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Storrick

Version A Version B
Version A Version B

Overview


Version A
(#652)

Front View: Closed
Front View: Closed
 
Open for Rigging
Open for Rigging
 
Top View
Top View

Technical Details

I had two of these boxes made for me in late 1976 or early 1977.

My Storrick boxes are 64 mm. long, 108 mm. wide, 80 mm. high, and weighs 229 g. They are double channel chest boxes consisting of an aluminum plate, a bent aluminum channel, and two rollers mounted on a common bolt through the channel. Each roller has a turned trapezoidal channel. Two bolts with wing nuts hold the channel against the back plate. The back plate has 51 mm. tall vertical slots for attaching the box to a chest harness.

These are noncommercial boxes with no markings.

Comments

These boxes are copies of the BlueWater box, but somewhat smaller and significantly lighter. The bolt heads were turned down to a minimal button, so they do not dig into the chest. The rollers were turned so that the rope and sling do not rub against the frame. Nothing was done to address the awkward means of opening the box. I used these boxes for years, then switched to the Gossett Box once it came out. Eventually, I moved on to the Fritzke Alpine Box, and I now prefer the PMI boxes.


Version B
(#2885)

Front View Top View
Front View Top View
 
Front View: Open for Rigging Top View: Open for Rigging
Front View: Open for Rigging Top View: Open for Rigging

Technical Details

I made this box in 2021.

This box is 152 mm. wide, 66 mm. high, 49 mm. thick, and weighs 333 g.

The central post supports a press-fit 8 mm. stainless steel axle. A hidden set screw locks the axle against lateral movement.

The axle supports a stainless steel deep U-groove bearing roller wheel on each side. Outside the rollers are 6 mm. 6061-T6 pivoting side plates. Each side plate is shaped so that contact with the back plate provides a positive stop in the downward direction. An 8-32 UNC stainless steel spring plunger threaded into the end of the side plate contacts a flat milled on the axle, providing a soft lock against opening upward. The ends of the axle are threaded, and 8 mm. stainless steel washers and lock nuts hold the side plates and rollers in place.

The back plate is made from 6.2 mm. 6061-T6. It has 45 mm. tall vertical slots for attaching the box to a chest strap and 26 mm. wide horizontal slots for attaching shoulder straps.

I stamped my logo on the front of the back plate.

Comments

I thought of an interesting mechanism, and built this box to test it. The back plate should not be taken seriously, as I quickly machined it out of a piece of spare stock. I took more care on the mechanism, but since I was brainstorming rather than working from a drawing or sketch, some of the dimensions are sub-optimal. In particular, the pillar should be slightly longer so that there is a bit more clearance for the rope to enter the gates.

After making the box, I sent it to a prominent TAG caver for testing. My friend tried it on several climbs of up to 135 m. while trying to get it to fail. My friend wrote the following comments:

"My concern, since it is not a "hard lock," is that when sitting down to rest (or maneuvering at a lip) that the plate could come open and potentially release the rope. The gap is pretty tight (almost too tight) when inserting/removing 11mm pit rope, though that doesn't affect the 10mm or 9mm some cavers are now using. …Of course, this means I'll be trying to make it fail, but that is all part of testing, isn't it? Darwin will always make a better idiot no matter how much we try to make it idiot-proof"

"It seems pretty stable. The roller not hurting the rope…. I tried, during a 440' [135 m.], climb to get the rope to open the box gate. I succeeded twice, but the edge of the gate held the rope inside due to the gravity deviation of the rope. If the gate had been a little smaller, with a taller center block, a lean to the right side might have been enough. From the tree here at the house, I tried a right lean (as if to retrieve my tethered pack for a drink of water) with the gate open and my a safety ascender on. The rope popped into plate/gate gap, but not out until I really leaned into it."

The advantage of a soft lock is its simplicity. There are no external buttons, knobs, or plungers to get in the way. Although I like the soft lock, the lack of a hard lock would make this design legally nonviable in the U.S. marketplace. In practice a strong soft lock has no adverse implications for a competent user (nothing but blind luck can save an incompetent user). Having the rope or the long foot sling come out of a box accidentally is an absolutely no-never-mind if one's ascending system is set up properly. All that happens (at worst) is that you end up sitting with your weight on the upper ascender. In fact, we rely on this when "coming out of the box" at the top of a pit. That said, I would prefer a slightly stronger soft lock and I would make the necessary alterations if I make another.

I made no effort to design a proper back plate. I made this one in a few minutes using an existing piece of 6061, and did not concern myself with its dimensions.

From a weight perspective, at 333 g. this box compares favorably with other full-size double-roller boxes such as the Bassett Metal Studios, Version D (395 g.) and PMI, double rope (353 g.). With some more attention to detail and a better back plate design, I might hope to be able to make it lighter than the old On Rope 1, Lightweight Double (315 g.) and comparable to the Fritzke Alpine Box (293 g). All I need to do is eliminate 14,800 mm.3, and thinning the back plate to 5 mm. would eliminate 11,000 mm.3 right from the start.