How to reduce the size of a dome

[john.n.johnson]

I am designing a garage fan base and wish to create a "low profile" dome shape for the base. If I use a sketch and 3-point arc and revolve the arc shape, I get a dome shape which is far too high. How do I reduce the height of the dome? Maybe my approach/workflow for this is incorrect. Any help will be greatly appreciated. (Attached is a copy of the model). 

[davebYYPCU]

Use a 2 point spline, make the tangent handles, vertical / horizontal, and adjust the shape with the handle length.

Might help....

[etfrench · Accepted solution]

Well, that is certainly a novel method for making a dome😁  If  you do the revolve  on the XZ or YZ plane, you can change the height of the dome without changing it's base diameter.

[jmillerXL6J2 · Accepted solution]

Here's how I would do it:

https://autode.sk/3Aovuqd

[john.n.johnson]

Thanks very much for the help.

[john.n.johnson]

Thanks very much. I do like the use of parameters to drive/change dimensions. Being relatively new to FUSION 360, I still struggle to articulate the spline tool to get the "right" shape. The spline tool certainly offers a lot of flexibility in setting the curve of the dome.

[g-andresen]

Hi,

I use parameters almost all the time but with splines it makes little sense in my experience.
For me, splines are a tool that should be subject to sense control. When I edit control elements (points and tangents), I have to see what effect it has on the shape. Also, one has to consider the interactions in such actions.
A fit point spline requires 4 determinations (dimensions or constraints) per control point. Control point splines, on the other hand, require only 2, but one additional control point.

günther

[john.n.johnson]

Thanks for sharing your spline approach. It makes perfect sense and helpful for future projects when using the spine tool.. For this project, I don't plan to use the spine approach.

[jmillerXL6J2]

My experience with splines is that they are prone to "losing their mind" when parameters change too much.

I still use them parametrically, but you have to review the results carefully when parameters change.

The advantage, of course, is that so long as your parameter changes are minor, your downstream solids (revolves, extrudes, etc) retain their sketch profiles.

FWIW, I don't think of myself as anywhere near a serious Fusion360 user, but one thing I've determined is that you always want to start with parameter definitions. You'll inevitably discover more parameters you need once you start modeling, but you should always have a list of basic ones in mind when you begin. Just the process of thinking through that initial list has a way of clarifying the task in front of you.

Regarding control point splines, I do probably lean on them more than most. That comes from years of working in 2D graphic design (Adobe Illustrator) where the "pen tool" is essential. New Illustrator users often find that tool vexing as well, but once it "clicks", you can do all sorts of things with it.