Counterweight Fly System Balance
Required arbor counterweight, out-of-weight amount.
Example
You enter
- Batten pipe weight (lb) 100
- Attached load (scenery / electrics, lb) 400
- Purchase type single
- Counterweight brick unit (lb) 30
- Counterweight already on arbor (lb) 200
You get
- Required counterweight 500 lb (single 1:1)
- Out of weight 300 lb light - add
- Bricks 10
Checked against published worked examples from: Theatrical counterweight rigging (single / double purchase).
Details, formula, and sources
ScopeRequired arbor counterweight, out-of-weight amount, and bricks to add or remove to balance a batten (required = (batten + load) x purchase_ratio). A double-purchase arbor needs twice the counterweight; an out-of-weight batten is the classic fly-rail hazard.
Formula or tablerequired = (batten_weight + attached_load) x purchase_ratio (1 single, 2 double); out_of_weight = required - existing; bricks = the whole count nearest |out_of_weight| / brick_weight, with the weight left over reported.
Source and editionTheatrical counterweight rigging (single / double purchase), by name.
Free accessStandard stagecraft counterweight-balance relation; the venue rigging inspection and the AHJ govern.
What governsEstimate. AHJ and licensed professional govern.
API field namesbatten_weight_lb, attached_load_lb, purchase_type, brick_weight_lb, existing_cw_lb, required_cw_lb, out_of_weight_lb, bricks
- Purchase ratio 1:1 single, 2:1 double (double travels half the distance, needs twice the counterweight)theatrical rigging