Week 3
Make working drawings (60 minutes)
Working drawings are guides that show us how to build a specific structure. Make a working drawing of your bridge. It should be drawn to scale and show as much detail as possible.
Each member of your team should make their own first-angle orthographic projection of the bridge, showing the front view, top view and end view.
Each of your drawings should show the measurements of the structure and the scale you have chosen. Use correct line types.
Have another look at Chapter 1 to remind you how to make orthographic drawings.
You will need the following equipment:
- 30 °, 60 ° and 90 ° set square,
- a sharp pencil, and
- masking tape to attach your drawing sheet to your drawing board.
Work out a budget (60 minutes)
All projects that cost money need a budget. A budget is a plan that looks at the various costs and how the money will be spent.
It is important to make sure that you have enough money before you begin any project. Otherwise, you could run out of funds halfway through the project. You also have to persuade the tender board that your bridge is cost effective, which means that it is safe for people and the environment, and that it is not too expensive for this purpose.
When you build the bridge, think about the things that will cost money.For example:
- materials,
- labour,
- designers and engineers,
- equipment that you hire or buy, and
- transport.
Remember that you are a contracting company and want to make a profit. Once you have worked out the other costs, add on an amount for your profit.
There will be other companies who will tender for the job, so keep your costs low to make your tender attractive. However, do not compromise the safety of the bridge or allow it to become unfit for its purpose. Balance the need to make a profit with the need to build a safe bridge.
For this exercise, you have to draw up a cost sheet. A cost sheet is a summary of all your costs.
On the following page, there is an example of a cost table for another bridge. You can use some of the material costs shown in this table when making your own cost table for your bridge design.
Example:
Item description
|
Quantity
|
Price per unit (Rands)
|
Total (Rands)
|
Materials
| |||
Cement (80 kg bags)
|
50
|
90
|
10 000
|
Pine Planks (200 cm \times 30 cm \times 2 cm)
|
200
| ||
Bags of nails (10 \times 3 cm)
|
10
| ||
Bricks
|
5 000
| ||
Steel I-beam (5 m \times 6 cm)
|
20
|
1 000
|
20 000
|
Subtotal
| |||
Labour
| |||
Unskilled labourers
|
25
|
25 per hour
| |
Carpenter
|
2
|
320 per day
| |
Foreman
|
1
|
600 per day
| |
Welders
|
3
|
720 per day
| |
Subtotal
| |||
Machinery/Equipment
| |||
Bulldozer and operator
|
1
|
2 000 per day
| |
Road grader and operator
|
1
|
2 500 per day
| |
Shovels and other equipment
|
25
|
10 per day
| |
Subtotal
| |||
Other staff costs
| |||
Engineer
| |||
Architect
| |||
Work manager
| |||
TOTAL
|
Your own list will be different, because it will depend on the materials you have chosen to use to build your bridge. If you are not completely certain of amounts or lengths, always add on a little extra to your final figure. It is better to have a little left over than to run short.
To help you to work out your costs, speak to a hardware shop owner, a building contractor, or a family member who is knowledgeable in these things. You can also look in the Yellow Pages for suppliers. They will give you information if you tell them about your project. Don't just make up the costs. You need your budget to be accurate.
Apart from the items on the above list you also have to account for VAT and insurance.
Total [10]
Profit margin
What additional amount are you going to charge?
Remember that you need to make a profit. This amount has to be fair to you and to the authorities who will award the contract.
Total all the subtotals and then decide on a percentage for the profit. You will then have the final total, which you will submit as the cost of building your bridge.
