CAD Software one minute nosecone surface

[kramer714]

been involved in a few discussion on here about freeform modeling vs parametric.. My general comment is for most stuff people do on here free for is faster and simpler... and doesn't prevent you from using the model for other sizes shapes. Recently talked to a friend he asked how long does it take to do a 'ogive nosecone' surface model, i told him about a minute. I did it and it took about a minute. here are the simple steps
1 draw a circle
2 draw some lines (note shown is a 4/1 ogive
3 draw an ellipse
4 trim / divide
5 scale it one way
6 scale it the other way
7 mirror / trim
8 fillet tip (sharp tip can be modeled but not really built, always a break of some kind)
9 revolve
10 extend shoulder

simple, fast

 

[Rschub]

Ok, now change it to 3/1 ogive.

 

[kramer714]

changing scale - aspect ratio

Once you have the surface it is easy to change the scale, length / aspect ratio, or diameter

11 Using the shoulder - simply scale 3d
12 Using the center of the shoulder as the base....
13 scale 3D
14 using the center of the shoulder as a base
15 scale 1D

ok 30 more seconds

 

[kramer714]

Make solids

Wall thickness (Madcow tubes) - making a solid at the correct wall thickness,
54mm tube 1.15 mm
3" tube 1.5 mm
4" tube 1.5 mm

from the surface model. 'offset to solid'
16 surface models
17 'offset solid - 1.15 for 54mm, 1.5 for 3", 1.5 4"
18 other view

another 30 seconds...

 

[kramer714]

Free form makes it east to modify / change.

What if I wanted a canopy for it

20 draw an ellipse (note can be any shape, and can have the orientation changed
21 revolve it into a surface
22 put it in position (and scale if needed)
23 / 24 trim / split both surfaces
25 variable radius fillet surfaces

 

[Rschub]

OK, I am a fellow rocketeer checking this out. How do I know what I am looking at other than a pretty shape? What's the diameter? The length of the shoulder? Is this a circular conic section or elliptical? The thinking you used to arrive at the shape on the screen is totally unknown unless you provide a multi screen tutorial.

Parametric modeling has a history tree that shows all the steps taken to arrive at the shape, which are absolutely numerically repeatable.

Both ways certainly work, my opinion is that parametric is better in these types of applications.

On the other hand, no-one is using a parametric program to make these types of models:

 

[kramer714]

free form doesnt mean just drawing lines, each line or shape is pure, the basis of the nosecone is a pure ellipse. the vertex is exactly 4X the diameter plus exactly the fillet radius. The shoulder is extruded the length I told it to. The part is exact, and exactly the aspect ratio I wanted.

I used a section from an ellipse in this example but I would have used any generated curve (can be generated in excel for example, just need the data points)

Not meant to be a tutorial, there are plenty of them online (look for Rhino 3d on You Tube Rhino Motorcycle). Just trying to get folks to understand that you can do exacting shapes VERY quickly without parametrics.

I have Solid works, and have worked on CATIA, Having said that, 90 percent of what i do / develop comes from Rhino, save a lot of time, even if I end up creating a block for Catia / solidworks in it.