Rex Sack Attack

Today was the first event of the season for Vex Sack Attack. Will we see any videos posted to show us how the game play is. If not it would be nice for a recap of how the event went, and who won awards.

I dont think any videos were taken, but it was definitely a good look into how the year will play out. Most games were won with about 50 or so points, but a few before the finals, and many in the finals went above 100.

The best robot there was probably 929W, which was a simple pivoting spatula on the end of an arm. The reason they did so well was because it was a full 18 in wide, so they could easily pick up multiple at a time, and the robot was on mechanums, allowing the robot to score and descore really fast.

The rest of the bots were either a fixed spatula, some form of a claw, or were modified NZ bots with a conveyor on the intake basket.

As for intakes, they varied. Some teams went with foot wheels, which could descore really well, but didnt offer a whole lot of control of the objects. Most teams went with some sprocket/chain/flap combo. Most had larger wheels, but my team used a series of 6 tooth sprockets with the small flaps around it, which ended up digging into the sacks like teeth.

Most teams went for the troughs, a few went for the high goals, and almost everyone went for the parking bonus.

A lot of people would place their preload onto the robot in such a way that when the robot moved forward, it fell off into the floor goal, to try to win the auton bonus. I didnt see any other scoring in auton and my team had probably the most complicated auton, which just retrieved two bonus sacks.

Not many people used the match loads until the finals.

The REX Gateway tournament had plenty of videos. Are you sure none were taken this year?

What kind of lifts were there? When you mean conveyor ramp the ramp had a conveyor for objects to ride on? Did these designs have a top roller? What do you mean by foot wheels? What problems/strengths did these designs had?

How often did teams cross under the trough?
Was sacks an obstacle for robots?

I dont remember seeing any, but I was mainly concentrating on my teams robot while there.

– 6 bar
– 4 bar
– Scissor
– Simple arm

Yes, the ramps that previously help the gateway objects now had a conveyor or two running along them. The main intake was in front of the conveyor normally as a top roller.


The largest trade-off for intakes was between speed and control. Those that could intake/output/descroe quickly often would accidentally spills sacks while doing so. Those that prioritized the ability to control the sacks often had to intake/output/ descore a bit slower.

As for the conveyor/ramp robots, some worked well, some didnt. It was mainly a matter of how well the team could get the sacks onto and off of the conveyor. My teams robot had some trouble getting sacks onto the conveyor early on and this cost us a few matches. On the other hand, we were excellent at getting the sacks off of the conveyor and could discharge quickly. Some robots were the same, others were the opposite.

The robots that had either a claw or a spatula only did well if they could score quickly, something that 929W did very well. The best way to defeat that strategy, however, is to not try to outscore them. You would need to concentrate on descoring their sacks. They could get sacks out of a trough, but couldnt gain control of them quickly. If a robot could remove sacks from a trough and the replace them, they could defeat the fast scorers.

Only a few robots could fit more than one sack into the high goal. These tended to do well, but were unfortunately often had some tweaking to do before they could work efficiently.

The only teams that really crossed under the troughs consistently were ones without arms. A couple of the ones with lifts of some sort crossed under occasionally, but most people tended to stay on their side.

The sacks were an obstacle to some, others (like the couple that had tank treads) just drove over them. One team managed to pin my teams robot between two piles of sacks towards the end of a match.

I was at the competition today. It was a lot of fun, though I realized a lot of things need to be changed on our robot.

929W was by far the best robot there. While others would struggle to get one or two sacks in the trough, it would just pick up like 5 or 6 at a time and drop it in a matter of seconds. Descoring was very effective (though 929W couldnt do it). Going under the trough seemed like a waste of time, especially when there are already plenty of sacks on your own side.

Getting the bonus sacks, the third trough, and the parking bonus are really important in accumulating a lot of points. Also, the five preloads were a great advantage.

It seemed that the simple, claw robots (in fact-a claw robot was the first place winner) did better than many of the larger, more complicated ones, which kept malfunctioning. Perhaps it is because of the short amount of time prep, all the glitches hadn’t been solved, but also, the sacks are pretty hard to deal with if something like a sprocket and chain is used. The sacks are so heavy, they just wont move the way you want them to.

The biggest problem for our team was getting stuck on the sacks. There are two big piles of sacks on each side of the field, and they are hard to maneuver around. It was quite frustrating. Once the robot is stuck, that’s it. Cant score, cant descore, cant park. Nothing.

your welcome for those sacks pushed under your robot i still cant believe that worked:D
didnt see any video being taken either

Did any robot try defending their goal by covering it?

About how many sacks on average were on the high goal? Were these sacks typically match loads?

Also, What were the high scores in programming skills and driver skills?

considering that this is the first competition
im guessing that only the top 5 robots out of the competition can “actively score” on a regular basis?
(no offence, ALL early season first competitions are like that)

Not true…
Singapore Vex Robotics Championship is always held about 1 to 2 weeks after Rex (still considered as early season for sure).

And normally, we will have about 50% of the robots “actively scoring” on a regular basis. And we are talking about a (about) 80 teams tournament.

And the skill challenge scores are not too shabby too.
Last season, the top 3 skill challenge scores were still good enough to qualify for the Worlds at the end of the season.

But of course, I have to agree that there are many robots that still needed more time to sort out their issues as well.

A big thank you to REX/Dulaney High for hosting this early season event.

Besides giving the teams a chance to get to see how the game can be played - it was a wonderful opportunity for veteran and new event partners to observe, along with those thinking of starting teams.

I was able to watch the time needed for field set-up, reset and scoring, and calculate realistic match cycles.

Thanks to Miller Roberts from RECF for the useful event partner trainings at this competition.

The season has definitely started.

No robots tried to defend their goals unless they were already there and an opponent was actively descoring it. Even then, it composed more of pushing hte other robot out of hte way than covering hte trough.

Some games had no sacks, some games 3 or 4 sacks. Normally, these sacks were match loads and bonus sacks

I dont know what the high scores were in driver and programming skills.

I have uploaded the videos our team took at the tournament to my YouTube channel. I have also added the links and team numbers/match scores to the Sack Attack Video Wiki.

High score in Driver Skills was 75 by 24C, and the highest Programming Skills score I saw was 11, by simply dropping a sack onto the Alliance Starting Tile and staying there. Not sure who all the teams were who did that, or if anyone added Match Loads to their robot and did the same, or even did more.


Some items I nocticed at the event-

There seemed to be two general approaches to getting a robot ready for the event. Some teams designed and built some simple, but effective scoop or claw robots that could pick up 1 to 5 sacks and score them, and most of those could descore. These robots tended to be reliable and did fairly well. The #1 ranked team was a very simple clawbot (nothing wrong with that, congrats to them for making great use of that design to do so well this quickly). The other category were teams that came in with more complicated designs that were still in the development process and did not have all the bugs worked out. The robots in this category did not do as well due to the short design and build period, but probably have great potential in the long-term to be the dominant robots by the end of the season. In general, these designs quickly swept up quantities of sacks as they move along the field (when they worked), and then dumped a bunch all at once. The fact is, the sacks are difficult to sweep up reliably without binding up most mechanisms occasionally, so these teams still have work to do in refining their designs. But congrats to those teams for taking a longer term view and working on developing a design that will strongly carry them through the season.

It appears descoring may be a big part of the game. We saw some very quick point swings with some teams simply pulling sacks out and onto the floor or, better yet, catching them as they pulled them out and then dumping them in their own goal. The game can change very quickly.

The sacks get caught everywhere. …in gears, sprockets, pinch points, drive wheels. Design carefully. As far as I know, no sacks were shredded, but a few did start to come unstitched.

There were robots that went under the trough. That did include robots that had lifts, despite what a previous post said. Though I am not sure there was a robot that could reach the high goal that was low enough to also go under the trough. I see benefits in going under, but other may disagree with me.

I am not sure that the high goal is as critical as some may think. It can only hold a limited number of sacks, and once the pile gets too high, simply hitting the trough or pipe knocks them off.

It should be an interesting year. There are going to be some very high scores.

One more point that I forgot to make about the event- the event was largely run by graduates from several local teams, with adult oversignt as needed. It was really cool to see these graduates from the past 3 or 4 years step up and do most of the work, making the event run smoothly. Kudos to those who are returning to give back to the community.

ahh! didnt realize it was 24’s competition :wink:
great intake btw
congratz on the drivers and the win!

+1 XD

It actually wasn’t run by Team 24. Team 1727 hosted it. We were just participating. The adults (myself included) didn’t need to do the hard work because the younger crew stepped up.

The tournament was a good starting point for us, and I suspect, for a lot of other teams. Many thanks to REX for hosting it.

Although we could not get it to work as was intended at the tournament, our robot has a vertical lift capable of scoring 5 sacks in the tall goal and yet short enough to be able to go under the troughs. Here is a youtube video of the robot in action (scoring in the high goal) at a practice run at home.

I noticed while watching the videos that the refs never bothered to tally up points in autonomous. Some robots accidentally dropped their preloaded sacks onto their starting tile, which still counts as scoring.