The following CMC videos provide a good understanding of the setup and use of the MPD.
Topics not covered by the above videos
MPD as a Slack Belay
1st Method (Hand Tight Tension)
This Method comes from CMC. (see MPD User Manual Information and Video below)
To ensure proper hand-tight tension of the Belay Line (such as during edge transitions), firmly grip the load end of the rope with one hand and apply friction, so that there is no slack in the rope between the load and your hand. The other hand feeds the running end into the MPD so that the rope is unseated from the sheave tread. This will reduce rope drag on the sheave and keep the MPD from inadvertently locking up. This technique allows the operator to match the speed of the Main Line. In contrast, the technique of trying to simultaneously shuffle rope into and out of the MPD will result in a repetitious start-stop motion of the belay rope and will likely result in frequent unwanted lockups.
2nd Belay Method (AFR Alternate Method)
Animal Fire Rescue has developed an alternate Slack Belay method based on the the following conditions:
- A Slack Belay is needed.
- A TTRS is not appropriate due to the need to keep the Belay at ground level.
- The CMC Hand Tight Tension method is causing jamming or unwanted lock up of the MPD.
The AFR Alternate Belay Method maintains the T-Handle open with a T-Cup Grip, while keeping the other hand on the tail of the rope in position behind the MPD. A small S-Shaped loop of slack is maintained keeping tension off the friction plate of the MPD. This method uses the same concept as a Tandem Prusik Belay in that a small loop is kept in the Belay Line.
If a Main Line failure occurs the Belay line will be held by the friction plate of the MPD since the operators hand is always behind the MPD. In addition the operator will be able to easily release the T-Handle due to the T-Cup Grip.
AFR recommends this method be practiced and only used by trained personnel.
MPD on a Bi-Pod Support Line
The MPD on a Bi-Pod Support line is very effective but it can also be difficult. When performing a swing of the Bi-Pod with a horse or other large animal the T-Handle can be difficult to open. The following items will help mitigate those difficulties.
- Set your MA out as far as possible. This will allow you to use the MA to assist with Lowering and Raising on a swing of the Bi-Pod with out the need for resets.
- When Lowering keep the MA in place and use the extra friction bar on the MPD.
- If there is a considerable amount of force on the system pull on the Haul Line to release the presser on the MPD.
- Keep tension on the Haul Line while it is brought back to the extra friction bar.
- Pull the handle and lower.
- You may need to position yourself facing the anchor to get better control of the MPD.