My thoughts on Track Design
Designing your track is the most critical part of building a circuit. Improvising as you go along is disastrous. A good circuit is going to need a lot of thought, materials, and construction work. You're only going to have the will and the money to do this once so you had better think hard, prepare well, and get it right first time. Building a working track is not for the faint hearted. There will be lots of unanticipated problems to get round once you get going but when you get it all done you'll feel great. (And then think about doing another one.)
Here are some of them.
1. What sort of circuit? Scenic, racing, commercial plastic, routed wood, permanent, removable.
Working out the circuit shape is time consuming. First consideration is whether it will be a fixed construction or dismantlable. A fixed set of tables is much easier to build on than a structure that can be broken down for storage. A lot depends on whether you are building with commercial plastic track pieces or cutting your own slots (routing) in wood or plastic board and whether your objective is a racing track or scenic model. Home builders tend to go for the scenic scenario, clubs and petrol-heads for the racing type. A beautiful model of a real circuit will not make a good racing one. A racing circuit rarely looks pretty. Although in principle I like the idea of being able to race with multiple cars on as few as 2 lanes, I'm wary of the complexity and value in digital tracks and elected to ignore the possibilities for my first home build.
Using commercial track restricts your options to just one or two curve radii and the more lanes you have the more restricted you are. These restrictions do make design simpler though. If you are routing the slots in wood / MDF / Sintra etc they say you can go anywhere but you still have to make sure that there is enough space between the lanes, nice smooth curves and no glitches. And if you screw up it's start all over again time. (That scares me)
As an unreformed petrol-head I went for the racing option. My concession to scenery was that I could include a bit of topography (hills) but it came about more by accident than design. I wanted to get away from magnetically induced down force and routing boards worried me too much, so I figured out how to replace steel rails with copper tape and went the way of a 4 lane Tyco commercial track. Most of my thoughts come from this experience but many are relevant to the whole concept of slot racing track construction.
2. How many lanes. You want to maximize side by side racing so you don't really want just 2 lanes over a long track. Even 2 lanes over 10m would be unexciting. I have 4 lanes over 11m and it's not bad.
3. Flyover. If you are to race seriously you need a design that equalises the lane lengths. There is only one way to do this - use an odd number of flyovers and the same number of left and right hand curves. One flyover is enough. Put a long straight underneath it to avoid inaccessible spin-offs happening out of sight and out of reach.
4. Drivers and marshals. Think about how marshals are going to access every corner. If you have 4 drivers and need 6 marshals with access to the corners you need a lot of participants in a big room to have a good race. If you are making a home circuit in a restricted space your drivers are often going to have to double as marshals so you must place them where they can access the corners best. Every part of the circuit has to be reachable from the edge of the table.
5. Straights vs curves. Try to maximize the long straights and reduce the number of corners. Close spaced, tight switch-backs are driven through at one speed so don't add much more of a challenge once that speed has been found. Better to straighten them out. Wiggly tracks need lots of access and lots of marshals all round the circuit too. Long narrow circuits with few turns may be less pretty but are much easier to manage.
6. Sighting. Don't place the drivers or marshals where they will block the view for each other. At the end of a long straight the inner lane is disadvantaged as it has to slow more than the outer as it goes into the corner. Placing the inner lane driver close to the corner gives a better view and compensates.
7. Wiring. Think about where you will connect the lane rails/tapes to the hand-controller and the DC supply. On a long circuit you may need jumpers to different sections of the track though copper rails / tapes are much better conductors and you don't need them on a 10m circuit. If your drivers are at each end and each side of the of the circuit there will be quite a bit of wiring needed. I used old telephone cable - it's single strand, thin, pliable, and easily stripped for connecting. It can take as much current as the cars (should) draw and controllers can deliver.
8. Track borders. Commercial tracks are very stingy with shoulders on each side of the track. You need to allow plenty of space for the drifting / swinging car to use without falling off the track. I used 8mm thick foam sheet (EDPM) to put shoulders all round my circuit. Besides providing drifting areas it retains the track in its right place.
9. Power supply and controllers. There are many other articles about these and I'm no expert. All I'll do is point out that you're going to need them. The ones that came in your Tyco/Tomy/Aurora sets are extremely primitive and the controllers have no braking capability. You need to plan for something better that can deliver at least 5 amps for a 4 lane circuit with out-of-the-box commercial cars. Controllers should have braking capability and if they have controls for sensitivity of braking and power delivery rate so much the better.
10. Lap counter and timer. If you're racing you will need to have one. Reliability is vital, if ever it misses a lap no-one will ever trust it. They work best where the cars are going slowest and in a straight line (no tail wagging). Near the end of a short straight is probably the best position unless you have some amazing electronics. That will define where your Start Finish line should be. It will need power and wiring too. Displays of lap count and times for all drivers to see is a necessity too. I used a tiny screen (2.8") connected to the computer for each driver. Ready made systems are rare and expensive. If you can program Python, set up a Raspberry Pi, and do a little electronics you can make your own. Infra-red sensors seem to be the most effective.
11. Design. I did all my layout planning using a CAD package on Windows. I would still be in a mess now if I hadn't used it. In my case it was an old but effective 2D app called Ecad by Evolution Computing. I bought it for work but I expect there are newer free alternatives now. If you are using commercial track you can draw each piece that you could use and then copy and rotate them into position. I see many circuit plans that use commercial track and simply don't join up. They rely on forcing the connection. This stresses the circuit and eventually leads to deformation, disconnections, and breaks. If you're clever you don't need to accept this.
If you are routing you can have variable radius curves but it is difficult to make sure that all lanes are equal length for racing. You can draw ellipses, spline, or bezier curves with a CAD package but it's tricky to get them evenly spaced apart, let alone cut them smoothly without a template of some sort. 4 lanes or more of this is only for the brave and experienced. (I'm not). Once you're ready to cut, I would recommend that you find a print shop which can plot your final design at full scale (1:1) on very large sheets of paper. Attach (tape?) these to the board to guide your router.
I've left out a lot of the details of how I did it all and I haven't even mentioned adapting the cars to the copper track. There is more to tell if you're interested or need help. Please get in touch if you want more, I'll be pleased to help.