Spring rate and torque: In my spring replacement above, the wire size was d = 0.2253 inches, and the ID was 2 inches, giving a mean diameter D = 2.2253 inches. The number of coils is L/d = 24 inches / 0.2253 = 107, less about 5 dead coils on the winding cones, or 102 active coils. Thus the spring rate is K = (π*28.5*10^6 * (0.2253)^4) / (32 * 102 * 2.2253) = 31.8 in-lb/turn (IPPT). Winding 7.5 turns * 31.8 in-lb/turn yields a torque of 238 in-lbs per spring.
Screw - Screw-driven lift systems attach a long screw to the motor to move the garage door. These systems are powerful, fast, relatively quiet and require less maintenance than typical chain- or belt-driven systems. Genie and Overhead Door are two popular brands that make screw-driven systems. Based on our research of Genie’s line, you can expect to pay $244 on average for a screw-driven garage door opener.
In my case, removing and replacing the relaxed springs required that I take down the assembly: torsion shaft, lift drums, and bearings. Doing that requires unbolting the center bearing plate from the wall, removing the drums from the shaft, and finally sliding the shaft back and forth out of the end bearings to remove the whole assembly off the wall. I am fortunate to have a lot of clearance in this garage to make the disassembly simpler. Tighter clearance to walls or ceiling would make disassembly a more difficult manipulation.
Install the stiffening strut on top of the top section of steel doors with the section lying flat. Then install the opener bracket that replaces the center bracket between the top two sections. While you’re working on the sections, protect them from scratches by putting carpet scraps on top of your sawhorses. Now, slide the rollers into the roller brackets.