Typical Brake Sizing

Material Unwind Operations

Sizing Specifications
Full roll diameter (in.) (FD) = 6 in.
Core diameter (in.) (CD) = 4 in.
Average Tension (lbs.) (T) = 4 lbs.
Velocity (feet per min.) (V) = 100 fpm

Sizing Formula
Average radius (in.) = (FD+CD) / 4 = (6+4) / 4 = 2.5 in.
Torque (in. lb.) = (T) x Avg. Rad. = 4 x 2.5 = 10 in. lb.

Check Tension Range
Maximum Tension = Torque x 2 / CD (10×2 / 4) = 5 lbs.
Minimum Tension = Torque x 2 / FD (10×2 / 6) = 3.3 lbs.
Slip Watts = Max. Tens. x V / 44.2  (5×100 / 44.2) = 11.3 watts
Specify: Model SMB-12

Coil Wind Operations

Sizing Specifications
Pulley/Nip Roll dia. (in.) (D) = 6 in.
Tension (T) = 6 lbs.
Velocity (V) = 100 fpm

Sizing Formula
Torque (in. lb.) = TxD / 2 = (6×4) / 2 = 12 in. lb.
Slip Watts = TxV / 44.2 = (6×100) / 44.2 = 13.6 watts
Specify: Model SMB-12

If diameter is not predetermined, calculate slip watts and select a unit with a sufficient dissipation rating. Determine maximum diameter of pulley or nip roll using the following equation:  Max. dia. (in.)=(12 in.lb.x2) / 6 lbs. = 4 in.