Check out Chainflex from Igus at
http://www.igus.com. They manufacture 2/0AWG x 4C, 2AWG x 4C, 350MCM x 1C, and a bunch of other stuff specifically for energy chains. Even though they are a German company they have a distributor here in Providence, RI. You can run the crane to one limit and pull the cable in the chain without opening it up, just as you might pull in a closed cable tray... Except for the last bit where the bend is at. We have had Chainflex in operation for about 6 years now and have had no problems. Don't use standard SO or welding cable... it isn't engineered for the continual flexing. All of your conductors will break and the insulation will get rubbed off requiring you to replace it quite soon. Hope this helps!!!
