Ball "Puncher" Assistance

I’m sure this question has been asked/answered several times already so if so I apologize in advance.

Our team plans to implement a ball launcher on our robot for this year’s game. We have the puncher working with two motors and a 36T High Strength Gear that has been turned into a slip gear. We are having issues with not being able to launch the ball with enough velocity to push the flags.

I was wondering if anyone had any suggestions on how to help our puncher work?

puncher 1.jpg
puncher 3.jpg
puncher 2.jpg

It looks like you are using the small rubber bands. We have a similar setup with two torque motors and are using 2 large rubber bands on each side. We can shoot roughly 14-15 feet and the torque motors seem to have no trouble pulling it back. I think you just need more bands.

With further testing once the system is fully diveable, we plan to use small ones, but probably 4-5 bands, so if one breaks it won’t be such a drop in capacity.

I would recommend adding more rubber bands

You could also take a look over at our Youtube channel, where we have a puncher tutorial. It consistently turns flags

That’s the issue; we can add several rubber bands but then the elastic force becomes too much for the two vex motors. We just cannot seem to find the “sweet spot” for the launcher

What sort of motors are you using?

Posting a video of your puncher firing would help diagnose the issue. It is a little hard to tell from the picture, but the issue appears to be your puncher angle. I recommend launching the ball at an angle between 30 and 45 degrees to get the most power behind your shots. Also, I recommend putting white lithium grease on your linear slide rail to reduce friction.

It looks like you are powering your puncher with a 1:1 ratio. I would suggest a 1:3 ratio with a 12t powering a 36t, which is on the same axle as the slip gear.

I tend to agree, It requires extremely good build quality and custom linear slides to make a 1:1 work efficiently.

I’m working with a puncher where two 393 motors turn 12t gears that turn a 60t gear on the same axle as the 36t slip gear we are using. I have as many rubber bands as the motors can handle. This setup is rather slow (1 shot every few seconds) and at the lower limit of a viable fire rate, but at the same time, it is just barely powerful enough to turn the flags consistently.

If I had to suggest one thing to improve your puncher, I would adivse you to switch to V5 as early as possible and use a high-torque gear ratio. The flags are particularly troublesome to turn, so you’ll need a lot of power to hit them reliably with a puncher.

2 cortex motors have more than double the amount of torque necessary to make a puncher. A gear ratio is not necessary whatsoever. A single motor puncher has enough power to toggle a high flag from far starting tile. 2 motors even at 1:1 on a 36 tooth gear is overkill. @HM_Engineering send a video of your puncher firing if possible.

We are re-installing the puncher and once it is setup Ill send you the vid.

For some reason this has been more troublesome than it has for past years using a puncher.

We are STILL waiting on our V5 equipment to arrive… :confused:

So we are using the older stuff to compete until it arrives (if it ever does)


I noticed your puncher doesn’t have anything attached at the end to hit the ball. This got me thinking. Is it better to have something blunt to hit it at the end or just using the linear slide itself?

@Gary Patel the end of the linear slide has worked fine for us

You might also want to take a look at where you’re supporting the actual linear slide. To me it looks like you’re supporting it quite far back, which could easily mean that the linear slide loses the parallel properties to the truck, which causes additional friction, or pinching. It might be easier to put the truck farther up, or “balanced”, because there is a good point where the rubber bands don’t cause too much extra force on the linear slide. The angle of your puncher also seems quite high, remember, the bigger the angle, the less of the power gets turned into x-direction power, which means less power is transferred to the flag. Air resistance is not negligible. Try aiming it “flatter” (45 degrees should be fine enough of a starting point), and reduce friction.-

Putting a little bit of foam at the end of the puncher won’t hurt either (a little bit of acceleration and follow through is always appreciated, and will not transfer energy significantly worse than a straight up hard impact - in fact it might transfer energy better (less of it goes to waste)).

We have rebuilt the launcher with a 1:3 ratio and have removed one of the motors. We applied the lithium grease and make the linear slide just a bit longer (15 holes). We have much more power launching the ball but still cannot launch a ball the complete distance across the 12x12 arena.

pictures are coming soon.