tension in a spring formula

{"title":"Precision Compression Helical Coil Spring SUS304 Hourglass Spring Stainless Steel","imgUrl":"https:\/\/img.chinax.com\/nimg\/85\/2b\/b5b9daa30aec7462f5bf83ce6fb5-200x200-1.jpg","attrs":{"Price":"$0.06 - $0.2USD\/ Piece\/Pieces","Brand Name":"HEZHI","Model Number":"N\/A","Minimum Order Quantity":"1000pcs","Delivery Time":"7-15 work days","Certification":"Rohs&Reach","Place of Origin":"Guangdong, China","Payment Terms":"T\/T, L\/C","Supply Ability":"10,000,000 Piece\/Pieces per Month According to the order","Packaging Details":"PE Bag with Carton Box","Product name":"Hourglass Stainless Steel Precision Bottle Coil Compression Spring","Application":"Hardware\/ automobile\/electrommunication\/ clamp\/ etc., For Car","wire diameter":"0.05mm-20mm","Material":"Stainless Steel, Piano Wire, Carbon Steel, or as required","Finished":"Chrome\/Zinc\/Nickel plating","Color":"Black, Silver, White, or as your request","Service Accept":"OEM; ODM"}}