2014 Game Ball Damage
 

This is a big heads up for FRC teams in 2014.

While building a replica of one of the Robot in Three Days pickup mechanisms, our team popped our game ball. Now, I wasn't there to witness it, but I did see the aftermath. Our students were using the same wheels as the Ri3d example (AndyMark white plastic treaded wheels am-0940 or similar) and they say they were spinning them a little too fast. Based on what I saw, the edge of the treaded wheel caught the fabric and tore it, then it tore through the ball. It wasn't a huge hole, maybe 3/4" or so. But any hole deflates the ball, right?

Takeaway message: THE 2014 GAME BALLS ARE MORE FRAGILE THAN THEY SEEM. Our students weren't doing anything to the ball that we wouldn't have expected to see in game play, other than running the pickup a little too fast. So, while testing, please be mindful of this. Also of note: these balls are not nearly as durable as the type used in 2008. The 2008 ball was a rather durable solid surface type. This 2014 ball is a very foamy type of material, which seems to be more susceptible to tearing. I checked the manual, and both are made by Sportogo. But, I recall quite vividly that the 2008 ball was a more durable PVC.

This is a scenario that I can certainly see playing out at events. We are going to see untested pickup mechanisms using similar wheels that will be run too fast. So, teams, PLEASE prudently test your mechanisms so events don't go through their supply of game balls on practice day.

Re: 2014 Game Ball Damage
 

Ouch, definitely will keep that in mind. We weren't sure how fragile they were, so we've been playing on the safe side. What wheel type were you using?

EDIT: oops, nevermind, second paragraph. Shows what reading can tell you!

Re: 2014 Game Ball Damage
 

The wheel was the 6" andy mark molded rubber wheel am-0940.

https://www.andymark.com/product-p/am-0940.htm

We had a 2012 version with the non-white tread, but per the AM page, they are the same wheel save for the pigment.

It appers to be the same wheel presented in the Ri3d pickup here:

http://www.youtube.com/watch?v=4WZ1t...c4-overview-vl

To be clear, I'm not saying the design is bad. I'm saying that if you run the wheel too quickly, you may run into damage.

Re: 2014 Game Ball Damage
 

This happened to us yesterday too, in a very similar situation :o. Off to the nearby hardware shop to pickup a bicycle wheel repair kit while waiting for our order of additional balls to arrive! :rolleyes:

Re: 2014 Game Ball Damage
 

I have a feeling that ball damage is why many 2008 teams used rollers (see: Bomb Squad)

As long as you don't tear through the fabric, you should be fine. At least that's what it seems...

Re: 2014 Game Ball Damage
 

I feel like non-smooth wheels like that would be more apt to tear the ball up, because of the constant change in surface and "snagging" of the balls fabric (magnified by a faster RPM).

Re: 2014 Game Ball Damage
 

We used the 6" white tread wheels from AM (previous kit wheels) on the outside and 4" kit wheels in the center. We compressed the ball pretty heavily (5-6"?) in testing tho settled in at much less 2-4". We fortunately never popped the ball and we abused it. During testing we approached the ball from many angles and optimized the compression on the ball via the Modulox channel.

As an idea for speed we were using the PG-27 with a 1:1 chain reduction. It was driven at roughly full power in an on/off state. I don't believe there was any coded ramp function.

It sounds like we may have been lucky, but the ball held up well in our testing. The wheels may also have some sharper edges leftover from manufacturing. It may be worth while to radius the edge via sand paper or a file. Also do everything you can to make sure no sharp metal edges are in the vacinity of the ball.

Re: 2014 Game Ball Damage
 

Ball damage was a problem in 2008. Field personnel came around to the pits of robots who had been observed damaging balls with pickups or other mechanisms and warned the teams that they would not be allowed to return to the field until an inspector had verified that they corrected the issue that was causing the damage. In many cases that equated to slowing down the roller on their intake.

Re: 2014 Game Ball Damage
 

We have also had ball damage, thanks to USPS have no backups, so we have made beautiful repairs with duct tape. https://drive.google.com/file/d/0Bw9...it?usp=sharing

Re: 2014 Game Ball Damage
 

We had a similar issue where the ball was punctured during our shooter test. For anyone else who has a popped ball and is waiting for AndyMark to get more in stock, we put a normal exercise ball in the cover as a temporary measure. Its 2.6lbs and is 25" in diameter. It has more give than the standard game piece, but has worked pretty well as a temporary stand in so far. Given how easily our ball burst, I wouldn't be surprised to see a graveyard of popped balls at the competitions.

Re: 2014 Game Ball Damage
 

Instead of waiting for AndyMark to get them from Sportogo and then buy them from AndyMark, why not just buy them straight from Sportogo? They don't have any with the official FIRST logo on them, but you can get a same size/weight ball with a tennis ball/magic 8 ball/etc. cover instead, and they are cheaper that way. Or, if you already ordered some extra balls from AndyMark and those popped, you can keep the cover and just order new bladders from Sportogo.

Re: 2014 Game Ball Damage
 

And to go with each popped ball, G10 will assess a FOUL. Do it repeatedly, and you may need to modify the robot to ensure it cannot happen again.

The point is: If your robot uses a mechanism that can pop a ball, best think of a redesign now, instead of at the competition...

Re: 2014 Game Ball Damage
 

I was going to say that G10 excluded the BALLS, then I read the Blue Box. Not the best way to write a rule, to specifically exempt something and then reinstate the prohibition.

So like Don says, don't pop the balls.

Re: 2014 Game Ball Damage
 

We just punctured ours. I hate it when that happens.

Has anyone had good luck patching their ball?
What materials were used (patch & adhesive)?

Thanks,
Waddell

Re: 2014 Game Ball Damage
 

After looking at that site, I really want to see one of those 8' or larger balls as a game piece. Not really sure how scoring would work, but I'd imagine the robots would be tanks.

Re: 2014 Game Ball Damage
 

Sorry to tangent, but WHY ON EARTH would you pay $2,800 for a 15 foot soccerball!?!

Re: 2014 Game Ball Damage
 

I've saved for it since I was 5.

My idea was to use it as a house.

Which could roll around like a hamster wheel.

On Mars.

Re: 2014 Game Ball Damage
 

A mental vision of that is disturbing. :D

Re: 2014 Game Ball Damage
 

Or you can buy the official FRC Ball directly from SPORTOGO. I believe the part number is SP-014ROBOT. I placed an order for two of the "25in Volleyballs" (one red and one blue), and received an email asking if I was part of an FRC team and that I could switch my order to the official balls. I don't think the balls are listed on their site, but give them an email or call.

The balls are still $52ea.

Re: 2014 Game Ball Damage
 

Our ball has 2 leaks. Has anyone used a inner tube patch kit. I worry that the solvent will melt the foam material. We are currently using a bladder from 5 below until we get our replacements.

I'd recommend just using an exercise ball and ordering a new one tbh, we had no luck successfully patching ours, the tear just continued to get bigger.

Re: 2014 Game Ball Damage
 

Could you say what RPM you were using when the ball popped so those of us who have yet to pop ours know what is "too fast"?

Re: 2014 Game Ball Damage
 

I'd rather have a smiley face ball personally.

Re: 2014 Game Ball Damage
 

It's not simply RPM. It's compression, wheel diameter, tread material, number of wheels, wheel placement (angle of contact with ball), ball inflation, random factors (hit the seam or the zipper the wrong way), etc etc etc.

Re: 2014 Game Ball Damage
 

Well, here's a photo of one of our prototype shooter wheels, and we did eventually pop the ball. But we repaired it (the ball) with a bicycle patch kit.
:rolleyes:

Re: 2014 Game Ball Damage
 

Thanks Don. You made my day.

Re: 2014 Game Ball Damage
 

The real question is, did it improve grip?

Re: 2014 Game Ball Damage
 

Very funny. Do you really expect us to believe that?

That you used a bicycle patch kit.:rolleyes:

Re: 2014 Game Ball Damage
 

Don, do you have any numbers on the coefficient of friction between your wheel and the ball?

Re: 2014 Game Ball Damage
 

coefficient of friction: 1.000000.....1
Yup, broke physics

Re: 2014 Game Ball Damage
 

I feel like this is a joke, and I totally don't get it at all. Do you think it is impossible to have a coefficient of friction >1? And that since your number is just marginally greater than 1, that you have broke physics? Well, hate to break it to you, but there are combinations of materials with coefficients of friction >1.

I'm probably just misunderstanding what you are saying though, so would someone kindly explain what he was trying to say?

Re: 2014 Game Ball Damage
 

It is possible to have something with a greater coefficient than one? I honestly didn't think its possible mainly because anything greater one would mean you get more force out than you put in. Because the force of friction=Fn*coefficient of friction. Friction can only oppose up to the magnitude of the force being applied. If the magnitude of the force of friction were greater than the force it opposed, that would mean that friction itself was causing one or both of the surfaces to accelerate. I did not think that was possible since it breaks the law of conservation.

Re: 2014 Game Ball Damage
 

rough top tread is the best example that comes to mind that is frc applicable. i believe that some rough top tread has a coefficient greater then 1. think about Velcro the hook and loop take a LOT more then the normal force to get the 2 to slide against each other. and other surfaces can have similar interactions

Re: 2014 Game Ball Damage
 

Ok I looked it up. I think I get it now. My bad for the failed joke :(

Re: 2014 Game Ball Damage
 

That's all right, it is a little bit counter-intuitive. Hey, but now you have learned some more physics, and who here doesn't want to learn more physics!

Re: 2014 Game Ball Damage
 

There are other cases besides friction where you can "get more force out than you put in". Gears are an excellent example of this. The important thing to remember is that there is no "law of conservation of force". The important conservation laws are those of mass, momentum, and energy.

The other tricky thing with static friction is that the maximum force that static friction can provide is your stated equation. Static friction can always provide less force than this, but never more. If the applied force is less than the maximum force from static friction, then the force from static friction will be equal and opposite to said force.

Anyway, you probably knew most of this anyway. It is still a good refresher for me though. :) Since this is a thread about ball damage...um...don't use spikes to get a greater CoF.

Re: 2014 Game Ball Damage
 

Lol ok:D

Re: 2014 Game Ball Damage
 

isn't that from your 35AD "Chariot Assist" game robot?

Re: 2014 Game Ball Damage
 

We popped a ball with a piece of Bosch. Fixed with Shoe Goop and a small piece of cotton cloth. The puncture was a 1/2" cut. We also bought a replacement bladder from Walmart (the Gold's Gym 65cm ball) This proved to be too small. The 75cm might work better. Actually the regular 65cm were suspiciously sold out, so we got the 65 stay put for 10 bucks more. The stay put was $10 of loose sand that took about 10 minutes to shake out! :D

We used a waterbed repair kit.

The ball is pvc, like waterbeds.

The bike patch will likely work for a short period of time, but will be leaky and fail over the course of a couple weeks of testing (good enough? I think it might be)

Re: 2014 Game Ball Damage
 

We haven't had any trouble with popped balls. Good job FIRST, for choosing a robust game piece.

Re: 2014 Game Ball Damage
 

Did you mean Shoe Goo?

http://www.chiefdelphi.com/forums/sh...3&postcount=10