by MikeF
Interesting. I didn't know the CTA had replaced the copper contact wire with aluminum.
In the compound catenary system that was used on the Skokie line, the bottom wire (which the pans run on) is called the contact wire, the next one up is called the secondary messenger, and the top wire (which mounts on the bridges) is called the primary messenger. The hangers every few feet between the secondary messenger and contact wire do not serve so much to aid in conductivity, but rather to keep the contact wire level.
In the compound catenary system that was used on the Skokie line, the bottom wire (which the pans run on) is called the contact wire, the next one up is called the secondary messenger, and the top wire (which mounts on the bridges) is called the primary messenger. The hangers every few feet between the secondary messenger and contact wire do not serve so much to aid in conductivity, but rather to keep the contact wire level.