pre-charged Pneumatics

[Mike Betts]

Eagle,

Unless you want to post your question to the GDC, we inspectors will not have a definitive answer for quite a while.

Let me suggest this: Volunteer to be an inspector at your regional (they always need more volunteers).

Furthermore, volunteer to work the sizing box and scale.

You need to process 60 robots in just a couple of hours (everyone waits until the last minute) and 30 to 40% will require multiple trips to your station...

Keep in mind it's not just you. it's 60 teams of students that are putting the robot into the box and onto the scale. One of them might include your son or daughter...

Now, what would you feel comfortable with?

Regards,

Mike

[Al Skierkiewicz]

Eagle,
It would seem that a simple application of surgical tubing in front of the kicker in your example would prevent it from extending beyond the FRAME PERIMETER and still allow sizing with the kicker in the fired (non-deflected) state. This is the requirement we used in your first year although only one or two robots used a system like this in Minnesota that year. As I remember it was one of the Cat teams who had discussed this with me prior to the regional and had it corrected by the time they were inspected. This is also an excellent example of Mike's previous post about needing a locking pin to hold the mechanism in place while moving the robot to the field. Although for the life of me, I cannot see a good reason that a team would need to pre charge this device before a match begins unless it takes many seconds to charge. The safety to students and field personnel in the event of an accidental discharge staggers the imagination.

[Ether]

Originally Posted by Al Skierkiewicz

It would seem that a simple application of surgical tubing in front of the kicker in your example would prevent it from extending beyond the FRAME PERIMETER...

Robots hanging from the tower at the end of a match may have their undersides exposed. Safety must extend inside the frame perimeter as well.

Just my 2cents.


~

[Al Skierkiewicz]

The surgical tubing would simple be holding the kicker inside the frame, it should not need any unsafe deflection to do so.

[Vikesrock]

Originally Posted by Al Skierkiewicz

The surgical tubing would simple be holding the kicker inside the frame, it should not need any unsafe deflection to do so.

I believe the point was that the danger of an accidentally fired kicker is not restricted to whether or not it leaves the frame perimeter. During removal of the robot from the tower hands may be placed inside the frame perimeter and within danger of a moving kicker device.

I believe this example helps prove the superior safety of a rigid restraint as suggested by eagle33199.

I also fail to see how surgical tubing can restrain a kicker within the frame perimeter without compromising the energy being imparted in the portion of the kick taking place between the edge of the frame perimeter and the edge of the bumper perimeter.

If a rigid restraint system (locking pin, harness, etc.) is recommended when transporting the robot, it would seem to me that it would also be prudent to keep this safety system in place for as much of the inspection process as possible, including during the jostling as the robot is inserted into, and removed from, the sizing box. As long as the device can be shown to remain inside the frame perimeter with the device removed (while not being jostled and while everyone is clear of the kicker) there should be no rules issues here.

Removing such a device for weighing should also fall well within the rules as it is not part of the robot when the robot is in the NORMAL CONFIGURATION on the field.

[Al Skierkiewicz]

Kevin,
I was addressing the fear that a kicker that is not in firing position would fall outside the frame perimeter during inspection. A small piece of tubing would suffice for that purpose.

[Ether]

Originally Posted by Al Skierkiewicz

Kevin,
I was addressing the fear that a kicker that is not in firing position would fall outside the frame perimeter during inspection. A small piece of tubing would suffice for that purpose.

<<A small piece of tubing would suffice for that purpose>>


Many teams are using surgical tubing for kicking. After kicking, they require substantial force to retract.



~

[Al Skierkiewicz]

Originally Posted by Ether

Many teams are using surgical tubing for kicking. After kicking, they require substantial force to retract.~

We don't know that yet.

[MrForbes]

Yeah, we do know that. We've seen the videos. Our own design is probably going to work this way. We are going to try our best to keep it inside the frame perimeter at all times, for various reasons. We'll see if we can get the distance we want from it that way....

[Vikesrock]

Our design will likely work this way as well. We will also be testing the "inside the Frame Perimeter" version, but we expect we will be going with a version that does utilize the 2 second exception. It will need to be in a partially retracted position for inspection and the start of each match.

A piece of surgical tubing strong enough to restrain the device inside the frame perimeter would slow the kicker down as soon as it reached the frame perimeter, negating the purpose of the extra 3" of travel (as soon as the kicker slows due to a force not part of the collision the ball will be traveling faster and lose contact).

We are making every effort to make this partially retracted state safe, including using a robust latch, but barring circumstances where we are forced to do otherwise we will have a separate safety device restraining the kicker when it is in this position and the robot is anywhere but it's starting position on the field.

It would be preferable to have this safety device in place when sizing the robot, but if that is not we will do what we can to make sure the process is as safe as possible.

[Al Skierkiewicz]

Ok Jim,
Using your robot as an example, what happens to the kicker when your tubing is not stretched? Does gravity affect it's position? Is it firmly held outside of the frame perimeter even though the tubing is not stretched? If all systems fail on your robot (a hard hit causes your battery to become dislodged and it breaks off a pneumatic fitting), what happens to the kicker? Same scenario but the kicker was not yet in a position to fire?

[MrForbes]

Originally Posted by Al Skierkiewicz

Ok Jim,
Using your robot as an example, what happens to the kicker when your tubing is not stretched?

The tubing is always stretched, in the "just fired" position there is a lot of tension on the tubing, pulling the kicker forward.

Does gravity affect it's position?

No.

Is it firmly held outside of the frame perimeter even though the tubing is not stretched?

The current designs have the kicker firmly prevented from moving outside the frame perimeter, because it hits the frame and stops.

If all systems fail on your robot (a hard hit causes your battery to become dislodged and it breaks off a pneumatic fitting), what happens to the kicker? Same scenario but the kicker was not yet in a position to fire?

That is a good question, we can't answer it because we dont' have the firing system all designed and built. A good answer might be to design it so that it can't fire accidently under circumstances like this, and that is what we're trying to do.

[Nadav Zingerman]

I would like to propose another hypothetical: A team's kicking mechanism uses a winch to pull back an arm connected to a torsion spring. To fire, the winch motor is mechanically disconnected (with a dog gear or the like), and the wire allowed to unwind freely. A mechanical stopping device prevents the arm from extending past bumper perimeter. The winch motor does not allow for backdrive.

In this case, the winch must be at least partially winded to fit in the box, but it may do so without power, and it is thus self-supporting. Would this be considered safe for inspection if it was only winded enough to fit in the box? What kind of safety devices should be used with this design, if the intention is to pre-load it before a match?