Best Catapult Pullback Mechanism

What’s your opinion on the best mechanism for pulling back and releasing catapult or linear puncher arm?
Here are all of the approaches that I know of, let me know if I missed any.
Direct Driven
The arm is pulled back and pushed with a few motors geared to swing the arm faster.
Main advantage: Speed of motors can be modified for variable distances.
Main disadvantage: Uses many motors.
Cam Driven
The arm is pulled back and released with a drop off cam.
Main advantage: Farther pullback.
Main disadvantage: Large mechanisms.
Radial Release Mechanism
This uses a mechanical linkage to pull back and release the launcher.
Main advantage: Better pullback angle, I guess? I honestly can’t think of one that a different mechanism doesn’t do better.
Main disadvantage: Requires more torque for pullback.
Slip gear
A driving gear has some teeth stripped off of one side to power an axil, and then release it.
Main advantage: Capable of having high firing rates.
Main disadvantage: Higher chance to fail.
Tensioner
Elastics are pulled back and then the arm is released.
Main advantage: Strong pullback.
Main disadvantage: Slow recharge.
Chain Grabber
A catch is attached to a chain that pulls back on a point and releases once it get back to a certain point.
(I don’t know of any teams that have done this, so I can’t say anything more about it without it being completely speculative.)

I don’t think that any of these are more or less accurate then each other, that’s completely a result of the ball holder.
This is kind of a follow-up to this thread.

I personally like the slip gear because I think it’s simple and motor efficient because one can easily make full court shots with a decent fire rate with just two motors. (However that is my opinion)

Linear punchers seem to work very well.

Slip gear appears the most viable option. Small size, low power requirement, low complexity, high firing rate.

My question was, what is the best pullback mechanism for a catapult or linear puncher. My question about the best non wheel based launcher was in this thread.

I have tried to make a chain grabber, based off a similar video, but it is near impossible to get to work. The chain either snaps or bends to the point of releasing early because there is no way to brace chain easily.

My teams has been able to make a catapult with a nautilus gear pullback mechanism shoot full court. It has been very accurate and much faster than our old nautilus linear puncher mechanism that we tried and could not shoot that well even with a 5:1 ratio (for torque). The catapult seems like a good shooter with a balance between fire speed and accuracy of shot. The one place that a catapult seems to not work as well as a flywheel would be in changing the power of the shot. A catapult only has one power setting and is not able to control the power.

I still think the slip gear is one of the best options. You can use a 36 tooth gear or a 60 tooth gear with multiple slips in them so you may increase the rate you are firing at. I also use a 1:1 gear ratio with two motors on a shared axle and can get about two balls per second.

We have used the chain grabber, but only for a puncher.

Could you display a picture?

No, sorry we’d like to keep our current designs confidential. But, in a gist, the chain pulls the puncher back, with the help of motors, and eventually releases due to rubber bands.

Does this mean that the release mechanism requires the chain to slip under a consistent load, or do you basically take a tooth (or multiple) off the sprocket, like a slip gear? Also, is the puncher screwed in to a link in your chain, or how do you pull it back? That’s a really interesting design, how well does it work for you guys at the moment?

The chain is not directly attached to the puncher, but when it turns, a link pulls back the puncher through pulling on the standoff connecting to a luncher. I don’t know how else to explain it, by my this is the best I can do without revealing anything else

We have sort of given up the design for now, as there are many problems involving the consistency. I’m sure if someone tuned to up, it could in theory work really well. But, our teams have not had a chance to do that. Fortunately, we may come back to this design. Another disadvantage this mechanism has is the number of motors it uses. But, this mechanism can shoot 4 balls in a little over one second

So you mean to tell us that it can shoot full court shots at a rate of ~3.5 balls per second? If someone could get that to be accurate, then that could get the 24 DCLs scored in 7 second (If you could load it fast enough) for 120 points max.
I should put high firing rate as the main advantage in the original post.

Stanley Shi uses slip gear. slip gear is the best. no need for discussion.

If I remember correctly, it was extremely fast, but also very inaccurate if fired that quickly.

It was around 0.38-0.4 seconds per ball. Don’t hold me on that, as we haven’t used that design in almost two months, but I believe that it was around that speed.


This is the launcher I was addressing used by 8000b on red. The driver purposely had to significantly slow down the fire rate, to improve accuracy. Even then, it was shooting at 2 balls per second. Another drawback with this punche, is the issue of a cool down period. Before shooting the last 5 balls, the launcher must cool down for a few seconds

Are you thinking of adding more motors or increasing the gear ratio to suffice for this?