The gear in my mech that hangs keeps slipping and I don’t know how to fix it. I have a green cartridge and my gears just can’t stay in contact. It just keeps making a machine-gun sound(the gears slipping) and it can’t lift. It used to be able to until we added more weight to the front.
Use zip ties to keep the axles together, prevents slippage 
can you send a pic and a video of what the gears look like and what they are doing, are you gears axles supported on both sides?
put zip ties on the axles. put a rachet on it to keep from slipping.
What’s the gear ratio?
It would be easier for us to help you solve this if you could provide pictures. H
Change the gear ratio so it has more torque so it will pull it up
If the problem is torque: swap to a red motor, it will give you much more torque and you don’t need speed to hang
If the problem are the axles slipping apart: try to add more supports to the axles in order to keep them in shape. Zip ties could work, but it’s not the greatest solution because you’ll probably need to change them.
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We recently had this problem with our catapult. We found out that it was a structure problem; we attached the motor/slip gear to a different l-channel than the catapult structure itself. The l-channels have a slight flex to them, but because there were 2 different L-channels, it enabled them to flex in opposite directions and ruin the gear mesh (making that machine gun noise).
The solution we found was to mount our motors on the same l-channel (later c-channel) as the catapult itself, so the whole structure flexes together (with the gear mesh intact).
So, either mount your motors to the same metal piece as the elevation mech, or use standoffs to connect the metal pieces so they flex together and keep the mesh intact.
So zip ties are a way of addressing the symptom of shaft bowing, but does not address the cause of this happening. Typically, what is occurring is that the structure supporting the shaft is not squared/parallel causing the gear teeth not to mesh. Additionally, teams sometime put too long of a shaft or the driving gear is cantilevered too far away from motor interface (mechanical advantage of a lever is a disadvantage when causing gear to lift off (machine gun sounds…).
My middle school teams all hit this issue, and then they point to zip ties to say they solved it, and then ask if it is ok to put ice pack on motors because they are are getting hot. (pro-tip fix the structural problems before relying on quick fixes).
Build Quality skills you develop over time.
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