KEVOS® MAKEOS · Power Transmission
Rail Travel Drive Sizing (Crane, Trolley or Transfer Car)
What force and motor does this wheeled carriage need to travel and accelerate on rails, and will the driven wheels slip?
Sizing of a rail travel drive: rolling resistance from the wheel and rail (coefficient of rolling resistance, as the rolling resistance tool) plus wheel bearing friction, a flange and skew allowance, acceleration force with a rotating-mass allowance, wheel torque and speed, motor power and the next IEC rating, and the adhesion check on the driven wheels.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Total moving mass | kg | Mass of the carriage plus its heaviest load. |
| Number of wheels | Total number of wheels sharing the load equally. | |
| Number of driven wheels | Wheels that are driven. | |
| Wheel diameter | mm | Wheel tread diameter. |
| Coefficient of rolling resistance | mm | Coefficient of rolling resistance (about 0.5 mm steel wheel on steel rail). |
| Wheel bearing bore | mm | Bore of the wheel bearings. |
| Bearing friction coefficient | Friction coefficient of the wheel bearings referred to the bore (about 0.005 for rolling bearings). | |
| Flange and skew allowance | Factor for flange rubbing and skewing. | |
| Travel speed | m/min | Travel speed. |
| Acceleration | m/s² | Acceleration when starting. |
| Rotating mass allowance | Allowance for rotating parts (motor, gears, wheels) when accelerating. | |
| Wheel–rail adhesion coefficient | Adhesion between driven wheels and rail (about 0.15–0.2 dry steel, less when wet). | |
| Drive efficiency | % | Efficiency of the drive gearing. |
Method and formulas
- Running resistance = W (f + μ_b d ÷ 2) ÷ (D ÷ 2) × flange allowance (rolling resistance W f ÷ r plus bearing friction).
- Accelerating force = rotating allowance × m a; total = running + accelerating.
- Wheel torque = total × D ÷ 2; wheel speed = v ÷ π D; motor power = total × v ÷ η, next IEC rating.
- Adhesion limit = adhesion × weight on the driven wheels; must exceed the total force.
- Example: 20000 kg at 40 m/min needs 5.2924 kN when accelerating and a 4 kW motor.
Limitations
- Level track; gradients, wind and buffer impacts need adding for outdoor cranes.
- Equal load on all wheels assumed.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size the long-travel or cross-travel drive of a crane
- Size a transfer car or trolley motor
- Check whether driven wheels will slip when starting
Who it is for
- Materials-handling engineers
- Crane designers
- Maintenance engineers
What you get
- Running and accelerating resistance
- Wheel torque, speed and motor power
- Wheel slip check
Interpreting the result
- If the wheels would slip, reduce acceleration or drive more wheels.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 165–167, 2569–2580. Topic reference; no source tables or recommended settings are reproduced.
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Open the Rail Travel Drive Sizing (Crane, Trolley or Transfer Car) calculator
