Magnets
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.
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 with very little added mass.
Drawbacks
- Loose debris in the arena can become attracted to magnets, resulting in the robot becoming high centered.
- 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.
Safety
Even small, powerful magnets used in insect class robots can cause injury. 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.
- Keep out of reach of children. Swallowed magnets can cause severe internal injuries.
- Always be sure to clear away all materials that may attract a magnet.
- When possible, use non-magnetic tools or jigs 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 used intermittently, e.g. to hold the bot to the floor at the moment of an attack. Because of their higher weight, current requirements, and added design complexity, electromagnets are rarely used, but they help to avoid the drawbacks listed above that may cause your bot to lose matches.