USCG Exam PracticeDeck machinery and ground tackle
The theoretical mechanical advantage of a luff tackle is which of the following?
- A. Two, because there are two blocks in the assembly
- B. Two or three, depending on which block is the moving block
- ✓ Three or four, depending on which block is the moving blockCorrect
- D. Five, because friction losses must be added to the ideal advantage
Why C is correct
A luff tackle consists of a double block and a single block and provides a theoretical mechanical advantage of three or four depending on which block moves. A gun tackle (two single blocks) gives two or three. Friction reduces — not increases — the ideal advantage.
Cited:NAVEDTRA 14343 §8-2