[Mike Betts]

Originally Posted by jkessler_22

We're using one of the 2" and one of the 0.75" versions of these magnets: http://www.magnet4less.com/index.php?cPath=1_95 . These seemed to be the least expensive ones we found. With 3:2 gearing (gearhead:wheel), they work fine. When we tried 2:1, we need more traction, so we will probably be going larger or adding additional magnets.

Keep your distance at least 0.25" from the pole, as these are very strong Neo magnets. If you're touching the pole, your minibot won't be going anywhere. Also be careful handling them, since there is a large pinch hazard. On a flat surface, the 2" one can support 200 lbs.

One other item to consider - since these have an intergral steel cup, there may be some question about their legality. They are marketed as "cup magnets", so we think they are safe, but you might want to order some without the cup (not as strong) just to be safe.

Happy hangin' !

Joe,

Most schools would not allow neodymium magnets in the hands of a student and some schools will not allow them on school property at all!

The pinch hazard you mention becomes critical if you loose your grip on the magnet as it approaches a ferrous object (such as n EMT pole). The magnet will accelerate to very high velocities in the inch or so of "free fall" and can shatter into thousands of shards at near ballistic velocities.

A warning from Edmunds Scientific on "high quality" neo magnets sold for educational use in classrooms:

Handle with care. 2 magnets can snap together with enough force to break a finger or shatter on impact.

Depending on the size and strength of a rare earth magnet, some may be physically impossible for a human being to hold onto if it comes close to a ferrous component. I actually had this happen to me years ago. I bought a neo magnet and brought it close to a sheet metal locker at the school. The device literally ripped out of my fingers and dented the locker. It was also a real @#$$% to remove from the locker...

Mentors should monitor the handling of these devices very, very closely and teams should expect intense scrutiny from robot inspectors if these are used on a minibot (or hostbot for that matter).

JMHO,

Mike