Multi curvature corners

This may be more complicated an explanation than you need but it is from the NMRA...

https://www.nmra.org/sites/default/files/d3b1.pdf

Short answer is yes, you can mix different radius curves to achieve a gentler transition into the turn but you will still be limited in your equipment selection by the most limiting selection of your curves.

Yes, it is best to have the larger radius going into the curve. If space allows, I will also add a straight if it is a full 180 degree turn to stretch it out a bit. BUT as Farmall-Joe said your large engines might not handle it however, it will look better in my opinion.

Mikki

In an effort to be helpful, don't forget to leave plenty of room between tracks so bigger engines can pass by each other without scraping or actually catching and crashing!   If I recall correctly (I'd have to go measure to be 100% sure) I think I made the closest point on my corners at 6" center rail to center rail.   I think I had 2 spots that came in closer to 5.5" -but no less.    The legacy big boy and the Vision 2-10-10-2 pass each other tightly in the 5.5" spots, but they do always pass -even at high speed- without touching.  The 6" curves have a nice margin.

Here is an example of using mixed curves.

First, this was done in RRTrack software.  I would recommend you get some sort of track layout software (many here use SCARM).  I purchased RRTrack 20+ years ago, before SCARM existed.  Using different curves in a layout is no problem but keeping things lined up can be fun.  The software allows you to test everything before you find out it doesn't fit right.

Below is a 4x8 canvas.  I wanted the widest loop I could fit within 4x8 with the smoother curve transitions, so I added some O72 curves and a short straight section to get the loop as wide as possible.  The key is to make everything symmetrical so the alignment works.  There could have been other options but I choose O36 FasTrack as my starting point because that is what I had at the time.  As Mikki pointed out above, the trains look way better using the wider transition curves, even in this tight space.

Tony

This comment is in regard to FasTrack on a 4 foot wide table.  Something to consider is that by putting a straight section in the middle of two narrow radius curve pieces within a 180 degree curve, there would be an abrupt curvature transition between that straight and the adjacent 036 curves pieces (blue arrows).

An option to have continuous curvature easements and use the full 4 foot table width would be to use a mix of 072, O48 and O36 curve pieces.  Here's one option: going clockwise from the top straight: O72 half-curve, O48 full-curve, O36 half-curve, O48 full-curve, O48 half-curve, O48 quarter-curve, O36 half-curve, O48 full-curve, O72 half-curve, and back to straight.

@SteveH posted:

An option to have continuous curvature easements and use the full 4 foot table width would be to use a mix of 072, O48 and O36 curve pieces.  Here's one option: going clockwise from the top straight: O72 half-curve, O48 full-curve, O36 half-curve, O48 full-curve, O48 half-curve, O48 quarter-curve, O36 half-curve, O48 full-curve, O72 half-curve, and back to straight.

I like your design better.  I didn't think of that but I was also trying to not replace all my fastrack curves.

Going back to the OP, this illustrates you can use mixed curves and the software REALLY makes it easy.

@Tony_V posted:

I like your design better.  I didn't think of that but I was also trying to not replace all my fastrack curves.

Going back to the OP, this illustrates you can use mixed curves and the software REALLY makes it easy.

Thanks.  I understand the desire to sometimes use what you already have.  In the past I have used straights in the middle of O36 curves and smaller equipment runs fine on that.  However, if one begins using longer cars and locomotives, in my opinion they look and operate better on wider curves.  Single short sections of O36 seem to have less of a detrimental effect if eased in between progressively larger radius curves.

@SteveH posted:

Thanks.  I understand the desire to sometimes use what you already have.  In the past I have used straights in the middle of O36 curves and smaller equipment runs fine on that.  However, if one begins using longer cars and locomotives, in my opinion they look and operate better on wider curves.  Single short sections of O36 seem to have less of a detrimental effect if eased in between progressively larger radius curves.

Interesting -- that brought to mind an early problem I had with trains staying on the layout through an O-27 right angle curve near the layout edge on the outer loop. In addition to adding a catch fence, for space reasons I substituted two O-42 curves between 2/3rds of an O-27 curve (not enough room for a full O-42 curve). It has worked well -- the rolling stock leans, but does not do the snap rolls off the layout they tended to do with the more abrupt turn, even at full speed.

@Steve Tyler That's a good point about speed.  Easements do allow for higher speeds through tight curves that would otherwise lead to derailments.

Maybe beyond the scope of this thread, but perhaps worth mentioning is super elevation; Banked Curves.

Thanks for all the replies. They all give me options to consider based upon my situation. That website Farmall-Joe mentioned has some really good information. Some a little too technical, but some helpful information nonetheless. After reading that website, superelevated curves is an option I will also keep in mind. I have multiple challenges ahead, but using easement curves will help solve them.