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What radius curve can I apply


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In that space you could put in an arc from a curve on which high speed running is genuinely possible, down a  long side. A scale mile radius or more...

 

In terms of 'mechanics' to return the line at the ends, in that sort of space use 36" radius in 4mm scale. Trouble free running, relatively little drag on curves even with a train round 180 degrees of it. Little point in going larger, 60" radius still scales as a really tight curve in reality, requiring a check rail for passenger operation and very slow speed.

 

Better to conceal the return curves in my view and use as much of possible of the long sides to show really easy curvature.

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Transition curves are great for this sort of situation.

 

If you have a "wide radius" curve from the end of the straight section, say 15ft radius, then down to 10ft radius then 5ft radius as mentioned above (do the reverse on the curve coming out, or from both ends - same difference).

 

It then makes the difference between curve and straight far less noticeable, and if you can hide the tightest curvature in a tunnel, for example, even better.

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The beginners idea of four sharp corners with straight lengths between them rarely looks natural. The advice of using transistion curves is good. Look at an Ian Rice track plan barely any straight track. If you can fit it in a 4ft minimum on main lines would be fine yes 3ft will work but 4ft looks better. A bit of curved track going through a tunnel  where you can see both ends looks odd to me  I find a deep cutting looks so much better unless there is a senic break.

Don

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Transition curves are used on the real railway and when used for models can permit realistic-looking curves with deceptively tight minimum radii.  A transition curve also helps the trains to ease into and out of the radius rather than suddenly lurching from straight to minimum radius then back again.  Wear and tear is reduced and there is generally less drag which can slow down trains and even cause derailments.  There is less chance of coupler problems as what ever system you use the pivot mechanism has a chance to transition steadily from one extreme (straight) to another (curved) and back again. 

 

There are other tricks which can be used to disguise sharper radii while still retaining that realistic feel.  Even with a lot of space available taking a sharper curve through a tunnel around the corner can help give longer transitions either side and perhaps a straight run along the shorter edge.

 

Take a look for example at my own layout thread (linked in my signature) which uses very tight radii around the top corners which are effectively concealed and which - with transitions and in my case also a little cant - mean I can run long trains with perfect reliability through curves which are near the minimum radius quoted for the stock in question.  But only that tight for a few inches!

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Certainly.  At the bottom of my posts there should be a couple of lines of grey text and three hyperlinks in blue.  Click on the blue link "Visit Penhayle Bay" to go to my current layout.

 

If you don't see that link on your device perhaps try a search for the name "Penhayle Bay" as it will come up on any search engine and usually link to this site as the tope result.

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Gwiwer, signatures don't appear on the "mobile" version of RMWeb - I don't know if jimikelly is viewing RMWeb on a mobile device though, if on desktop I believe there is an option to "turn off" signatures somewhere in the control panel.

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Gwiwer, signatures don't appear on the "mobile" version of RMWeb - I don't know if jimikelly is viewing RMWeb on a mobile device though, if on desktop I believe there is an option to "turn off" signatures somewhere in the control panel.

 

Ah.  Not using a mobile to browse the web (I'm of an age where "phones" are used for making phone calls - sending texts at a push) I wasn't aware of that.

 

Click on this link which directs to a post in the thread including a half-decent view of the tightest curves on the layout as described.  http://www.rmweb.co.uk/community/index.php?/topic/6296-penhayle-bay/?p=1425071

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Following up a couple of the comments about tightening radius as you go round the corner, this, I think, gives the idea.

 

post-110-0-83485800-1404412925_thumb.jpg

 

The radius in the foreground is about 6ft, tightening to 3ft around the gantry beyond the lattice one. There's no tunnel or anything, the scenery just falls away as the fiddle yard is entered as here;

 

post-110-0-50878900-1404413120_thumb.jpg

 

The locos are almost at the end of the scenic section, on a 3ft radius curve. The embankment to the right of the camera drops to ground level beside the camera

 

 

 

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