The complexities of designing a CAD model

     I love to model in CAD.  Period.  It is one of my favorite things to do, both professionally, and for my hobby.  It is to me similar to sculpting or woodworking, using digital means to work with my hands and mind.

     Keystone Details receives several design requests each year and while I would love to model each and every one. Many folks may not understand how much time and effort goes into even the simplest CAD model and how that is compounded exponentially for a very complex design.

There are four cost factors that go into each and every model.

  • Time Cost- modeling can range form 5 hours to thousands of hours depending on complexity, in example:

I spent 6 hours last night developing a PRR bogie whereas I spent nearly 1000 hours developing my PRR 3768 Streamlined K4 kit, or just an hour for scaling an N Scale design into a larger scale.

  • Monetary Cost- Hours spent * pay rate

I typically do not charge a rate, but i do use $10 to compute examples of the cost of modeling.  In the time examples above, at $10 per hour the bogie represents $60.00, and the 3768 Kit at $10 per hour would be $10,000.00.

  • Human Cost- not measured in currency but more effectively measured in lost personal time used

The time spent modeling is also time spent after work, stealing time from my family and my model railroading hobby.  I find myself stealing hours when everyone else is busy with their things, or after everyone is asleep modeling into the wee hours of the next day.  Imagine being away from you family for 33 days- that is what I missed (collectively) when working on the 3768 kit.

  • Research Cost- the availability of enough information to develop a design

Photos or text may not be enough to develop a complete design.  While I can visually proportion things in my mind, they may not be accurate enough to consider it scale.  I may ask for a part from another scale to be mailed to me so I can measure it and scale it to another scale, or need research from a customer from a Railroad Historical Society. These things are invaluable to good design an will positively influence the Time Cost, Monetary Cost and Human Cost.  Remember that EVERY part in a locomotive or line side detail had an individual drawing so that the part could be made  and inspected to specification.  Diagrams and such are not drawings, they are more like art.

     There are additional factors that go into the consideration to design a CAD model that I develop for myself or for someone else:

  • Do I or will I ever want/need the design?  

I weigh this factor heavily in considering modeling something for a customer.  If I can justify needing the model on my railroad, I may choose to model it, if I can't I won't.

  • Is it PRR related? 

This should be obvious from the Keystone Details website, but there are many times I have modeled non-PRR stuff, just visit the Keystone Customs page.  I will admit that most PRR N Scale designs are for my own personal use, that I have decided to offer to others.

  • Is there a genuine reason to model it for someone else?

Many designs on the Keystone Details pages are designs that were done to return favors or folks that compensated me in some way.  Or for PRR folks in dire need because I can scale something up or they are willing to pay for the design.  One reason I will NOT model for free, is the thought that I should spend my time "for the love of the hobby", "this has never been available, can you design it for free?", or "I guarantee you will sell X many of these".

  • What is the overall cost factor?

Lastly I weigh the overall cost factor, to see if it is worthwhile to me overall.   One factor I ignore is potential sales, particularly for designs I need.  profits are intentionally small, just enough to keep my model railroading hobby alive and to make up for some lost Monetary Cost, mentioned above.

     Finally there are also design considerations:

  • Designing to be printed, such as wall thickness requirements and wire cross sections, etc.  Surface finish that can be assisted by the design, fit and finish qualities, and function.
  • Engineering difficult solutions to get the design to work, for example, I designed three unique iterations of the Stillwell coach before I allowed it for sale.  Unfortunately the shoddy tolerance control of the printing process let that model down after lacking sales.   

     I am writing this not to chastise folks in any way, but to help them understand what it takes to develop a CAD model, how much it REALLY costs, and what is a reasonable response to expect from Keystone Details for a prospective request.  Yes there are other designers out there who will jump at a design for free, but with Keystone Details you are working with a 35 year product development designer as a profession, that also understands the intricacies of quality design and function.


Keystone Details

John LeMerise