Gantt Chart Mechanics: Polish Harmonogram, Soviet Plans, Float Time

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

A Gantt chart is a bar chart with tasks on the vertical axis and time on the horizontal, built from terminal elements, the smallest actions, and summary elements that group them into a work breakdown structure. Planners usually schedule each task at its earliest start time, which banks float time at the end of the project. The idea predates Henry Gantt. In 1896 Polish engineer Karol Adamiecki, managing a rolling mill, created a harmonogram, but he published in Polish and Russian and his work stayed isolated. In 1912 German engineer Hermann Schürch published similar but static charts for construction.

Gantt developed his version between 1910 and 1915 and used it to track worker productivity, marking shortfalls in red ink and on-target work in black. During World War I, Army chief of ordnance General William Crozier used the charts to coordinate contractors and supplies. In 1929 Gantt's former collaborator Walter Polakov brought them to the Supreme Soviet of the National Economy, where they helped carry out the first five-year plan. Charts were later redrawn by hand or kept on wooden pegboards until personal computers in the 1980s and web software in the late 1990s.

• Scheduling software estimates task time from optimistic, most likely and pessimistic guesses, weighting the most likely value by four and dividing by six.
• In the episode's example, 2, 4 and 10 hours to paint a room produce an estimate of about 4.6 hours.
• Progress charts shade completed work and add a vertical today line to show who is behind.
• Linked charts with dependency arrows can turn into an unreadable web on large projects.
• Experts consider critical path network diagrams better for complex logic, but executives prefer bar charts because they need no training to read.