Straighting the curves

[mikec069]

On a purely curious note, if one were to 'straighten' out an 18 or 22, or ANY curved piece, how long would that straight piece be.  I as because I was laying track and noticed the 18" curved seemed longer than the 22".
On a slightly related note what is the divergent turn on a standard turnout? (18, 22, 26, 375)

Thank you all and one
Mikec069

[rustyrails]

Well, a full circle of 18" radius track has a diameter of 36".  The formula for the circumference of a circle is Pi times the diameter or 113.04 inches.  Since there are 12 pieces of track in a full circle, each piece is approx. 9.4 inches.  You do the math for a 22" radius circle. 

As far as the turnouts are concerned, in the real world, the route through a turnout is not a curve.  Rather, it is a straight line diverging at an angle determined by the frog number.  For example, the diverging route separates at an angle of 9 1/2 degrees through a #6 frog.  Check with your LHS for a good track planning book.  It ought to show you how to draw turnouts "by the numbers."

In our model world, Atlas "snap track" turnouts are an 18" radius curve through the frog.  Other brands have secitional track with similar geometry.  I believe that Peco turnouts are also curved through the frog.  These trunouts can be drawn with an arc of suitable radius. 

Hope this helps.
Rusty

[jward]

the 18" and 22" curves atlas makes are designed to be as close to 9" as possible and still have a reasonable number of pieces peer circle (12 for the 18", 16 for the 22")......if you are trying to figure out a grade, 9" per section is a reasonable estimate.

[Keith Brann]

I'm confused.

I'm using a long string of 9" long 18' radius curves to go a length of ten feet along the edge of a wall.  The pieces obviously face different ways one after another.  Before I get to the corner I want to straighten out for two feet.  Would I use an 18' radius half curve to perform the straightening, so I can then attach the two feet straight track?

If not the half section, then which?

I'm using the snap track.

Thanks for any help and advice.

[Doneldon]

Keith-

If I understand your most recent post correctly you want to use a series of 18" radius curves in an alternating pattern for your track along a wall. That set-up will cause serious operational problems. A short interurban (car, not train) might be able to handle this set up but no train will do so. Okay, a short industrial switcher and some ore cars might work, but nothing else.

What you are describing is a series of reverse curves. These are a challenge even when you only have two curves in opposite directions. What you're describing would be hopeless. Yes, you probably have more curves than you need because you got a circle of track with a train set but stringing them together like you seem to be planning won't let you put them to good use. The rule of thumb on reverse curves is that you need a length of straight track between the curves equal in length to the longest car you'll be operating over the track. I'm not sure that a straight section between every piece of curved track would make this set up operational because you will be going back and forth like a snake. This will look lousy and as though it were laid out by a drunken surveyer on a blind mule, as my father used to say. Well, he actually said something a little different but it was quite non-PC and most certainly not suitable for a family discussion board.

The reason that the 18" curved sections are longer than the 22" radius curves is that the 18" curves have 30^o of curvature but the 22" radius curves have only 22.5^o of curvature. This is why you need 12 sections to complete an 18" radius circle but 16 pieces of 22" radius track.
                                                                                                                                                                                           -- D

[Keith Brann]

Well I guess you can tell that I'm a rookie.
Thanks for the advice.
KEITH>