George’s Bicycle Creating a Gantt Chart. George is keen to build his own bicycle by using an old bike that he found in the garden shed. He believes that.

George’s Bicycle

Creating a Gantt Chart

George is keen to build his own bicycle by using an old bike that he found in the garden shed. He believes that by salvaging the parts from this, and obtaining some parts from second-hand sources and others from the local bike shop, he can make a customised bicycle, at a far cheaper price than if he bought a new one.

He’s got all the parts, bar the back-wheel, the handle-bars and the rear gear-changing mechanism.

He needs to get the bicycle ready for a local race in 2 weeks time.

He’s worked out his work breakdown structure, and has estimated that each event will take this amount of time to complete:

AA1 – take apart – ½ a day

AA2 – clean – 1 day

AA3 – painting – ½ day

AB1 – order – ½ day

AB2 – delivery – 7 days (The shop has to order the parts)

AC1 – re-assemble old parts – 1 day

AC2 – assemble new parts – ½ day

AD1 – 1st short test run – ½ day

AD2 – adjust & fine tune – ½ day

AD3 – final test run (race equiv.) – 1day

We need two things first:

• A dependency list

• A critical path analysis (sometimes an optional extra)

These two sound quite high-tec, but hopefully we can explain them quite clearly here.

Dependency ListFirstly, just list all the tasks, possibly from a Logic Diagram you’ve

created. Also include the estimated time the task will take.

Code Description Time (days)

STARTAA1 take apart 1/2AA2 clean 1AA3 painting 1/2AB1 order 1/2AB2 delivery 7AC1 re-assemble old parts 1AC2 assemble new parts 1/2AD1 1st short test run 1/2AD2 adjust & fine tune 1/2AD3 final test run (race equiv.) 1

FINISH

13

But some of these tasks cannot start until others before them have finished (called a finish-start relationship). So we need to note this. -

(Sometimes a task can start once another task has started – a start-start relationship. And what about a start-finish one?)


START 1 2 3

AA1 take apart 1/2 0

AA2 clean 1 AA1

AA3 painting 1/2 AA2

AB1 order 1/2 0

AB2 delivery 7 AB1

AC1 re-assemble old parts 1 AA3

AC2 assemble new parts 1/2 AA3 AB2

AD1 1st short test run 1/2 AC1 AC2

AD2 adjust & fine tune 1/2 AD1

AD3 final test run (race equiv.) 1 AD2

FINISH

13

Dependencies

Some tasks need more than one other task to finish before they can start -

So here you can see that you can’t assemble the new parts until you’ve painted the frame (AA3) and the parts have been delivered (AB2)

Now – we have our dependency list from the work breakdown structure


START 1 2 3

AA1 take apart 1/2 0

AA2 clean 1 AA1

AA3 painting 1/2 AA2

AB1 order 1/2 0

AB2 delivery 7 AB1

AC1 re-assemble old parts 1 AA3

AC2 assemble new parts 1/2 AA3 AB2

AD1 1st short test run 1/2 AC1 AC2

AD2 adjust & fine tune 1/2 AD1

AD3 final test run (race equiv.) 1 AD2

FINISH

Dependencies

What about the critical path?

We need some posh terms here again.

The most used approach to critical path analysis is thePERT method (Programme Evaluation Review Technique).

This uses a “Node Box” as the base unit for storingInformation. Again, sounds high-tech, but hopefully we canexplain this.

The Node Box

The idea here is to contain information about a particular task in one clear diagram:I’ve taken task AC1 (re-assemble old parts) as an example.

Duration

earliest start time 1 earliest finish time

latest start time latest finish time

Total Float

AC1

This centre-top box says how longthe task will take.

This centre box has the task codeor title.

We need to have a box for each task, laid out in a structure like the logic diagram.This is where you’ll need a long piece of paper for a ½ decent sized project if you’re doing this manually!

0 0.5 1

0

0.5 7

START

AB2

AA1 AA2

AB1

And so on for all the tasks. To see the whole diagram – please go to the fileshare area – and open the spreadsheet titled “PERT Chart – Georges Bicycle”

The “Forward Pass”

We now need to start putting numbers in some of the other boxes.

The first ones are for the top row – earliest start time (EST) and earliest finish time (EFT). Doing this is called the forward pass, and essentially all it means is:

0 0 0.5 0.5

0

0 0.5 0.5

START AA1

AB1

START has an EFT of 0:

Transfer the EFT of the previous node box to the EST of the next box, add the duration to this, and put the total in the EFT box.

Continue along the whole path – but watch out when you have two boxes going into 1:

0 + 0.5 = 0.5

2 1 3

8 0.5 8.5

7.5 0.5 8

AC2

AD1

AC1

watch out when you have two boxes going into 1 – choose the highest EFT from the two previous boxes (because that’s the earliest you can start the next task!).

8 is higher than 3 – so 8 goes to next EST box.

To see the whole diagram – please go to the fileshare area –

and open the spreadsheet titled “PERT Chart – Georges Bicycle”

The “Backward Pass”

Once you’ve gone along the whole chart, you will have a number in the EST box of the FINISH Task. Transfer this to the Latest Start Time (LST) box of the FINISH task:

10

10

FINISH

And we now work back from this box along the whole chart

(Bear with me – we’re nearly there now!)

The “Backward Pass”

When working back – transfer the lowest Latest Start Time (LST) of the leading tasks to the Latest Finish Time (LFT) of the preceding task:

8.5 0.5 9 9 1 10 10

8.5 9 9 10 10

FINISHAD2 AD3

10 – 1 = 9

Take away the duration and put the answer in the bottom left (Latest Start Time (LST) box. Eg for AD3, 10 minus 1 = 9!

Remember – when two boxes go into one – choose the LOWEST figure to transer back in the backward pass:

1.5 0.5 2

6.5 7 2 1 3

7 8

7.5 0.5 8

7.5 8

AC1

AA3

AC2

The lower of 7 and 7.5 is 7!

To see the whole diagram – please go to the fileshare area –

and open the spreadsheet titled “PERT Chart – Georges Bicycle”

All that’s left to do is to calculate the difference between:upper left hand corner & lower left hand cornerlower right hand corner & upper right hand cornerfor each box.(These two figures should always be the same!)

5 5

2 1 3

7 5 8

0 0

7.5 0.5 8

7.5 0 8

AC1

AC2

And enter that figure in the centre bottom box.

7 – 2 = 5

8 – 3 = 5

7.5 – 7.5 = 0

8 – 8 = 0

And where this figure is zero – this is your critical path!! (In technical terms – this means the “float” is zero) – You’ve no time to be flexible with these tasks!

5 5

2 1 3

0 0

7 5 8 8 0.5 8.5

0 0

7.5 0.5 8 8 0 8.5

7.5 0 8

AC1

AC2

AD1

Task AC1 has a float of 5 days.

Tasks AC2 and AD1 are on the critical path.

Now - to see the whole diagram in a manual format – please go to the fileshare area – and open the spreadsheet titled “PERT Chart – Georges Bicycle”. The complete analysis is the 5th sheet.

SO WE NOW HAVE OUR CRITICAL PATH

Next – create a table of tasks against time

Time - days

STARTAA1 take apartAA2 cleanAA3 paintingAB1 orderAB2 deliveryAC1 re-assemble old partsAC2 assemble new partsAD1 1st short test runAD2 adjust & fine tuneAD3 final test run (race equiv.)

FINISH

Day 4 Day 9 Day 10Task Day 5 Day 6 Day 7 Day 8Day 1 Day 2 Day 3

Next – put in bars to represent the times for the task – and maybe link up the dependent ones with lines / arrows.Put the bars in the days that you can start them -

Time - days

START

AA1 take apart

AA2 clean

AA3 painting

AB1 order

AB2 delivery

AC1 re-assemble old parts

AC2 assemble new parts

AD1 1st short test run

AD2 adjust & fine tune

AD3 final test run (race equiv.)

FINISH

Task Day 1 Day 2 Day 3 Day 8 Day 9 Day 10Day 4 Day 5 Day 6 Day 7

Now, tidy up the order to avoid crossing, add a legend, and add milestones!Time - days

START

AA1 take apart

AA2 clean

AA3 painting


AB1 order

AB2 delivery





FINISH

Old parts - strip and renew

assembly

new parts

trial period

final test before race

Task Day 1 Day 2 Day 3 Day 8 Day 9 Day 10Day 4 Day 5 Day 6 Day 7

Assembly complete!

Race-ready!

YOU COULD HIGHLIGHT THE CRITICAL PATH IN RED –

Time - days

START

AA1 take apart

AA2 clean

AA3 painting


AB1 order

AB2 delivery





FINISH


assembly

new parts

trial period


Day 8 Day 9 Day 10Day 4 Day 5 Day 6 Day 7Task Day 1 Day 2 Day 3

Assembly complete!

Race-ready!

Then you could start adding resources at the bottom:Time - days

START

AA1 take apart

AA2 clean

AA3 painting


AB1 order

AB2 delivery





FINISH


assembly

new parts

trial period


George

George's Son

The Garage

Day 8 Day 9 Day 10Day 4 Day 5 Day 6 Day 7Task Day 1 Day 2 Day 3

Assembly complete!

Race-ready!

And that’s it!

George’s Bicycle Creating a Gantt Chart. George is keen to build his own bicycle by using an old bike that he found in the garden shed. He believes that.

Documents

day slide

ab2 slide

old parts

eft box

new parts day ad1

day ac2

gantt chart slide

particular task