An underhung trolley carries a hoist along a runway beam while the hoist raises and lowers a load. This calculator illustrates a simplified vertical-load balance only.
Considering a separate actuator-driven linkage
The wheel-load comparison below cannot select an actuator or replace the rating of a hoist. For a separate actuator-driven linkage, force and stroke must be checked through the complete motion using the actual mounting geometry.
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.
Traveller Hoist Interactive Calculator
Enter trolley-and-hoist mass, suspended mass, a user-selected total-load multiplier and the assumed number of equally loaded wheels. Results are an ideal vertical-load illustration, not a runway or hoist design check.
Equation Used
- Vertical gravity force uses standard acceleration g0=9.80665 m/s^2.
- The entered multiplier is a user-selected load-case assumption, not a prescribed impact factor.
- All entered wheels remain in contact and share the vertical force equally.
- The suspended load acts centrally with no side pull or horizontal force.
- Beam capacity, flange bending, deflection, trolley rating, braking, end stops, dynamics, fatigue and safety factors are not checked.
Underhung Trolley and Hoist
A trolley supports a hoist and rolls along a runway. The hoist provides vertical lifting while trolley travel provides horizontal positioning along the beam. Rated equipment, compatible components and a properly engineered supporting structure are separate requirements.
The animation shows four schematic wheels. The calculator can divide an assumed vertical force among four, six or eight wheels, but it does not model the actual contact pattern.
What This Calculator Does
The tool adds the entered trolley-and-hoist mass to the suspended mass, converts that mass to force using standard gravity, applies an entered multiplier, and divides by an assumed count of equally loaded wheels.
It is useful for checking arithmetic and understanding the equal-share assumption. It is does not show that a hoist, trolley, runway, beam flange, connection or building structure is adequate.
Assumed Vertical-Load Arithmetic
F_total = m_total g0 K
F_wheel = F_total/n
kgf equivalent per wheel = m_total K/n
g0 is 9.80665 m/s², K is the user-selected multiplier and n is the assumed number of equally loaded wheels. Kilogram-force is shown only as a force-unit equivalent.
Worked Arithmetic Example
For 80 kg of trolley and hoist, 1000 kg suspended mass, K=1.25 and four assumed equally loaded wheels, the entered total mass is 1080 kg. The assumed total vertical force is about 13.24 kN and the ideal equal wheel force is about 3.31 kN, equivalent to 337.5 kgf per wheel.
Model Boundary
- Calculated: mass sum, standard-gravity force, entered multiplier and equal division.
- User assumption: the multiplier and count of equally loaded wheels.
- Not calculated: rated-load compliance, dynamic amplification, acceleration, skew, side pull, eccentricity, wheelbase reactions, loss of contact, local flange stress, beam bending or deflection, connections, stops, braking, fatigue, inspection or safe operation.
Frequently Asked Questions
Is the multiplier a code-prescribed impact factor?
No. It is an entered load-case assumption.
Does each wheel always carry the same force?
No. Equal sharing is an idealization; real reactions depend on geometry, contact and stiffness.
Does the output approve a runway beam?
No.
Is a 125% load test the same as this multiplier?
No. OSHA discusses test loads in a specific regulatory context; the calculator does not prescribe or simulate a test.
What is rated load?
OSHA defines it as the maximum load for which the crane or individual hoist is designed and built by the manufacturer and shown on its nameplate.
Can the calculator establish safe working load?
No. Use manufacturer documentation, applicable standards and qualified engineering review.
References
- OSHA 29 CFR 1910.179: definitions for rated load, runway and trolley-related crane provisions; rated-load test requirements within its scope.
- OSHA interpretation on load testing of underhung trolley/lifting devices and scope limitations.
- NIST Guide to the SI: standard acceleration of free fall, 9.80665 m/s².
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