Can someone please shed some light on an issue for me.

Working with Revit MEP, I am creating new pipe fittings and have come stuck on one parameter (how to obtain or how to calculate it)

On a fitting that has a bend (an elbow say) where that bend is governed by a “Centre Radius” parameter to keep the bend consistent when the fitting is used on various sizes of pipes and at various angles. This “Centre Radius” parameter is governed by values that are obtained from the lookup table for the fitting but I can’t find how to calculate this value to put it into a lookup table in the first place. I am trying to create a new fitting and lookup table for a new pipe type, the MEP tutorial gives you the "Centre Radius" distance and it gives you the lookup table with all the values already entered for each pipe size, but doesn’t actually tell you how to calculate it for new pipe sizes. I have also tried using an existing fitting and lookup table that I can re-name, but I want to add a few more sizes to the lookup table but I can’t find that one measurement or how to calculate it, I have tried to work out how they did the existing ones but can’t seem to crack it. This measurement is integral for the bend to perform properly, if it is done incorrectly the bend will still get inserted when you draw two pipes at an angle but the centre part of the fitting, the bend between the two couplings, gets omitted and of course the pipe fitting then doesn’t look right.

I was hoping that someone out there, with more MEP experience than me, was able to explain to me how I calculate this value so that I can put it into the lookup table for new pipe sizes.

Any assistance would really be appreciated.

Thanks