Our weight is 115lbs, but we're going to be losing weight. Right now we're running steel sprockets on our pick up and dumping systems, we're going to be running aluminum sprockets on the output end of the reduction.
Our hopper is built in three panels, each made of .0625" lexan. The pickup scoop, dumper backings are made of .125" lexan. We formed all of our plastic with a series of fixtures and two heat guns. It's quite easy. We spent a total of 2-3 hours cutting and forming all the plastic for one and a half robots.
Our belts are made of 5/16" urethane. We found a cheap source of cord stock and a belt welder that is half the cost of the one McMaster sells. Without these two finds we would not have used urethane. The rollers are made from UHMW tubing with aluminum end caps.
While this design looks simple, there was a lot of testing done. We originally were running 10 belts for pickup and 19 for dumping, but when we first ran the two systems we were pulling over 100 amps! After optimizing the efficiencies in both systems they now pull about 28 amps per motor. We did this by tuning the chain tension, increasing the reduction, cutting down the number of belts, testing different groove depths and widths and remaking some of the belts to be a bit loser. All in all we spent about a week optimizing our pickup and dumping systems.
Our goal with this design from almost day one was:
- Able to pickup and score any ball, without discriminating between 'good' and 'bad' conditions.
- Pickup effortlessly from the floor and to quickly get the balls in our hopper
- Provide a large opening for PS to throw into.
- Keep the hopper low so immobile alliance partners can dump in our hopper as well over/under-thrown balls to land in.
- Fill a trailer within seconds, knowing that opportunities to score for a dumper would have potentially very narrow time windows.
- Make sure that any balls we missed during a dump could easily be recycled back into our robot.
- Have our exit point be high enough to score at any location around the trailer
- Keep the number of mechanical systems to a minimum.
- Make everything accessible and simple to repair.
So far our robot has accomplished all of these to some degree. At our pre-ship scrimmage held over the weekend we were pleasantly surprised by how many points we can score with even the smallest windows of opportunity.