Dome Construction

[ABJ]

Hi Guys

I am trying to draw the flange on a dome and I am finding it impossible.

http://www.livesteam.com/heavymikado/B-2109.jpg

It will ultimately require bolt holes round it at right angles to the flange face.
Does anyone have any tips please.
I am using AutoCAD 2004

[aledtaylor]

I'd draw half the cross-section of the dome and flange combined (including the internal and external surfaces) ensuring all the lines, arcs and polylines join up at their ends. Turn them into a region and revolve around the axis.

For the holes I'd extrude a circle into a cylinder and polar array it. Then position them and subtract them from the dome.

This sounds like a straightforward 3D solid exercise but perhaps I'm missing something.

[scj]

It seems to be possible in AutoCAD (2000).
If someone is interested in the description, please ask.
(See the direction of the boreholes - here they are straight downwards.)
Regards
Jochen
www.black-cad.de

http://www.cadimage.net/postimages/Dom.jpg
http://www.cadimage.net/postimages/Dom.dwg

[aledtaylor]

Is it a 'saddle' flange you’re after. Like you'd find on top of the boiler of a locomotive?

If so, you could cut a section out of a hollow cylinder (use another cylinder and the 'intersect' command). But this will give vertical sides and would not give the impression of a round metal plate that has been bent.

If you want something more accurate, you could do it this way:

Using 2D projection techniques, draw the shape of the upper and lower surfaces of the flange. Use these to extract sections of a hollow cylinder as described above. explode the solids. They will now be surfaces. Delete all but the correct upper surface and the correct lower surface. Bring these together with the correct spacing. Copy them to the side. Explode the copied surfaces. They will now be splines. Draw 'Ruled Surfaces' between the splines (Don't forget to set surftab1). Move the surfaces together.

You can then use M2S.lsp to convert it back into a solid.

http://www.cadimage.net/postimages/flange.jpg

Note: I scaled one of the surfaces rather than construct it. That's why the flange does not look exactly right. I only want to demonstrate the technique