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    Pipe fitting bend radius issue

    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
    :banghead:

    #2
    The sizes in the lookup table are probably based on manufacturers info. What you need to know is how each size relates to another.
    Theres two possible solutions I can think off:

    First I would open the lookup table in Excell. Its a csv file so it should be possible to get the data formatted in columns.
    Then suppose you want to know how Size A relates to Diameter, Plot a graph of the Size A column against the Diameter column. Depending on what the relationship is between the two sizes you might get a straight line (Eg Size A = Diameter x2 or something) or a more complex curve. Select the datapoints in the graph and add a regression line (Choose the best fit). Then select Show Formula on graph. Now you have a formula for how Size A relates to Diameter.

    Personally I hate lookup tables. Making a family dependent on an external file for it to work seems stupid to me and its one more thing to manage and correctly set up. So I would use the formulas directly in the family. For example Centre Radius = Pipe Diameter * 3 + 100mm, or whatever the formula is. You might want to use a rounding function to get standard sizes or whole numbers.

    The other solution, if you really want to use lookup tables, is to put the new sizes you want to make in to the formulas in excell and then fill in the calculated values in the lookup table file.
    "One must imagine Sisyphus happy." Albert Camus - "The innovator has for enemies all those who have done well under the old conditions, and lukewarm defenders in those who may ​do well under the new." Nicolo Machiavelli -"Things that are too complex are not useful, Things that are useful are simple." Mikhail Kalashnikov

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