I’m building a robot similar to this one but that will lift cubes.
http://www.team323z.com/uploads/1/0/0/6/10062475/9091558_orig.jpg
I’ve never built a robot design of this type and was wondering if anyone could shed any insight on how to go about building one like this.
Start with the end effector and work down.
Thing that actually handles the game object → thing that lifts or moves that → towers or attachment points for the lift → base → wheels.
I found something on youtube that kinda looks like this robot and does squares and rods: https://www.youtube.com/watch?v=9ijcvsahHYc
Is this the methodology that most teams use? It makes perfect sense now that I see it written so plainly. I’m embarrassed to say that we have always done the exact opposite of this. We tend to start at the bottom and work our way up…chassis, then lift, then intake…or perhaps a bit of all subsystems at the same time.
Perhaps this is why we have some of the technical problems we run into…
Our teams work opposite direction of what cody has described. We do decide on an end effector first, but it isn’t built until the chassis and lift are done, in that order. When you build the end effectors first, you tend to ignore the space required for the rest of the robot. Generally, driving is the most basic function of Vex robots. If they can’t do that, they aren’t that useful. Lifting is only less important than driving…
Think of it this way: a robot with a working drive and lift but no end effector can do a whole lot more than a robot with a working end effector and no working drive or lift.
Yes it is VERY normal to work bottom up but it is my experience that its totally wrong to do so.
How strong of a lift will you need? You won’t know until your end effector is designed.
How far apart should your towers be? Same story.
How wide does your base have to be? Depends on the towers.
etc.
I find myself wanting to start with the base all the time, and while I can guess reasoably well what these values need to be, I constantly run into issues because of bottom up design.
I mean let’s say the season starts and your team divides and conquers, half the team goes and works on the lift / manipulator and half the base.
And time goes by and the manipulator team comes up with something wild, just awesomely wild.
Small problem, its nothing like what the base team assumed. Their work is now virtually useless.
Its even worse if the whole team starts on the base, they all assume some traditional lift / manipulated, and bam you’ve instantly put yourself in a design lock.
You’ll never go for the wildly awesome design because even IF you eventually think of it, your whole team will only be willing to accept designs that are comparable with the current work.
Admittedly I need to practice what I preach more in this case but I do feel strongly that top down has it here.
Looking for dependencies and starting with them first is something a programmer does. Since my whole mind has been poisoned by, um uh I mean “educated” in such a way, it probably explains why I see it this way.
In practice at least in programming I tend to run into chicken and egg situations all the freaking time, so for those projects I tend to bounce all over the place in terms of doing work, my point being, its entirely possible that any ideal solution won’t actually happen quite this way IRL.
But eh, engineers should understand that the conversion from paper to Real Life TM isn’t a straightforward process.
-Cody
I guess I can see value in both methods. However I think Cody has a very good points. Your intake design should influence how your going to lift that intake, which will influence the spacing of your base…etc…can’t really deny that logic.
Is your heart set on using those side spinners to pull in the cubes? I haven’t seen very many robots nowadays using that technique. Many designs these days are using chains with hooks on them that can grab a couple of cubes and pull them into the center area of the robot. Some simpler robots can grab a single cube and plunk it on a post using an arm with a claw or gripper of some sort.
One way to “shop” for ideas is to go to YouTube and search Vex Skyrise or, if you want to see the more advanced robots, search for Vex Skyrise finals. To get started, you can also go to some of the posts on this forum where kids have showcased their designs.
https://vexforum.com/forumdisplay.php?f=6
Sometimes you can literally count the metal holes in the photos and get some idea of the robot dimensions, linkage sizes, etc.
As others have indicated already (via expounding and debating ad infinitum their various approaches to design and building), the robot creation process is an iterative one, especially during the design and conceptualization phase.
Feel free to ask questions, even ask teams for some detailed info, including close-up photos of their designs (since some are now out of the running in competitions, they won’t be guarding their precious secrets so jealously), and don’t be discouraged by all the hair-splitting that sometimes takes place on the forum as the more seasoned members debate how many angels can dance on the head of their standoffs. 
This is very similar to the robot I used this year. Keeping in mind my cube intake was of the central flipper design rather then side rollers.
In terms of building your lift, I would look at some of the other designs for 6 and 8 bars that are currently available. If you use the standard triple diamond design then you might have some difficulties reaching a useful height.
I started with the diamond design and changed it in favor of the rectangle design. This change gave my robot an extra 10".
The robot in this video is using the rectangle design.
(This is not my robot, all credit goes to the designer of the robot)
The scoring mechanism on this robot deserves some thought as well.
While I see what some say about building top to bottom, I always go bottom to top because it makes more sense to me. Also if you are making something similar to the picture you should be able to make the drive then towers etc…
Personally I would use this method. A really quick build that would serve you well this season would be to throw an 8-12 bar lift together on an Omni-wheel chassis with the intake quoted above. I’ve seen a multitude of robots this season using this design and doing incredibly well. It’s a fairly simple design and pretty easy to construct, this late in the season I would recommend something simple rather than having to worry about lift tuning and power on a vertical lift. From my experience, you don’t have time for anything complex.
I agree. with the time you have now, you need to go with something simple like a 8-10 bar linkage or what some people call a double four bar or d4b for short. this is different from a dr4b in which one of the lifts if facing the opposite direction of the other. iv even heard it called a 6 bar 8 bar or even aulterd 6 bar.
with the time you have for a build, I would either spend it on building a good cube bot (like smiles1217 explained) or skyrise bot (a robot with an arm that makes a single movement from autoloader to skyrise base) but not both. simplicity is your best friend now. don’t go all out on your design
Definitely go with something simple!! Rebuilds at this point must be done quickly so that you have some time for testing. I have a 6-bar on my robot but it is built with almost full-length pieces and we can reach almost everything. I would consider doing something like this or an 8-bar because they are relatively simple. I would not recommend doing a scissor lift or a dr4b, just because they are harder to perfect. I like to build from the bottom up, just because it seems more logical in my mind but if building from the top down seems better to you, go for it! Do whatever you need to do to get it done good luck!
1 Like
I think the preference for top-down vs. bottom-up design depends greatly on whether you’re a highly experienced or beginning team.
Experienced designers have a strong sense of what designs are likely to be practical and an intuitive sense of what geometry issues need to be considered. Having previously encountered (and solved) problems of moving parts bumping into essential structures, they know what how the actuator will need to fit in and around the lift and chassis, sometimes without consciously thinking about it. They are capable of creating workable designs from the get-go, because they know the most obvious mistakes to avoid.
Inexperienced designers are more likely to build “pie in the sky” designs. In an attempt to think “out of the box”, their design will frequently fit out of the 18-inch cube, and they have no idea how to cram it back in. They may build a manipulator and not even know how it will attach to a lift. Or they may build a manipulator or lift but once they attach the motors, they find that the motors are constantly bumping into other structures. For them, building something simple that works reasonably well is far preferable to a complicated design that doesn’t work at all. For these teams, starting with the chassis, then moving to the lift, and finally, the manipulators is the way to go.
I think an important part of having a successful experience is being realistic about what your abilities are and maximizing what you have. For a beginner, that means going from zero to something, and for a high-level team, it means stretching to infinity and beyond.
1 Like
If you’re a beginner team you start anywhere you want, just starting is important. I once built a two speed transmission for a 12 wheeled (the enormous 5 inch heavy grippy wheels no one uses) robot I built for no particular reason other than I wanted to and thought it’d be neat.
It couldn’t turn, and the shifting stuck half the time but it worked and I learned things.
Technically I started in the middle (with the gearbox).
For a beginner team starting anywhere is A’Ok.
I usually design from the top down, but I always build from the bottom up (except for maybe some rough proof of concept prototypes) . I usually go back and forth between the sub systems making design adjustments (some people use CAD for this) until I feel ready to start building. I think the reason some people design from the bottom up is because they just start building without a detailed plan, and the chassis is the most logical place to start building. The more experienced you are, the less you have to plan ahead because things just work out intuitively
The first thing I do is make an intake or manipulator then once set on that I build from bottom up (chassis, towers, and lift) to fit around and adapt to the desired intake.
[FONT=“Georgia”]Whenever designing a robot it is important to decided what you are planning on being able to do with the robot. I highly recommend as well researching about different designs and their pros and cons. If you are on a team it is and i can not stress this enough, but it is super important to have team meetings. As a team you guys should decided how you want your robot to look. The robot should be optimized for an autonomous and efficient for the driver. Now when actually building the robot I find it is best to start with the most important element first. Some may argue which is totally okay, but this year having a tall and efficient lift was on the top of the list. But really all the subsystems should be well designed/built. Hope my little rant helped[/FONT]! :o