# Circle base vs. Rectangle base

We have decided that we are going to try to hurdle the ball. Our biggest disscusion right now is whether to have a 28x28 circle base, or a 28x38 ractangle. What do you guys think?

It would probably be a little difficult to cover at least 2/3 of a circle base with bumpers…

Depending on what wheels you use, a circular base may/may not be moved around more than a rectangular base. In general, I’d think that a rectangular base would be more sturdy, but that could just be an opinion. However, welding and cutting a circular base would surely provide a significant problem, unless you are associated with a metal fabrication shop. But other than that, there’s really not much difference (that I can see). A circular design or two would certainly add some variety to the competition.

The further apart the wheels are, the less likely the robot is to tip over…and handling that big ball might cause problems with this.

A round robot probably has the wheels closer together than a rectangular one.

What advantage do you think a circular base will give you? What disadvantages do you think it will give you?

Have you considered other shapes? Perhaps a triangular or hexagonal base? I would think that a circular base would be harder to manufacture, due to not having straight lines. Another shape, like a hexagon, might give you a close-enough approximation to a circle to gain whatever advantage you expect to get from a circular base, while still being relatively easy to cut pieces for.

Personally, I think that since most robots will be rectangles of approximately the same dimensions, it would be nice to see some variety out there. I recall seeing one robot a few years ago (2002?), which was based on a triangular base. It had three wheels, 120 degrees apart from each other, and functioned as an omni-drive. I’ve heard of another similar drive which, in 2003, drove and turned so fast it would bank up on only 2 wheels.

ideally fewer wheels are better in that you are less likely to get caught in corners

It all depends on your manipulator. How big is it going to be? How much surface area will it take up? circular bases tend to have less area to work with. However circular bases can turn quicker. Rectangular bases have more surface area and i my opinion are easier to work with.

I don’t think a round base would be very good unless you had a lot of excess weight, if it exists, and can put a few heavy blocks in the center to keep a good center of gravity and lower weight. you could also lower the base a little too, just to help u from tipping over. in this competition, it doesn’t give you much of an advantage. if ur stuck on a circle design, but can’t fabricate it, why not try an octagon, it will make it a little bit easier and allow for the same minute advantages as well.
I personally kinda like the square base design, but only cus it allows for so many wheel options. if u do it year after year it gets a little boring, so u can round the corners or random stuff like that, but it’s probably the way to go.

one nice advantage of having a circular base is that in a game where one’s ability to maneuver in traffic will be at a premium, never getting caught on someone’s corner and the ability to always turn in place, regardless of what’s nearby could come in handy.

You cannot have a perfectly circular base. You can have an n-sided polygon that approximates a circle. This is because of the mandatory bumper rule. Bumper pieces must be at least 6" long, and must be backed by 3/4" plywood. So unless you can find some circular plywood …

A company that I used to work for made curved panels for office cubical dividers all the time. Given the concern over the eighty inch max. dimention I could easly see where a curved bumper designed so that the outer edge of the noodles is curved at the same arc as the 80" circle could become a possible solution. It would be rather easy to sandwich 1/2 plywood with grooves cut into it between outer skins of 1/8" of whatever wood product you chose.

“STANDARD BUMPERS must be designed as shown in figures 8-1 and 8-2. This is the only acceptable design for STANDARD BUMPERS”.

Looking at the quote above, figure 8-2 shows only straight bumpers. If anyone decides to construct curved bumpers I would suggest getting a Q and A answer. My guess would be that the GDC would reply with a statement along the line of: Please refer to Rule R-8 for the ONLY ACCEPTABLE design. Making curved bumpers illegal, not impossible to construct.

Boy, oh BOY is that round base alot bigger of a bite that what you may realize. I’m not sure of the size/experience of your team, but I think that you may be biting off more than you can chew. Your team MUST have machines (CNCs, mills, etc) that are capable of machining perfect circles (no matter how skilled you are with a dremel, it will NEVER happen hahahaha). Also, the bumpers will have to be curled in a perfect circle (and I dont think an English wheel will work too well with that, as it put a more spherical curve in parts). But hey, if you guys can do it, you will have my absolute amiration. GOOD LUCK!!!

I’m on the same team, and yes, I think one of our sponsors can help us with bending the metal. However, I think we have dumped the circular base. It would really only be good for a bot whose only job is to run around and score points that way.

But having a circle bot would look awesome, wouldn’t it

Its not the bending that would give you the trouble. That would be NOTHING compared to the geometry and CUTTING involved with a circular base.