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Let's say I want to make a 28" radius loop in HO. When I come out of the loop into straight track is a transition that can cause problems for the train. A video I watched shows how to do this in a 20" segment. Can I just use a 32" radius at the beginning and of the loop as a transition?

 

[LateStarter]

Try not to over think it. A proper transition can happen almost naturally as you work flex track into a curve.
[Edit]: Never mind... I was thinking of something else.

 

[Dennis461]

If I had 28" radius track, connected to a straight section, all of my equipment would make it through with no problems. And I have some articulated steamers.

Are you talking a simple section like this?

 

[traction fan]

Easements

Let's say I want to make a 28" radius loop in HO. When I come out of the loop into straight track is a transition that can cause problems for the train. A video I watched shows how to do this in a 20" segment. Can I just use a 32" radius at the beginning and of the loop as a transition?

samliz,grham;

What you're talking about is called an "easement curve", or just, an "easement." The name tells what it does, ease the train's transition from curved, to straight, track, or vice versa. Since you have a generous curve of 28" radius, you may not need an easement at all. Easements are generally used on much tighter radii curves commonly used on model railroads, like 18" radius curves. However, if you just want easements, it certainly won't hurt anything to have them.

There are several methods of creating an easement. One "crude but effective" way is the one you suggest, simply add a section of broader (32") radius curve at each end of your 28" curve.
There is also the "bent yardstick method '. To use this, you draw your 28' radius curve accurately with a tramel, or stick radius tool. Then draw a straight line slightly outside where it looks like that straight line might meet the curve. The straight line should stop a least a foot short of the curve however.
Now pin a yardstick right along the straight line. Let the yardstick protrude well beyond the curve. Then gently bend the end of the yardstick toward the curve until some middle part of the stick meets the curve. Trace along the yardstick between the straight line and the 28" radius curve. That connecting line you just drew is the easement curve.
There is also an engineering math formula for determining an ideal easement curve. I've never bothered with it, but both the math formula, and drawings & text for the bent yardstick method, are in John Armstrong's classic book "Track Planning for Realistic Operation." It's a great book to have, as it explains a whole lot about building a model railroad that can be operated like a real one. If you want the book, it's available through www.amazon.com or https://kalmbachhobbystore.com/products/books

Hope that answers your question;

Traction Fan :smilie_daumenpos:


P. S. You should not use your personal E-mail address on the forum. Set up a screen name to prevent misuse of your E-mail.

 

[gregc]

 

[mesenteria]

Let's say I want to make a 28" radius loop in HO. When I come out of the loop into straight track is a transition that can cause problems for the train. A video I watched shows how to do this in a 20" segment. Can I just use a 32" radius at the beginning and of the loop as a transition?

There are two* kinds of transitions possible here:

Curve easement

Super-elevation easement

The curve easement is properly in the form of a 'cubic spiral' portion, but flex track will do a close approximation of that curve if you let it do what it wants between the extremes of the curve...where you leave and regain tangent motion. If you are using sectional track of determinate lengths, then yes, you can use a larger radius at each end of the middle part of the curve.

However, as one previous responder says, it should not be necessary to keep things railed on curves wider than about 24" radius. It is strictly for looks (we're not discussing more restrictive and demanding brass rolling stock...are we?)

The other transition is into and out of super-elevation. Super-elevation is not necessary on our models as it serves no purpose other than gee-whiz esthetics...it looks realistic. However, it is often overdone by newer modelers. You only need about 0.8 mm at the apex of the curve under maybe 15-40 ties, depending on the length of the curve. Again, flex track will do the transitions naturally. You only need to place ballast under it all carefully so that the tracks will keep their geometry when weight-bearing with a locomotive overhead.

*There's also the more complicated case of a curve on a grade, or even at the start/end of a grade. I won't get into that in this response.

 

[Sam4014]

New UN from samliz.Thanks for advise.
If I keep my radius's at 24" and above , then I should not need easements. I think I still like the idea of first and last curve greater than the 24" curve - 26" or 28". I'm still trying to decided on tracks to use. I want to go with Kato flex track, Peco turnouts and Kato Unitracks if they all connect well?

 

[65446]

I don't think anyone has posed it this way: Easement need is determined by how fast trains roll, and automobiles, on hwys.
A main line with potential 90mph traffic simply has to have easements into curves as well as superelevation (banked curves).
Slow moving short lines, spurs and curves within yard limits obviously need none of that.
Fast-traffic curvature easements are about keeping down centrifugal force against the outer rail; the potential to climb it..
We might then call this RR track-laying procedure, climb-it control !!!

 

[traction fan]

Kato flextrack?

New UN from samliz.Thanks for advise.
If I keep my radius's at 24" and above , then I should not need easements. I think I still like the idea of first and last curve greater than the 24" curve - 26" or 28". I'm still trying to decided on tracks to use. I want to go with Kato flex track, Peco turnouts and Kato Unitracks if they all connect well?

Sam4014;

I didn't know Kato made flex track. Peco, Micro Engineering and Atlas all do make flex track. Maybe Kato does too, but I have not heard of Kato flex track before. Their Unitrack gets lots of good comments here.
The Peco turnouts are excellent. In my opinion, and that of many other experienced modelers, they are the best commercial turnouts available
. Joining Kato Unitrack to Peco turnouts would require some basic modification, but it's quite doable. For one thing the Peco turnouts would need some cork roadbed or other support, under them to shim them up to the same height as the Kato Unitrack. You might also have to replace the Kato rail joiners with Peco, or Atlas, rail joiners.
Kato makes Unitrack turnouts which, of course, plug right into other Unitrack pieces. They are decent turnouts, but not as good as Peco. The attached file, "All about turnouts" has lots of general information on turnouts and a rating of seven common brands of commercial turnouts.

Good luck, have fun!

Traction Fan :smilie_daumenpos: