Vex Sack Attack Robot Design Idea

Here is a design I have for a robot, and I would like some feedback on if this is a good design or not.

About my design:

The front of the robot has a conveyer belt that will be able to go down, pick up sacks, and then raise up to either put the sacks in the 30 inch platform, or in the basket in the back of the robot which can raise up using linear slides and dump the sacks into a trough. Also, on the conveyer belt are two bars that can fold out and go over the trough to prevent other robots from scoring their sacks or descoring our sacks.

What we want our robot to do:

Overall, we want this robot to be able to score in all of the goals, block other robots from scoring their sacks, or descoring our sacks, as well as move quickly and powerfully.

How we plan on playing:

At the beginning of the driver control period we should go for the bonus sacks and put around 3 sacks (which is my estimated maximum for how many sacks can fit on the platform) on the 30 inch platform to get as many points for the platform as we can. We will then put a majority of our sacks in the 18 inch trough, and as a backup, we can score in the floor goals in case our robot’s arm breaks.

We were in an early Sack attack event, and we had a robot that was able to go under the troughs, but I don’t think that there is a big enough advantage to being able to go under the troughs because the only reason to go under is to descore the opponents floor goals, and we rarely see sacks scored in the floor goals due to the amount of points you get for scoring in floor goals vs the troughs.

Also, even though we could go under to score the sacks on their side, we don’t have that much time in the match, so we most likely won’t run out of sacks to score before our time is up. So I don’t see us really needing to go under the trough. If our opponents have a robot that can go under the trough to try and take our sacks, we will block them from descoring anything until they give up. We should use the full 18 inches of building space we have to make a robot that can go up to the 30 inch platform.

The link at the top seems to be broken, but I’ll reply to what you’ve written:

Have you tested this mechanism? I have found that just a conveyer belt by itself is insufficient to pick up the sacks. I’m not saying it’s impossible, just that I wasn’t able to do it.

Any particular reason for having 2 seperate lifting mechanisms? It seems like a huge waste of motors and space to me, where you could just make a single lift that could reach all the goals.

I assume you intend to do this pneumatically? Just remember rule <G11> when considering any kind of expansion to block something, as your robot could no longer be subject to protection from pinning etc. while expanded.

Whenever I see say someone say something like that I cringe :o. In Vex, power and speed tend to be opposites. The only way for a robot to move powerfully and quickly is to add more motors in the desired mechanism. Considering you are already looking at:

2 motors for intake
4 motors for lifts (2 for each)

You would have 4 leftover for the drive. I would say this is sufficient to make a relatively quick drive, but not a powerful one (in comparison to other robots).

There is more than one reason to go under the trough. Being able to go under the trough gives you access to almost twice as many game elements. This is useful not only in competitive matches, where you can potentially score more points, but also in matches against poor opponents, as it is easier to score higher SP. I would seriously reconsider about this, I think being able to go under the trough is a vital thing for a robot.

While this may be true at this stage of the season, it is likely that your and others’ robots will improve dramatically throughout the season, and the scoring rates will be much faster. I would design a robot that is ready for that eventuality now, instead of having to completely redesign later on.

Also, do you plan to be able to descore from the opponents trough? I identified this as a key feature of a robot very early in the season.

Sorry if this post seemed harsh, I’m just trying to give constructive criticism that will hopefully help you out :).

The picture for me isn’t working, so I can only go by the description. It sounds like you have two separate lifts, a trough lift, and a high-goal lift. You might want to consider (if you haven’t already) making them connected, so that they work as counter balances. So when the trough lift goes up, the high-goal lift goes down, and vice versa. If you don’t know what I mean, you could look up GER’s robot that did this in Round Up.
It’s interesting that you say that going under the troughs isn’t a big advantage, and you bring up valid points. However, I think you should try to think about further into the season when robots will be able to collect sacks much faster.

Hope that helps!

I can’t see the picture you posted so I can’t say much about the design. I’m not sure if it’s on my end, the forum’s, or yours.

However, I can provide feedback based upon what you have written on strategy.

I think your set of goals is great and covers all of the bases. I’m curious, do you plan to horde sacks, score, then cover? Or quickly score multiple sets of sacks, covering your trough when it’s in danger? (I can not tell strictly by your description) I like your idea on scoring the bonus sack in autonomous, but be careful you program your routine so that the sack can’t accidentally end up on their side of the goal.

Personally, I lean towards having a smaller robot that can go under the troughs. Strategically, I favor having as many options possible. This allows you to be flexible and counter your opponents while adding an element of surprise so that your opponents can not predict your strategy. I have seen on many occasions an excellent team’s single solid strategy be broken down late in a competition because others adapted. And remember, just because you can travel under the trough doesn’t mean you have to or should. It depends on your opponents.

While traveling under the troughs allows you to take sacks from the other team, it also provides another advantage. You can “surprise harass” the other robots, thereby decreasing their efficiency. A fast enough robot with a practiced driver could effectively immobilize the other alliance.

Clearly I favor the under-the-trough route, but I will say do not do it if it sacrifices performance. Going back to the idea of multiple options, a robot solely designed to harass others can be easily countered. But if it is possible to simply make your robot shorter and still achieve all of your goals, I would recommend it. I think we will see it become a major part of the game later in the season.

Not seeing picture, but sounds very similar 2 ours … great minds think alike :smiley:

Our early design (on paper) was just like yours, but we modified it. Telemascope, UnforeseenGamer & capow08 explain it perfectly (thanks). Now we are building the base (drive train). Thanks any way for “encourage” or confirm (support) our decision. :wink:

Hello everybody, I am Honmeg287’s team partner in team 2001. Thank you for all of your comments! We will be responding to them as soon as we discuss them together. In the mean time, here is the picture he was trying to post (it’s big so you can see the details):[ATTACH]6670[/ATTACH]
tgr robotics design.jpg

Thank you all very much for the feedback! My teammate Vacation9 and I are going to go over all of this again when we have our next meeting. I have changed the place web page where the photo is hosted, so it should work now. :smiley:


Do you have pneumatics available to use? To achieve your goal of a fast strong robot you are going to need to dedicate as many motors to your drive system as possible.

Do you plan of being able to open and close your basket, or is a a one time deal?

Where are your blocking flaps stored? I couldn’t tell from the drawing.

How does this conveyor work? Like Telemascope said, they seem difficult to make for the sacks and would be very interested in seeing what it looks like once you get it working.

Also, keep in mind that your basket will have to be inclined to let the sacks slide out. You will have to test different angles to find out what works with your basket material (since the coef. of friction is different for each)

I designed something similar to this back in May. The “conveyor” part is at a much lower angle to the ground then yours in the drawing, however, it can’t reach the high goal.

I really like how you guys started with what goals you want to accomplish and how to play before actually designing. It’s a common mistake a lot of people do and it ends up wasting time in the long run.

Overall, i think that is a good start. One of the best things about this robot is it’s powerful and massive(potentially) storage. Your idea of using a linear lift that’s well centered can lead to massive lifts as long as your gears/sprockets devices do not skip or bend. Your usage of rotational motion will also lead to very fast lifting speeds, which is necessary for scoring low amounts of sacks within the high goal. Also, the use of an elevated tank-drive over elevated holonomic drive with possibly 5 inch wheels, will give your robot high speeds, very powerful sideways traction(which is important for scoring large amounts of sacks at a time or capping goals), and less issues from sacks.

However there were also a few problems.

One of the biggest problems others have mentioned are dividing motors. Not only does that make the robot harder to build, but it causes some motors to be idle during the match. especially in this case, you waste 2(possibly 4) motors on a lifting system you may or may not use only once. Like you said, your not going to let another person get to your side of the field(which then they can de-score your goal). To fix this, i recommend using an arrangment similar to this(storage=goal lift while conveyor belt= arm). This makes your conveyor smaller and the arm longer, but it consolidates your motors.

Another potential problem is the conveyor belt. From what i can tell, the robot acts similar to a scoop by shoveling up the pieces. From there the conveyor belt feeds to the intake. The main issue will be the actual shoveling portion. Since in your drawing you have fins, your belt wont exactly be flush with the ground, making it much harder to pick up sacks. to fix this, i recommend adding a large roller and chain together the conveyor belt.

as you know, motors only come in ether speed or torque. So, i recommend installing worm gear brakes on the robot. It allows you to remain at a decent speed, but it also locks up your wheels if another force tries turning your wheels.

I’m glad someone else is trying that mechanism. Currently the way it’s design( flips towards your opposing alliance) is a bit risky. I believe that it’s possible for another robot to push away the cap simply by driving into it. What i do is have the flaps flip open like wings. That way, if you make it sink into the troughs, it becomes extremely difficult to remove.

Anyways, with the proper modifications, it can be a challenging robot

The problem with that is, there are times when both the basket and the conveyor need to be down. Perhaps the motors could have a transmission that controls which mechanism they’re lifting.

I am a parent/coach for team #2001 and I am very grateful to everyone who responded to the current design idea. I have a question about the engineering notebook. An entry has been made into the notebook that is basically the same as the original post. When the next entries are made, I am wondering how we should incorporate all the points that have been made here on the forum. The team members will go through all the points raised when they meet again, and when they go to write their entry in the notebook, I would think they should acknowledge all the input and help they received here on the forum. I am wondering if they should print out the comments, or should they go through the main points that they discuss and write down their thoughts and plans on each point while specifying where the points came from?

We don’t have an engineering VEX mentor, so this forum is all we’ve got! Thank you again.


Oh right xD. I didn’t think of that.

I’ve never done a notebook before, but I would assume you would write an asterisk with the idea, and at the bottom of the page give credits. I could be completely wrong though, thats just how I would do it.

Or maybe you can make them practice their “MLA” citations :wink:

That is a great idea! I don’t know about MLA though, maybe just the asterisk after the post and something like “Design assistance from VEX Forum - (usernames)” at the bottom.

I think they would prefer to leave that to English class. :slight_smile: I am wondering how an engineer would make note of outside feedback.

I would do both, but divide it. Keep your main section easy to read, but keep a sub section with the very detailed info

In CAD class we put notes on our drawing with little symbols that looked like check valves with numbers in them, some what like this: O>

We then added notes of to the side with corresponding numbers. For in the text itself, the Wikipedia, super-scripted, blue, numbers in brackets is also an option.

We will do our best to help!

That is a very good idea! We might be able to make something that goes under the trough with the space we would save. We will consider this. :slight_smile:

What is rule <G11> and where do we find the list of rules you are referring to?