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Lithuanian Bots
Wheel and Weapon calculator
Smart solutions for robots – faster, simpler, more efficient
Robot calculators
Work out drive speed, weapon tip speed, and how hard your robot hits. Results update as you type.
Motor & wheels
For gearmotors, use the RPM after the motor's own gearbox, at your battery voltage.
Gear ratio as a:b (e.g. 3:1), as teeth (36:12) or as one number (3). 1:1 = wheel directly on the motor.
Real robots reach about 70–85% of no-load speed. Use 100% for the theoretical maximum.
Result
Top speed—
Speed—
Wheel RPM—
Across the arena—at top speed, no acceleration
Motor RPM used—
This speed is also used for ramming and for weapon bite on the "Hit energy & force" tab.
BLDC motor & drive
Reduction as a:b, pulley teeth (36:18) or pulley diameters. 2:1 = the weapon turns at half the motor speed. Direct drive = 1:1.
100% = theoretical maximum at full charge (how tip-speed rules are usually checked). Real spinners reach about 70–85%.
Result
Tip speed—
Weapon RPM—
Motor RPM—
Voltage used—
Rotations per second—
Theoretical values at full charge. Always check your event's tip speed limit (for example, UK beetleweights: 250 mph ≈ 112 m/s).
Weapon
Uses the weapon diameter above (bar spinner: bar length). For a real part, the value from CAD is more accurate.
In CAD (Fusion 360: Inspect → Properties) read the moment of inertia at the centre of mass, about the spin axis. A beetleweight weapon is often ≈ 3×10⁵ g·mm².
Impact
Only part of the stored energy goes into the opponent in one hit. Impact distance = how far the tooth "pushes in" while stopping (dent + deflection). 2–10 mm is typical.
Result
Stored energy—
Tip speed—
MoI—
Bite per tooth—how deep a tooth can reach
Energy per hit—
Average impact force (estimate)—
Impact force depends heavily on materials and how the hit lands, so treat it as a rough comparison number, not an exact value.
Robot
Pushing force (drive motors)
Ramming hit
How far the robots squash / slide into each other while stopping.
Result
Max pushing force—
Motor force at wheels—
Grip limit—
Ramming energy—
Momentum—
Average ramming force—
Pushing force is the smaller of what the motors can give and what the wheels can grip before slipping. Ramming force is a rough estimate.
How it is calculated
Voltage = cells × full-charge cell voltage (LiPo 4.2 V, LiHV 4.35 V…)
Motor RPM = kV × voltage · Output RPM = motor RPM ÷ ratio × load %
Speed (m/s) = RPM × π × diameter ÷ 60 000
Energy (J) = ½ × MoI × ω², ω = RPM × 2π ÷ 60
MoI: disc ½ m r², ring ½ m (r₁² + r₂²), bar m (L² + w²) ÷ 12
Bite = closing speed ÷ (RPS × teeth)
Average force ≈ energy per hit ÷ impact distance
Pushing force = min(motors × torque × ratio ÷ wheel radius, grip × mass × 9.81)
Ramming energy = ½ m v²
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