BIZOMAT 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. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Total moving mass
- What it is
- Total moving mass: the crane, trolley or transfer car plus the heaviest load it carries.
- Units and format
- Enter a number in kg: kilograms. The form accepts 0.000001 kg to 10000000 kg. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20000 kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Number of wheels
- What it is
- Total number of wheels, assumed to share the weight equally.
- Units and format
- Enter a plain number with no unit. The form accepts 2 to 64. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Number of driven wheels
- What it is
- Number of wheels that are driven; only their share of the weight gives traction.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 64. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The adhesion limit rises in proportion to the share of wheels driven.
What this means: Wheel diameter
- What it is
- Diameter of the wheel tread that runs on the rail.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 5000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger wheel lowers the running resistance and the wheel speed.
What this means: Coefficient of rolling resistance
- What it is
- Coefficient of rolling resistance expressed as a lever arm: the effective offset of the rail reaction ahead of the wheel centre.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 50 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- A length in millimetres, not a dimensionless coefficient.
What this means: Wheel bearing bore
- What it is
- Bore of the wheel bearings: the diameter at which bearing friction acts.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 80 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Bearing friction coefficient
- What it is
- Friction coefficient of the wheel bearings referred to the bore diameter, from the bearing maker.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 0.2. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.005 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Flange and skew allowance
- What it is
- Multiplier on the running resistance for wheel flanges rubbing the rail and for skewing of the carriage.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 3. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.3 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Running resistance is proportional to it.
What this means: Travel speed
- What it is
- Travel speed of the carriage along the rail at full speed.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 1000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 40 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Motor power rises in proportion to speed.
- Get it right
- Metres per minute, not metres per second.
What this means: Acceleration
- What it is
- Acceleration of the carriage when starting from rest.
- Units and format
- Enter a number in m/s²: metres per second squared. The form accepts 0.000001 m/s² to 5 m/s². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.2 m/s² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The accelerating force is proportional to it.
What this means: Rotating mass allowance
- What it is
- Multiplier on the accelerating force to allow for the inertia of rotating parts such as the motor, gears and wheels.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 2. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.1 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Wheel–rail adhesion coefficient
- What it is
- Adhesion coefficient between the driven wheels and the rail, which limits traction before the wheels slip.
- Units and format
- Enter a plain number with no unit. The form accepts 0.02 to 0.8. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.15 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Wet or contaminated rail gives less adhesion; use the worst condition expected.
What this means: Drive efficiency
- What it is
- Efficiency of the drive gearing between the motor and the wheels, from the gearbox maker.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 20% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 90% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Motor power is inversely proportional to it.
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