Easements

[justind]

Trying to understand what an easement is...is it coming into a turn hard and then easing out of it (the curve gets more gradual the longer it is) or is it like banking on a roadway to counter centrifical force on turns by putting one rail higher than the other?

(Also been working on my webpage, not that great, but time is an issue for me...hope to be able to post some images of the local rail lines here in Provo.)

 

[shamus]

Hi Justin,
What you call an easement curve is a transition curve from straight to curved and back to straight.Here's a photo to show you how it's done. RED track is the transition - Blue is a standard curve.
Shamus

 

[billk]

Justin - What easements do is ease the transition from a straight to/from a curve, thus reducing problems caused by sharp radius curves.

Say you have a 20in radius curve joining two straights. Easement curves would be used to join each end of the 20in radius curve to the straights. The easement curves would not be a constant radius, but would start out at an infinite radius (i.e. straight) and then would constantly tighten to 20in.

If you have Armstrong's "Track Planning for Realistic Operations", easements are described very well in there, much better than above. (If you don't have it, get it!).

The above book also suggest several ways to lay out an easement or a simulated easement. The real way uses a cubic spiral formula or something, but they can be simulated just by using a section of larger radius track at the start/end of the curve.

Hope this helps, Bill

 

[justind]

thanks

Thanks guys

 

[Woodie]

Webpage

Justin,

Looks good. Let us know when you have a webpage up and going, so we can check it out.

 

[justind]

It there...sort of

My webpage is there...well sort of...a lot of the pics and info I haven't had a chance to post. And something happened to some of it that I had updated...oh well, not a whole lot of work to replace it. Anyway, here is the link (sorry, the TRAINS link is the least updated so not much to really see).

http://www.angelfire.com/ut2/justindennis