Magnets

Two Magnet Assisted Bots Battle

If permitted in the rules of the competition, magnets may be used in combat robots.

• If the arena floor is a ferromagnetic material like iron or steel, you can increase the apparent weight of the bot by having it pull itself down with magnets, making it harder for other bots to lift, push, or flip. Remember that when deployed, these make your drive motors work much harder! Conversely, magnets might help a lifter or suplex bot to get "solid footing" for a better grip when grappling. Consider any benefits or challenges related to your bot's weapon.
• It is possible to use magnets to attract steel parts on other bots. If you become stuck and can’t release the other bot, though, you may draw a forfeit or a loss.

This calculator may be useful for force estimates.

Permanent magnets

Rare-earth neodymium magnets are extremely powerful and can provide a significant advantage to a robot. If used on the bottom of your bot to add downforce the robot can have the pushing power of a much heavier robot. Also, with the increased down-force but no extra mass, robot acceleration can increase dramatically if the motors can provide the needed power. There are drawbacks to using permanent magnets. Loose debris in the arena can become attracted to them resulting in the robot becoming high centered. Another drawback is that these magnets attract all the time which can make safely handling the robot challenging, especially in larger robots.

• Safety: The powerful magnets used in robot combat are not like the ones you've used to stick things to your refrigerator. They are very powerful and even the relatively small ones used in insect class robots can cause injury. While small magnets may cause painful pinches or small cuts the larger magnets are truly dangerous and special care must be used when working with them. The magnets can move suddenly and unexpectedly and can crush an unlucky hand that gets between them.
  • Always be sure to clear away all materials that may attract a magnet.
  • When possible, use a non-magnetic tool or jig to move and place the magnets.
  • If others will be close to or moving your robot, inform them of the dangers.
  • And above all use common sense. While sharp edges are obviously dangerous, the dangers of large magnets can be largely hidden and easy to forget.

Electromagnets

A simple coil of insulated wire around a suitable core material makes an electromagnet. Typically these require a lot of power and are typically used intermittently, e.g. to hold the bot to the floor during an attack. Because of their weight and added design complexity, electromagnets are rarely used but can be useful when your design benefits from the magnetic forces being turned off.