True Bobbins

Bobbins are mechanical descenders where the rope path follows the S-shaped path shown in the figure. In general the braking surface consists of two non-rotating bollards fixed to a sideplate, with a second pivoting sideplate provided to keep the rope from jumping off the other end of the bollards. A third (usually smaller) bollard may be provided. The seat maillon usually attaches to holes in extensions of the two sideplates; these holes are aligned when the sideplates pivot to the closed position.

I distinguish true bobbins from false bobbins by whether the spools (or bollards) move with respect to the frame. On true bobbins the center of the spools is fixed although the spools may rotate (on stop bobbins, the lower one usually does). On false bobbins, the center of the spools can move. I don't believe that there is necessarily any advantage of true bobbins over false bobbins or vice versa, it's merely a means of classification.

Bobbins are quite popular among European cavers, but then again, they all seem to use almost exactly the same system. This has advantages, but stifles creativity. I've used bobbins as my short-drop device, but they really don't have enough friction for my weight (I'm 1.91 m, 88 kg). They should work better for a 50 to 60 kg lightweight.

[ Additional Comments on Bobbins ]

ID Device Description Acquired Weight Height Width Thickness Std. volume

430 Austrian Rod frame, solid spools, lower spool cut & pivots on frame, noncommercial Peter Ludwig, 1991 195 143 45 40 257

434 Kong-Bonaiti Bent frame, solid spools, plastic gate Inner Mountain Outfitters, 1994 269 193 55 32 340

951 Kong Banana Curved bent frame, solid spools, aux bar, stamped gate Inner Mountain Outfitters, 2004 233 193 55 30 316

439 Petzl, double rope version A Bent frame, unfinished, 2 groove upper spool, 1-groove lower spool Al Fincham, 1981 311 194 45 41 358

440 Petzl, double rope version B Bent frame, unfinished, 2 groove spools, stamped gate Al Fincham, 1981 324 191 45 41 352

441 Petzl, single rope version A Bent frame, unfinished, solid spools Speleoshoppe, 1979 220 187 45 31 261

442 Petzl, single rope version B Bent frame, unfinished, solid spools, stamped gate Speleoshoppe, 1979 240 182 45 31 254

444 Petzl, single rope version C Bent frame, solid spools, aux. bar, stamped gate John E. Weinel, Inc., ~1987 248 195 45 32 281

443 Petzl, single rope version D Stamped frame, solid spools, aux. bar, stamped gate 1990 248 195 45 32 281

1010 Petzl, single rope version E Stamped frame, solid spools, aux. bar, plastic gate Inner Mountain Outfitters, 2006 237 197 42 32 267

450 Russian Bent frame, solid spools, aux. bar, wire gate 1994 353 195 45 32 281

929 Spider Bent frame, solid spools, aux. bar, stamped gate Inner Mountain Outfitters, 2003 251 197 52 29 297

ID	Device	Description	Acquired	Weight	Height	Width	Thickness	Std. volume
430	Austrian	Rod frame, solid spools, lower spool cut & pivots on frame, noncommercial	Peter Ludwig, 1991	195	143	45	40	257
434	Kong-Bonaiti	Bent frame, solid spools, plastic gate	Inner Mountain Outfitters, 1994	269	193	55	32	340
951	Kong Banana	Curved bent frame, solid spools, aux bar, stamped gate	Inner Mountain Outfitters, 2004	233	193	55	30	316
439	Petzl, double rope version A	Bent frame, unfinished, 2 groove upper spool, 1-groove lower spool	Al Fincham, 1981	311	194	45	41	358
440	Petzl, double rope version B	Bent frame, unfinished, 2 groove spools, stamped gate	Al Fincham, 1981	324	191	45	41	352
441	Petzl, single rope version A	Bent frame, unfinished, solid spools	Speleoshoppe, 1979	220	187	45	31	261
442	Petzl, single rope version B	Bent frame, unfinished, solid spools, stamped gate	Speleoshoppe, 1979	240	182	45	31	254
444	Petzl, single rope version C	Bent frame, solid spools, aux. bar, stamped gate	John E. Weinel, Inc., ~1987	248	195	45	32	281
443	Petzl, single rope version D	Stamped frame, solid spools, aux. bar, stamped gate	1990	248	195	45	32	281
1010	Petzl, single rope version E	Stamped frame, solid spools, aux. bar, plastic gate	Inner Mountain Outfitters, 2006	237	197	42	32	267
450	Russian	Bent frame, solid spools, aux. bar, wire gate	1994	353	195	45	32	281
929	Spider	Bent frame, solid spools, aux. bar, stamped gate	Inner Mountain Outfitters, 2003	251	197	52	29	297