Scoping out project time in advance

[student123]

I should start by saying this isn't meant to be about setting a stopwatch against model engineering. We can (hopefully usually) take pleasure in working at a pace where we enjoy model making.

A little story: years back I taught myself computer programming. Wrote many thousands of lines of code.
More recently I decided to add a theoretical basis to that practical experience & went to college for a course in software engineering.
At one lecture I was introduced to 'COCOMO'. It’s a set of formulae that can be used to estimate how long it takes to create software, based on nature of the job, skill of the programmers etc.

My first reaction was : nah : you cant estimate a project time that way , there's just too many variables
But it turned out I found COCOMO to be very useful (after allowing for things like modern code generators). I even reversed it for my final year project & worked out , for the number of hours available, how many lines of code I could write.
(if interested more on COCOMO at
http://en.wikipedia.org wiki/COCOMO )


So… what's this got to do with model engineering?

Well I've wondered if there's an equivalent set of formulae/approach anywhere for model engineering ? Or an attempt at one.
Google searches didn’t reveal much when I looked, and of course the home shop environment is different to the commercial.

More generally I'd be interested in anything you might use to scope out a project time in advance, any anecdotes etc.


Mike

 

[Tin Falcon]

no doubt there are at least several job shop/ machine shop estimating programs out there. how applicable they are to hobby uses and how affordable are other questions.
Having hobby time management software could be an oxymoron. while it is an interesting concept of plugging in a bit of raw data into the home computer and getting a cost breakdown of a model one may want to build i would think that in and of itself would take a bit of time.
A cnc machine can be a useful tool or almost a hobby unto itself. Some see cnc as a useful addition to the home shop others see another invasion of the computer and pushing aside traditional thinking and craftsmanship.
Interesting to see where this thread goes.
Tin

 

[stevehuckss396]

I have been making models for almost 5 years now. In that time I have never kept track of "hours" worked. I have been asked many times how many hours something took and I have no answer. I guess I just don't care. If I were doing this for profit I would know exactly how long it takes. I would also be broke!!

 

[f350ca]

Time spent on models is a totally different thing but for general fabricating in my metal or cabinet shop 20 minutes per part is almost uncanny close. Take the assembly count the parts not including nuts and bolts multiply by 20 and you have a fairly close approximation. I've built reals to hold tubing for geothermal grouting, power feeds for wood chippers, ramps for big trucks to load equipment, display cabinets, dressers, kitchen cabinets, etc and it always seams to work till you get to putting on the finish. Finishing furniture and precision machining are the exceptions.
Greg

 

[Tin Falcon]

I only have a couple engines I have any Idea of how much time I spent on them . My first two were started on a Saturday and finished on the following Saturday. The last one completed took a month and I was in between jobs at the time. Hobby time can be hard to track. How many coffee breaks you take, naps, trips to the hardware store,distractions like stopping to clean the shop(a never ending battle for me), the day job ,family time, house and car maintenance. .... in other words, Like one of the Beatles said: "Life is what happens when planning something else."
If you want to write a program I suggest you find a book or two on machine shop estimating. Also books on cutting tool selection.
I did an excel spread sheet a while back for Elmer Versburg mine engine it was more to track material cost and progress than time.
Tin

 

[dvbydt]

You can get close with time estimation but the problem is non linear because work expands to fill the time available.

Ian

 

[student123]

Guys, thanks for all your views.
Where I'm coming from is I have limited shop time , along with limited experience/relatively limited equipment. So if I found say, ten hours a week, what sort of project might be do-able over a couple of months, maybe 80-ish hours. Cocomo had proved useful to me, I confess I had my fingers crossed on the OP, in case there was a like algorithm out there for machining I didnt know about.
Thanks in advance for any further info.

Mike

 

[shred]

I figure on one part a night, for anything but the most simple ones...

 

[slkride]

Hi to all

My approach to building models may be some what different than the normal. I get out the prints for the project at hand, study them over for a few evenings making a plan of attack. Start with the most complicated part first and work my way on till I have everything done. Then assemble all the parts.
I like to think about a project liken to eating a elephant, you eat one bite at a time and if you get to full it's time to mow the lawn or plow snow or what ever else their is to do on the home front. Being retired is a great advantage as time clock is no longer in my vocabulary. Look forward to meeting some of you a N.A.M.E.S.

 

[t_ottoboni]

Don't forget the 90+90 law: 90% of the job takes 90% of the time. The remaining 10% of the job takes another 90% of the time! ;D

 

[Troutsqueezer]

I'm with Shred. I'll shoot for one part a night. If it's an easy part, I'll finish it in about 45 minutes or so and spend the rest of the time in the shed working on other hobbies/projects. But if I fall asleep in my office chair, it takes longer. And if I stop to play air guitar to the shop music, it takes longer. Of course if I switch on the back massager in my office chair, it takes longer. Also, if I have to stop and adjust gibs it takes longer. Finally, if I have to stop and make a tool....yada yada yada.

Any algorithm must take these variables into account to be accurate. ;D

 

[bentprop]

Let's see,wake up,get dressed,breakfast,shave,etc.By then it's 9.30.At the moment,daughter has no job,since her place of employment fell down in the earthquake.Hence she spends most of her time here.No car,so guess who has to go and pick her up.it's now 10 am.mow lawn.11am.
Go into workshop.fit piece of material in lathe.find calipers,which i used last time.spend half hour looking for calipers.find calipers exactly where i left them,on the bench.
Measure part,find it's too small.Look for more suitable piece of material.find piece,and chuck in lathe.Look for calipers,which i put down just a few minutes ago.check drawing again before starting,and find caliper battery gone flat.
fit new battery.Now it's 12 noon,time for lunch.
Have lunch,have rest.fall asleep in chair,wake up 3pm.wife needs to go shopping.4pm.
Take daughter home,pick up milk.get home 5pm.
Time for the news.Now i can't be bothered going out to the shop again,cause it's getting cold.Spend rest of night in front of idiot box.
Go to bed.
Wake up,get......oh wait,we've been here before.
Sometimes i wonder how i ever found the time to go to work.Never mind how much time i get to spend doing what i want to do.

 

[dsquire]

bentprop

Are you spying on me? How else would you be able to describe my day so accurately. :big: :big:

Ain't it the truth, I sometimes think I should go back to work so I could get some rest and have more free time. :bow:

Cheers

Don

 

[Maryak]

Yes,

Retirement is a real eye opener Most of us are left wondering how we ever had time for work.

Scoping out the day is simple.....................My plan is that whatever I had planned to do will be modified by wife, friends, neighbours and finally me. So the plan is....................DON'T PLAN..................That's good for an afternoon nap ??? ??? ???

Best Regards
Bob

 

[90LX_Notch]

Allot of it is going to be dependant on available equipment, tooling, and fixture needs. Also, available funds to purchase such items, as well as needed materials. My current build has consumed a huge amount of time making tooling and fixtures. The design of the fixtures alone burned up allot of time. The good thing is that some of it will be useful for future projects.
-Bob

 

[Groomengineering]

Don't forget the 90+90 law: 90% of the job takes 90% of the time. The remaining 10% of the job takes another 90% of the time! ;D

Ain't it the truth! Rof}

Cheers

Jeff