Combat Robot Spinner Weapon Kinetic Energy Calculator Help File

Combat Robot Spinner Weapon Kinetic Energy Calculator Help

Run Amok Combat Robotics

Spinner Calculator: Help File

The Run Amok Spinner Weapon Calculator performs several functions to aid a builder in the design of an effective spinning weapon. More advanced graphic analysis of spinning weapon performance is available from the Run Amok Excel Spinner Spreadsheet.

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
Hollow Drum Spinner a tube with two end disks, entered as one double-thick disk
Rectangular Egg Beater two impactor bars plus two end bars, each pair entered 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.

See: Example analyses of three weapon types

The Calculator provides the kinetic energy storage and approximate spin-up time for the weapon when powered by a specific PMDC electric motor. There are two versions of the calculator that differ in the style of motor that powers the spinner weapon:

The Brushless Motor Version emulates a non-linear torque curve to match the brushless motor controller software reduced current at low motor speeds. This version requires input of motor specifications commonly available for brushless motors: Kt (RPM per volt) and motor Ri (internal resistence). The calculator also asks for the selected battery voltage and the reduction ratio between the motor and the spinner weapon.
The default motor specifications for the brushless version are for a Turnigy Aerodrive SK3 3536-1200kv Outrunner Motor.

The Brushed Motor Version uses the linear torque curve characteristic of manual commutation with peak torque at stall (zero speed). This version requires the no-load (free) RPM of the motor and the motor stall torque, both at the selected battery voltage. The calculator also asks for the reduction ratio between the motor and the spinner weapon.

The default motor specifications for the brushed version are for an AmpFlow F30-150 motor at 24 volts.

See also: Ask Aaron: Brushless Motor Selection

Conversions between english / metric units are available in the section above 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 weapon performance 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.

Brushless Motor Stall Torque Estimate
Voltage:	volts	Battery:	mΩ
Kv:	rpm/volt	Speed:	rpm
Ri:	mΩ	Torque:	N·m