An overhead travelling crane carries a hoist trolley across a bridge while end trucks move the bridge along runways. This page illustrates simple plan-view geometry only.
Resources for separate linear-actuator projects
The linked resources below concern separate FIRGELLI linear-actuator projects. They do not select a travelling-crane hoist, bridge drive or load-bearing structure. In an actuator linkage, mounting positions determine the available moment arm and required stroke.
With leverage, force is traded against travel. A bracket change that improves force can also increase required stroke, slow the output motion, or move the actuator into a poor mounting angle.
The actuator stroke should also be checked against the useful motion, not just against the visible travel. End clearance, hard stops, bracket rotation, and wire routing can all reduce the usable stroke in the final build.
- Calculate actuator force at the worst bracket angle, not just at mid-stroke.
- Check stroke, retracted length, and extended length against the mechanism envelope.
- Confirm the structure can accept the higher loads created by a stronger actuator.
For a FIRGELLI actuator application, run the FIRGELLI actuator force calculator, then compare available stroke, force, and mounting envelope in the FIRGELLI linear actuator range. If the goal is to replace an existing unit, use the linear actuator replacement finder before assuming the new actuator is a direct fit.
Travelling Crane Interactive Calculator
Enter bridge span, an illustrative transverse endpoint offset and a selected comparison denominator. Outputs are direct geometric ratios, not alignment tolerances or structural limits.
Equation Used
- Span and endpoint offset form a two-dimensional right triangle.
- Offset is a user-entered geometric illustration, not a surveyed runway tolerance.
- The selected denominator is a comparison input, not a code requirement.
- No wheelbase, rail parallelism limit, structural deflection limit or utilization approval is inferred.
- Loads, stiffness, dynamics, skew forces, wheel reactions, fatigue, connections and safety compliance are omitted.
Bridge, End Trucks and Hoist Trolley
A travelling crane bridge spans between runways. End trucks carry the bridge along those runways, while a hoist trolley moves across the bridge and raises or lowers a freely suspended load.
Actual crane type matters: ASME B30.2 addresses specified top-running configurations, while ASME B30.17 addresses cranes and monorails with an underhung trolley or bridge. This calculator does not determine which standard applies.
What This Calculator Represents
The tool constructs a right triangle from the entered bridge span and illustrative endpoint offset. It reports their dimensionless ratio, the corresponding small plan-view angle, the quotient L/R for an entered denominator and the diagonal-length excess.
These values describe geometry only. They are not installation tolerances, acceptance criteria or evidence of safe crane operation.
Direct Plan-View Geometry
skew angle = atan[e/(1000L)]
selected quotient = 1000L/R
diagonal excess = sqrt((1000L)^2 + e^2) - 1000L
L is entered in metres; e and the two length outputs are in millimetres. The ratio is displayed in parts per million and the angle in milliradians.
Worked Geometry Example
For L=20 m and e=20 mm, offset/span is 1000 ppm and the geometric angle is about 1.000 mrad. With selected denominator R=800, L/R is 25.0 mm. The right-triangle diagonal exceeds the span by about 0.010 mm.
Model Boundary
- Calculated: right-triangle ratios, angle, quotient and diagonal difference.
- User-selected: endpoint offset and denominator.
- Not calculated: allowable rail alignment, crane skew, end-truck wheelbase, wheel forces, girder or runway deflection, loads, strength, fatigue, drive behavior, braking, controls, inspection, testing or regulatory compliance.
Frequently Asked Questions
Is L/1000 a universal rail-alignment limit?
No. This calculator does not supply an allowable rail-alignment limit. Use the applicable equipment documentation and installation requirements.
Is L/7 a required minimum end-truck wheelbase?
This tool does not determine end-truck wheelbase. Span alone is insufficient to select it.
Does selected L/R equal allowable deflection?
No. It is only the arithmetic quotient for the entered denominator.
Does the skew angle predict wheel forces?
No.
Which crane standard applies?
That depends on crane configuration, jurisdiction and use. ASME distinguishes top-running and underhung scopes.
Can this calculator approve a crane installation?
No.
References
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