Go Ahead Draw This

Original Article Date: Nov 14, 2003 

This is a companion article to An Introduction to the 3D Primitives and will give you an opportunity to practise what you learned. With thanks to Sean Forward for this exercise!


In the above mentioned article you learned how to place 3D primitives and how you can use them in modeling an object. So, where do you go from there? Well, how about using your new skills to model a simple soap box cart!

Step 1 - Base: The base is made up of three slabs. The two end planks will be supporting the axels while the middle board will support the seat. The middle board is positioned on top of the ends and all boards are centered with respect to one another. Since this is easy stuff, no detailed instructions are provided to put these planks together.

Step 2 - Axles: Once the planks are positioned, you can place the axles which are little cylinders centered on the bottom of each end plank. Notice that each axle extends 20mm from the end of the planks. Again, no detailed instructions are offered for this step.

Step 3 - Axle Fittings: To secure the axles to the bottom plank, you need to draw a funky little fitting that's made up of several components as shown below.

Start by placing a 5mm sphere in some blank drawing space.
In the front or side view, place a horizontal line through the middle of the sphere. This will become the cutting element to chop this thing in half.
From the 3D Modify tool box, select Cut Solid
Adjust the settings: Cut Direction = Both, Cut Mode = Through, Split Solid = On
Identify the sphere
Identify the cutting element
Accept
Delete the bottom half.
Copy the resulting half 15mm horizontally.

Place two cylinders under the caps as shown below. Each cylinder has a radius of 2.5 and a height of 15.

Place a torus with a primary radius of 7.5, secondary radius of 2.5 and an angle of 180 degrees. When done, group the components together so that it's easier for manipulation.

Position one fitting 75 from the end of each axle.

Step 4 - The Wheels: To allow for multi-coloured wheels, the rims are made up of four wedges positioned in a polar array. Although you can draw these "in place", it may be easier to create one entire wheel, group the elements together and then position them when complete. This will be the method outlined here. To start, place four wedges as shown.

To create the tires, position a torus around the rim. The torus will have a primary radius of 75, secondary radius of 5 and an angle of 360. When done, group the wedges and torus together to create a single element.

Place one wheel at the end of each axle.

At this time, you should have the base consisting of three planks, the axles, fittings, and wheels.

Step 5 - The Seat: The seat is made up of four slabs: one for the bottom and three for the sides. Notice that the sides sit on top of the bottom. Once created, group the slabs together for ease of manipulation.

Position the chair on top of the center plank. Match center lines as shown.

Step 6 - The Bolts: The cart needs to be bolted togther so in some clear drawing space draw two sizes of bolts as shown below. Note that the heads of the bolts are spheres cut in half....just like the axle fittings done earlier. So, you can either re-draw them or simply copy them from the axle fittings. Once each bolt has been drawn, group the elements together.

Position the short bolts as shown below.

Position the long bolts as shown.

Step 7 - Wheel Spurs: The final task is to place wheel spurs which will deter opponents from getting too close. Each spur consists of cone and and two cylinders

Position the spurs so that they are butted up against the wheel centers as shown in the top view below.

Well that's it for the little soap box cart. A nice final touch would be to assign some materials, place some lights and do a little animation. But, whatever you choose do, have fun with it!

AskInga Article #166