Yet another rocket cone and two questions

[cyucelEJ2QP]

Hi all, hope you are well,

A bit stuck again. Designing a rocket cone, f3d file is attached, having two issues.

Please see the Cone component, and the Cone Side sketch:

1. The top point of the construction line on the right (see the screenshot if it is not clear), this point is constrained to stay on the spline (works fine), however I cannot add the distance of this point either from the top of the cone or the bottom. I can move the point with mouse up and down, so it is not constrained, but does not allow me to specify the distance. What is the correct way of defining that distance ?

2. Having the sketch fully defined, I was hoping to be able to change the height of the cone, using the User Parameter called noseConeHeight, however F360 does not allow me to change this parameter. What am I doing wrong ?

Many thanks

[davebYYPCU]

Others may chime in, I don’t have access to the file for some time.  Based on the picture,

point on a Spline?  I see an end point on a locked (green) line.  Unlock it and then fully constrain.

Might help.....

[Bunga777 · Accepted solution]

I have selected the parts of the sketch that might be problematic.

In particular, the middle midpoint constraint is very troublesome and should be removed.

This inverted triangle midpoint constraint is the cause of the inability of the vertical center line to stretch vertically up or down, which is why the cone does not move when the parameter is changed.

The dashed line defining the perimeter thickness is in the wrong position and has been corrected.

Here is the revised sketch.

Oh,...the line for thickness is wrong, I will correct it and affix it.

Perhaps this is the ideal.

I took a video of the rest, so there you go.

https://knowledge.autodesk.com/community/screencast/bc2bd724-89d9-4164-aec1-e3da6e37de93

Data also affixed.

[davebYYPCU]

I think the midpoint is design required,  keeps the spline midpoint relative to height. (Height / 2)  Its length has to be adjusted with height changes.

@cyucelEJ2QP Do not use green lines, (they prevent parameter changes.)

Try tangent arc/s for better control.

Might help.....

[cyucelEJ2QP]

Wow, thanks a lot for your time an effort, this makes perfect sense.

One problem I've got now is as we removed the midpoint constraint when I change noseHeight, the mid fit-point of the spline does not adjust itself, creating funny shapes. What is a good way to do this properly without using midpoint ? Perhaps a distance of noseHeight/2 from the bottom ?

To create the shell of the cone I ended up revolving the spline, stitching the bottom and shelling resultant body. I can see you preferred an offset, however when I do offset the top of the spline it crosses y-axis, needing to trim. When I trim it loses its constraint. Any recommendations for this scenario ?

[Bunga777 · Accepted solution]

I see, I was not aware of such an intention, sorry.

Delete this.

Add horizontal restraints here.

To select the midpoint, hold down Shift.

Is this as designed?

 

I am not sure about the wall thickness thing going over the Y axis.

What do you mean by that?　It would be great if you could elaborate a bit more.

I will think about it some more.

[davebYYPCU · Accepted solution]

Do not trim.  Select correct Profile. Change centre line to solid, or centre line type.

Mid point is recommended, but yes height /2 is same thing only different.  You have to change the midpoint diameter if changing the height, and avoid the grief - use two point spline, top horizontal handle, bottom vertical handle.  Adjust handle dimension/s.

still think two tangent arcs fully constrained will be even less grief.

Might help.....

[g-andresen]

Hi,

---

@cyucelEJ2QP  schrieb:

One problem I've got now is as we removed the midpoint constraint when I change noseHeight, the mid fit-point of the spline does not adjust itself, creating funny shapes. What is a good way to do this properly without using midpoint ? Perhaps a distance of noseHeight/2 from the bottom ?

try a relative length like 0.65*nose height...

Any recommendations for this scenario ?

Leave it at the rotation of the surface and subsequent thickening

günther

[Bunga777 · Accepted solution]

Perhaps this is what you mean?

I tried to keep the same form as the first data as much as possible.

The data up to this point is also attached.

But it may be easier to do the wall thickness with the Shell command at the end.

Parameters can also be used in Shell commands.

[cyucelEJ2QP]

This is amazing, I can see I overly complicated things 🙂 Everything works now and the sketch is way simpler. 

@Bunga777 this is what I meant by offset crossing the axis (screenshot). Then I close the ends (to obtain a profile) and trim the excess offset line (because it looks ugly). As soon as I trim that piece, offset line's built-in constraint is removed, and I couldn't find a practical way to re-constraint it. 

My problem is solved, but more than happy to hear your opinion on above.

[Bunga777 · Accepted solution]

Okay, I'm out of my mind that I didn't notice that it says Y-axis.

First of all, if you are just building the shape, you don't need a sketch design for this offset inner line.

So I feel it is best to remove the spline offset and build with this timeline.

(The centerline was changed from Construction Line so that it could be used in Revolve.)

And if points are needed for incorporation, only those points can be inserted later in the sketch.

There is a big possibility that no spline offset is needed there.