Weighted Victims Definition and Build Guide

Dear RoboCuppers,
as a follow up to the newly added re-clarification of victims in Rescue Line, we are providing you with a short document containing a simple guide on how to build a victim with offset center of mass. Note that this is not a strict rule, rather a suggestion on how to make them from easily obtainable and affordable materials. Victims that will be at the competitions may be different, depending on local organization!

In the near future we will also upload this document to our website.
We wish you all best of luck!

RCJ Rescue committee


Hey @Matej, thank you for this clarification. We just asked us this question and found the answer here thank you! But I had problems finding it over the search. I first searched with the exakt words in the rules: sphere with an off-center center of mass

Hope this post will make it searchable and helps others to find this thread!


Thank you for the guide. We made a victim using this recommended method. We added 14 grams of sand and resealed the hole. The victim does not roll unless thrown. Is that the desired outcome of this recommended method?

This is how much sand was added.

14 grams added for a total victim weight of 17 grams.

Here is a video of the victim being tossed and not rolling at all.

Edit: Filling the ball with water instead of sand helps it to roll a little bit while still having off-center center of mass.

Thank you,


Thank you for your videos! I’ll have to write a longer (and unfortunately not definitive) answer whether and which outcome is desired.
Basically, the reason this change was introduced was the following. In past competition we noticed victims rolled a lot in the evacuation zone after a minor contact or sometimes even without any contact at all. This effect was further intensified when the floor was not perfectly level, which is obviously out of everyone’s control at the time of competition. All this gave the element of luck a way to high impact. This is of course not something we want. At the same time we like the variety of solutions round victims bring so we ideally wanted to keep the spherical shape. Which then led to the designed with off center of mass, which from what I can tell from the video you executed really well.
So to answer the question “Is that the desired outcome of this recommended method?” and if the water or sand filling is better: Both are achieving the goal we wanted to achieve so I would say both are acceptable. We will discuss within the committee further and I will let you know if one is decided to be preferred.

Thank you once again for your videos, it is a great feedback to us!


Thank you for the clarification.


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