How do you guys come up with track layouts?

Okay, while not a track builder, I can give you a few generalities here that might help.

-What I have found through messing around with a couple of short pieces rain gutter is that, yes, it is wide enough to run two cars down, side by side. However, there is a problem: because of the shape of the rain gutter itself, the outside wheels of the cars are going to be riding up on the curve of the rain gutter walls, forcing the cars literally door to door with absolutely no room for passing. Any races you run through a rain gutter will be one car getting ahead and no chance of a second car passing at all.  While this may work for drag racing (and actually is probably not a bad idea for a single car in each gutter), this spells trouble for open track racing.

-The 45* pipes are going to be a MAJOR headache to work with.You will have to modify the hell out of them to get them even somewhere close to functional, and even then they still may not work because of the sharp corner where the two pipes come together. (I've messed around with one in the store by running a car through it, and every time, the car bangs head-on right into that intersection. Plus, if you slot a straight pipe into the end of the curve, the car rams right into the lip of the straight pipe and flips.) You're going to need something the cars can cruise around easily, like the flat Carhooner Corner at Chaos Canyon's track, or a curved bank like a Crash Racer's corner so the cars can enter at speed. Someone made a nice banked curve out of a huge salad bowl that actually worked pretty well ..... Get a piece of coroplast (cheap real estate or political signage, available on many street corners for free!), and start playing around with it. I saw someone use the edge of a bicycle rim as a template for putting a fence around the outside of the curve, and thought that was a really neat idea on keeping a perfectly aligned curve.

-How long are you going to make the course? How much room do you have to work with? What kind of drop are you looking at for the downhill runs?  Too steep, and the cars will be a blur: too shallow, and the cars will drag and stop on the track. Someone had a measurement for track angle here somewhere ... something like 1-2" for every foot of track, which gave the cars enough speed to run good, but not  enough to outrun the cameras.too much.  Look at the space you're going to use, and plan accordingly. If you need templates, cardboard boxes are cheap and pentiful - cut up a bunch, tape them together, and visualize your track layout that way, including where you will need to support the track and curves.

It ain't much, but I hope it helps answer one or two of your questions.

I have yet to build a road course but there's space in my toy room that is just waiting. So when I get to that point, my first step is defining the space and building to that. Your limits on physical real estate is the first step.

After that, I think you look at your materials. What are you using to build? If you're going with retail track, then that has its limits. If you're using cardboard, that has its limits. Build to the limitations of your materials and space, not the other way around.

But I guess ultimately, I think it's also what you're trying to do with your track. If you're building it just for fun for yourself and friends, then build how you want. If your intent is to record races and share them on YouTube, then designing for the camera is also something to consider. You might have the best track in the world but if its a pain to shoot, then you're stuck.

Don't discount trial & error though...that's supposed to be half the fun too, just exploring and seeing what works. I mean one person made a giant wheel out of a table, so if you're willing to fail a lot and have fun doing it, then shoot for the moon!

Back again with another design, but still the material I'm going to choose is still keeping my brain in a knot. Here's the design:

Originally I was going to use The Adventure Force fat track, but on closer inspection it seems that the banked curves are angled to form the cross-section, so now I'm stuck for a loop on what material to use. Any suggestions?

How do I come up with designs? I think of a something that seems impossible then make it.

For me I had to figure out what kind of track I wanted. There are a ton of large road course tracks out there, so I wanted to offer something a little different. I went with a short fast track that was mostly corners. That how the idea for the Mullet River Sprint Track was born.