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  #16   Spotlight this post!  
Unread 17-01-2010, 22:51
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Re: Kicking System Design Considerations

Well, what if you have one in your possesion and you're about to kick it. And out of nowhere a ball gets close enough to be affected by one of your kickers and you end up kicking two at once. Is that a penalty?
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Unread 17-01-2010, 22:55
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Re: Kicking System Design Considerations

Quote:
Originally Posted by Enigma's puzzle View Post
If you need to increase the force coming from your piston, and/or speed it up you could always consider adding a spring or tying some surgical tubing in a way that it will assist the firing mechanism(up to doubling the power of a single piston stroke), however if you lose too much pressure, you may not be able to retract the pneumatics quick enough to abide by the rules.

I though id throw this power and thought generating idea out for you to kick around.
Agreed, 397 did this PART of the year in 2008 to throw the Trackball and it worked pretty good. We eventually switched to using just 4 1/5" diameter 12" stroke cylinders to lob the ball the length of the field (Kettering Kickoff and WMRI) If you are curious about the arrangement of these I can find it and send you a picture. We were able to shoot it over the overpass from ~12 feet at 30psi. (In competition we ran at 60psi)

You may also want to consider the kinetic energy of a moving object is 1/2 * m * v^2. In a perfect world (which this is not) in a collision the energy from the kicker would be transferred to the object being kicked. Therefore you will get a lot more omph if you increase your speed. Consider using a lever to increase your speed.
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Unread 17-01-2010, 23:01
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Re: Kicking System Design Considerations

Quote:
Originally Posted by squirrel View Post
842 is using a 2" bore by 12" stroke piston....

http://www.youtube.com/watch?v=QLH-XqNyQ-0

takes a lot of power to move that ball fast, so you need a pretty big cylinder
Its really an 8 " stroke, it was a type on the video
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Unread 17-01-2010, 23:03
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Re: Kicking System Design Considerations

Quote:
Originally Posted by JB987 View Post
Only one that is in your possession...
To my knowledge there is no rule against kicking multiple balls, only possessing more than one.
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Unread 17-01-2010, 23:13
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Re: Kicking System Design Considerations

Thank you for the information on the pistons and on the kicking rules.
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Unread 23-01-2010, 10:25
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Re: Kicking System Design Considerations

BTW, does anyone know if the ball is allowed to come off of the ground for a split-seconde before a kick so that we can get the ball over the bump? You see, with our design, we managed to get the ball over the bump, but it needs to be a little bit off of the ground to make it. So, can anyone help with this problem?
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Unread 23-01-2010, 10:28
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Re: Kicking System Design Considerations

Without seeing more of your design, it's hard to say....but there is a rule that says you can't CARRY the ball.

Quote:
CARRYING: POSSESSING a BALL that is not in contact with the FIELD.
Quote:
POSSESSION: Controlling the position and movement of a BALL. A BALL shall be considered in POSSESSION if, as the ROBOT moves or changes orientation (e.g. backs up or spins in place), the BALL remains in approximately the same position relative to the ROBOT.
Quote:
<G44> BALL CARRYING – ROBOTS may not CARRY BALLS. Violation: 2 PENALTIES for each CARRIED BALL.
Sounds like fun!
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Unread 23-01-2010, 11:57
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Re: Kicking System Design Considerations

Quote:
Originally Posted by PortugazD.Ace View Post
BTW, does anyone know if the ball is allowed to come off of the ground for a split-seconde before a kick so that we can get the ball over the bump? You see, with our design, we managed to get the ball over the bump, but it needs to be a little bit off of the ground to make it. So, can anyone help with this problem?
Try hitting the ball in an upward motion from low. Look at 842's kicker video for an example of this. A version I saw was hitting them ~40 feet accurately. The only problem is fine tuning it to get the right amount of loft and not just blasting away at it.
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Unread 23-01-2010, 12:15
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Re: Kicking System Design Considerations

Quote:
Originally Posted by PortugazD.Ace View Post
Well, what if you have one in your possesion and you're about to kick it. And out of nowhere a ball gets close enough to be affected by one of your kickers and you end up kicking two at once. Is that a penalty?
Just to clear this up, it was deemed legal to kick multiple balls at once on the FIRST Q&A: http://forums.usfirst.org/showthread.php?t=13900
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Unread 24-01-2010, 16:52
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Re: Kicking System Design Considerations

It is better, when possible, to use cylinders-pistons in TENSION than in COMPRESSION, but if this requires cables, then it becomes nore complicated
Tension loading tends to keep the forces aligned along axis of rod, which is where cylinder has most strength. Compression force tends to initiate torque and bending forces at an angle to the piston as objects try to "roll" around and past each other.

Since a hinged kicker rotates and moves away from cylinder, angle of force on kicker changes. Max acceleration happens, with a hinged kicker, with cylinder's force applied at 90 degrees to a line out from kicker pivot point to where cylinder is attached during the arc of the kick. As kicker moves away, this change the 90 degrees force angle, and applied force drops off. So, the cylinder should be oriented such that the force applied stays close to 90 degrees during critical acceleratiom range of the kick arc. This is easier to achieve when the piston's attach point stays closer to the pivot point -- but. this also reduces the leverage of the cylinder for accelerating kicker, so a larger bore is needed to gain more force.

There is also the issue of rate of pressure build up inside cylinder. Since the energy delivered to the kicker (then to ball) is the force times the distance over which it gets applied, reaching maximum force early in the stroke is important, since there are only so many inches of travel in which to apply it.
Having piston connect nearer to pivot point (low leverage) means force builds up faster in the cylinder. So having a stronger cylinder that pushes a shorter stroke on a spot nearer the pivot point can deliver more energy early in the stroke than a weaker cylinder attached further away from pivot having better leverage, but also building up force more slowly.
Finding the sweet spot between these two extremes is the key to a good kicker design.

-RRLedford


stance traveled during by point that piston connects to kicker is short.

Last edited by RRLedford : 24-01-2010 at 16:54. Reason: spell
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Unread 24-01-2010, 19:30
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Re: Kicking System Design Considerations

my team is working on our kicker design, we are using a 5" stroke-9/16" bore(I think) piston, mounted to the bottom of our hinged plate(which is hinged at the top, so we get the most leverage) we get about 20" hight and about 5ft of distance in the air. this is enough to kick the ball over the bump from about 4ft away, but we need it to go further and higher, we could use a bigger piston but we dont really have the space. how could we make it kick farther?(I've thought about surgical tubing and springs already, but i was wondering if there was any other way?)
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  #27   Spotlight this post!  
Unread 24-01-2010, 20:41
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Re: Kicking System Design Considerations

I didn't say carry. I was wondering if, when the robot is stationary, the ball can be lifted so that it can get more air when kicked.
  #28   Spotlight this post!  
Unread 24-01-2010, 22:00
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Re: Kicking System Design Considerations

Quote:
Originally Posted by PortugazD.Ace View Post
I didn't say carry. I was wondering if, when the robot is stationary, the ball can be lifted so that it can get more air when kicked.
It doesn't matter if the robot is stationary or moving. Look at the definitions quoted above. If you lift the ball, it's not in contact with the field. If you are possessing the ball - controling its position - you can't lift it off the ground or you are carrying it.
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Unread 26-01-2010, 03:52
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Re: Kicking System Design Considerations

Quote:
Originally Posted by gorrilla View Post
my team is working on our kicker design, we are using a 5" stroke-9/16" bore(I think) piston, mounted to the bottom of our hinged plate(which is hinged at the top, so we get the most leverage) we get about 20" hight and about 5ft of distance in the air. this is enough to kick the ball over the bump from about 4ft away, but we need it to go further and higher, we could use a bigger piston but we dont really have the space. how could we make it kick farther?(I've thought about surgical tubing and springs already, but i was wondering if there was any other way?)
Double your bore and connect at 1/2 way up the swing arc (not at bottom).
Four times more force plus faster pressure build up will reach higher much higher velocity before kicker contacts ball.
-RRLedford
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Unread 26-01-2010, 09:02
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Re: Kicking System Design Considerations

Quote:
Originally Posted by FoXy92 View Post
To my knowledge there is no rule against kicking multiple balls, only possessing more than one.
To clarify my original quote...It would be clearer if I had said "Only one [b]if it's[b]in your possession", sorry if I mislead.

Last edited by JB987 : 26-01-2010 at 09:04.
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