Resistance and Voltage drop of Code 332 & 250 SS Track : LUSENET : Wiring for DCC : One Thread

In the track & wire resistance section of ' there is a great table that shows measued values of resistance and voltage drops of 332 code brass track used in garden railroads. More and more manufacturers are now vigorously promnoting Stainless Steel track for this application since it oxidizes less and any oxide formed is in fact conductive. However, the conductivity of stainless steel is much less than brass. Has anyone ever taken resistance measurements and voltage drop measurements of stainless steel track from different suppliers? Looking up the conductivity of stainless steel in tables is somewhat useless since there are so many different grades with different characteristics; I'm interested in real measuyred numbers of real 332 and 250 code track.

Thanks, Knut

-- Knut Schartmann (, October 19, 2004


This text in the webpage is intended to answer your first question:

"I estimated the voltage drop per foot of track or for a pair of parallel wires a foot long representing buses and feeders. To get the voltage drop for a single wire, divide by two."

Also, if you want the voltage drop for a single rail, you would divide the resistance by two. I did it this way because you will always be working with two rails. Also, you have two wires going back to your booster. Let me know if this is not answering your question.

Yes, I used the 10kHz resistance values to determine voltage drops.

If you have some log-linear paper, you could make a plot and estimate the resistance at DC. Just "eyeballing it" I would guess that the resistance would be about 0.00035 ohms for a foot of track (which is two rails) or 0.000175 ohms for a single rail a foot long.

-- Allan Gartner (, October 20, 2004.

I also have a question about the tables in the "Track & Wire Resistance" article. It states that the voltage drop is estimated per foot of track. Can I assume from that, going backwards, that the resistance measurement shown in the table is also per foot? It doesn't actually state that anywhere. And then the voltage drop is calculated based on the measured resistance at 10 kHz (closest to DCC)? For code 332 brass, which I was looking at, the resistance at 100 Hz is a bit less than half that at 10 kHz assuming the meter and the test method can measure these small resistances accurately. I wonder if that is really true; begs the question, what happens to the resistance at DC.

Regards, Knut

-- Knut Schartmann (, October 20, 2004.

Moderation questions? read the FAQ