1471A Sack Attack Omnomnom reveal

Our club made our first entrance into the public eye at the world championships last year after playing for 2 seasons. This year we hope to continue to improve. Here is our current robot for sack attack.


Yes, that is an offset chain bar. We love it very much. (and yes the chains are off in the picture!) The chain bar is designed to tilt the intake downwards as the arm raises, reaching about 45 degrees at trough height.

This robot has 10 393s, 4 each on the drive and lift (1.6:1 and 1:5, respectively) and 2 on the intake (1:2). We wanted to create a robot capable of hoarding sacks originally, so we made a bot that could score 65 sacks at once but it eventually fell through on us, so in the last few weeks we migrated to this design. We decided that it would be more beneficial to hold about 10 sacks and be able to score them all easily and intake them instantaneously. The robot can hold those 10 sacks and sometimes a little more. We built our robot to be a fast driver for this game at 1.6:1 and also to have a fast lift for this game at a ratio of 1:5. We see many other teams resorting to slower drives and much higher gear ratios on their lifts but we wanted to be fast and nimble. The robot can suck up sacks at full speed without stopping and score them quickly. We also have the ability to descore and are working on descoring into our own intake at the moment. We are also trying to get the robot to score the high goal.

The robot won the Sahuarita robot Skills challenge last weekend with a score of 140, but we have scored 195 in practice and expect to improve upon that. There have been no tournaments in AZ yet this year, but the first one is in two weeks. We hope to qualify for worlds as soon as possible this year, so we hope to see you all there!

Any questions or suggestions?

Just a quick update: We’ve got the arm converted to aluminum and have noticed it goes up faster. We’ve also learned to descore into our own intake and we can descore about 10 sacks into our intake then score them in our trough in ~15 seconds.

more pics!



We would appreciate any input you guys might have!!

Your robot is the perfect partner for ours! see you at the Chandler, Arizona Competition! :smiley: We are 4191. look for the flames on our intake.

4191, what kind of robot do you have? Will you post pictures? I look forward to seeing you and 1471A this weekend…

Can’t wait to see you guys there! There should be a lot of good robots showing up this year.

4191, you should post some pics for us!

Also, we believe the “perfect match” for us will be whoever else can score the most :stuck_out_tongue:

Hey I was just wondering, what did you guys do for a lift? Or could you explain it alittle?

Sure! Our lift uses four 393s that are geared 1:5 for torque. We wanted a lift that was fast, but could still hold a lot of weight, and we found that this works well.

And if you’re asking in regards to our offset chain bar, the easiest way to explain it would be for you to grab a couple sprockets and some chain and look at it. Basically the difference in sizes causes the angle of the intake to go down as the lift goes up. Due to space constraints we also had to move the chain lift to the inside at the middle of the arms, but the ratio of the chain linkage is just the top gear to the outer middle gear.

Could you post a picture? We started with a scissor lift and realized it was to slow, so then we tried a 6 and 8 bar design which worked but be wanted a stronger lift. So we have been experimenting with compound gears and just keep hitting a wall. Here is our lift prototype. Do you have any recommendations?
LIFT 3.jpg

I need to know a little more about your robot and strategy before I can give you any good recommendations. Do you want to reach the high goal with only your lift? How many motors do you have dedicated to it? What is your intake like? How many sacks can you hold at once? Some general recommendations are to use aluminum, and to try to avoid trying to make your lift go too high.

Our goal for our robots lift is kinda the same as yours, fast but strong. We would like to be able to pick up 10 sacks and lift them efficiently. We use to worry about top goal but decided we are going to focus on troughs. Our strategy is that we would like to hold those 10 sacks until scoring so that they are harder to descore. We are working on an intake using plexiglass and pnuematics to score and then having a thing like your mouth and comes down and can be used as a descorer at the end of the match

I don’t know what you mean by our mouth that comes down, but our robot has no problem lifting 10 sacks with 4 393s at a 1:5 ratio. Just make sure there’s no excess friction, your arm isn’t too long and there’s not extra weight. Also use rubber bands to try and cancel out (most) of the gravity (blahblahblah spring constants and 1/2kx^2 lol)

Alright!! thanks we will try that out! Good luck

Well we were first seed and won the tournament today! Thanks to 2114a and 2114b for being great alliance partners, this is our third time in a row as an alliance taking the champion trophies in Arizona :smiley:

I kind of like this robot.

Can you pick up the 11 sacks (gold plus two stacks of 5) without stopping? If so you should be able to improve a lot in the skills particularly if you get the high goal scoring going.

Can you expel 10 sacks quickly on the troughs… less than 2 sec?

Any video posted yet?

No videos yet, maybe some of today later on. We got 60 in the high goal in most of our matches today, and we can descore basically an entire full trough in 10-15 seconds, or fill our intake from it in about 5. We can’t hold both piles, we sacrificed high capacity for higher speed, especially on our lift. We find that that was a pretty successful trade off.

Here’s a video of us scoring 60 points on the high goal in the first bit of driver control. We only dropped them once at the whole tournament, but we’re going to see if we can make the stack a little bit less precarious while we drive it up to score.


Congrats on your win!! We watched your video and its pretty impressive. We are still having troubles with ours… Could you possibly email a picture the back of the robot’s lift? We get the offset chain lift, but we are really confused when it comes to the gear ratio and keeping them strong yet fast and also keeping it within the 18x18x18
my email is damian.mcalevy@ravenna.k12.ne.us if you would be able to email it