The wall mounted apparatus comprises a lower stationary plate attached to a sturdy wall mounting bracket. On top of this stationary disc sits an upper aluminium alloy plate whose shaft rotates in ball bearings but which is in direct contact with the stationary plate.
Sandwiched between the lower and upper plate are three friction discs, each of different diameters. Each disc is positively located on pins to ensure they remain stationary. The minimum force on the friction disc is the self weight of the upper plate, but the contact pressure can be increased by adding weights to the upper plate.
Pure torque is applied to the upper plate through two loaded cords and pulleys. The cords wrap around a groove in the upper plate.
A set of calibrated weights is supplied which enable the loading force to be varied and applied torque to be adjusted also.