Measure outermost edge of curve on lofted body

[Anonymous]

Hello,

I am stuck trying to measure the outermost edge of a curve created by a loft. I have been able to approximate the measurement in several ways, but with the final goal of creating parametric object that is adjustable later, approximations just do not work.  My goal is to create planes, extrude onto the body, split the body, etc, but it seems fundamental to any of these that I am able to measure the body first.

Can someone please lend some insight?

I have created a somewhat contrived example to simplify the drawing while illustrating the point. I have created a very simple fishbowl shape using the following workflow (also attached as an f3d file) :

Sketch center circle (254mm diameter) on the XY plane.

Create an offset plane above XY and sketch top circle (185mm diameter)

Create an offset plane below XY and sketch bottom circle (150mm diameter)

Use loft to connect the bottom, center, and top circle sketches.

Here are some of the ways I have tried to measure, unsuccessfully:

Approach:

Project body onto a sketch and use a vertical line as a tangent.

Reason it did not work:

Cannot make a line tangent to projected curve.

Approach: 

Create an offset plane in the YZ plane using the body as the To Object extent. 

Reason it did not work:

Cannot select the body.

Approach:

Sketch a large square in the YZ plane, extrude from offset of body.

Reason it did not work:

Error: Fail to project profile to remote surface

Surprisingly, the Bounding Box found in Part Properties is also very inaccurate -- for example the length of this bowl should be around 255mm and shows 289mm. This is consistent with my other parts created this way as well.

[davebYYPCU]

Measure Tool, select the line (highlighted)

Cannot make a line tangent to projected curve, only when that line is a Spline.

I don't understand the other approaches.

Might help.....

[Anonymous]

Thank you for the reply and sorry for the confusion. I can see how my description of "outermost edge" was not specific enough.

I am looking for the outside circumference at the widest point of the object. Image below for added clarity -- obviously this image shows an estimate, not the exact value and could not be used effectively in a parametric drawing.

[davebYYPCU]

Ok, makes more sense, 

Due to the geometry of the model, the way to get the accuracy, is to project the outline to the top or bottom plane, 

to do so, it only worked by selecting the body from the browser as depicted, 

Your tangent line snaps to the projected top view.....

@jeff_strater Project > Project, selecting the body or face of this body (article mode toggled) in the window did not work, (Selection filters ok,)   Is it this model, or 

more work for Chad?

Might help....

[Anonymous]

Interesting, I had not tried that approach.

Creating that projection (XY plane), I still can't seem to snap tangent lines to the outside of it to get measurements.... However, if I then create then a second sketch on the XZ plane I can do this:

The horizontal dashed line is the XY projection you mentioned.

The outer edge is the XZ projection I was previously using.

I was able to constrain the ends of lines coincident to the ends of the XY projection, constrain the lines as vertical, then constrain the opposite ends to the XZ projection.

Quite the workaround to get this line, but I can't argue with the results.  Thank you for your help on this!

[davebYYPCU]

Yeah, I can see what you wanted, but from here, knowing what didn't work, 

You only needed the diameter of the projected circle I delivered, anything else will follow what you want to do next, if you get what I mean, 

I tagged Jeff, (the Autodesk guy with better diagnostics,) so that the bug?, if that is what it is,

is only in your model, or is an unexpected limitation. 

I Project > Intersect, often and always thought you could project a body/face to the sketch by selecting in the window.  

I suspect there's something in your model, but have not found it, it has no unusual features in it.

Might help....

[wmhazzard]

I came up with a slightly different measurement. I got 255.01 mm by sketching on the XY plane and projecting the seam in the face which gives a point to snap to and then measure to the origin. 

[davebYYPCU]

Widest part is not on the origin plane, 

might account for that error.

[wmhazzard]

I know, that is why I showed the image with the snap point outside of the model, at the widest point. 

[Anonymous]

It seems that the 'correct' answer to my question, as you probably imagined is: Don't do this.

The better approach is using an arc in the XZ plane:

Create a new sketch in the XZ plane.

Project each of the three circles to be lofted as flat lines into a new sketch.

Connect the outermost edge of each circle using a 3-point arc.

Mirror arc across centerline.

Create the same lofted shape, but use the arcs as rails.

You get a near identical shape, but now you have a sketch that you can reference. Inside the sketch you can use a vertically constrained line as a tangent to get measurements, create construction geometries, and make a bounding box.

Thanks everyone for the ideas and for bearing with me through this exercise.