Puncher Help


My team and I have a built a puncher. It uses 6 rubber bands and is powered by 1 motor. Pictures are attached below.

The problem is that it does not shoot very far. How can we make the puncher shoot further?

My first observation I would like to make is the distance between the motor and the 12t gear. Such a large distance can and will cause torsion if you were to increase the amount of rubber bands. Another thing is power. Generally speaking a shooter should have at least 2 motors otherwise you are damaging speed or distance. Currently you are losing distance because you don’t have the necessary torque to push the mechanism back with more rubber bands. I would recommend either having more motors or have a larger gear ratio. Another thing I would like to point out is the fact that when you add more rubber bands the rack gears and gear may strip due to the sheer power to accomplish punching the ball a distance. I would recommend making the axle be as short as possible from bearing a and bearing b to prevent bending out. Those type of rack gears are discontinued, and the newer rack gears are wider and are higher strength. This can help a ton as well. I would recommend to screw the two 36t gears together to prevent torsion too. Also because the balls are plastic you may need to have some sort of foam or anti-slip mat where the mechanism impacts the ball.

So here’s a list to do:

  • Either adding a a second motor or increasing the gear ratio
  • Make sure that the 12 tooth gear is as close as possible to the motor to prevent torsion
  • Make sure that you screw the slip gear 36t gear and driven 36t gear together to prevent torsion
  • Add more rubber bands
  • Make your gearbox be as narrow as possible
  • Replace the rack gears with the higher strength rack gears if necessary
  • May add anti-slip or a foam where the mechanism impacts the ball

Another question: Where is your stopping mechanism? Are you making sure it has a type of foam on it as well to decelerate the puncher safely and not as dramatically?

By stopping mechanism, do you mean the part that prevents the hammer from losing contact with the slip gear? If so, the stopping mechanism is a nut on the linear slide. It does not have foam yet.

@[TVA]Connor I have two questions.

  1. Isodynamic used a 1 motor 3:1 puncher which managed to shoot the balls far. Is it necessary to add another motor or change the gear ratio?

  2. Where would I find the high strength rack gears? I found it on robot mesh but I can’t purchase items from there.

Stopping mechanism is what brings the puncher to a stop after it shoots forward

In the first photo, my stopping mechanism is the two horizontal standoffs slamming into the metal loop and the vertical standoff slamming into the slip gear. Obviously this is a terrible design and warped that c channel practically into a triangle.

In the second photo, the stopping mechanism are the rubber bands pulling the puncher backwards. unfortunately you lose a lot of power this way.

basically your stopper should be on something solid and it should be padded either by anti slip mat or by rubber bands if you don’t have that.

To answer the main question, I’m pretty sure having the puncher slam into the ball is more effective that having it push it so make sure that at the fully cocked position, the ball isn’t touching the puncher head. With the second motor that Connor mentioned, you can add more rubber bands to create a stronger punch. While I can’t say for sure if this has any impact on power, a flat head is probably better as it can only hit the ball in one way and allows for more consistency.

For more help there’s this thread I started a while back where people discuss the physics behind the whole thing https://vexforum.com/t/vex-forums-referrals/18680/1

Honestly it looks like your mechanism is built well and should have enough rubber bands. If your shafts are twisting you could try moving the motor to the other side of the mechanism, but the set up is very similar to how I would do it.

An elastic collision is defined as a collision where no energy is lost. This type of collision really only exists in a physics textbook, but you can make your collision much more elastic by adding some sort of padding to the face of the puncher.

That video does a pretty good job of showing how effective 8044’s elastic friction matt paddle was. Below is a very rough prototype I slapped on my ITZ chassis in June (sorry about the build quality!) but it shows how I adapted the concept to this game. My version used rubber bands for a paddle instead of friction matt. I also used an orange IQ ball since my game elements hadn’t shipped at the time, but I drilled a whole in the ball and filled it with enough clay to weigh the same as a yellow one. The launcher was geared 3:5 with 1 motor

Check it out here

In that video, it was stopped by the blinds in my room (sorry about that by the way :stuck_out_tongue: I filmed the video mostly for my own documentation) but in an open area, it launched the ball just over 11 feet.

At the end of the day, you can use the green rubber from 4" tires, you can cut rubber links in half, you can build a rubber band paddle face, you can use friction matt, and there are probably 50 other ways you could improve your power transfer. I don’t want to give you screw for screw instructions based on how I would do it, but the general concept is pretty simple and makes a huge difference.

To summarize, your mechanism looks great, but your power transfer is probably the source of the issue. If you can fix this, you will see a dramatic improvement.

Good luck!