Does anyone know if teams can put dead weight on their robots in order to control/refine their center of mass?
You can put any kind of ballast you like, as long as it follows other robot rules. For example, you cannot use spare robot batteries for ballast. But chunks of steel, etc are fine as long as they are secured safely to the robot.
I don’t believe that anything specifically forbids it, as long as it’s well secured and not a safety hazard. I recall multiple teams tying down spools of wire in their robot last year as a quick way to add weight.
You should be fine as long as others have said don’t break the rules, no extra battery, keep your weight under 125 lbs., etc.
In 2018 our team literally added weights to the robot to bring it up to 120 lbs.
When I was inspecting last year, one of the other inspectors disallowed ballast that could spill out onto the field. It was either a bag of bb’s or a bag of pennies.
Make sure the weight is secure. We added weight at one of our events and the inspectors weren’t a huge fan of our last minute double stick tape and zip ties holding it on. For future events we created weights that we could screw in to our frame rails.
We did this to help keep the robot balanced, and make sure we had sufficient weight on the rear of our robot to pull ourselves onto the platform.
If you do this, make sure you do it in a way to comply with i3 and i4. You should bring all your ballast to your initial inspection and get inspected and weighed with it in enough variations that the inspector can be sure it won’t cause a problem. What you can’t do is get inspected with ballast and then decide to also some on later without getting reinspected.
One year we had a removable canister bolted to the frame filled with sand. We wanted to change the weight in order to balance better. Complicated, but could have worked. We were just a young team and ran out of time to understand the complication.
And rightly so. That’s actually in the rules every year, which is why things like sand for ballast aren’t acceptable. The ballast must be secure and unable to be spilled on the field. The relevant parts are found this year in rule R8:
j. Any ballast not secured sufficiently, including loose ballast e.g. sand, ball bearings, etc., such that it may become loose during a MATCH.
k. Exposed, untreated hazardous materials (e.g. lead weights) used on the ROBOT. These materials may be permitted if painted, encapsulated or otherwise sealed to prevent contact. These materials may not be machined in any way at an event.
That’s likely what the RI didn’t think was the case, since the bag might be split and dump it’s contents. If it had been a hard, sealed unit (like the plastic case of a weightlifting component that also has sand inside) that likely couldn’t be broken open, they’d probably have passed it.
There is a reason for the non-secured ballast rule. One year a team had a bag of shot that broke open during a match. Hundreds of BBs strewn across the field is not good for anyone, and makes a horrendous racket when vacuumed up. Stick to plates.
Last year, we bolted weights to our side rails. It was simple purchased steel. It was for making it harder for defense to push us.
If we have any weight left when we’re done building — and it looks like we’re going to — we’ll be bolting steel plates inside our frame to lower and center our CG.
You can. Last year, we used steel inserts in our bumpers to properly balance our octomeccanum base. Our bumpers weighed 15.0 and 14.9 pounds. It was very effective, and did not take up space in the robot.
Please clarify what you mean by this, bc it almost sounds like you mean physically inside the bumpers, with the noodles, which is in violation of R. 24
I’m pretty sure you can put the weights on the wood frame facing inside your robot, you would have to make sure they don’t interfere with the fit between your bumper and frame though.
Our brackets were quarter inch steel, with another plate underneath them
In Power Up we used beefy steel mounting hardware on our rear bumper that put our CG lower and farther back, to avoid tipping. It turned out to be a very important consideration.
While BUMPERS construction is very constrained, you can use whatever mounting system you want to ensure you meet R24.G:
G. must attach to the FRAME PERIMETER of the ROBOT with a rigid fastening system to form a tight, robust connection to the main structure/frame (e.g. not attached with hook-and-loop, tape, or tie-wraps). The attachment system must be designed to withstand vigorous game play. All removable fasteners (e.g. bolts, locking pins, pip-pins, etc.) will be considered part of the BUMPERS.
We also have used very robust BUMPER side mounting plates in the past. We also have used steel plate as ballast and to tweak CG. Just got a large stack inspected that brought us to max weight and then could add/remove during competition. As many have said, ensure you have a very robust mounting system for your ballast.
Last year it was allowed. At the end of competition we changed to a more defensive posture (ie the shooting mechanism broke). We added 30 lbs of lifting slabs to our ultra lightweight bot. It made us hard to move out of the way for the one spot shooters.