“We need to see when we need how many people,” said Fred.
“I agree. Let’s display how many we need based on the network diagram. Now we need lots of laborers for the demolition. Tomorrow we can still use some laborers to demolish the rest of the palace but we need foundation men to start digging out the foundation hole. Also we need Sawyers to be getting the right amount of wood for the tower and a Quarryman to decide how much extra stone we need and obtain that for us.”
Fred had created a chart that was titled, ‘Laborers,’ and had written ‘Number’ on the y axis and ‘Day’ on the x axis. He placed marks indicating 1 through 12 on the y axis and was filling in ten units for how many men they were using on the first day. “How many laborers will we need tomorrow?”
“I think some of the men acting as laborers today are really sawyers and foundation men so they will be coming off to do their jobs. But we could use as many as we could get to tear down the palace.”
“But demolishin’ th’rest of th’palace is not on th’critical path, Gwilym.” Fred pointed this out on the network diagram.
“You’re right, Fred! Why don’t we leave that work for filler work when our men are waiting around for something to do? That way they can focus on the critical path. What are you doing?”
“I’m seeing how many we need of each type of people each day so tha can see when tha need to send extras home and when tha need to bring more on board.”
“I like it!” exclaimed Gwilym. “Let’s fill it out.” They each took sheets of paper, titled with the various skill-sets and, using the network diagram and the calendar as a guide, filled out the resource requirements in what Gwilym called the resource histograms.
They noticed two things:
First, there were times that there was a greater need for a particular resource than they had. They indicated this by drawing a horizontal capacity line at the number of men they had on their crew with a particular skill. They chose not to do this on the laborer skill-set since they could add people there from other skills when they were not working.
Second, there were occasions when the need for a particular skill was far lower than the number of people they had with that skill. “These will be times of furlough,” said Gwilym. “The men wanted warnings of when they would be furloughed so that they can tend to their farms. This will work for that.”
“But what about times like these,” pointed out Fred, “when we have not enough carpenters?”
“First we have to see which activities put that demand on. If they are on the critical path, we can’t delay them but there may be some demand coming from activities off the critical path. If that is the cause, we can delay those activities and see what that does to the schedule.”
The two of them worked through that example and were able to put off some work which delayed another path of the plan and solved the carpenter resource problem. But now limited mason time caused another resource constraint. Plus it caused them to have to redo all the resource histograms; a lengthy and complicated process.“Let’s see how the men are doing while we think about a better way to handle this problem,” suggested Gwilym.
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