Duration dependant on another task(s)?

[PaulPW]

I've been struggling with this one all day, trying different things out and
scouring the web for an answer. Hopefully someone out there smarter than I
am is willing to help me out!
I have a few effort-driven FS dependant tasks in a section of my project.
They are phases of a demolition job, with a resource assigned (a contractor).
I have inserted a task for another resource (equipment) - a dumpster for the
demolition debris. The duration of the dumpster task needs to cover the
entire duration of the other tasks - I do NOT want to set the duration or the
dates manually, but let Project calculate when and how long as it needs to
be. This will help me plan when to order the dumpster & for how long.
The duration says "1 day?" since I have not specified it.
I have tried various SS & FF relationships:
With SS as the successor (i.e. "demolition can't start unless the dumpster
is there"), Project puts the dumpster task starting right at the beginning of
my project (since there are no predecessors).
With FF as the predecessor (i.e. "dumpster task cannot be removed until
demolition finishes"), Project places the dumpster at the end of the
demolition task, BUT the duration is only one day!
In fact, both of these SS & FF statements are true, but Project will not
allow me to enter the same task # as SS successor & FF predecessor. I tried
it with SS on the first demolition task and FF on the last, but that kicked
up a circular reference error.
Any ideas? I'm sure it must have something to do with resources that I am
getting wrong.
Sorry this is such long explanation.
Paul

 

[JulieS]

Hi Paul,

I think what you may be searching for is a hammock task: where the start
of the task is determined by the start of another task and the finish is
determined by the finish of yet another task. The duration should
expand or contract as the series of tasks expand or contract.

Please see FAQ 19 "Hammock Tasks" at:
http://project.mvps.org/faqs.htm

I hope this helps. Let us know how you get along.

Julie
Project MVP

Visit http://project.mvps.org/ for the FAQs and additional information
about Microsoft Project

 

[PaulPW]

Thanks for the quick reply & solution Julie.
…And I swore I'd looked all through that FAQ and MS's Knowledge Base and
couldn't find an answer! I just wasn't scanning for the right terms.

After some experimenting, I realized that you first need to insert Start and
Finish columns in order to copy the date cells. You CANNOT do it from the
date fields in the Task Form view (split screen), nor from the Task
Information dialog (pop-up when you double-click a task). This is not
spelled out in FAQ#19 or the MSKB.
When a link is pasted it puts a small green triangle in the lower right of
the date cell. I can't seem to click on the triangle, nor make it pop-up any
information about the link and there is nothing in the Task Info dialog to
indicate that there is a link either - weird! (BTW, I'm using Project 2003).

I got a fun result the first time I tried: First I erased all successors &
predecessors from the dumpster task. Next I pasted (linked) the Start time
from the first demolition task - this moved the dumpster bar to the correct
start date (same date), but was still only 1 day duration. Then I pasted
(linked) the Finish time from the last demolition task (tasks linked by FS).
When I did this the 1-day-long dumpster bar started hopping back and forth
between the start and end of the demolition tasks! At every cycle, the
status bar displayed "Leveling…". This loop repeated until I manually
changed the Finish date by clicking on a fixed date - it then prompted me to
break the link. Try it out - it reminded me of some sort of Project Pong
game!!
I finally found the cause: In my efforts to get it working previously I had
made the dumpster task NOT effort-driven and with a Fixed Duration. Once I
changed it to effort-driven it worked as intended.
FAQ#19 says to select the "START DATE of the task driving the finish date of
the hammock", but I chose the FINISH DATE and it worked fine.

All pretty strange, but it works though, which is what counts, eh?

A limitation: I have one other stray task that also needs the dumpster
resource, but is not part of the dependencies of the other demolition tasks -
no way to accommodate that as well, since I can only link one date at a time.
Unless I make it (falsely) dependant, but then I loose the effort-driven
resource leveling/scheduling.

Thanks so much for your help Julie.

 

[JulieS]

Hi Paul,

My responses are embedded.

Julie
Project MVP

Visit http://project.mvps.org/ for the FAQs and additional information
about Microsoft Project

Thanks for the quick reply & solution Julie.

[Julie] You're more than welcome Paul and thanks for the feedback. I'm
glad your were able to work things out.

.And I swore I'd looked all through that FAQ and MS's Knowledge Base
and
couldn't find an answer! I just wasn't scanning for the right
terms.

After some experimenting, I realized that you first need to insert
Start and
Finish columns in order to copy the date cells. You CANNOT do it from
the
date fields in the Task Form view (split screen), nor from the Task
Information dialog (pop-up when you double-click a task). This is not
spelled out in FAQ#19 or the MSKB.

[Julie] - Yes, sorry. That's probably a case of some assumptions gone
awry. Usually people are working with the Gantt chart view and the
standard entry table (left side) does contain the task start and finish
field.

When a link is pasted it puts a small green triangle in the lower
right of
the date cell. I can't seem to click on the triangle, nor make it
pop-up any
information about the link and there is nothing in the Task Info
dialog to
indicate that there is a link either - weird! (BTW, I'm using Project
2003).

[Julie] True. Usually I suggest placing a note in the task reminding me
that the start and finish dates are being driven by the other tasks. If
you double click on the linked field (with the triangle) Project will
select the source field.

I got a fun result the first time I tried: First I erased all
successors &
predecessors from the dumpster task. Next I pasted (linked) the Start
time
from the first demolition task - this moved the dumpster bar to the
correct
start date (same date), but was still only 1 day duration. Then I
pasted
(linked) the Finish time from the last demolition task (tasks linked
by FS).
When I did this the 1-day-long dumpster bar started hopping back and
forth
between the start and end of the demolition tasks! At every cycle,
the
status bar displayed "Leveling.". This loop repeated until I manually
changed the Finish date by clicking on a fixed date - it then prompted
me to
break the link. Try it out - it reminded me of some sort of Project
Pong
game!!
I finally found the cause: In my efforts to get it working previously
I had
made the dumpster task NOT effort-driven and with a Fixed Duration.
Once I
changed it to effort-driven it worked as intended.

[Julie] Well, that behavior is odd. I assume it has to do with your
project being set with automatic leveling and the dumpster resource
being overallocated. Make sure the equipment is assigned to only the
dumpster task and not the demolition tasks.

The "leveling" message you are seeing is from the Resource leveling
command. Try going to Tools > Level Resources and select manual for the
leveling calculations. You also shouldn't need to set the duration of
the Dumpster task to "Fixed Duration." The duration is being calculated
by Project based upon the linked start and finish dates.

FAQ#19 says to select the "START DATE of the task driving the finish
date of
the hammock", but I chose the FINISH DATE and it worked fine.

All pretty strange, but it works though, which is what counts, eh?

A limitation: I have one other stray task that also needs the
dumpster
resource, but is not part of the dependencies of the other demolition
tasks -
no way to accommodate that as well, since I can only link one date at
a time.
Unless I make it (falsely) dependant, but then I loose the
effort-driven
resource leveling/scheduling.

[Julie] I'm not sure what is going on. I was able in quick testing to
address the issue of the equipment overallocation by simply adding the
other "stray" task, assigning the equipment. The task was initially
scheduled at the same time as the hammock task creating an
overallocation for the equipment. Using manual resource leveling, the
"stray" task moved to the end of the hammock task.

Thanks so much for your help Julie.

[Julie] You're very welcome, Paul. Do let us know if we can assist
again.