Creating an eccentric reducing shape

[Ferroequine]

Hi All,

I need to create a shape that is cylindrical & reduces in size along the path. However, unlike a regular cone, it needs to be flat on one side (similar to an eccentric reducer).

I've been out of 3D for a while, and I can't remember how to do it...:banghead:

Help!

- Vince

[Glenn Pope]

I don't mess in 3D all that much, but could you create another solid, place it at the spot you want flat and subtract it?

[David.Hoole]

Hi Vince

I think you need to supply a few more details before anyone can really advise you on this one. Could you upload a sketch of what you're trying to achieve? Vanilla AutoCAD isn't too good at this sort of thing, but it's surprising what can be achieved with a little persisitence. You might find it simpler to use surfaces rather than solids to model this kind of shape, if surfaces are acceptable.

[Ferroequine]

OK, here's what I'm trying to achieve. It is the transition section on a chiller (I work in oil & gas). I've seen the shapes in AutoCAD solids before, but don't know how they accomplished it. As you can see, the two diameters are different sizes but line up on the same longitudinal axis. The bottom is flat.

[jaberwok]

I work in solids almost all the time.
This is one of the few forms that I've never managed to create using only acad's solids tools. I create them with surfaces then use M2S.lsp to convert to a solid.

John B

[Ferroequine]

John,

Thanks for you insight, I don't feel as frustrated now...:D

Can you tell me more about M2S.lsp? I have no problem creating this shape with surfaces.

[Mike.Perry]

Hi

Check out the following threads -

3D Meshing and Solids (http://forums.augi.com/showthread.php?t=4555&highlight=M2S.lsp)

converting 3dFaces to 3dSolid??? (http://forums.augi.com/showthread.php?t=7097&highlight=M2S.lsp)

Have a good one, Mike

[jaberwok]

To use M2S.lsp effectively, you need to position your UCS so that it "looks" parallel to the length of your mesh from the small end toward the larger end.

John B

[David.Hoole]

This is a method I've used which produces satisfactory results:

1. Draw centrelines of pipes to be joined.
2. Draw centreline of reducer.
3. Create section plane perpendicular to reducer centreline.
4. Create 3D pipes to be joined allowing overlap with reducer.
5. Section larger pipe perpendicular to reducer centreline.
6. Calculate taper angle required.
7. Extrude region created by section along reducer centreline with calculated taper.
8. Use slice to remove unwanted elements of pipes.

It's quite a difficult process to describe quickly in a small space. I hope I've given enough info?
I've attached a couple of images to show the construction & the finished object.

[Ferroequine]

Thanks for you help, David. That was the missing link. 8)

Much appreciated! :beer:

- Vince

[David.Hoole]

Hi Vince

Glad I could help. The method doesn't produce a perfect offset reducer, but it's close enough for most purposes. I haven't been able to produce a better one using vanilla AutoCAD.

[GraemeCooper]

Hi Vince

please see attached dwf for a simple step by step to creating your BW Eccentric Reducer model.

Hope this helps

Graeme

[Ferroequine]

Thanks Graeme, that was very informative and useful! I hadn't even thought of doing it that way. It reminded me of descriptive Geometry somewhat! :lol:

:beer:

- Vince