Power?

re: "The resistance of a track is made up of the resistance at the joints plus the resistance of the rails."

See, the thing is, you have to start by imagining the copper tape on top of the rails all the around to get my point. If so...at any small section along the rail...the effective resistance in that section is the least of the following actually: the copper itself, the rail (and/or joint) itself or the combination of copper and rail and/or joint. That's one. The second point comes from extending this idea. Suppose you have amazingly good conductivity (low resistance) along the rail for 40% of the way and then suddenly have a bad joint...and of course the copper tape is on top of the rail all along...at the very point where the rail voltage would drop dramatically, the copper tape "kicks in" and delivers higher voltage, effectively becoming a power tap. And because it is right there, all along the rail, just waiting until it becomes the path of least resistance at any point...is effectively a semi-infinite power tap. That's the point I was trying to make.

One other point...I'm not sure what copper tape you guys are using, or how amazing your rail steel is, amazing joints, huge cross-section etc...but in my experience (and i prefer thick and wide copper tape personally), the copper tape alone is superior to the steel and/or joints anywhere and everywhere. I used to run it on my Carrera track (which admittedly has more nickel and chromium content and less conductivity than Scalex steel) and now run it on a wood track with no parallel run of steel at all (and no power taps)...and I get no noticeable voltage drop, and actually run at significantly lower voltages than I used to (partly because of so much less mechanical resistance from eliminating the joints, and less hysteresis at the tire/track interface).

I know some people have very strong feelings about this...steel vs copper etc. For me it's just a practical problem/practical solution situation...no strong feelings either way. But I do have the sense that it's worth reminding people once in a while that copper is actually a superior conductor to steel (like 10:1 better). Your rails aren't steel because it's a superior conductor, but rather because it's less likely to deform with use, more resistant to abrasion over time, and cheaper to obtain. To my mind, the ideal combination...the more robust design...is to let the steel do it's "rigid" thing and then clad it with copper for superior conductivity and even for the decreased mechanical resistance (negative impulse) at each joint.

Anyway, those are my thoughts sitting here with my afternoon smoothie *grin* No big deal...

with best regards,
John

PS I'm tempted to pose another question...why do you think your power taps help? Is it (more) because they are shorter runs, or because you are using continuous, copper wire? *grin*

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