The higher initial cost of sash chain, compared to sash cord, is offset by the chain's longer useful life. Chain should be selected for material, load rating and size.
For many years, brass or bronze sash chain was preferred because it was less susceptible to corrosion than common steel chain. Brass and bronze sash chain are both relatively soft however, which causes problems under heavy loads. CENTURION high strength alloy sash chain, developed by Phelps Company, has twice the load carry capacity as brass or bronze sash chain, and superior corrosion resistance, making it the best choice for both new and replacement applications.
A sash weighing thirty pounds will place a static load of fifteen pounds on each of the two sash chains that suspend it. Suddenly raising, lowering or stopping the travel of the sash, however, will create an instantaneous load exceeding the normal static load by many times. For this reason, it is advisable to select chain with the highest load-rating capacity whose width will fit the pulley wheel groove.
Sash chain is manufactured in trade sizes determined by width, links per foot and gauge of material. As stated above, chain should be selected for the maximum load-carrying capacity that will fit the pulley groove.
For double-hung windows, the approximate total required amount of chain can be calculated by the following formula: (1/2 the sash opening height + 2 feet) x 4.
Weight and Pulley Design Checklist and Calculation Examples A worksheet to assist in designing a weight and pulley system for wood windows. Includes two examples showing calculations for a typical system ... read