My G8 students finished their fling-bi robot (the main one in the Pitching-in challenge) but they have problems with the arm when they try to shoot the ball. If you already built that robot and were able to throw the ball, could you please let us know how you did it?
If you haven’t yet, read through this thread:
Lots of good info about Fling in there.
What worked for me to get the firing mechanism running smoothly was to take off the “shaft bushings” (the little nubs that stick out from the gears) and replace them with a pin and a spacer:
The pins stick out from the gear a hair less than the shaft bushings did, which is just enough for them to clear the 1x6 beams as they pass by.
Can you post a picture of what you are talking about?