Two years in development the D4 Work/Rescue descender from ISC has been released and it looks like it’s been worth the wait. Up until now there really hasn’t been a lot of choice available for Work & Rescue descenders, so it’s good to see some more options and innovations starting to appear.
|Best Uses||Work & Rescue, rope access, rigging.|
|Pros||Manufactured from all metal parts. Simple to use. Smaller than some descenders.|
|Cons||Heavier than other descenders, slightly awkward to belay with.|
So what’s different with the D4? Well its biggest feature is a unique progressive cam action that aims to give the user more precise control at slow or fast speeds. Essentially one cam operates inside another cam, and both are made from stainless steel to improve durability in the most demanding of environments and no nasty teeth to destroy your rope.
ISC has made the D4 a lot simpler to use with a handle that rotates through 360 degrees and the handle itself made from aluminium rather than plastic, so much harder to break. Audible clicks during rotation help the user identify the correct position for the handle.
The D4 has a WLL of 240kg so is perfectly suited to two-man rescues without needing any extra friction. During testing ISC discovered that when the rope is fed in over the nose (top-bobbin) it is possible to reduce friction, to aid long descents with a heavy rope below the user. The rope can also be side-fed over the lead-in.
The double-action side-plate release mechanism with push button release is easy to use even with gloves on, but very difficult to release when loaded, making the chance of accidental opening very small. The design of the side-plates mean the user can attach and detach from the rope without removing the device from their harness. A small ramp on the top plate stops the karabiner being caught between the side-plates.
Having used an ID for the last two years, I was excited to get my hands on a D4 and see what life was like on the other side of the Petzl fence. The first thing I noticed is how solid it feels compared to an ID or Rig. The decision to make the device from all metal parts and no plastic clearly means it’ll be a lot more durable, but does of course mean it weighs a little more.
Descending with the D4 is a seriously smooth experience, no annoying jolting or sudden stops at sensible speeds. Because it automatically locks when you remove your hand from the device, work positioning can be carried out a lot quicker and paranoia is reduced.
Belaying was a bit of a pain at first, but when you get used to thumbing the cam properly, it isn’t too bad.
Overall the D4 ticked all my boxes and is what I’ll be using from now on. The real thing that I noticed was the smoothness of descent, which not only makes it more comfortable, but also safer. An excellent new innovation and coming in cheaper than the ID it’s a no brainer really.
About the Author
Alex Palmer is the co-owner and founder of Cold Mountain Kit and started climbing back in 1989. He's climbed extensively throughout the UK, French Alps and has been as far afield as Yosemite, Northern Patagonia and South Africa. A total trad climbing snob.