Robot NEEDS more weight (high density preferably)

So currently, our robot weighs in at around 60 pounds. we want that number HIGHER.
our biggest priorities are lowering the center of mass for less “tippyness” as our design has approximately 40% of the weight up high, and getting as much weight as possible so were better at defense/not being effectively defended against.

Our drivetrain has a few places that are perfect for small, dense weights. but we don’t know what types of weights we should buy. below is an image of the drivetrain to get an idea of the space were working with:

the weights would go in the two rectangles on either side, and in the two triangles next to the battery. most of the weight of the robot is on the front (bottom of the image) so that’s why were thinking we’d put the weights in the back (top of the image)

our main question is this: what type of weights would be best?

we found these weights with a quick google search, but we are a little hesitant to use lead because of safety concerns.
we also considered cutting off the shelf exercise weights to fit in our space, or making a bracket for them.


Maybe a steel bellypan or three?


Chunks of steel. Not little ones, either: STEEL. BLOCKS.

Bonus if you can find them with a hole drilled into them already, but if not go slow with a drill press.


We have sponsors that were able to donate copper tungsten blocks. It’s really dense and adds about 12 pounds to our base. I’m sure you’d be able to find similar dense material by reaching out to sponsors for any excess material they may have. Uncut belly pans also add a lot of weight, I think a 28 x 28 1/8th belly pan is close to 10 lbs so maybe increase the thickness or have multiple belly pans.


Cim motors? :slight_smile:


Quikrete in a trash bag, or a cast iron cylinder head. I have seen both irl.



Slightly incorrect.

Quikrete mixed with water in a couple of trash bags. That way the hazard to health known as “concrete dust” isn’t present. Pro-tip, mix on the dry side of what they say just to make sure it sets faster.


There no specific rule banning lead being used as ballast asking for a friend?




Okay so we are good our lead is in a welded steel box encapsulated on both ends AND painted white so I think we are covered.

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I’ve seen teams just add 1-2 inch sheets of steel to the top of their belly pan. If cost is no concern, then I might suggest large quantities of this.


Cost is a concern due to the $600 COTS limit

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we just run a solid 1/4” alu bellypan + solid steel bars as ballast found on mcmaster allowing us to pretty much max out our weight

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The best weight / $ we found was barbell weights. They come in exact weight sizes and are carried at most sporting goods places.


Steel is the easiest for sure.
Probably the fastest would be to “borrow” a couple weights from the local gym and zip tie them to the drivetrain.
Alternatively, you could just grab a bunch of CIMs like someone else said.
If you’re really limited on budget but not time, look up local machine shops - There’s a good chance they might let you rummage through their scrap bins for pieces you can bolt to your robot.

The densest elements are mostly radioactive or extremely expensive, the most affordable is tungsten. For FRC purposes, though, steel is more than enough.

Also, @Zatack7, DU is radioactive which I’m fairly certain would invite very close inspection at least, if not disqualify the robot entirely. If you can get past that, I’m not even sure where you’d get that stuff, not to mention that it’s probably more expensive than other high density options


Methinks the carcasses of Iraqi tanks would be a good starting point



Rebar zip-tied in bundles or inside hollow tubes.

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Beware of zip ties. We were told that “zip ties are not rated for dynamic loads” at inspection. We had to run out and get U-bolts to hold down the dumbbells we were using as ballast.


We built the EveryBot.

We used these 2 20 pounders from Amazon. She still a little light and slightly tippy and we will probably add more small weights. But this 40 lbs was a huge improvement. I forgot to get a photo before the wood covers.

Titan Fitness 20 LB Cast Iron Ruck Plate, Weighted Plate for Rucking

We took our Bot off Jenny Craig diet…she weighed about 46 pounds on week 1…week 2 she was on fast food and gained about 20 pounds.

On the Andy Mark frame we added 4 pieces of bar stock…equal lengths and put two in the front and two in the rear. That gave us a bot that weighed 66 pounds…not including bumpers.

What this did for us was it made the Bot smoother to control…and it prevented swerve teams from pushing us around like a school yard bully!

IF you want look at match 21 in Belton for what we were able to do…We had a lot of positive feedback on it, We were driving with CIMS and standard white tires…nothing but a base bot.