Building biped legs

These are the robot's new legs. Both legs (now completed) will have a tendency to revert to an upright state when no force is applied to their joints. Tension is provided using bungee cords as synthetic muscle to provide tension in one direction. The knees contain metal brackets that prevent them from folding over backwards in a fashion that would be uncharacteristic of human legs. The holes drilled out of the legs help to make them lighter without compromising the robot's structural integrity. From this point on everything that goes into the robot will have to be evaluated for ways to make it lighter. Weight is a huge limiting factor for humanoid robots. The more a robot weights the more power it consumes when moving and so operation time is greatly reduced. At the moment most humanoid robots can only operate for an average of 15 to 30 minutes. I want to make Salvius's battery life last as long as possible so form now on every gram counts.
I don't yet have an exact measurement of how much the robot weighs. My guess is that it is just under 160 lbs (that is including the robot's upper body along with the legs).

The photos below show the framework for the pair of legs as I started building them. The paper template is made based on the average dimensions of an adult human leg. The is currently composed of wood but eventually I may need to replace them with a stronger and lighter weight material.
Previously, I worked on making a pair of brackets for the robot's legs. I used a template to measure and mark the steel before cutting and sanding it.
The template and the bracket that stop the knee of the robot from folding back on itself.