Linear Punch Ball Launcher NOT Working

So my team, 687G, decided that we use a linear punch for shooting balls for Turning Point. It was working perfectly fine until we actually competed. We did everything we could to fix it… from shaving off more teeth on the slip gear to changing the motors… Anyone have any ideas as to how else it could possibly stop working?

I don’t really have a good video of the bot but you can see it at 1:18 and at 2:04 in this video

New to the Forums.
Thanks. Hehe.

AND here’s a picture of the robot. (Don’t judge plz we’re new and scared. Fun fact: We’re a new team. This is our first time competing in VEX!)

Welcome to the forums!

I couldn’t really tell from the video - was the problem with the puncher not responding to controls or was it stalling? If it’s the former, it might be a programming or electronics error (such as a while loop that prevents the puncher from being controlled simultaneously with the rest of the robot, or fried cortex ports, spoilt motor controllers, broken/exposed/loose wires).

Sorry for how all over the place the video was, but to answer your question, the puncher was stalling. When it did punch, it’d be too weak to shoot the ball high enough to hit a flag.

Try to provide a time in minutes:seconds into the video so people can jump to see examples of what you’re talking about. It’s really hard for anyone to watch this whole video and try to guess which robot is yours, etc.

Maybe make a more in depth video of your mechanism so people can better diagnose it. Just show close ups and stuff, show what happens when you activate it, etc.

Make sure you’re using a fresh battery also. Motor power decreases as the battery goes down. That’s all I can think of without knowing more.

How many motors are you using, how are they connected to you slipgear and what size gear are you using on your slipgear?
If your launcher is stalling you probably need to give yourself more torque. We have 2 torque 393motors directly connected and it works really well. If your using one 393 motor you can do a 1:3 gearbox to triple that motors torque.

If it fired, but it was too weak, I’d say your problem is that your rubber bands snapped. Or your braces for holding the rubber bands slipped.

Also, your ball holding mechanism might have bent, adding friction.

Ah, of course. Thanks for pointing that out. I added a time.

I will be making a video tomorrow and I’ll post it here. We’ve also changed the battery and it didn’t make a difference. Thank you for the help!

We are using two motors and a 36-tooth gear connected by a shaft.

I will let my team know about this. Thank you so much for the help. We’re inexperienced in these things since this is our first year competing.

Here’s a photo of our robot.

We changed the rubber bands multiple times and unfortunately, it didn’t solve the problem, but thank you for the help.

If you remove the rubber bands and manually rotate the slip gear so the slider-puncher can slip back and forth, does the slider-puncher still move back and forth with very little friction? I’m wondering if perhaps your linear bearings might have become somehow jammed or dirty or perhaps the impact of hitting the balls might have slightly bent the slider rail and that is putting lots of friction on the system. Just something to check if you haven’t already.

If it’s not bent but there’s still alot of friction, you might want to consider greasing the linear slides or adjusting the rubber band mounting position

Make sure that the slide mount is only attached with two screws with only one being tight.

That’s a good point. Sometimes by leaving the mount slightly loose, it prevents jamming and allows the slider to find its path of least resistance. But not too loose - obviously you don’t want it to fly apart.

I made the mistake of putting in four screws all tightened fully and the amount of friction was ridiculous. I didn’t have rubber bands on at the time but I’m sure if I did it wouldn’t have worked very well at all.

Welcome to VEX! No judgement. We all were new once.

We have a very similar setup. I would suggest taking the motors off and try running it just sitting on the bench. If it doesn’t work, you’ll need to check out for motor issues or wiring issues. Could your motor cable got caught in the punch mechanism and its broke?

If it does work, put a shaft in one of the motors, start the motor, and pinch the shaft with your fingers to see if the motor stalls under any load load. Try the other motor too. If it does, it could be motor or battery issue.

If all works fine when disassembled, check that the slide and puncher work freely. Make sure where there is a seam between slide trucks, you sand/grind the seams so there is no steps. Loosen the screws on the trucks and slide the puncher through them to make sure nothing is blocking the movement. Tighten the trucks back down with the slide in place to make sure things stay aligned. Lube up the slide mechanisms and make sure the slide moves freely - like it falls out on its own freely when its held upright.

If all that is complete and works fine, reassemble and try it again.

Here is a good video from our friends at team 574 on a puncher. Maybe there is something in the video that will help…

Good luck!