There are several horseshoe "magnetron" magnets in the department, with 4 cm pole piece diameter and about 5 cm gap. These will slow the disc from 1500 rpm in a few seconds. The "monster magnet" in cabinet D in 302 will bring the disc to a halt in 2 or 3 seconds -- beware of reaction forces. Note that the base of the disc motor MUST be clamped to the table if you run above 1000 rpm.