Robot extension revisited - arc of motion beyond 20" plane

I teach geometry and trigonometry as well as robotics, so it was with an interested and trained eye that I watched Mr Toubans video above (which was posted in another topic he wrote entitled Robot Expansion) and those robots in the video will clearly be out of size limits as they go through an arc of motion. They Look like the same robot, two teams from same school possibly. And they are both maxing out the size limitations before the top mounted arm and tray ever begin to rotate forward and up. The video also says it is the final match which seems to indicate this is a significant round in which to have a major advantage impact the outcome of the event.

Having built and tested very similar robots, I would say there is absolutely no way those robots are in size compliance. They are starting in positions that show they are filling close to the full 20" space before the arms radial motion begins. The arm starts at 20" and then As the arm arcs upward the leading edge of the tray will be forward of 20" by close to 4.5 inches, depending on exact dimensions of the arm, tray and height of pivot point. But certainly no less than 23" extension given the rough approximations you can make from this video.

Consider the arm of a clock: it is a set radius, but as the arm rises from 7pm 9 pm the arc it inscribes makes forward progress, moving both vertically and horizontally as,it rises from the 7 hour toward the 9 hour position.

There is no chance those robots are legal based on the rules posted to this forum, specifically that a robot can not exceed 20" length at any point of its motion.

Given any basic geometric analysis, There is no way those bots arms and collector tray are staying under 20", with a design Leigh starting at 20" before the top pivoting arm swings forward and up while lifting a tray that protrudes even further.

The judges must have measured the bots in a single position but didn’t look at the range of motion.

What will be the inspection process / standard for State and World championships? Is arc of motion not to be considered?

With that design arcing well forward of 20 inches it is enabling a tray that has capacity to be picking up 8 or 9 balls at a grab, it would be hard to envision this not being a major advantage to use arc motion to exceed 20".

Thanks for clarifying.


I take this to mean you have built similar Robots on your own for fun that are completely independent of any VEX IQ Challenge teams. Or that you have have supervised students building similar robots. As we all know, adults building Robots in the VEX IQ Challenge is prohibited.

<R4> is to be strictly enforced, especially the bolded text:

Thus, the arc of motion is to be considered. The Robot must always fit within a 13" x 20 area.