Full Version: Trying to truncate a cone to get a "bucket"

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Hi Bryan, so 2D drawing steps would be like this -

Go to Options and set Unit system = "Millimeters"

On the bottom toolbar click "Front" on the view tabs since you'll be working only in that view for a while.

Run the Line command, Side pane > Draw curve > Lines.

The prompt in the upper right of the window says "Pick start point" (look here to know what MOI is asking you to input next).

Type 0 and push Enter to put the start point at 0,0,0

The prompt will now say "Pick end point".

Type 34.89/2 and push Enter. That will set a distance constraint of 17.45mm so the line will be that length and you need to give it a direction. Click along the x axis and you'll have this line made:



Then I think the line for the cone is meant to be at a 10 degree angle from vertical?

Draw in another line with first point snapped on to the end of the initial line, and move close to the vertical direction so it snaps to that direction about 40 units or so tall. Click on the line to select it, looks like this:



Now run the Transform > Rotate command, the prompt will say "Pick center of rotation", pick the bottom of the vertical line where it touches the first line. The prompt will say "Pick first reference point" and there is also an Angle field. Type in 10 and push Enter.

So now you have the profile of the cone but you need to find where it is supposed to end.

Your drawing doesn't directly specify the end point of the cone profile, it has some slab widths it looks like which you could draw in by selecting the bottom line and using Transform > Copy and for the 2nd point of the copy type in the slab height to set distance constraint.

But it looks like it does give the radius for the sphere at the top so it is probably good to make that part next.

It looks like the drawing has a mistake that it says 28.575 R (for radius) but think that's actually meant to be the diameter. So instead use 28.575/2 for the radius.

The drawing also does not seem to give the coordinates of the origin point for the arc so we will need to generate that ourselves, I think it's supposed to have the center point on the vertical axis (the world z axis) and be tangent to the cone profile.

So I drew in a circle with center point on the vertical axis and radius = 28.575/2 and then moved it downwards until it was visually close to being tangent to the cone which looks like this:



So what this means is you will need to use Construct > Offset to offset the cone line and the arc center point will be where the offset and vertical line intersect:



Then drawing an arc, center point here:



First point here:



Angle point vertical here:



Then the cone line is too long, you can either trim it using Edit > Trim or you could just delete it and draw in a new one snapping to the other ends.

Then you're ready to revolve I think.

- Michael

Image Attachments:
bryan2d1.jpg  bryan2d2.jpg  bryan2d3.jpg  bryan2d4.jpg  bryan2d5.jpg  bryan2d6.jpg  bryan2d7.jpg 

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Or alternate way to generate the tangent arc is make a triangle for the full cone profile:



Select it and run Construct > Fillet, pick just the top point to be filleted and put in radius = 28.575/2 and you'll get this you can send this directly into revolve with an axis line down the middle, it will cut it in half for you:



- Michael

Image Attachments:
bryan2d8.jpg  bryan2d9.jpg 

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Hi Bryan, ok now when I re-read your post I think I understand that the drawing is a little wonky because you don't have the original drawing just some things written on the object?

But as long as the cone and sphere are supposed to be tangent where they touch it's enough to have cone angle, cone bottom radius and sphere radius. The station measurements aren't needed. However if it's not meant to be tangent then those slab thicknesses would probably come into play.

- Michael

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Greatly appreciates all the help. Lots of options. Of all the models I'll be working with this was likely the most complex. The rest are just cylinders attached to each other.

last night I generated a Calendar and Chamfered it. the generated a sphere and, and copied it then merged one of them.

Then did the Boolean Dif operation to remove the upper part, then dropped the copied sphere onto it.

the Dim's are for a 1/24th object, but the final object will be 1/144th, so the issues will be all but invisible.

This is a common object to multiple models.

Bryan Wilburn

Attachments:
Nosecone.3dm

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