Power?

Most ohm meters are not all that great for measuring low resistance values and one problem that I have run into is that the connection betweenn the test leads and the body of the meter or in the contacts of the selector switch can cause trouble. Here is a method that I have used. First disconnect the last track section before the one where power comes in. Put a car with the rear axle removed on that last section and apply full power. Hopefully the motor will run, if not move the car to a place where it does. Using a volt meter take readings across the joints, stay on the same rail, do not take readings between the right and left rail. If a joint is good you will read no voltage, if the joint is defective it will act like a resistor and you will read the voltage drop. Fix defective joints as you go.

hi, Al
I appreciate your comment...I think we are all using the term "power taps" the same way, but yes, speaking past each other. I'm trying to explain why the copper works so well...and it's not only that the material itself is 10x more conductive but that it has no joints. As far as I can tell, noone (else) is quantifying the effect of the "choke" points of minimal contact area and/or air losses/arcing at each joint. This is a huge effect (well, huge percentage of overall power drop in a plastic slot track). I get the sense that most think that "transmission loss" is the larger culprit. It's not in most cases. About the "semi-infinite power tap", to reiterate...you have to imagine the copper tape on top the rail as not just a part of the rail (which it is with that conductive paste), but also as a true power tap, made of copper just like a normal wire power tap, and simply running the path of the track instead of the usuall path in a straight line from the power source to power tap location. This is a model of part of it's behavior. It's not literally true, but effectively true...it behaves that way as well as creating a jumper over any bad joint. The cumulative effect of these three regimes (jumper, power tap basically whereever it's needed, as well as acting as a bi-metal rail of increased conductivity) is why it works so well.

Meanwhile, the "4th regime" is that the copper tape acts as a ramp to minimize "negative impulse" as the car literally collides with each new section of (slightly raised) track. I mean "negative impulse" in the sense of "force multiplied
times time, acting in the direction against travel." And just to be clear, in a steel braided system transmission loss is indeed the largest factor in voltage drop (assuming the braid is continuous).

with best regards,
John

To recap what I was saying (and I think John was saying rather the same thing?)
The first place to look for power drop problems on plastic track is the joints, and joint problems frequently give much larger power drops than the resistance of the rails. We seem to agree that copper tape laid on top of the rails acts as a loop and that the joint problem pretty much disappears once the loop is in place.

Not sure if there is real disagreement over the "semi-infinite power tap" thing, or if we are just saying the same thing in different ways.

The effect of a loop conductor is the same as a pair of power taps to wherever the car is on the track. In a sense that is a "semi infinite" number of power taps, but with only two of them working at once. The resistance is these power taps is the resistance of the length of tape travelling clockwise round the lap to the car in parallel with the length of tape travelling clockwise to the car. The effect of a "semi infinite" number of connections between the copper tape and the rails underneath is to make them conduct in parallel. As the number of connections increases, they more precisely approach running perfectly in parallel at whatever point on the lap the measurement is made.

QUOTE (300SLR @ 10 Apr 2012, 13:08) <{POST_SNAPBACK}>To recap what I was saying (and I think John was saying rather the same thing?)

The effect of a loop conductor is the same as a pair of power taps to wherever the car is on the track. In a sense that is a "semi infinite" number of power taps,
but with only two of them working at once.

Yes, exactly...that perfectly describes the one point I was trying to make, 300SLR. And I do acknowledge as well the argument you've been making about that
positive and negative are running in opposite directions/ratio of two unequal lengths, etc. Clearly we agree (and Slotracing Al was correct about that). Thanks
for taking the time to make that clear, and please forgive my earlier crotchetyness...I believe I may have PTSD from previous such discussions *grin*

with best regards,
John