M_Rectangular Length Eccentric Transition - DTL

[ukpxm021]

Background:

I'm in the UK and I'm working on a design project involving lots of rooftop AHUs.

Due to design/political constraints, I've used a number of instances of the above fitting (about 68 in total). Initially, I did use concentric fittings but the Client insisted that fittings were flat on bottom so that proper assessments could be made of visibility lines and screening requirements. The design is such that I've used transitions which are at an angle greater than the standard 22.5 degrees (sometimes up to 45 degrees). Eccentricity is mainly needed in the vertical plane, although a small number are also eccentric in the horizontal.

Grateful:

First, I should state that I'm grateful that there is a fitting out of the box that I can use for this purpose (the fitting listed above). I don't think we had this in ABS and it was a big shortcoming. So we are making progress.

The Problem:

First, the object has to be edited after insertion to suit the particular instance. Then, every time I alter a duct size, the fitting reverts from "flat on bottom/concentric on plan" to "eccentric in both planes". The eccentricity then has to be individually edited again. Furthermore, editing is not possible at all unless there is sufficient length of duct on either side of the transition. Since I'm dealing with heavy spatial constraints, there is no room for any length of duct between fittings. To make any modifications (without Revit deleting the part) I've had to stretch out the ductwork, make the modification, and then stretch back the ductwork to suit.

Time Consuming:

As you can imagine having to edit the part about 68 times for the initial insertion, then having to re-edit things again for any change has been very time consuming.

Has anyone else come across this and found a better way of doing it?

The project was done in Revit 2010, but I've checked and the same part is used in Revit 2011.

Request.

Is there any possibility that Autodesk can review the fitting/application and come up with a better solution?

I've had a brief look at the part in the family editor but I think it would take me some time to come up with an alternative and I don't currently have a budget for the time.

Has anyone got any experience/tips?

Attached is a copy of the object.

Thanks.

[julianjameson8403]

Have you set up a the duct type to use the eccentric fitting as a standard when changing size? This will prevent the fitting reverting back to the concentric one when editing ducts, etc.

To ensure you have flat base duct lengths, you could also investigate the justification tool which will allow ducts to connect base with the base continuously flat.

[ukpxm021]

Julian

Just to clarify, the fitting is not reverting to a concentric fitting, it is still the same fitting.

The eccentric fitting is set as the default for the duct standard in use.

[ukpxm021]

Here are some screen shots showing before and after.

The duct is initially FOB and Concentric in plan.

After reducing the duct height by 100mm, the duct is then eccentric in both planes.

Hope this clarifies.

[julianjameson8403]

If you set the justification of the two ducts to be bottom centre do the ducts and fitting still behave like this vertically? with regards to the horizontal amendments, have you tried aligning the ducts using the centrelines and and then locking the alignment?

[ukpxm021]

Changing the ducts to bottom justification makes no difference to the result.

[embolisim]

"To make any modifications (without Revit deleting the part) I've had to stretch out the ductwork, make the modification, and then stretch back the ductwork to suit."

Thats typically what I do too & yeah its frustrating.

OOTB the same fitting family is used for eccentric & concentric fittings. I duplicate & rename them so I can schedule them separately, but care needs to be taken that the right one is used in the right place!

If you are not scheduling the fittings, make the part you need as a duct accessory family & just draw it to the right size with no parameters. It doesnt take long as a transition is just a blend with a connector on each end.

Not an ideal solution but will get you out of a bind.

[ukpxm021]

embolisim

Thanks for the tip.

I'll probably do that in future.

Cheers.

[Anonymous]

I am trying to produce an eccentric fitting in the X-Y plane and I have not been able to.  I tried to create a new family and modify the existing duct fittings. but that did not work.  I have a situation where only an eccentric transition will allow for the size change in the space I have to work with.  Can you be more clear about "...setting up the duct type..."?  I have been in mechanical engineering for a long time and I know that things will fit, I just need to show it.