The Calculator gives the mass and moment of inertia (MOI) of a rotary weapon made up of tubes, disks, and rectangular bars of known dimensions and material densities - and the MOI of impactors of known mass and distance from the rotational axis.
You may combine elements sharing a common rotational axis to make up more complex shapes:
Full-body Spinner - a tube plus a top disk
Drum Spinner - a tube with two end disks [enter as one double-thick disk]
Egg Beater - a pair of impactor bars plus two end bars [enter as one double-thick bar]
If you know the MOI for a complex or asymetric weapon designed with CAD software and wish to use only the spin-up features of the calculator, enter the MOI directly into the 'Asymetric' input box in the 'Weapon Elements' section and skip the dimensions.
Fill in the blue boxes in the 'Weapon Elements' section of the calculator as appropriate for your design and click on the red 'Calculate' button.
The Calculator provides the kinetic energy storage and approximate spin-up time for the weapon when powered by a specific PMDC electric motor. The default motor speed and stall torque specifications are for an AmpFlow F30-150 motor at 24 volts.
The Calculator models weapon spin-up for brushed Permanent Magnet Direct Current (PMDC) motors using their characteristic linear torque curve. A brushless motor has a non-linear torque curve because the motor controller software reduces current at low motor speeds.
A very rough approximation of a brushless stall torque value suitable for the calculator can be obtained from the voltage and specifications commonly available from the motor manufacturer: RPM per volt (Kv), and internal resistance (Ri). Fill in the blue boxes below and click 'Solve'.
Conversions between english / metric units are available in the section below the motor data inputs. Type a value into any field and click 'Convert' to obtain the value in the matching field above or below.
What do these numbers mean? How much kinetic energy is enough? How quickly should your weapon spin-up? Is crazy high RPM a good idea? See the Ask Aaron Spinner Weapon FAQ.