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O gauge loop size - larger than set track


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Dan,

 

A transition curve starts at a greater radius than the minimum radius of the curve.

 

It makes the curve more elliptical, so you start with a straight that gently starts to diverge and then progressively tightens up until it reaches the 5 foot you have set yourself, it then eases off as it come out the other end.

 

 

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img016.jpg.d79f3639eeb32f7f63818cd67fb1a295.jpgDan further to my last:

 

This is a very crude illustration of how to make up a transition curve.  There is no doubt a formula, but this will give you some idea of what you are looking for.

Edited by Happy Hippo
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2 hours ago, Happy Hippo said:

img016.jpg.d79f3639eeb32f7f63818cd67fb1a295.jpgDan further to my last:

 

This is a very crude illustration of how to make up a transition curve.  There is no doubt a formula, but this will give you some idea of what you are looking for.

 

Fantastic, understood perfectly. Thank you for taking the time to draw it.

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Transition curves are a good thing, great where space permits, but do they actually, of themselves, prevent buffer-locking?

 

I ask because, frankly, I can't see how they would. If the buffers ride past one another on the tightest part of the curve, surely they will lock as the train moves through the transition to straight, won't they?

 

 

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33 minutes ago, Nearholmer said:

Transition curves are a good thing, great where space permits, but do they actually, of themselves, prevent buffer-locking?

 

I ask because, frankly, I can't see how they would. If the buffers ride past one another on the tightest part of the curve, surely they will lock as the train moves through the transition to straight, won't they?

 

 

Exactly what I've been saying!! (or trying to, at least!)

 

As illustrated by Mr Hippo above, transition curves will also widen the diameter, so a 180° turn of 5ft radius will have a diameter wider than 10ft if transition curves lead into & out of it. In the OP's case, because it's touch-&-go whether it'll work with long stock or cause trouble, it might be better if space is tight to forego transition curves and use a constant 6ft radius anyway which should work fine with scale couplers & buffers without additional compromises.

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45 minutes ago, Nearholmer said:

Transition curves are a good thing, great where space permits, but do they actually, of themselves, prevent buffer-locking?

Yes, they do.

 

45 minutes ago, Nearholmer said:

 

I ask because, frankly, I can't see how they would. If the buffers ride past one another on the tightest part of the curve, surely they will lock as the train moves through the transition to straight, won't they?

 

 

When two vehicles are fully in the same curve, their buffers overhang the rail by the same amount and on the same side and so they can't ride past each other. The difference in their outswings is effectively zero.

 

Imagine track that simply goes from straight directly to a constant radius curve. The end of the vehicle still on the straight will have very little outswing but the one fully on the curve will have maximum outswing - maybe enough difference for the buffers to ride past each other.

 

A properly designed transition curve just ensures that the outswing of adjacent vehicles both increase gradually together so that the outswing difference is never greater than a buffer width.

 

Sorry if that's teaching Grandma to suck eggs.

 

(Did someone say Euler Spiral?) :wink_mini:

 

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On 26/09/2020 at 21:24, Harlequin said:

A properly designed transition curve just ensures that the outswing of adjacent vehicles both increase gradually together so that the outswing difference is never greater than a buffer width.

That's where the complicated maths comes in... :read: :mail:  :help:

 

The length of the coupling chain/link needs to be accounted for too; this also dictates minimum radius, even if the buffers behave. 

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