We are using window motors to articulate our arm, and we have a complication with the system. The arm goes in an almost full 360 degree motion, but with the gripper on the end, we cant get it to lift more than horizontal on either direction. it seems that we need a tension system to act as a counterbalance for the joint. would it be possible to use bungee cords? do they provide enough tension to help counteract some of the weight? we need this fixed today because tomorow is the ship day! this isnt good at all. the rest of the bot works great. ill post a pic on the portal of what we got. its team 3329. thanks!
We suggest surgical tubing. Think about using a cam that tightens the tube as the arm moves down so it adds increasing tension on the tube and adds strength to the tube. good luck!
I would suggest using surgical tubing as a counterbalance. It usually works very well. 
We had the exact same problem, we considered counter weights (but they obviously add weight) so we just replaced the window motor with a FP motor and it works fine.
We had this problem on sat. so we tied surgical tubing on to it and it lifts with no problem now!
We’ve done something very similar with surgical tubing, and it works pretty good. If surgical tubing doesn’t give you enough force, talk to your local dive shop about spear gun tubing. Similar to surgical tubing, but it has a greater force-stretch ratio, and doesn’t seem to retain the stretch “memory” as much.
Surgical tubing and or bungee cords (tubing is better because it’s adjustable) work GREAT for arm counterbalancing. We successfully used it to make our arm work off of a single Window motor.
We had the exact same problem but the claw alone wieghed 9.2 lbs… so we decided to change it completely. Now it works GREAT!!! the claw has only a back stop and a hook to grab the tube(made from U channel from the KOP chassis and IFI tred). before it was belts driven by window motors. 