Glass Weight and Suction-Cup Lifter Count
Glass weight and the suction-cup lifter count it takes.
Example
You enter
- Lite / unit area (ft²) 32
- Total glass thickness, all lites (in) 0.5
- Safety factor over the cup figure (1 if the cup figure is the maker's rated load, which already includes its design factor) 4
- Per-cup capacity (lb): holding capacity, or the maker's rated load with factor 1 150
- Glass weight (lb/ft² per in) 13
You get
- Glass weight 208 lb
- Suction cups 6
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Scopeweight = area x thickness x density (~13 lb/ft^2 per in for soda-lime); cups = ceil(weight x safety factor / cup working load). A 4 x 8 ft insulated unit with a half-inch of total glass weighs 208 lb and at a 4:1 factor on cups holding 150 lb raw needs 6 cups (on cups RATED 150 lb, which already include the maker's design factor, enter 1: 2 cups); a monolithic 1/4 in lite of the same size is 104 lb and 3 cups. The cup's rated load and its design factor come from the lifter manufacturer; a competent person and the rated lifter govern the pick.
Formula or tableweight_lb = area_sf x glass_thickness_in x glass_density_psf_in; cups = ceil(weight_lb x safety_factor / cup_wll_lb).
Source and editionSuction-cup lifter identity by name (glass weight from area x thickness x density; cups from weight at a safety factor over the cup WLL); first-principles arithmetic.
Free accessThe weight and count arithmetic is public first-principles; the safety factor and cup working load come from the lifter manufacturer.
What governsEstimate. AHJ and licensed professional govern.
API field namesarea_sf, glass_thickness_in, safety_factor, cup_wll_lb, glass_density_psf_in, weight_lb, cups
- Glass density ~13 lb/ft^2 per inch of thickness for soda-lime glassglass properties
- Safety factor / cup WLL a factor on the raw per-cup holding capacity; 1 on a maker's rated load; the lifter manufacturer governsANSI/ASME lifter rating