Column Family Behaviour

[grantkjones]

Hi, I'm new to Revit, I've been searching but I cant seem to explain to google well enough so, straight to the source.  I am drawing up a simple skillion roof structure like an open carport.  My Columns (100mm steel posts) have tabs on them for bolting, but they are behaving strangely.  I have angle cut the top of a column to 20 degrees, and want to put a tab on the low side, also at 20 degrees, so a purlin will sit on top and be bolted from underneath.  The tab, however wont associate with anything and is miles high up in the drawing and i cant seem to get it to attach to the column in the correct position. 

Also I'm not sure how my void extrusion works.  In the family it has shown to cut the post on the 20 degree angle, but in the project, the top of the post is still square.  I have attached the family and some screenshots

Any help on this would be appreciated.

Ta

Grant Jones

[barthbradley]

Wow! Been doing this a long time and I have never seen "simple" skillion roof structure support columns that looked like this. Do you have pictures of the finished construct?  

[grantkjones]

@barthbradley No, sorry, still just getting started on it.  Its a bit of a strange design, I could just run the purlin rafters next to the posts instead of having everything centred, but I'm using this to learn about how to manipulate things.  It took me 2 hours just to figure out that i needed the posts connected to the top ref level, otherwise when i loaded them they just shot up into the sky.  It seems when i put my tab on the angle it disconnects and wont attach to any levels.

[barthbradley]

do you have a design visualized by why of pictures you downloaded off the internet , or buildings  that are adjacent  to the property you are building out?   I mean, where did you get the idea to do it this way.  Not saying it wrong. It's just not typical in my neck of the woods.   

[grantkjones]

No its nothing existing, I have put together a few similar to this at the coal mines I worked at, each one was slightly different.  At this point its more about working out why my tab isn't playing the game rather than good design! I could have just changed the post positions but I am stubborn and want to know why my angled tab wont stay put.  I am happy to hear your thoughts on a more standard way of designing this thing.

[lucdoucet_msdl · Accepted solution]

@grantkjones 

Contrary to the vertical plate, the sloped plate is not constrainted to the top level in any way and therefor stays at a constant height above the bottom level. I would suggest you model the void and the plates in a seperate family and embed it in the column familly. This additional step will help later with the constraints.

The same thing is happening with your void, it is not constrained to the top level and staying in a fixed position with respect to the bottom level. You can see this by moving the top level above the sloped plate and the void bites a chunk out of the right side of the column.

1. Create a new generic model (Which I'll call "TopPlate") and add the same reference planes that you have in the column family;

2. Model the void, vertical plate and angled and constrain them to these reference planes

3. Insert the TopPlate family into the Column family and contrain them the align and constrain it with the top level.

A good family modelling practice is to place and constrain reference lines and planes to each other first then model and constrain the objects to the reference objects. This allows you to test that the reference objects relationship work before committing to modelling something complicated. So at any time in the steps above, move the reference objects to see how they behave in the family editor before inserting them in a project.

Good luck,

-luc

P.S. Now, why do all this work for a fixed 20 degree angle when it could be parametrically driven. For that, I would suggest you look at the "open reference circle" solution on the Simply Complex Blog. This will help avoid the family breaking at an angle of 0 degrees. It's a more advanced workflow but more flexible.

: http://therevitcomplex.blogspot.com/2012/04/rotation-rigs-that-do-not-use-angluar.html

[grantkjones]

@lucdoucet_msdl thanks for your reply, apologies for not replying sooner, having some post op health issues atm.  When you say embed, I'm assuming you mean nested? I googled embed and nested kept popping up.  I did try (in the main post family) with an angled reference plane to associate the angled plate to, but it didn't seem to make a difference.  I cant see any way to create another ref level, not sure whether that would change anything?  As for embedding families I'm going to have to spend some time getting my head around that, and i had a look at the link, well over my head atm but i will keep it bookmarked for a later read when i can understand the words hahah