User Area
> Advice
How to create a helix in Modeller?
The
cross-section of the helix should be modelled first.
In the example shown here, a circular cross-section has been
created using four arcs in the XZ plane.
If the helix is to be solid then the cross-section should be made
into a surface (as shown above) otherwise the helix will be hollow.
The lines forming the cross-section surface should then be
meshed with the required number of null divisions so that when copied
and swept later these divisions will also be copied.
The
cross-section should then be rotationally swept by 90 degrees about
the centre of the helix to form one quarter of a toroid as shown.
The rotation transformation used to sweep the cross-section
should be saved for later use.
The pitch of the helix, a, is the vertical
distance travelled when one complete revolution of the helix has been
made. The newly created
surface forming the opposite end of the helix must now be translated
by a distance a/4 in the vertical direction (Z in the example shown)
and the mid-points translated by a/8 in the same direction.
The a/4 translation transformation should be saved for later
use.
The lines running between the two ends of the model should now be
meshed with an appropriate null dataset.
One quarter of one rotation of the helix has now been created and
all that remains is to copy this (n x 4) times using the saved
transformations where n is the number of helix pitches required.
This is carried out by selecting the complete quarter model and
using the copy command with the Compound option.
Both saved transformation datasets are used in the compound
copy.
In this example n is equal to 5 and therefore the
quarter model was copied 20 times.
The helix can then be meshed with 3D solid
continuum elements for a solid helix or 3D shells for a hollow helix.
|
