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Version A
Version B /w Spool Bars
Version C /w Rack Chock
MegaRack
Rollerbar Rack
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| Version A | Version B; /w Spool Bars |
Version C /w Rack Chock |
MegaRack | Rollerbar Rack |
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| Front View | Rear View | Side View |
I acquired this rack from Robert W. Storrick in the early 1970s.
Version A is 346 mm. tall, 70 mm. wide, 25 mm. thick, and weighs 713 g. The frame is made from 9.5 mm. 328 stainless steel hot bent into shape, with an internal width of 37 mm. and a 23 mm. diameter coiled eye. There are six 6061-T6 aluminum brake bars. The top bar is made from 19 mm. square stock and is 73 mm. long. The remaining bars are round, 19 mm. in diameter and 70 mm. long. Allowing 45 mm. for the rope gives a 68 mm. for spreading the bars.
I had a number of racks made in the early 1970s, and gave away a number to people in the Pittsburgh area. Note the bevel on the end of the eye coil. The first batch had this nice touch; it helps keep the rack from catching on clothing, etc.
The top bar is square for a simple reason: I had a supply of 6061-T6 bar stock that I used to fashion new bars as old ones wore out. This rack saw a lot of miles….
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| Front View | Rear View | Side View |
I acquired this rack from Robert W. Storrick in the early 1970s.
Version B is 368 mm. tall, 70 mm. wide, 23 mm. thick, and weighs 723 g. The frame is made from 9.5 mm. 328 stainless steel bent into shape, with an internal width of 36 mm. and a 23 mm. diameter coiled eye.
This rack originally had six 6061-T6 aluminum brake bars. The bars were 19 mm. in diameter and 73 and 70 mm. long. Allowing 45 mm. for the rope gave a 98 mm. for spreading the bars. I later replaced the first and fifth bars with spooled brake bars.
Horton H. Hobbs III described the spooled brake bars in The Nylon Highway #25 in 1988, but he attributes the design to Buddy Rogers in early 1970. I made my pair in 2004, with some slight changes to the design to suit my own preferences.
I turned the top bar from 1.25" (31.9 mm.) 6061-T6 rod. There is a two-groove spools on one end of the rack (13 mm. semicircular grooves) and a 16 mm. carabiner hole on the other end. The rack in Horton’s article appears to have a 19 mm. bar diameter, but I followed Horton’s recommendation and made mine 25 mm. I also included ideas from Ed Seaman’s brake bar design (The Nylon Highway #9) and included a turned groove to keep the rope centered.
The lower spool bar has only one groove and no carabiner hole. I made the bar portion 19 mm. in diameter. The resulting bar weighs 69 g.
The completed rack with the spooled brake bars installed is 346 mm. tall, 127 mm. wide, 32 mm. thick, and weighs 822 g. Allowing 45 mm. for the rope leaves 92 mm. for spreading the bars.
Horton showed a five-bar rack in his article, but I included a sixth bar for better control. Of course, this eliminates much of the reason for having the spooled bars in the first place, since the upper spool was designed to increase friction on rappel. Not only do they provide a greater braking angle, but looping the rope over the top spool tends to lift the lowest engaged brake bar, providing the same "power brakes" effect that one has with the J-Bar. The spools can also be used to tie off. If one follows the pattern laid out in Horton’s article, the lower spooled bar should be in the fifth position, not the sixth, so that the rope acts to close the bar.
The carabiner hole allows one to clip a chest harness to the bar to keep from falling over backward on rappel. This is not strictly necessary, since one could also clip to the rack frame. A better solution for many people is to go on a diet and lose upper body weight.
I relieved the unstressed side of the bar holes so that they would pivot on the back side of the rack frame. This reduces the likelihood of the bars being knocked loose.
The spool bars add over 100 grams to the rack. The top bar is particularly heavy - about 128 g, similar to many Figure Eights. Worse, the bars make the rack considerably wider, which makes it more difficult to pack. Ironically, one of the benefits of spooled brake bars is that they allow shortening the rack by one bar to save weight and bulk. There is a tradeoff, and each person can form their own opinion, but mine favors a standard rack.
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| Front View | Rear View | Side View |
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| Front View of Rack Chock | Top View of Rack Chock |
I acquired this rack from Robert W. Storrick in the mid-1970s.
Version C is 366 mm. tall, 70 mm. wide, 23 mm. thick, and weighs 707 g. The frame is made from 9.5 mm. 328 stainless steel bent into shape, with an internal width of 37 mm. and a 25 mm. diameter coiled eye. There are six 6061-T6 aluminum brake bars. The bars are 19 mm. in diameter and 67 mm. long. Allowing 45 mm. for the rope gives a 96 mm. for spreading the bars.
I made two rack chocks in February 2005 from a piece of 316 stainless steel - it is easier to make two than to only make one. Instead of making a new rack, I used this rack to demonstrate the rack chock. My rack chocks are each 15.5 mm. thick and sized to tightly fit this rack’s frame. Once I installed the rack chock, I used a hammer to crimp the groove closed on the rack frame to keep the rack chock from falling out.
This is another version of the racks I had made in the early 1970s, this one coming from the second batch. This one does not have the eye bevel. The eye was bent cold.
I have to thank Warren Anderson for bringing the Rack Chock to my attention. He sent me an email saying,
In about 1980 a bunch of us were exploring some alpine caves in Wyoming including Columbine Crawl. I think that a caver from Idaho Falls named Rick Rigg invented this device - at least he had a friend that owned a machine shop and manufactured these. Most of us used this device in those days. It’s a doughnut turned out of hard steel and then sawed in half. It’s quite abrasion resistant. This one has been in my rack since then and has never worn out. The great things about it are that it effectively makes your rack longer and that it centers the rope…[T]he rope goes through the notch in the chock. On my rack this makes it about 7/8" longer.
This is a really wonderful invention. I've always been surprised that it hasn't caught on or that someone else hasn't thought of the same idea.
What surprised me is that Rick Rigg is the caver that got me into the NSS back in 1971. He and I caved together in Wyoming around 1980 as well, but I don't remember seeing his rack chock. Perhaps I saw it and just forgot? I can't believe that!
I made a pair of rack chocks, as follows:
Warren is correct about the rack chock wearing well, and about its effectively making the rack longer. One down side of the rack chock is that stainless steel is not a great heat conductor compared to aluminum. I may make an aluminum version someday to test it for wear. Another, more serious defect is that it is only designed for single-line rappels. Of course, if one needs to rappel a doubled line, they can simply bypass the rack chock.
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MegaRack|
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| Front View | Rear View | Side View |
My father Robert W. Storrick had this frame made for me in in 1977. I then borrowed the third bar from Storrick Monster Rack, Version A, and made the remaining bars myself.
The MegaRack is 400 mm. tall, 87 mm. wide, 43 mm. thick, and weighs 1327 g. The frame is made from 9.5 mm. 328 stainless steel bent into shape, with an internal width of 50 mm. and a 22 mm. diameter coiled eye. There are six 6061-T6 aluminum brake bars. The bar sizes are as follows:
| Bar | Desired Relative Bar Size (#3=1.00) |
Thickness | Height |
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| 1 | 1.19 | 25 mm. (1 in.) | 32 mm. (1-1/4 in.) |
| 2 | 1.68 | 25 mm. (1 in.) | 41 mm. (1-5/8 in.) |
| 3 | 1.00 | 25 mm. (1 in.) | 25 mm. (1 in.) |
| 4 | 0.59 | 25 mm. (1 in.) | 19 mm. (3/4 in.) |
| 5 | 0.38 | 19 mm. (3/4 in.) | 19 mm. (3/4 in.) |
| 6 | 0.14 | 19 mm. (3/4 in.) | 19 mm. (3/4 in.) |
The second bar has a locking tab mounted on a 1/4-20 UNC stainless steel bolt with a wing nut. The rack has 25 mm. tall, 19 mm. square spacers between the top and second bars. Allowing 45 mm. for the rope leaves 97 mm. for spreading the bars.
This is a specialty rack that I designed in 1977. My idea was to design a rack where the size of the bars was proportional to the amount of heat that they would absorb during a long rappel. I described the analysis in an article Design of Specialty Racks in The Nylon Highway #9.
The last two bars needed to be made larger than the theoretical size based on thermal calculations. The rope groove on the top bars are not circular - instead, they are shaped to distribute the heat input into the bar better. Fortunately, the rope tends to wear the bars while maintaining approximately the right shape.
I've used this rack on 250 meter drops without cooling it with
water. At the bottom, the bars were cool enough to lick without
burning my tongue (but they tasted like aluminum). Because of
its excellent (and well-designed) thermal properties, this rack
deserves a star.
I try not to laugh when I see people use an oversize bar on their rack, but put it in the top position. Not everyone understands that the second bar receives more heat than the top one, because the rope bends more around the second bar.
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Rollerbar Rack|
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I made this rack and the roller bars in 2022.
This Rack rack is 455 mm. tall, 70 mm. wide, 38 mm. thick, and weighs 1471 g. equipped as shown.
The frame is made from 9.5 mm. 1018 steel bent into shape, with an internal width of 35 mm. and a 25 mm. diameter coiled eye. The top four bars are experimental roller bars milled from a 27.5x11.4x11.5 block of Fortal (7075). Each supports a 8x22.5x14.5 mm. stainless steel deep U-groove track roller bearing riding on an 8 mm. stainless steel steel pressed into place. The bottom bars are assorted commercial bars in various sizes.
The second standard bars are stamped with the SMC logo while the third and fourth are stamped "SMC." The other bars have no markings.
Everyone knows that a rope running through a device generates friction, and that the rubbing friction is reasonably approximated by the snubbing formula T1/T2=e‑μθ with everything having the obvious meanings. Less well appreciated is the internal friction generated by bending the rope. The idea behind this rack is to utilize this friction to dump heat into the rope and reduce the tension difference on the top friction bar to reduce its heating. Using information obtained testing my Roller Rack and considering practical limits in rack lengths, chose using four roller bars and designed them for 11 mm. rope. Six standard bars ensure that the rack will have a normal 6-bar rack's friction, even if the roller bars provide none.
The effectiveness of the roller bars is highly dependent on the rope being rappelled. They are most effective on very stiff ropes such as PMI Pit rope. I sized the bars for 11 mm. rope, and the roller bars should touch while in use, if possible. On thin, highly flexible ropes, the roller bars provide no benefit. Four roller bars do not provide as much bending braking as I might like, and I would consider replacing one of the standard bars with a fifth roller bar, had I made one.
The top two standard bars are arranged in order of decreasing diameter. This is not the normal arrangement, but makes sense in this context because the bottom roller bar increases the friction angle over the top bar compared to what the top bar sees on a standard rack. The top standard bar here will see the most heat input, while on a standard rack that would be the second bar.
[ Top | Version A | Version B /w Spool Bars | Version C /w Rack Chock | MegaRack | Rollerbar Rack ]
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