Motor Lead Wire
The Many Faces of Motor Lead Wire
Obviously, we offer our Motor Lead Wire so we're a bit biased. That said, it wasn't a matter of just finding some wire hanging around on the workbench, cutting it into 3 foot lengths, sticking it in a bag with an SCC label and offering it for sale on our website. Like all of the SCC products we offer, there was a lot of upfront design and testing that took place. Here are some of the design criterion we used to evaluate and test our SCC Silicone Motor Lead Wire.
- Gauge (o.d.) - For 1/32 RTR cars, most motors generally draw no more than about an amp of current (and then only very briefly when the car is at a dead stop and you pull the controller trigger to get it moving). As such, there are a wide range of wire gauges with sufficient "ampacity" (maximum safe current carrying capacity) for most 1/32 RTR motors. As the wire gauge gets "bigger" (lower numerically), the overall diameter of the wire (strands + insulation) also increases. Smaller gauge wire (higher numerically) has a smaller o.d. but can be more difficult to work with and less forgiving (e.g. there may be fewer wire strands to start with which means less wiggle room when stripping insulation and inadvertently nicking/cutting strands). Larger gauge wire generally has more "spring" than smaller gauge wire - this is important for racers who configure the motor lead wire to help self-center the guide whenever the car deslots.
- Stranding (flexibility) - In general, for a given gauge wire, more strands of finer wire will be more flexible than fewer strands of thicker wire. For example, stock (think stiff) motor lead wire typically has between 7 and 21 strands. In comparison, our SCC wire has 168 strands!
- Insulation Material (flexibility) - Silicone is generally more flexible than PVC and other common wire insulation materials. Silicone insulation is also generally more expensive. Most stock motor lead wire has PVC insulation.
- Insulation Thickness (flexibility + o.d.) - In general, for a given gauge wire and insulation material, the thinner the insulation the more flexible the wire. For example, take 2 lengths of identical 24 AWG motor lead wire (just the copper wire) - one with silicone insulation that is .010" thick, the second with silicone insulation that is .015" thick. The silicone wire with the .010" thick insulation will be slightly more flexible.
- Overall Wire o.d. (wire gauge + insulation thickness) - On many cars, there is a very limited amount of space between the front (underside) of the body and the guide/motor lead wire. Carefully shaping and routing the motor lead wire can help to reduce some interference but in some cases, as can compensating for the interference by loosening the front body mounting screw more than you might want to. In these cases, a motor lead wire with a smaller overall o.d. can eliminate (or at least further reduce) the interference altogether while allowing for a full/wider range of front body mounting screw adjustment. The 2 design elements that affect overall wire o.d. are wire gauge and insulation thickness.Insulation (heat) - Silicone wire is much more forgiving (resistant to heat) when soldering motor lead wires to the motor tabs. PVC insulation has a tendency to melt.
- Bare copper vs. tinned copper - For a given gauge wire with the same stranding, wire with bare copper strands will generally be more flexible than wire with tinned copper strands. Practically speaking, can this difference be measured? Probably not (at least, not with any measuring device/apparatus we have at our disposal). Nonetheless we prefer motor lead wire with bare copper strands.
As you can see, flexibility and o.d. are key requirements for motor lead wire. If the motor lead wire impedes guide movement and/or prevents proper adjustment of the front body mounting screw, it will have an adverse effect on a car's performance. Given the above criteria, we worked with a wire manufacturer to produce a motor lead wire that met our specifications. Is this overkill for motor lead wire? It depends. For the casual racer, they may never replace the stock motor lead wire and the above criteria is of little interest (and that's OK). For more serious racers, we've done the hard work for you!
Our own SCCC Motor Lead Wire is available here.