How do rubber bands help the flywheel? Do they slow it down?
Where did you see someone putting rubber bands on flywheels? I think it’s more likely that you saw them use rubber bands on a ratchet mechanism to conserve energy and prevent the motors from overheating. Rubber bands on a ratchet mechanism serve the purpose of pulling the “clicker” to one side so that it does not disengage when the driver is trying to shoot balls. Ultimately, the rubber bands are not “going on the flywheel.”
The other thing you might have been asking is why do teams put rubber bands on the actual wheel? I have yet to see a team do this, but I assume they would put on the rubber bands in question on the wheel to increase friction between the wheel and the ball, thus increasing the flywheel efficiency. However, there is little to no slippage that I am aware of during a launch from a flywheel. Additionally, if a rubber band breaks or falls off (which is quite possible when spinning at the incredibly high and constantly fluctuating angular velocity that flywheels require), or if it is put on incorrectly at the start of the match, the flywheel might have a larger or narrower gap between the other wheel or the hood, and might shoot the wrong distance. Again, I have not yet seen a team do this, but some probably will.
Yes, ultimately, rubber bands on a flywheel shaft serve no purpose and decrease efficiency by adding friction. The motors work hard enough to spin a giant wheel with almost no torque; extra friction can only be bad. But I’m not sure that’s what you were asking, so I’m sorry if I misunderstood.
Separately, could you please delete the other thread you made that says the same thing?
Hope this helps.
They could technically help if you wanted to improve the traction of it. If it doesn’t grip the ball that well, then you would want to do this. But otherwise, you would want to improve the speed by making better speed gear ratios. My team’s flywheel was spinning so fast that rubber on the flywheel has come off before, so I guess you can use the rubber bands as support to make it stay on.
I have seen a lot of teams doing this in our local competitions. Apparently its to attempt to increase friction between the wheels and the ball, some of the robots I have seen have seen pretty massive improvements using rubber bands on their flywheels. In some cases its just to compensate for the wheels being too far apart. I have also yet to see it used on anything other than 4inch wheels
Their was also another reason that had something to do with the rubber on the wheels, but I think teams experiencing problems similar to this have generally used cable ties to hold the wheel in place, instead of rubber bands.
TLDR: Rubber Bands are the answer to life
+1 to this.
Yes, rubber bands help with the traction and kinetic energy transfer. It seems to help when using a sprocket/tank tread style delivery flywheel. The downside (there is always a downside isn’t there) is that the sprocket based flywheel style is generally is too light and you end up adding other wheels as mass that don’t necessarily touch the ball.
When will the lead sprockets/gears/wheels be introduced to make really heavy mass flywheels?
My team wrapped rubber bands around our wheels for our first competition. They made a difference of almost two feet. They really help with getting touch on the ball and transferring energy to it
Some teams are talking about adding mass to the flywheel to increase efficiency. I have some experience with bicycles and the first thing a bicyclist will do to increase efficiency and acceleration is reduce the weight in the wheels. It has a far greater effect than reducing weight on the frame.
The reason to increase mass on a flywheel is not because it reduces the energy needed to sustain an RPM like on a bike. Increasing mass is so that when energy is transferred to the ball that the wheel speed is impacted lass. A 0 mass flywheel would come to an immediate stop the moment a ball made contact. An infinite mass flywheel would not change speed at all when load is applied.
This quote came to mind
“What do you think you know, and how do you think you know it?”
But it takes a lot of effort to get the increased mass rolling. I guess I’m just trying figure out how this seemingly contradictory information works. I understand that the increased mass in the wheel will not slow down as much once it is rolling, but if the flywheel is started and stopped all the time it would draw a lot of current.
Woo hoo! More trade offs!
Nothing is free. You can either get a more steady state by adding mass but you have to use more power (and time) to get it up to speed initially. If it takes an extra second or two to get up to speed but takes two tenths of a second less between shots, over the 1:45 drive time it may make sense to add mass.
Mass is also in the kinetic energy equation so you should be able to go to a lesser RPM to transfer the same energy.
There has to be a sweet spot some place between the two.
my team uses rubber bands on the wheels for exactly, when we fire a ball, we disengage our wheels from a ratcheting mechanism, so the motors are no longer connected to the wheels, and do not input any energy, so all that is firing the ball is the momentum of the wheels, and more mass = more momentum
I have actually seen some teams add an extra wheel to try and increase the mass of the flywheel. They have reduced the time in between shots quite significantly, but at the expense of a the time and power required to power up their flywheel.
Is the tradeoff worth it, probably… But personally I am waiting for Osmium Wheels and car motors to hit the main stage!