Ascending and Descending with CMC MPD

Utilization of the CMC MPD for ascending and descending as a moving brake.

[@EightiesTV]

2:43 you have created a 3:1 mechanical advantage if you are lifting yourself or a 2:1 mechanical advantage if you are getting lifted by someone on the ground. Every pound of force you pull on that rope is a pound taken off the MPD at the harness. If you + gear weigh 200lb, there is 66.7lb tension in the downline between the Gibbs and the MPD, 66.7lb tension in the upline from the MPD to the pulley, and 66.7lb tension in the downline between the pulley and your arms (while ascending). Your arms are holding 1/3rd of the weight and the harness is holding 2/3rds of the weight... Until you stop, then 100% of the weight is being held by the MPD at the harness. On the other hand, if you are being lifted from the ground, the forces are: Gibbs to MPD = 100lb (50%) MPD to pulley = 100lb (50%) pulley to ground crew = 100lb (50%) force in main line from Gibbs to anchor = 300lb (150%).

[@jeffm9227]

Correct. Richard Delaney has a video on this: kzbin.info/www/bejne/b2SkiWWXhc6VkMU

[@nohands3255]

Even if you have the strength you don't want to burn all your energy going up a 4:1 is a very viable setup

[@fredcsensits4476]

Rope going through a MPD with a double pelley on a Gibbs and a single on the MPD is a 5 to 1 according to the class I just had through CMC

[@FalenAnjel2]

So there are rescuers on the rope that can't lift their own body weight. I think their strength might lay in planning and coordination perhaps. Letting the other team members that meet to requirements would leave the nonfit bodies less likely to be injured and be able to help the P/T if they need to lift them too. It's like sending a person into the CSE and they may or not have a 2nd rescuer tailing them depending on the size and rescue level required and having to haul 200-350 lbs > worker out while only being 150lbs with adv or below strength ( so decent fit but nothing remarkable or reliable for rescue).

[@bwyo29]

Even though the load is minimal, you agree with loading one side of a double pulley?

[@jeffm9227]

It's a good observation. My guess is he is using a type G rated 40+ kN, so his body weight is negligible relative to its WLL. Still, most manufacturers don't approve their doubles for single sheave use.

[@KB-gd6fc]

That has got to be a pain in the ass to ascend any kind of real distance with. I'm sure it is possible but there are way more practical ways for a person to get up a rope... even an out of shape person. Why I don't see more frog systems in rope rescue is a mystery to me.

[@mikemccord8399]

So, did you call CMC and get the approval to use it as a decent device by chance?

[@handsomemick3558]

"The MPD is UL Classified as a Pulley, Descent Control, and Belay device," that quote is from the CMC website. Check out "CMC Rescue MPD User's Guide by CMC Rescue School Instructor video" at this time stamp. kzbin.info/www/bejne/d5evqHSNmLOrmcU