Hello! This my team’s first video of the Nothing But Net season! This is our first test model for a flywheel wheel.
Looks like a great start. Just curious: how did changing the gear ratio help reduce the backspin? Was one side spinning faster than the other?
The bottom was at a 21:1 speed ratio and the top was at a 7:3. We changed the top to a 35:3 ratio to provide better energy transfer.
Just a thought… Couldn’t you also vary the speed of the top wheel by changing the power in the programming?
Bill
I’m curious why you are running the top and bottom at different speeds. Are you adding spin to the ball intentionally?
I think he is doing it intentionally. It seems to actually make a big difference in the video. I’m curious to test this myself.
We did have the wheels geared differently on purpose. You could have just changed the motor speed to create spin but I think gearing provides a much more reliable spin. And as shown in the video the backspin yields much better distance and angle.
Would you mind explaining your reasoning and/or the physics of why this is so? I can think of the Magnus Effect, maybe, or perhaps you want the ball to stop faster once it hits the target??? My first impression is that putting spin on the ball “consumes” some energy that might otherwise go into the actual ballistic trajectory, but since my kids haven’t built a launcher yet, I’m just an armchair engineer wondering what’s up. :o
The backspin theoretically provides an upward force on the ball that should cause it to go further and achieve greater height that would give a better angle for scoring in the high goal. This is shown in our video when we switch from topspin to backspin. Our initial gear ratios for backspin were consuming too much energy in creating the spin so in the last iteration in the video we increased the speed of the top wheel which transfered more energy to the launch and less to the backspin. This seemed to provide the best balance and as shown in the video by far gave the best height and distance.
In 2006 FRC had a game called “Aim High” that involved shooting nerf balls. Although at a slightly different scale, your flywheel shooter is not so different from some of the better nerf ball shooters that FRC teams (like 1114) used.
They had the wheels mounted left and right, rather than top/bottom, and had independent drive for each wheel, with encoders providing speed feedback.
By dialling in specific velocities for each wheel they could not only control their range, but also put side spin on the ball to aim “a little to the left” or “a little to the right”.
The encoders also allowed them to maintain a consistent wheel velocity so that repeated shots would not affect their aim.
Nice tech demo, though… expect to see the idea copied several times. The trick won’t be who can build a shooter, but who can build the best one… and figure out how to use it to maximum efficacy. I’m looking forward to this game!
Jason
Did you test how fast you can load new balls into the launcher? because pace is an important factor in overall analysis of the robot.
How far have you gotten the balls to launch with backspin and top spin? And this flywheel is being powered by two motors, correct?
My team is currently developing a system to pick up the game objects; however, our main focus right now is to perfect our launcher with different gear ratios and speeds
We havent specifically timed it but I think its about 2-3 seconds between each ball to give the flywheel time to spin back up to full speed. And with our current backspin ratio we get around 16ft. But we will keep prototyping and im hoping we will eventually get above 17 ft. And yes this uses only two motors
Does it seem to you like those two motors will be able to handle running full speed for 2 minutes a match times dozens of matches? Are the bearings holding up ok?
The motors are handling well because we do not plan on running them the entire match because that would drain our battery supply. The bearings are holding up because our system has enough support so there isn’t a lot of awkward angles the axles are being held in.
Seconding what my teammate said, the motors/launcher do seem to be doing just fine despite lots of testing. We’ve had no problems with them and they seem to be able to run off of one battery for well over two minutes.