How to edit the radii and height of a truncated cone

I have a truncated cone. How do I change the radii and the height to a specific value?

For example, in the truncated cone shown, how would I set the smaller radius to 1", the larger radius to 2" and the height to 3"? These settings do not appear on the object’s property panel.

I don’t think there is a practical way to modify the radii and the height, but its just as easy to make a new one as it would be to modify an existing one.
Using Center osnap, you can use the old cone as a reference and when your done making a new one delete the old.

That is because Rhino is not parametric, the construction parameters are not stored in the object.

As Jim says, it’s probably just fastest to make a new one, but you can modify the existing one by sub-object selecting the top or bottom circular edges and moving them to change the height, or 2D scaling them to change the diameter.

This looks like a giant miss to me. The truncated cone is one of a number of “primitive” types (they’re sitting right there on the solids tab). It seems if you select a primitive type like that, it should tell the Properties panel what fields it supports (e.g. big radius, small radius, height).

Having to “get it right the first time” while dragging with the mouse doesn’t seem like the correct approach.

@Helvetosaur explained how to modify your object to get your desired results.

If you want parametric control, you can use grasshopper or a python / C# script.

It took a couple of minutes to put together this grasshopper script. Drag the sliders to get your desired result then bake to the Rhino document. (10.0 KB)

If you don’t know grasshopper (or python / C#), simple scripts like this are a good way to start learning.