Better Defense: Jump Bot

There’s a lot of talk recently about what makes a good defense bot. I have an idea that I’m pretty sure still fits in the rules that could potentially dominate, while simultaneously making the spectators go wild. What if the robot jumped to block the net? How awesome would it be to see a robot repeatedly bounce up and down blocking shot after shot? Anyone want to try building this?

I think that that would be incredible, but it would be so difficult to have a robot jump up high enough and at the right times, not to mention robots with higher firing trajectories. All while keeping within 18"^3. I think no matter how good it is, it wouldn’t be worth it, unless maybe it can drop balls in the goal while it’s up there. I might win you a judges award though.

Obviously everyone’s first thought.

Even seeing that I can’t imagine its very practical.

Thats amazing

I really want to build a jumping robot now

I’m guessing that the leap up might be possible with Vex parts, but I wonder how the landing might work, especially if you intend it to be a controlled landing. Most likely you’ll want it to go straight up and come straight down. Maybe start out with some very rough energy calculations.
Ignoring inefficiencies, (Potential energy) = (Work done on the robot to lift it) = (Weight x distance lifted).

How high would the robot need to jump, especially to block an arced trajectory? Maybe your best blocking capability would not be near the net but would instead be close to the front of the shooter?

An 8 pound robot leaping 4 feet into the air would require 32 foot-pounds of energy. That’s about 44 joules. A single 393 motor provides about 4 watts, or 4 joules/second. If your shock absorbing system can store some of the energy for re-use, then that might help on the next leap upwards.

You might also figure out a way to “cheat” the potential energy requirements by employing a system somewhat similar to the concept of how olympic high jumpers clear their bar. Their center of gravity never actually travels over the bar but instead they curl their mass around the bar. Maybe you can build a machine that actually leaps up only a little bit but then it swings its lower part upwards and into the ball’s path without needing to lift the entire robot mass that high. Then it continues to swing down until it lands on its feet again. If the robot’s center of mass is high up on the robot, and the lower part is not very massive, then you might be able to “cheat” a little. Of course, you would need to consider how much energy is getting pumped into all that wild swinging motion - it might not be worth it. But it might be fun to think about.

It’s a good idea, but any human driver just wouldn’t fire while the bot is in the air and fire when the jump bot is on the ground, the jump bot would need to be able to jump the second it hits the ground or somehow spend a long time in the air blocking the net.

That may be true, but even so it would significantly slow down an opponent if they are having to wait in between each shot. It’s a fun thought exercise nonetheless.

Even better, what if it could somehow deflect the balls into the other net? XD

When you are a defensive robot, you have to stop 51% of their points because your team will only make 50% of the points that your team would with 2 offensive robots so you would need to jump that fast or that long to achieve the 51% but if you put a tennis racket or something that might even the odds… If you can time and angle the swing…

Jumping to block the goal is possible but I believe that jumping in front of the shooting robot instead would yield better results. Realistically most robots won’t shoot straight up in the air so the block point would be lower by blocking the shot on release rather than before it goes in the goal. Blocking at the lowest point is good for obvious reasons for the robot so if this idea is ever fleshed out to an actual prototype I think blocking the shot would benefit more than blocking the goal.