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Permalink Reply by Jason Brooks on March 31, 2009 at 6:40pm

The Petzl I'd is the same type of idea, lot less money too. The I'd is gaining popularity very quickly.

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Permalink Reply by Joe Smith on March 31, 2009 at 10:42pm

I am very familiar with the ID, just trying to get the feel for how they compare. I would like to know if anyone is actually using it, or is everyone just going with the ID?

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Permalink Reply by SkydiverBC on June 29, 2011 at 6:37pm

I know this is an old post, but the CMC MPD only became available about a year ago and recently they released an 11mm version as well. I have also used the ID on several occasions. Last weekend I finally got my hands on an MPD and tried it out on a series of raises and lowers. The MPD is an amazing piece of engineering. Simple and easy to use, switching from a raise to a lower is easy - do nothing! I know you can haul through an ID, but there is a significant amount of friction added by the ID. There is no more friction from a MPD than a regular pulley.
I find the ID is very touchy when not loaded (as a belay for example). As you feed (or push) rope through the ID, if there is ANY pull on the load side it locks instantly. At first, one would think that is a good thing. I find it very annoying. The operator tends to leave the belay with more slack than they should to ensure the ID does not load. If the belay line is allowed to take 10% of the load, then the handle can be used with grip strength to control the feed of the belay. As a DCD, it works better but does put some twists into the rope.
The MPD allows quite a bit of room for the rope to pass through it when not loaded. This allows the operator to provide a lot of rope very quickly if needed and makes for easy operation. Even with a slight (very slight) load of the belay rope, the MPD will not lock up like the ID does. This allows the operator to keep the rope tighter as it is less likely to lock accidently. As a loaded belay, it operates the same as the load line. Lots of control, easy to rig, and as a load increases, pressure on the control dial increases. For example, if operating a loaded belay with 10% of the load and a load line failure occurs, the sudden load increase will pull the braking foot farther into the device twisting the control dial in the operators hand quite suddenly. It does not go far enough to injure the operator, but it does prevent the belay rope from continuing down the mountain/building.
What actually causes the MPD to grab a rope? The sheave only turns in one direction. This makes hauling very efficient. In the other direction, the sheave stops turning. With a little force applied to the sheave, it will move in the reverse direction but it rotates the braking shoe with it squeezing the rope between it and a friction plate. This stops the rope. As soon as the rope gets loaded, it digs into the sheave tread forcing the sheave to rotate backwards engaging the brake. It works extremely well.If the rope is not seated in the tread it will not lock the brake making for easy rope passage through the device when not loaded.
Yes this is a price piece of hardware, but when you see how much work went into building it, I think you will understand the price. I think in a few years, everyone will be using this device. It's amazing. - No, I do not work for CMC, LOL.

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