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Puzzle Contest: Extravagant Purchase

Posted in Puzzle

Above is a very odd block-and-tackle configuration. Odd, as in has-no-practical-use. But rather than waste it, we’ve made it this week’s Puzzle: What mechanical advantage does this configuration have?

Assume that the sheaves have no friction, that all leads are parallel, and that equal force is exerted, straight down, on both tackle ends (arrows). The uppermost block will move toward the deck.

You don’t need to explain your answer in order to win, but as long as you get the purchase number right, your explanation doesn’t have to make sense, so hey, go for it.

Bonus points if you can approximate the maximum range of motion, up and down, of the uppermost block. Assume that the fiddle block is one foot long, and that the tackles end at the arrows.

Send your entry to puzzle@briontoss.com. The winner will be randomly selected from the pool of correct entries. Deadline for entries is noon Pacific time, Monday, March 19th.

This week’s Fabulous Prize is an autographed first edition of Kaci Cronkhite’s wonderful best-seller, Finding Pax. You can find out more about this wonderful book  here

Note: Painter Frank Hanavan recently posted our Puzzle’s photograph, from Petersson’s book on ship model rigging. It appears to be a nice enough book, but the image, as near as I can tell, shows a configuration that has never been found outside the pages of that book. If such is not the case, please let me know.

 

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6 Comments

  1. Steve Cobb
    Steve Cobb

    2 separate purchases. Each will result in the other going slack. Fiddle block 8 to one, 6″. Plain double 4 to one, 3′.

    March 14, 2018
  2. Dan Reasoner
    Dan Reasoner

    Dan Reasoner There are two separate lines to pull. The cascade one on the right 8:1, and the one on the left 4:1, so if you pull both lines together with equal force, I believe you add them together to get 12:1

    March 15, 2018
  3. Well it is a weird one. I counted the falls and both of the lower block combos have 4 ) “falls” I think they may be called, so it looks like they are equal, but the right one is connected directly to the halyard, throught the block, to lift the dinghy or whatever. The left “handybilly” goes to a another block that doubles the purchase. So I think maybe the left combo is a 6 power, and the right only 4. I expect they will be double blocked and not able to get the dinghy out of the water shortly anyway.

    March 15, 2018
  4. Matr Capt Tungsten
    Matr Capt Tungsten

    2/1 on the fiddle block only, with about 6 “ of travel.
    Center contraption is faux..
    Great teaser!!

    March 15, 2018

Comments are closed.