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.
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:
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.
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.
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.
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.
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.