It may be dangerous to generalize, but spools provide the smoothest operation of any descender class. This is one reason that spools are the preferred lowering device for the ascending races at the NSS convention each year. Their disadvantages offset their advantages, and they are seldom used for caving. The biggest problem is their weight, and to a lesser extent, their size. They are also incremental friction devices at best, since one can only change friction by changing the number of loops that the rope makes around the spool. Some designs allow this to be done on rope, others do not.
Some spools are susceptible to having the rope come off if the user is not careful. I've marked the worst offenders with a warning icon.
|579||Cuddington Spool||Chrome-plated steel spool, guide coils||John E. Weinel, Inc., 2000||1272||225||129||92||2679|
|1268||Drum||Bronze spool ,fixed & pivoting side plates, pivoting guide arm with screw lock.||Julian Turner, 2010||699||157||106||72||1210|
|418||Forrest Rope Rider
||Al tube on steel frame, Al rope retention pin||John E. Weinel, Inc., 1985||412||219||122||39||1042|
|419||Forrest Rope Rider Jr.
||Al tube on steel frame, Al rope retention pin||John E. Weinel, Inc., 1985||300||170||76||39||504|
|420||Garre A. Connor
||Al spool and 3 Al bollards mounted on Al back plate. Noncommercial.||John E. Weinel, Inc., 1985||719||300||91||57||1556|
|550||Lewis Spool||Steel tube /w welded steel bar eye arm and rope guides. Noncommercial.||Warren Lewis, 1998||1462||272||114||142||4403|
|424||Rappel Hammer, Version A
||Galv. pipes welded in "T" shape, with end plate rope guides. Noncommercial.||Dr. Gary D. Storrick, 1991||1957||250||160||110||4400|
|1071||Rappel Hammer, Version B
||Hammer shaped, 1018 steel Noncommercial.||Dr. Gary D. Storrick, 2007||2263||340||82||75||2105|
|1240||Steinke Spool||Steel spool, 1 welded and 1 rotating bolted arm, wide flange, no guides||Ted Steinke, 2009||849||214||103||79||1730|
|427||Storrick Spool||SS spool, SS arm /w eye, SS guide coils, rope retention bolt. Noncommercial.||Robert W. Storrick||1264||170||108||113||2075|
|1137||University of Virginia Rappelling Log||Wood spool bolted between angle-iron sides, cold shut eyes||Dwight Deal, 2007||1927||304||204||78||4851|
|1281||Unknown||Al spool, 2 guide pins, 2 arms, cold shut tie-ins||J. W. Jackson, 2011||803||177||113||82||1639|
|423||Vertical Supply Rappel Tube||SS tube sliding on SS shaft /w eye & rope guide, two vertical pin guides, cooling sponge||Vertical Supply, 1993||498||145||112||49||796|
|422||Vertical Supply Rappel Tube Prototype||SS tube sliding on SS shaft /w eye & rope guide, two horizontal pin guides.||Vertical Supply, 1994||438||168||84||100||1411|