Personal blog on early retirement and analytics projects. I write about what I learn as I am learning it.
A resource loading chart is the histogram that sits under a Gantt chart: for each day of the plan, how many people that day needs. It is the least glamorous drawing in project management and the only one that ever told me anything I did not already know from looking at the bars.
Here is one for a 21-task house renovation, before and after the schedule was made to fit inside the crew that actually exists. The two panels hold exactly the same amount of work.
Resource leveling vs resource smoothing is usually taught as a pair of definitions to memorise for an exam: leveling may push the finish date out, smoothing may not. Both true, both useless the moment you are standing in front of a schedule that needs fixing, because neither tells you which one your plan can actually give you.
They are not two techniques. They are one trade-off, read from opposite ends. I solved the same 21-task renovation both ways and the two answers landed on exactly the same curve.
Continue reading “Resource Leveling vs Resource Smoothing, Measured”
Every project management course teaches fast tracking vs crashing in the same order and with the same moral: if the date is at risk, fast track first, because overlapping tasks costs nothing but risk, and crash second, because crashing costs money. I have repeated that advice myself. Then I put both through a solver on the same plan and got the opposite of what the order implies.
Fast tracking pulled eight working days off the schedule and one day off the job. Crashing pulled six off the schedule and eleven off the job. Same 21-task renovation, same solver, same afternoon.
Project crashing is what you do when the date is wrong and the work is not going to shrink on its own: you pick tasks and do them a different, faster, more expensive way. Rent the spray rig. Order the wall panels prefabricated instead of stick-framing them. Hand the drywall to a subcontractor. The version in the textbooks is a tidy table of crash cost per day, and in twenty years of doing this for a living I have never once had a job hand me that table.
So I ran it properly instead of describing it. Same 21-task house renovation I have been using all series, three general crew, six alternatives a real builder could actually buy, and a solver that has to choose which ones are worth it. Here is what crashing bought, change by change, with nothing rounded in my favour.
Continue reading “Project Crashing: How Many Days Can You Actually Buy?”
Most of what gets offered as a critical path method template is a Gantt chart with a column called Start that you fill in yourself. That is not the critical path method. The whole point of CPM is that you never type a date — you type durations and predecessors, and the dates are computed. If the template makes you enter the start, it has quietly handed the work back to you and kept the chart.
So this is what an honest one has to do, which half of it a spreadsheet handles well, which half it fights you on, and the file I ended up with. Numbers throughout come from the same 21-task renovation plan the template ships with.
