# Firepit Design Exercise

## Purpose:

Master use of the  ARRAY command to facilitate design tasks using AutoCAD.

## Background:

Many design tasks require that some form of repetitive pattern of features be created. The array command allows users to rapidly copy objects in either rectangular or polar patterns. Tools such as ARRAY and MIRROR make designing objects with symmetry much easier. It is important when drawing, modeling, or designing anything to make note of any symmetry in the object before you start in order to create it in the most efficient manner possible.

I had to do this design task with my dad when I was about 10 years old. I still have some of the extra bricks (we bought way too many). All we had then was a slide rule...

## Applications:

In mechanical design polar patterns are common in objects that rotate such as gears, wheels, fans, pipe flanges.etc. The application of rectangular patterns are just as numerous in all forms of designs.

## Exercise:

Open the drawing file http://phyzx.net/patio.dwg

You will see a representation of a concrete patio with a 37" diameter hole in it. The hole is for a fire/BBQ pit with a 36" diameter grill in its center. The grill is mounted on a threaded shaft that allows it to be raised and lowered by spinning it.

To complete the installation we need to border the pit with bricks.

### DESIGN CRITERIA

• The bricks must be of a standard shape available at a typical building supply store.
• The minimum space between bricks should be less than 1"
• The bricks must not overlap

### SUGGESTED DESIGN PROCESS

• Determine the size of the bricks you intend to use (use web sites below or go measure one outside)
• Draw the first brick at an appropriate location at the edge of the firepit without intruding into the 37" diameter hole
• Extrude the brick into a 3D solid
• Use the array command to complete the pattern around the pit to meet the design criteria above

## Assessment Criteria

To complete this assignment:

• Annotate the drawing with a note stating the number of bricks
• Place dimensions on the drawing to show the size of the brick, the angle between bricks, and the distance at the closest point between bricks
• Use Cross-Hatch with the predefined 'GRATE' pattern to represent the grill
• Create a drawing layout that shows a top view looking down at the patio showing the dimensions zoomed in to show just the firepit, border and annotations
• Generate an isometric view in another layout showing the 3D Shaded view of the layout
• Use a standard scale for the view with the dimensions in it and create a note in the layout PAPERSPACE that specifies the scale of  the viewport with the annotation
• Copy both drawings into your PowerPoint portfolio

• Try the 3DARRY command. How is it different than the 2D version.
• If the firepit were rectangular or diamond shaped could we still use the array command to help design the border.

## Online Tutorials For Array:

copyright (c) 2008 S. B. Egli