a cubic parabola.

Edit: Here is a link to a PDF that talks about track easements, among other things:

http://www.arema.org/eseries/scriptcontent/custom/e_arema/Practical_Guide/PGChapter6.pdf
4. ### IronheadNew Member

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I work easement into my curves, and wow, what a difference. It takes the edge off the tighter radius for sure.
5. ### cidchaseActive Member

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What I like best about using the easements is that the engines and rolling stock ease out of the curve onto the straight track. Without the easement, they're on the curve, then Wham! they're straightened out. It operates much more realistically with the transitions.:thumb:
6. ### Glen HaasdykActive Member

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I've done easments on my visible curves. operation looks alot more smooth that way. Mostly I added a couple inches to where the curve would begin and 'eye-ball' the easement in.