Cavechat.org

I was setting up my jigger and wanted to see what set up to use, so I pulled out my highly accurate hardware store fish scale to do some tests.

For weight I used a 5 gallon bucket with random stuff in it.
Up force is the force to start upward movement of the bucket.
Down force is the force at which the bucket begins to lower

Pulleys are CMI double micro bushing pulleys and PMI double becket (sp?) single pulleys.

Bucket Weight: ~27 lbs

Pulley system: 2:1 (One PMI single)
Up Force: 17 -18 lbs
Down Force: 11 lbs

Pulley system: 3:1 (One PMI single and One CMI micro double)
Up Force: 16 -17 lbs
Down Force: 5 lbs

Pulley system: 4:1 (Two CMI micro double)
Up Force: 15 -16 lbs
Down Force: 2 lbs


Bucket Weight: ~37 lbs

Pulley system: 2:1 (One PMI single)
Up Force: 22 -23 lbs
Down Force: 17.5 lbs

Pulley system: 3:1 (One PMI single and One CMI micro double)
Up Force: 21 -22 lbs
Down Force: 6.5 lbs

Pulley system: 4:1 (Two CMI micro double)
Up Force: 21 -22 lbs
Down Force: 4 lbs

I’m too lazy to figure out the loss for each pulley. For now I’m going to set the jigger up as a 3:1.

L.J.

Geek!

Nice info. You should try if with a person next time! My jigger also uses CMI double micros (two of them) and is rigged with 8mm accessory cord. I normally leave it pre-set for either 4:1 or 5:1, depending on which way up I use it. I've also played with the 9:1 configuration detailed on page 16 of Ken Laidlaw's Considerations for Rope Rescue (2002).

It might be interesting to duplicate your testing after switching the pulleys out for 2 inch bearing models. It's always nice to see how practical it might be (or not) to carry larger and heavier items to do essentially the same job.