Naive design questions (NDQs): "How do I design ______?"

Question

There have been a few questions where users with little to no training are requesting instructions on how to design some object.

Some examples (both happen to be structural):

• Asking for a "set of equations" to design a solar dish loaded by wind
• How to design a custom structure "for example a ladder"

Questions like these are probably to be expected, and although they do present a problem, it should first be recognized that:

1. This is a good problem to have since it means people are finding the site, and
2. It is understandable that people with no knowledge of the nuances of engineering design will underestimate the complexity required to design even something as simple as, e.g., "for example a ladder" (sigh), much less a wind-loaded, parabolic solar dish.

I can't think of a rigorous definition for "naive design question;" like Justice Potter Stewart's obscenity test, "I know it when I see it." But it would be helpful to come up with one. I think "poorly researched" would be a primary characteristic.

I think we as a community need to think hard about how to handle NDQs, and what, specifically, we can do to make people feel like they can come here and "get some answers", while at the same time being honest with them that "Um, this is a lot more complicated than you seem to believe, and might be beyond your ability at the present time."

Answer 1

The Engineering Stack Exchange is best able to answer specific questions that have a right and wrong answer. While we are populated by engineers, we can't solve all levels of engineering problems, because broad questions require weeks or years of research, modeling, calculations, and analysis. They also require a lot of specific information about usage conditions, location, and service requirements. Questions about how to design a whole project whether it's a ladder, a bicycle, or a skyscraper are simply too broad. This post is meant to guide you from a large idea to specific questions we may be able to answer.

The first step of most design processes is to make sure you really understand your goals. What are you trying to build? What is important about it? For example, if you're building a ladder how tall does it have to be? Can it use conductive materials? Does it need to last for weeks or a century? How many people need to be able to climb it at a time? What climates may it be used in? Start by figuring out these parameters for your design. In many cases, you'll need to do some research in various codes. For example, there are codes that dictate the wind and earthquake loads you need to plan on when designing a structure, or the strength you need to design in a piece of rigging equipment.

Next, draw a sketch of how you might build the thing you're thinking of. Think about if it's actually possible to build. Is it going to be so expensive that nobody will ever build one? What kinds of processes are going to be involved in making it? Are the materials you plan to use actually readily available? What are the critical components and which are less important?

At this point, you have a starting point for a design. Lots of things may change, but at least you understand what you're getting into. The next step is to start looking at each piece, connection, and subsystem and really explore how it works. Is it strong enough? Will it work at the temperature you need it to work at? Do you have to build it from scratch, or can you purchase it? Will it be able to last as long as your whole device, or does it need to be replaceable?

As you look in more detail at your idea, feel free to ask specific, answerable questions. Here are some examples of questions we may be able to help with:

• For a structure of this shape and size, at this location, governed by this code, how do I calculate the wind load?
• For a member subject to these forces as a part of this system made out of this material, how do I make sure it's strong enough?
• I have designed a connection in this way, how do I figure out if it will work at this temperature?

Answer 2

One suggestion: it might be worth writing an article which can be the standard reply (in a comment) to NDQs.

The article would:

1. explain that the question, as stated, demonstrates a lack of appreciation for the complexity of the problem being asked and does not meet the site standard for question quality
2. give examples of what a "good" How do I design a ___? question looks like.
3. (optional) give suggestions on where to go to research the problem*

*#3 might turn out to be unwieldy since there are so many different types of engineering, and it might be impossible to create a thorough "start here" research list. One solution to that problem could be to have some standard "do your research/you are missing some basic knowledge" articles for the larger sub-disciplines (structural, mechanical, electrical...) and a catch-all article for everything else.

Answer 3

"Design" questions should be on topic here. On the other hand, we don't want "naive" design questions.

On many other SE sites, such as the language or programming sites, the OP is supposed to make an attempt to solve the problem himself/herself (and show relevant work). Thus, a question of "How do I design X?" might not be a good question, because someone is being asked to answer "from scratch."

A better question is, I've tried method A to solve problem X, and that didn't work because...What is a better way to solve his problem? or "Is there a variation of method A that might work?" or even, "I'm thinking of using methods A or B or C; what criteria should I use to choose between them?"

That way, the OP has shown some effort, and displayed a certain level of aptitude (or lack thereof), thereby making it easier for someone to identify the OP's problem and answer at that person's level of understanding.