Masonry Magazine April 1997 Page. 25
Towers
Towers must be manually engaged and disengaged. (Most have adopted the automatic safety device introduced by Non-Stop Scaffolding.)
Most carriages have rollers to overcome the friction against the towers when the platform is loaded with materials. Compare the size and type of rollers. They range from 2" aircraft grade aluminum rollers on stainless steel shafts, to 1 1/2" plastic rollers on plain metal rods.
How low the carriage will descend on the tower is another important consideration. If the upper platform can be lowered to within 34" above ground level, the scaffold can be erected and stocked before starting the wall. This eliminates the process of running walls up "scaffold-high" and then moving your crew. The net effect is an additional gain of one or two courses of production for every wall started.
All the systems have a base tower or stub base that supports the entire scaffold structure. They stand from 2 feet to 9 feet high. The shorter base towers are touted as an aid to erection, but all but one system can be snapped together on the ground and "walked" up 18 feet high by two or three laborers. In all cases, it's better to assemble towers on the ground and tilt them up with a forklift.
Compare x-brace locks. They range from gravity locks that be fastened one-handed, to bolts with wing nuts.
The extension towers for the various systems are available in 4'-6" to 9-0" lengths. All are somewhat ladder-shaped, but some have additional diagonal trussing that virtually eliminates racking. Compare the materials they are made of. Some use mild steel and others use high-carbon scaffold grade tubing.
Weight is not an indicator of strength (ounce for ounce, the high-carbon steel is stronger). The warranties against bending range from none to lifetime.
Elevating Carriage
The carriage physically supports the planks that constitute the work platform. It generally carries 8 planks on the upper platform, and 2 or 3 planks on the lower platform for the masons. Most come in three pieces that must be hooked together on the job. One company's carriage is made all in one piece so there are fewer parts overall.
All have a safety device built in to stop uncontrolled descent. Some
Winches
All the systems consist of a carriage that supports the work platform and climbs a tower via a winch and cable. All employ some type of ratchet, or hand-crank winch. Since the platform should be raised every 16" as the wall is built, you want the most lifting power available to keep from exhausting the laborers. Gear ratios are meaningless. To determine how powerful a given winch really is, compare how far the platform travels with each crank. Less is better. 1/2" of lift per crank is easier to turn than 1".
Winches pull the platform up the tower with a wire rope cable. Galvanized cables offer better resistance to brick cleaning solutions and the elements. There are "single-cable" and "double-cable" configurations. Double-cable is actually one cable that threads up, through a pulley, and back down to the winch. It can quickly be changed over to single-cable to let the scaffold down 65 feet in one shot, with 1/6 of the cranks it took to go up.
Some manufacturers offer two-speed winches. The idea here is to let the scaffold back down to the ground quickly once the wall is topped out. This feature can save significant amounts of labor. One company accomplishes this by using the one handle that is welded to the winch and you simply shift gears. The others require the winch handle be moved to a different shaft, or use a different handle all together. These handles have been known to get lost between jobs.
Be sure the winches have a positive device to prevent free-spinning (backlash). The winch should be made so this device must be manually held out of engagement while the winch is reversed.
Compare warranties. They range from none to ten years.