Finding volumes of rotate shapes

There has to be a way to do this, but I can't figure it out! I'd love to know the difference between a cylinder & a cylinder with a simple chamfer in it. Does anyone know of a quick way to do this? Or any way to do this??

Are you trying to find the volume of a cylinder, or how to make one in AutoCAD 3D?

I'm trying to find the difference in the volume between a cylinder and a cylinder with a chamfer. How do you find the volume? I know how to make them, but how do I tell what the volume is of each?

Luckily AutoCAD has a tool for this. MASSPROP will show just about all the information for a solid you can handle, kind of like LIST does for lines. This can also be found on the Inquiry toolbar, as the third option (Distance, Area, then Regions/Mass Properties).

Well you could use Math or...[Edit: been awhile since I've done 3D with CAD]

If you can't find the properties, I can tell you how to do it Math-wise.

Edit: Or you could try it that^^^ way too...

Well you could use Math or...I believe selecting said cone, right click properties should list its volume as long as it's a 3D object.

 

If you can't find the properties, I can tell you how to do it Math-wise.

 

Edit: Or you could try it that^^^ way too...

what's math?

Thanks maxwell!

what's math?

AutoCAD has made us all lazy in the that regard I guess. I actually had to look up what formulas you would need as a refresher, and I minored in Math in college. I am ashamed.

If you do per chance want to know how to do it without AutoCAD, a chamfered cone is basically a Frustum Cone.

actually, after making a sweep of a triangle (1"x1") along the diameter of a circle (1") i've realized that I can't exactly do that because it didn't make it a solid... and I was unable to union it all into 1 shape. So maybe this deserves a new topic, but how do you make that shape a solid to obtain said volume with massprop?

Did you try Rotate?

Oops, I meant Revolve.

yes, i've done both sweep and revolve and the message when trying to union the objects is:

"Union"

Select objects:

At least 2 solids or coplanar regions must be selected.

Are you trying to put the chamfered cone on top of the other? If so, Union doesn't work that way.

Try describing exactly what you're trying to do. That should help us help you.

well it's just a triangle revolved around an axis (2" diameter circle), 360 degrees... which ends up being 3 surfaces (revolved). so I guess my question boils down to: how do I get the volume of that? I'm not sure why I'm not able to make it a solid to get that volume via massprop is the real issue.

To get a solid when using sweep or revolve, you need to ensure you are sweeping a closed geometry. If you drew the triangle with lines, or with a polyline left open, it will create surfaces. You can ensure that a polyline is closed in the properties palette (scroll all the way to the bottom).

If you just have lines and don't want to go through the hassle of tracing or converting them to polylines, you can use the BOUNDARY command. This creates a closed polyline or region by picking a point and inferring all its surrounding boundaries, similar to selecting for a hatch. If your linework contains elliptical arcs, you will only be able to create a region. These can still be extruded, revolved, or swept to create solids. If your shape is very detailed and you only want the outside boundary, draw a rectangle around it and then pick a point between the rectangle and your linework when creating the boundary.

I hope this helps

i re-traced the triangle with using the polyline function... it worked

you lost me on the boundary command, it kept erroring when i picked a point... but that's ok since I got it with the polyline.

Also, can't you just join the lines by making a block out of them or something to make revolving more complex objects easy?

I took the liberty of working out the formula you're looking for:

V = PI*h * [(R^2 + R*r - 2r^2)/3]

h is height of triangle

R is 2"+triangle width

r is 2"

PI is...well PI(3.14...)

I took the liberty of working out the formula you're looking for:

 

V = PI*h * [(R^2 + R*r - 2r^2)/3]

 

h is height

R is 2"+triangle width

r is 2"

PI is...well PI(3.14...)

hehe, I appreciate the effort, and there is a good chance we'll use that formula rather than re-model it every time we want to know the volume change of a chamfer... so thank you!

You can't perform 3D transformations on a block. There are some LISP programs which will turn selected lines into polylines (search for "convert"+"polyline"+"LISP").

Boundary likely gave you errors because the geometry wasn't really closed. Kind of like using the paint bucket in Paint, one little gap and the whole drawing is red. This "fuzz" distance can be adjusted, but it's usually best to correct the problem rather than working around it.

I usually try to draw closed geometries whenever I'm doing linework, especially when It will be used for a 3D model. Rectangle and polygon are your friends.

I did a little messing around with the 3D Cone feature in AutoCAD. You can make the cone as you described with it, then make another cylinder inside it to subtract away from the cone to get you're 3D shape rather quickly.

Let's put this one to rest.

Attach the file here.

I think it's all figured out Mather.

By the way, how are classes these days? Any knuckle heads like you had with my group?