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2900 Views 29 Replies 11 Participants Last post by  Stubacca03
My new layout uses the SCX Rally Chrono, SCX Chicane and Scaley Sport Track for the rest. I've noticed a reduction in power on certain bits of track.
Whats the best option to create a consistent voltage throught the whole track?

I've looked at the SCX and Sport Boost cables, would they work with SCX sport combination, if so how? Or are ther better options?

Please be aware I'm a total noob when it comes to electrics so keep it simple!

Thanks in advance.

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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.
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Rich is right about most multimeters not being all that great for measuring low resistance values.

Measuring on no load with a multimeter is a lot less sensitive than applying full power, putting a load across the rails (22 ohm resistor for example) and measuring the voltage drops at the joints.

I agree any connections over 0.3 ohms is normally a problem, but several joints a little under 0.3 ohms add up to a significant problem so ideally you want to aim lower than that. That's easily done by the method above.
QUOTE (300SLR @ 4 Apr 2012, 09:18) <{POST_SNAPBACK}>So you are saying the copper tape bridges a bad joint in the rails, pretty much eliminating the resistance at the joints problem.
Yes that's true assuming the tape is in good contact with the rails.

No, I'm saying the copper tape is not just a bridge, but effectively a power tap at each bad joint.
I could address your other comments, but I'd simply be repeating myself. I yield to superior endurance.

QUOTE (John Cahill @ 9 Apr 2012, 17:19) <{POST_SNAPBACK}>No, I'm saying the copper tape is not just a bridge, but effectively a power tap at each bad joint.
Could it be you and 300 are talking at cross purposes?
To me a power tap is a separate feed wire from at or near the main power input to some point round the track.
Perhaps there are other ideas on what it means?
Most digital meters made in the last 20 years are perfectly suitable for measuring low resistances. Why start soldering and sticking on conductive tape when a bit of easy self disgnostic testing should fix the problem? Even if a meter shows a higher reading than expected it will still show an obvious difference between a good contact and a bad one.

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 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 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,
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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.
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I've not been on the forum for a while so I was surprised to see all the suggestions and comments, even if some of it is over my head. Thanks.

So far I've changed the braids on a couple of cars, cleaned up the track a little and that has made some improvement, however its still seems down on power to the Scalextric Sport power base I was using prior to getting the SCX Chrono.

I'm swaying toward the copper tape at the moment as it seems like it may give me the best results for my setup. I still need to check/crimp some of the joints but some of the track is fixed to the board using Scaley fixing clips so I'm loathed to pull it all up...........but I may have too.

Any recommendations on copper tape? (UK suppliers)
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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,
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Very interesting discussion. What do you guys do with the lane change sections on digital track in regards to copper tape?
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