Adjust the inputs or use + / − above. Both diagrams and equations update together.
Side diagrams are schematic. The ballast-supported outreach is a moment calculation, not a manufacturer’s permitted extension. Missing stall data leaves the result as a rated-load baseline.
Roof reactions are idealized static loads, not roof capacity or factored bearing requirements. Beam tare and its center of gravity are entered assumptions.
OSHA scaffold tiebacks · OSHA independent fall-arrest anchorage. These checks cover selected geometry and entered capacity; they do not certify the installation.
A runs from the front fulcrum to the suspension line. B runs from that fulcrum to the counterweights’ center of gravity. Extending A increases the overturning moment; extending B increases the counterweights’ resisting moment.
For the idealized powered-hoist setup:
Required ballast = max(4 × rated hoist load × A, 1.5 × stall load × A) ÷ B
Round up to whole counterweight blocks. If stall load is missing, the result is only the rated-load baseline. Beam self-weight and tiebacks are not credited toward this calculation.
OSHA 1926.451(a)(2) ↗The stage’s own weight is distributed equally between its ends. The people/tools load is represented by one movable point. Moving it toward one end increases that hoist’s load. Hoist, rope and rigging weight is added at each support.
Left share = live load × (length − position) ÷ length
Right share is the remainder. This static model assumes vertical suspension lines and end supports.
Compare each working line load with its hoist and beam limits, and the platform load with the actual assembled stage rating. Adding counterweights cannot authorize overloaded hoists, beams, platforms or racks. Capacity depends on the product and configuration.
OSHA scaffold capacity requirements ↗This mode illustrates a powered single-point chair supported by a rated suspension hoist. The manual RDS chair is in the Roof anchors & RDS lesson; its support requirements must come from its own equipment design.
Spider powered-hoist uses ↗Use specified, secured counterweights, suitable supporting surfaces, required tiebacks and independent personal fall protection. This lesson does not evaluate wind, snagging, dynamics, roof structure, local bearing, beam strength or equipment compatibility.
OSHA suspended-scaffold guidance ↗These are separate manufacturer examples for comparison. They do not identify the conceptual equipment shown or approve a combined system.
For the listed assemblies, published maximum reaches are 74 in at 750 lb; 66 in at 1,000 lb; 54 in at 1,250 lb; and 48 in at 1,500 lb.
At a 1,000 lb hoist rating and 48 in outreach, the chart lists 27, 18 and 16 of the 50 lb blocks for 16, 22 and 25 ft assemblies, respectively. Use the exact chart configuration.
Beam specifications ↗The manufacturer lists discrete section assemblies with different weights and ratings. Examples: a 5 m assembly has a 399 lb self-weight and 2,000 lb platform rating; a 10 m assembly has a 662 lb self-weight and 1,000 lb rating.
The simulator’s adjustable length is illustrative. Enter the tare and rating for the actual assembled platform; changing length does not establish a new product rating.
Platform manual and assembly tables ↗The inspected hoist manuals did not supply a numeric stall force for use here. Ask the equipment manufacturer. The OSHA ceiling of three times the rated load is not a measured stall rating.
OSHA 1926.451(a)(5) ↗OSHA 1910.27(a) directs general-industry scaffold work to the scaffold requirements in 1926 Subpart L. Confirm the equipment type and application when choosing the governing requirements.
OSHA 1910.27 ↗