General Notes

Technical Details

I acquired my John Blum, Version A box from Inner Mountain Outfitters at the 1988 Old Timers Reunion. I acquired another in 2017 as part of Bob Thrun’s collection.

My John Blum, Version A is 77 mm. long, 127 mm. wide, 44 mm. high, and weighs 256 g. It is a double channel chest box with a cast aluminum frame. The back plate has 51 mm. tall vertical slots for attaching the box to a chest harness. The roller assembly pivots at one end, and is held by a quick-release pin at the other. The rollers are nylon, with a larger nylon bushing to keep the rope and foot sling separated.

The frame is stamped "JB1A"

Comments

One thing I don't like about the Blum box is that it opens both sides at once. There is no way to open the foot sling side without releasing the main line and vice versa. For this reason, I never used this box for regular caving.

Version B
(#1879, 2710)


Front View: Closed	Open for Rigging

Technical Details

I acquired my John Blum, Version B from CarolJo Rushin-Elron at the 2016 NSS Convention. I acquired another from Bill Liebman at the 2017 Old Timers Reunion, but gave that one to Artyom Babin (Артём Бабин) in 2021.

Version B is 76 mm. tall, 125 mm. wide, and 44 mm. thick, and weighs 254 g. The rollers are different colors than those on Version A. The roller closest to the hinge is 19 mm. in diameter by 14 mm long, the central spacing roller is 35 mm. by 14 mm, and the outer roller 20 mm. by 19 mm.

The body on the one from C. J. is stamped "JB1A" and "9060." The one from Bill is stamped "JB1A" and "92040."

Comments

C. J. bought hers from Inner Mountain Outfitters at an unknown NSS Convention many years ago. The serial numbers indicate that this version was made in the early 1990s.

Version C
(3788)


Front View: Closed	Top View

Technical Details

I acquired this Blum box from Galen Hekhuis at the 2022 Old Timers Reunion.

This version is 127 mm. wide, 77 mm. high, 44 mm. thick, and weighs 239 g. It is similar to the previous version, but replaces the round holes with 30 mm. slots suitable for use with 25 mm. webbing.

The body. is stamped with "JB1A."

Comments

The webbing slots facilitate attaching the shoulder straps of a chest harness directly to the box, if desired.

Version D
(#636)

Technical Details

I acquired my John Blum, Version D from Bob & Bob at the 1993 NSS Convention. I acquired another in 2017 as part of Bob Thrun’s collection

My John Blum, Version D is 64 mm. tall, 175 mm. wide, 43 mm. high, and weighs 327 g. It is a double channel chest box with a cast aluminum frame. There is a 42 mm. tall trapezoidal opening on each side for for attaching the box to a chest harness. The roller assembly is similar to Version A & B’s but the Version D rollers are brass.

The frame of the one from Bob & Bob is stamped "JB2-9322" and the one from Bob Thrun’s collection is stamped "JB2-9339" with an inverted "B."

Comments

Version D has a larger frame and brass rollers. Even with the large cutout, Version D is 28% heavier than Version B. As far as operation goes, it is similar to Version B.

Version E
(#1899)

Technical Details

I acquired my John Blum, Version E in 2017 as part of Bob Thrun’s collection.

Version E is 177 mm. tall, 66 mm. wide, 44 mm. thick, and weighs 332 g. It is a double channel chest box with a cast and painted aluminum frame. There is a 42 mm. tall trapezoidal opening on each side for for attaching the box to a chest harness.

The QR pin is stamped with "AVA BLS3BA10S."

Comments

If you've ever mislaid a piece of gear in a cave, you should appreciate the bright orange-red color. The paint in the roller channels can wear off and leave a mess on the rope. I would scrape it off prior to use.

Other than the paint, this is essentially the same as the previous version. I prefer the QR pin on this one to previous pins as it seems to be easier to use.

Version F
(#2711)