kicker

[rytcd]

hey, would a pneumatic pendulum style kicker be more powerful than a straight horizontal pneumatic punch? also, might it be better to use a kicker with a smaller surface area?

[lbarger]

Originally Posted by rytcd

hey, would a pneumatic pendulum style kicker be more powerful than a straight horizontal pneumatic punch? also, might it be better to use a kicker with a smaller surface area?

That is a tough question to answer as there are many variables. Desired ball velocity, cylinder size, total air flow (Cv of valve or valves), mass of the kicker, etc. all interplay with each other.

With unlimited air flow, a horizontal punch would deliver the higher force. However, you may not need to deliver 100 pounds of force to the ball to get it to move the way you want. Speed may be more critical than force. If so, then the pendulum will give you more speed at the cost of some force.

Here are a few formulas:
1) (1/2)*acceleration*time^2 = Distance (assuming uniform acceleration and initial velocity of zero)
2) acceleration*time = velocity

Rewriting the second equation you get acceleration = velocity/time
Substituting that into the first equation and simplifying you get...
(1/2)*velocity*time = Distance
Rearranging you get to
3) Time = 2*Distance/Velocity

What speed do you want the ball to travel? (I'll assume 15 ft/s)
How much distance do you have to accelerate it? (Assume 3" inside frame + 3" under bumpers = 6" or 0.5 ft.

Plugging these numbers into equation 3 you find that time of acceleration should be close to 0.05 seconds. Putting this back into equation 2 and solving for acceleration you get acceleration = 15(ft/s)/0.05s or 300ft/s^2.

Divide the acceleration by 32.2 ft/s^2 (force of gravity) and you find the acceleration is 9.3G. Now the weight of a soccer ball is about 0.95 pounds. But to accelerate at 9.3G you have to multiply (0.95*9.3) and you find the force to accelerate the ball to 15 ft/s in 0.5 ft is averaged out to be just 8.9 pounds of force.

Of course I pulled the velocity off the top of my head and you may want to use less total distance. Actually, it would be safe to assume the ball does not stay in contact for the full stroke.

So use the equations, not the numbers and good luck!

[thatoneguy23]

We tried both, and our pneumatics were either not strong enough to get the ball rolling, or not fast enough to extend. so, i would not go with straight pneumatics.

[JamesCH95]

Originally Posted by thatoneguy23

We tried both, and our pneumatics were either not strong enough to get the ball rolling, or not fast enough to extend. so, i would not go with straight pneumatics.

Make sure you're not using flow-control that are mostly shut... smaller diameter pistons will also fill and deploy much more quickly.

[BradMello]

Originally Posted by rytcd

might it be better to use a kicker with a smaller surface area?

By using a smaller surface area you will be losing an unnecessary amount of energy to ball deformation

[terryo]

Originally Posted by rytcd

hey, would a pneumatic pendulum style kicker be more powerful than a straight horizontal pneumatic punch? also, might it be better to use a kicker with a smaller surface area?

HI- we are using the pneumatic pendulum-with-surgical tubing spring assist, and it's working very well. The cylinder extends the spring, and then releasing the air lets the spring pull the pendulum forward to kick the ball.

It took a bunch of testing to get the spring force vs. exhaust flow correct on the cylinder- we had to use (3) valves in parallel coupled to a manifold on the cylinder in order to evacuate the cylinder quickly to take get good speed from the surgical tubing to kick over the bump. The other end of the cylinder has no fitting and vents to atmosphere.

The interesting side effect is that we are able to fire the valves 1 or 2 or 3 at a time in order to control the kick distance (scoring, passing, or over the bump). Now it's up to the drivers to remember which button to push!

Good luck!

[dtengineering]

We tried both pneumatic/elastic pendulum style kickers and a pneumatic/elastic linear "puncher".

The pendulum worked better for us, as we could get a bit more "loft" on the ball by contacting the ball with the pendulum beginning its upswing.

The horizontal "puncher" despite having an angled front edge to try and give the same effect, just didn't give us the "loft" we were looking for.

The pendulum design also made it easier to increase leverage, allowing the kicker to move faster despite the speed limits imposed by moving air out of the pneumatic cylinders.

So, based on our testing, we have concluded that the pendulum is a better way to kick. Your mileage, of course, may vary.

Jason

[Safety3rd]

Originally Posted by terryo

HI- we are using the pneumatic pendulum-with-surgical tubing spring assist, and it's working very well. The cylinder extends the spring, and then releasing the air lets the spring pull the pendulum forward to kick the ball.

It took a bunch of testing to get the spring force vs. exhaust flow correct on the cylinder- we had to use (3) valves in parallel coupled to a manifold on the cylinder in order to evacuate the cylinder quickly to take get good speed from the surgical tubing to kick over the bump. The other end of the cylinder has no fitting and vents to atmosphere.

The interesting side effect is that we are able to fire the valves 1 or 2 or 3 at a time in order to control the kick distance (scoring, passing, or over the bump). Now it's up to the drivers to remember which button to push!

Good luck!

i love that idea cus we're using the horizontal and the ball is moving to sluggish to do anything with it. can u post a picture of you pendulum?

[Vermeulen]

We tried a straight pneumatic kicker earlier in the season, and it was too slow, and had too little power to get the ball over a bump. Pneumatics aren't the best at speed, since there is only so much air that can go through the valves. What pneumatics are good at, however, is pulling or pushing power. We're using a pendulum with elastic bands to power the kick, and pneumatics to reset it, and it seems to work fine. However, we now have 10 days until ship date, so this isn't the time to redesign your whole kicking strategy if you already have a functional kicker.

[terryo]

Originally Posted by Safety3rd

i love that idea cus we're using the horizontal and the ball is moving to sluggish to do anything with it. can u post a picture of you pendulum?

I don't have a completed pic since we're migrating mechanisms from the test rigs to the real bot, but here's an partially installed unit. I'll repost when it's finished.
kickerpic1784.doc

[JamesCH95]

We have changed our design so that we can draw back the kicker with two big pistons, then latch the kicker (it's spring loaded) and then deploy the pistons so they're out of the way, release the latch, and BOOM! Big kick, lots of speed, and (I hope) bullet proof reliability.

PM me and I'll see if I can take some pictures...