Continue to Site

# Help from person who made 'Tumbleweed'

#### rishidass

##### New member
Hi! This question is for the creator of the model 'tumbleweed' which is currently in the downloadable files section of this web site. Can you please tell me how you made it? I did sneak around in the intent manager, but couldn't get the head or tails out of the equations nor could I determine how to apply them either!

#### skiddy

##### New member
I am not the creator of tumbleweed but:

Create a datum curve from equation using spherical coor:

eg

rho=cos(t*90)

theta=90*t

phi=t*90*50

The sphere should be created.

Next create a surface var sec sweep, pivot direction, using the datum curve as the trajectory.

In the sketcher section, draw a line at 45 degrees to the vertical datum, coming out from the start of the trajectory.

What ever the sd? is for the 45 degree angle, use the following equation

sd?=trajpar*360*150 150=no of rotations

You should have a surface twisting around the datum curve created from the equation in the first step?

Use the outside of the surface to create a solid protrusion, sweep.

Hope you understand that???

#### rishidass

##### New member
Hi skiddy!

Thanks a lot for helping me out! The datum curve created successfully, but the surface creation is giving me problems. Pro-E is not able to generate the surface according to the equations given by you. I tried reducing the no. of rotations but still no success.

I made the line both really small so that there are no intersections between two spirals, and also made them big enough so that there are intersections - both didn't work.

What can be the problem?? Help needed.

Thanks again

-Rishi

#### proed

##### Moderator
Hi.

I created the tumbleweed as an experiment, after using datums curves & equations on a simpler part...

The spherical co-ordinates give the globe spring.

Then - use that old technique of varying a line round a trajectory to create a weird helix. Then add a sweep onto the helical path.

I just tried a few values until I got the size that worked in the model...

You'll be able to tear apart the model & check the sizes I used - the sweep must not intersect itself as it goes round the path.

Any more detailed help - give me a shout.

Ed

#### skiddy

##### New member
Just checked my equations:

Not too sure but try:

Rho=cos(t*90)

theta=90*t

phi=t*180*25

to create the initial datum curve, then i think the surface is the same equation as i gave before:

sd?=trajpar*360*150

Hoping this works?

#### skiddy

##### New member
ooooo.... just remembered, on my model i did the surface length as 0.03 (the length of the curve out of the origin for the var sec sweep)

Should work??

#### proed

##### Moderator
These are the original equations for the 3D curve:

rho=cos(t*90)

theta=90 * t

phi=t * 360 * 20

This is the surface:

sd6=trajpar*360*200

View attachment 253

Ed