I designed this catapult using a choo-choo mechanism. I decided to post it on the forum because I personally recommend using the slip gear method.
The motors are internally geared to torque. You could use speed gears but I just built this to test.
I’m not putting much detail into this description so please feel free to ask and I will answer as soon as I can.
I do really like the concept of it. Congratulation on getting this to work.
What kind of firing rate and accuracy does it have?
I’ve seen this mechanism used before, for example:
With the motors internally geared with torque we get about 1 ball every 1.5 - 2 seconds. If you look in one of the pictures you can see another catapult arm laying down. Both catapults are functional and exactly the same so when using both you get about 2 balls every 1.5 - 2 seconds. If motors were internally geared toward speed one catapult arm could get about 1 balls every 1 second.
Using the video you posted at reference my catapult has about the same accuracy. Out of all the preloads we average about one ball missing every time either due to the ball not settling correctly on the arm (human error) or sometimes ball density.
Hey, can somebody reattatch these files? They’re not working for me
same!
me 2
Cant get the images 
The images are also not working for me.
Try uploading them to www.imgur.com ?
I really want to see this - it sounds really awesome 
~Jack
They havent been active in 5 months. I doubt they are coming back