Let's build a dragon robot!  You start building the head, and I'll start building the legs.  We'll keep building until we meet in the middle and then add rubber skin and the part that makes it breathe flames!  Ready?  Go! . . .  All right, I'm finished with the legs.  Have you finished the head yet?  Excellent.  Okay, now you start building the neck while you build the . . . wait a second.  I made the legs short and stubby, but the head you built looks like it belongs to a T-rex!  They won't fit!  Also, now that I think about it, how are these legs going to move?  I just stuck them in the ground.  Sigh.  It looks like we're going to need to start over.  There must be a simpler way to do this . . . 


When building a dragon robot for the first time . . .  Well, when building anything for the first time, you want to come up with a plan.  But even if we had talked about what we wanted to build before we started, we still might mean different things.  Once we start building, we might not be happy with what we made and might have to start all over.  We should take a note from engineers and start small.  A model is when you build or draw something that looks like what you are trying to build.  If we start small, we can see what it will look like and do not have to spend lots of time and money building the whole thing.  We can look at problems and plan out our measurements.  A model can be something as easy as a drawing, but can get much more complicated.  Let's start by drawing out our design, then try it with Popsicle sticks instead of metal pipes, shall we?  They are a lot cheaper and a lot easier to lift. 


Now before we start wasting all of our Popsicle sticks, we are going to need to work with numbers.  If we take time to measure everything right, it will look much better and everything will fit together like we want it to.  When a model is to scale it means that it has the same proportions as the thing you are trying to build.  If you were to build a model person with a head that's eight times as big as the body, it is not going to look like a person.  Let's make this easy.  Let's say we want our dragon to be six feet long and one foot tall.  Then we can make our scale model six inches long and one inch tall.  See how I did that?  I changed the feet to inches.  Now our model will be able to fit into your hand, but each part will still have the same size compared to each other as the big one.  The small one's head will be as different in size from its tail as the big one's head will be from its tail.  It will be to scale.  Working with the small one will make it much easier to figure out how it works.  


Let's get building!  Oops.  We already ran into a problem.  The head's too heavy!  The whole thing will tip forward.  Let's make it lighter.  Uh-oh.  Now the ribs are falling off.  We need to find a better way to fix them to the spine.  Oh great, now the spine broke.  Wow.  Good thing we tried this on a small scale.  Since the model was so small, we can rebuild it a couple times to make sure everything looks good.  Once we have all of our problems figured out, and we feel good, we can use our model to build something that does more than looks like a robot.  We will build something that works!  This will not be easy and it might take weeks.  Or even months!  But let's keep working until we make it happen.  A prototype is a working example that is made to test if an idea will work.  For this we will use metal and wires.  We might have to try a few times to make sure a different.  We had to get rid of some of our best ideas (like the fire) and make it a bit smaller, but we finally have one!  I wonder if it works . . . 


People are coming around and looking at our dragon robot!  They scream when it waves its head!  They duck when it waves its claws.  They are admiring all of our hard work!  And get this: everyone wants one for their school!  That's right.  We can sell copies of these!  We send the prototype to a factory and they'll make thousands of them for us.  To manufacture means to make a lot of something using machines.  Factories will make it super fast to build each part and can put them together for us much faster than people could do by hand.  We can copy our prototype so that every school around here can have a dragon robot! 


It's never a good idea to just jump into something.  You need a plan.  And when it comes to engineering, it takes a lot of other steps too.  It's good to make a model, something smaller that looks like what you are planning to build.  This should be to scale -- its parts should have the same proportions to each other as those of what you are trying to make.  The first version of what you build is called a prototype.  You can build many of these until you find just what you want.  Last, if people really want what you built, you can manufacture it, or make lots and lots of them with machines.  Now that everyone has a dragon robot, ours does not seem so great, does it?  What should we build next? 


References:

TeachEngineering.  "Engineering Design Process"    Teachengineering.org, 2016.  <https://www.teachengineering.org/k12engineering/designprocess>