where do you get the hanging tetra magnets? and do we need them?

you can get them from part number 5685K32
and you only need it if you plan on building the field elements to simulate the competition field.

Please note that the referenced magnet from McMaster-Carr is NOT the same as the regulation magnet that will be used on the competition fields! This McMaster-Carr magnet is rated for 38 pounds of pull. The 2005 FIRST Robotics Competition Game Team Field Elements Materials List lists the magnet to be used as Part #3G901 from Grainger. The Grainger magnet has a 20-pound pull rating. Make sure that you use the correct magnet (or one with approximately the same pull rating) to ensure similar performance when testing your robot.

Note that for reasons I do not understand, the Grainger magnet does come with a Hazardous Materials Information Sheet, which includes an admonition against shipping the magnets by air. I have never heard of any issues with ceramic magnets before, so this was news to me (and when I brought this to the attention of FIRST, it was also a surprise to them). Can anyone shed any light on this?


thanks for the insight. I’ll make sur ethe team is aware of this…

thanks again.

Dave -

Here’s a link to some good info on air shipment of magnets :

I think it’s a product of technology and post 9/11 regulations. With the drop in price of rare earth magnets, it is possible to cheaply obtain very strong magnets now. Magnets are considered hazardous material. Some foreign airports will not even accept any magnets for shipment. A company that ships magnets of any kind needs to adhere to the IATA reg’s or risk big fines. It is probably much easier and less expensive to ship warning material with every magnet - whether it actually has the potential to interfere with airplane instruments or not - than to take the risk and liability. It’s a crazy world.

That sheet explains why a few people were freaking out when we wanted to ship the magnets to Israel. Thanks for the info!


That problem probably doesn’t crop up with INTERPLANETARY shipments, does it?

You’d be surprised at how much grief magnets can cause on spacecraft.

For some scientific spacecraft, you have to use twisted pair wires, non-magnetic fasteners (titanium screws) and non-magnetic connectors (no steel allowed) in the flight hardware. Before any equipment is mounted on the spacecraft, it is “scanned” for magnetic fields. If the field exceeds 10 nanoTesla at 1 meter measurement distance, it does not pass the magnetic “cleanliness” spec - sometimes that’s a BIG problem. (BTW, the Earth’s magnetic field at the surface is about 0.5 Gauss or 50,000 nanoTesla).

Curiously, the Huygen’s probe didn’t quite meet the magnetic cleanliness spec for Cassini (but it was close). When the probe separated from Cassini on Christmas Day, the science magnetometers (magnetic field detectors) on Cassini measured the residual field from the probe. The MAG investigators were able to confirm the proper spin and separation rate for the probe.

See the story at: