The toy truck example used earlier is very simple. It represents the basic Gantt chart characteristics. The Gantt chart shown in Figures. 6-7A, 6-7B and 6-7C is taken from the real world. Although it does not take us through the whole "Build a New Style Disk Cleaning Machine" project, it does take us four and one half months into the project and takes us to a major checkpoint "Lay out 3D design." There are 15 task leaders on the project team at this point. The names of the workers who will execute the project are identified by a code. There is one work team, "Mfg shop," that is represented on the project team by the manufacturing supervisor of the tool room the facility providing the manufactured parts for this part of the project. The manufacturing supervisor is designated as "Mfg" on the Gantt chart. He or she is responsible for discussing tasks with the machinist in the tool room when he or she develops task estimates for their work. In the case of "work order make," the work will take up 30 percent of the effort of the tool room machinist over thirteen days, 20 percent over seven days, and 40 percent over 5 days. The tool room is budgeted on a cost-per-day basis. For budgeting purposes, the project cost for this task will be calculated as tool room cost-per-day times days needed times the percentage of tool room effort needed each day.
On the project team, the Test Foreman, "Tst1," speaks for the test helper, "Ttst hlp."
There are five major work packages that lead up to the 3D design layout, and there are 46 tasks within these work packages. One of the five major work packages, the prototype design work package, must be completed before the other work packages can start. (a milestone review is scheduled at the end of the prototype's design.) The four other work packages can each begin when the last task of the Prototype Design package finalize design sketch is completed. These four work packages proceed in parallel there are no task dependencies in any of these work packages that depend on a predecessor in another work package.
This project was planned exactly the way the toy truck project was planned. There were 36 task leaders on the full project team (this is a very large team). The project manager invited all of them to the task list meeting where all the tasks for the project were identified. Because the team used an affinity diagram to form the task list, the groupings of tasks easily emerged in work package clusters. This formation of groups confirmed the work packages identified in the original work breakdown structure analysis. The entire affinity diagram exercise was completed in two hours.
The project manager invited only the 15 task leaders dealing with the portion of the Gantt chart shown to attend the first Gantt chart meeting. The rest of the team and many of the original 15, who had continuing task responsibilities, came to the second and third Gantt chart meetings.
As one looks at the Gantt chart, one sees that there is a stair-step characteristic to the task sequences, and that some tasks and the last four work packages are proceeding in parallel. Note that the project manager is assigned full time to the project and has no task team responsibilities!
Tasks that proceed in parallel like the "mech dsn sketch," "fluid flow sketch," "electrical," and the "software specification" task do not require the same amount of time. They all are predecessors for the "revise comp sketch" task. The "revise comp sketch" task cannot start until the longest of its predecessors the "software specs" task is completed. Note that there is a time lapse between the ending of each of the other tasks and the beginning of the "revise comp sketch" task. We call this time lapse slack. These characteristics are important as we determine the critical task path through the project. (The critical path is the subject of the Chapter 7.)