Curve realignment question

[Ploughman]

I suppose this will be more a question for Old Timer
I recently did a curve realignment scheme for a Reballasting / Formation rebuild scheme over approx 400m at an average of 300m radius jointed 110 / 113 FB on F27 sleepers.
Is there a rule of thumb guide or a formula for estimating the expected gap if all slews are outwards on the curve?
Due to requirements of the site 200m of the slews were over 300mm and up to 750mm.

All other requirements of the scheme were met with Cants and radius's within limits for speed.

 

[Old Timer]

I did a similar job a while back but we just cut in a closure because it was in CWR.

This is one for one of the clever Engineers.

We will come back to you.
.

 

[Ploughman]

That was the answer we used as well, except we will have to go in and weld up the 30ft closure, otherwise we will end up with a bad bit of line.
Just wondered if there was a formula of sorts to estimate the gap.
I am used to CWR calcs but that would not work in this case.

 

[Old Timer]

You could try a bit of geometry, raduis, diameter, etc. subtract the new from the old measurement but to be honest its not the sort of question that I have ever heard asked before.