Almost without exception, track builders dedicate considerable time and effort to all aspects of the track construction, except one. Wiring. Perhaps it's because electricity is a mystery to many people. Often people are so pleased that they wired something and it actually worked that they don't consider the fact that there might be far better methods and material choices. But it doesn't have to be difficult. Indeed, there is no one correct way to wire a track, but once armed with a little basic knowledge, a track builder can handle all his/her wiring with the satisfaction of knowing that the job was done competently, appropriately, and safely.

UNDERSTANDING WIRE

Electrical wire has two basic forms - solid and stranded. I suppose you could argue that solid wire is single-strand, stranded wire. Solid wire is the stuff in your house wiring, and is used when maximum capacity and minimum cost are needed in a wire that will NOT be flexed in any way. Stranded wire is like rope - multiple fine strands twisted around each other to form a larger wire. For a given size, it has marginally lower capacity than solid wire, but it can withstand repeated flexing (within reason) without breaking like solid wire. Slot tracks almost invariably use stranded wire. They certainly will for power hookup and controller leads. Solid wire could be used for under table wiring, but it is uncommon. We will talk here in terms of stranded wire.

The size of a wire is called its "gauge", and is specified as a number (such as "14 gauge"). The higher the number, the smaller the wire - 14 G wire is smaller than 12 G wire. Smaller wire has a lower capacity, in terms of the electrical current that it is capable of handling. If you think in terms of your garden hose, you will quickly see why this is. If you hook 1/8" tubing to your faucet, you will get very little water compared to a 1/2" or 5/8" garden hose. This is because the size of the tubing restricts the amount of water that can pass through it. The flow of electricity is subject to similar physical laws. We say that the smaller wire has a greater "resistance". This resistance to the flow of electricity is measureable, and we measure it in terms of "Ohms" (an acknowledgement to the man who developed the basic electrical formula still in use today, called "Ohm's law"). We'll talk later about the side-effects of using wire that is too small. For now, just accept that the lower the "Ohms", the greater the capacity of the wire.

The following table depicts the relative sizes and resistance of common wire sizes. Again, don't worry about what the Ohm ratings are, but note that they rise very sharply for wire smaller than 18G.

DETERMINING YOUR REQUIREMENTS

Before you can even think about wiring your track, you should determine some very simple parameters which will help you decide if you are using a wire that will meet your needs (both present and future). The key parameters are:

Power source - What will power your track? Wall wart? Batteries? Power supply?
Cars - will you run T-jets? Magna-Traction? Tomy, Tyco, Life-like? Neo/Polymer?
Track size - A simple 2 lane on a 4'x8'? A humungous 6-laner on a 6'x24' table?

Wait a minute, you say! These aren't high-tech electrical parameters! True, but these are the real-life decisions that will determine what your electrical needs really are. Your track wiring should be suitable for the power source you use, the electrical needs of your cars, and you need to think about the length of the wire runs that your particular track will require. The results will be very unsatisfactory, and possibly dangerous, if, for example, you wire your track with 24G wire and then use 18V worth of car batteries to power it - I can almost guarantee that at some point your wiring will go up in a cloud of smoke as a result of a short circuit, even if you use fuses (more on them later). Conversely, if you are absolutely certain (absolutely!) that you will never use anything other than wall warts and T-jets, it would be ridiculous to wire your track with 12G wire - it would be akin to using a 12-gauge shotgun to kill a fly.

Now, let me repeat that you need to think about your needs for today and for tomorrow. Your track, the table, and all that beautiful scenery (what? no scenery!), will work fine with any cars and power source you might eventually choose to run. Your wiring may not. Rewiring is not fun. So think about it.

Your choice of power source will probably be dictated by the type of cars you intend to run. Wall warts (notice the plural), are fine for stock T-jets - I recommend one per lane. Neos and Polymers require high-current electronic supplies or batteries. Everything else falls somewhere in between. Oh sure, you say! That's a definitive statement! Okay, okay, I'll present a table that roughly shows the requirements for different levels of car performance. Bear in mind that these values are very subjective, and depend on a lot of factors. Add-on parts, like armatures, magnet variations, gear ratios, tire diameters, etc. will have an effect. But these numbers should give you some basic guidelines. There are two assumed constants here - voltage (for these numbers, I am assuming an 18V supply, which is a common value in HO slot racing) and a power feed length of 20 feet (remember that the return is counted so this is really for a 10' length of wiring). For other common voltages, don't worry, this data is still relevant - the chart would be only a tiny bit different. Oh, and forget the fact that your set came with 1 wall wart - the data below is for each lane - yup, a single wall wart is insufficient on more than one lane with ANY type of cars! One last caution in using the numbers below - they assume that each lane has a separate ground return to the power source - this is rarely the case - by using a common ground wire the effective capacity of the wire is seriously diminished.

The yellow zone in the chart above should perhaps be better explained. Wire has a resistance, expressed in terms of Ohms. The resistance of the wire determines the amount of current that the wire can pass for a given voltage. As the limit of the wire's ability to handle current is approached, two very simple things occur.

First, because the wire cannot pass the required current, it is forced to dissipate power in the form of heat. When a wire is heated its resistance increases, further limiting its ability to pass electrical current. It is a snowball effect.

Second, because the wire begins to act as a resistor to the current flowing through it, and because the car's armature is in itself a resistor, the voltage that the car sees begins to drop as it is now an integral component in what is known as a voltage divider. The positive power pickup sees only a percentage of the power supply voltage - any point between two resistors has a voltage equal to the relationship between the resistors. As the wire's resistance increases, less voltage is available to the car.

If you're thinking that the yellow zone should really be thought of as part of the red zone, you're absolutely right. The manufacturer ratings for small gauge wire is normally based on 12V. This reduces the total wattage that the wire is dissipating when faced with the same sort of current loading that we use. I am being conservative with the ratings because a slot car does not demand a continuous current - it fluctuates greatly over the course of a lap. But when we get into the yellow parameter zone, we are definitely pushing the capabilities of the wire. And if we spend too much time in the yellow zone, we have exceeded the wire's capabilities to deliver.

What we want to ensure is that our wiring is capable of handling our power requirements without repeatedly entering the yellow zone. We want the wiring to deliver the power we need, when we need it, without worrying about whether it is dynamically altering our effective available power. It is okay to occasionally cross into the yellow zone (even very briefly into the red zone!), but if we do it too often we will not be seeing the maximum power that our supply is capable of generating and we may induce heat which will increase the resistance, which will move the yellow (and red!) zone lower, which means we'll enter it more often, which will induce more heat....etc, etc, etc.

But note also that any time we pass into the yellow zone (even for a microsecond) we see a noticeable drop in the effective supply voltage. This means your car is seeing neither the full supply voltage, nor the current that it was attempting to draw. The wiring may not even get noticeably warm, but you are exceeding the limits of the wire and you are not getting full power to your car. You may be prepared to live with this but it is a phenomenon that you should be aware of. Particularly if you race on multiple tracks and attempt to tune a car on one track for use on another (ever done this and wondered why the car performed very differently?).

RECOMMENDATIONS

Armed with the above information you can probably determine the correct wiring for your own particular needs. But if you are still uncertain, here are some simple guidelines:

If you will only run T-jets or Magna-Traction, go ahead and wire your track with 20 or 22 gauge wire.
If you will use current cars, such as the Tomy SG+, Life-Like, or Tyco 440X2, in stock only form, then 18G wire is suitable.
If you wish to ensure your wiring is capable of handling everything, including modified, Neo, and Polymer cars, then go with 16G or heavier wire.

You might ask, "Well, why not just use 16G wire and be done with it?". This is exactly the question I pose to everyone. Why not? Many people spend more money preparing one single car than they would wiring their entire track with 16G wire, but they seem reluctant to do so. It is a philosophy l will never understand.

SIDE NOTES

I mentioned fuses earlier, and that I would talk about them later. Well, it's later, so let's talk about them! All tracks should incorporate fuses. There should be one fuse per lane, wired into the positive lead from the power supply to the controller. Fuse holders can be had from any electrical/electronic source, including automotive shops, electronics houses, even Radio Shack. Use them! Select a fuse value that lies within the amperage range of the wire and cars that you will use on your track - T-jets on wallwarts, 1.5-2 amp; SG+ on a 6 amp supply, 5 amp; unlimited Polymer on batteries, 8-10 amp. The purpose is to protect your wiring from overloads, the most common form of which is a short circuit. Bear in mind that you DO NOT want to use standard fuses, or you will be blowing them often - slot cars are notorious for momentary short-circuits, particularly when they leave the slot. However, slow-blow fuses have a latency time that means you should be confident that the wiring in your track will not be the equivalent of a fast-blow fuse - 24G wire on batteries will be just that! I also recommend using a master fuse that will protect your power source (if it doesn't already have one).

Connectors are another important issue. Any time you connect one piece of wire to another, you should be sure that the connector exceeds your anticipated requirements. Terminal blocks with spade connectors soldered to the wiring are a great choice - twisted connections wrapped with electrical tape are not! Most automotive connectors are great with 14-20G wire. Electrical/electronic shops carry a vast array of suitable plugs, sockets, and terminal strips. For multi-conductor wires (like that used in trailer wiring) look at polarized connectors - they can only be connected one way. Your controllers can be wired with a plug/socket arrangement, or the standard post/alligator clip method. If you use the latter, be sure to color-code them to help avoid incorrect hookup.

Under track wiring should be well secured. Use insulated wire staples, or cable clamps. Avoid wiring that is loose, or hangs down as it can easily be snagged and torn away from its connections.

FINAL WORD

I hope that the above information is helpful. By spending a little time thinking about the wiring of your track, you can avoid a number of problems (both seen and unseen!). It really isn't a complicated issue, and if you ensure that your track is wired adequately, you can avoid a slew of problems, both now and in the future. Give your power a chance!

Continued