I agree with Mark Jenkins' assessment of using a single pulley to change direction of a winch pull. I must point out, however, if the winch line is doubled back to the vehicle that the winch is mounted on, it does indeed double the effective pull of the winch. You do not need two pulleys to gain a mechanical advantage, you just need the line doubled to the pulling vehicle. I am sure you have noticed that when you double-back line to the vehicle with the winch that the line speed is effectively halved. That is because you are pulling double. You can verify this for yourself by using Mark's method while standing on a scale. Whatever force you exert in the pull will reduce your weight on the scale by the same amount.
Larry HuffstutlerElectra, Texas
I have attached a PDF file of some schematics describing the winching setups covered in Off-Road Mail in the April '06 issue. Specifically, your article speaks of single and double line pulls. The descriptions and explanations Mark Jenkins provided differ from what is described in the attached PDF file. I don't claim to be an expert, but I would like to state my points and clarify a few details.
Mark is correct in his Figure #1 on page 16 and partially correct in his Figure #2, but the details are clarified in the attached PDF files.
In short, a single pulley block can be used to obtain a mechanical advantage. Mark illustrates that, but notice the pulley in Figure #2 is the winch drum, which thus creates a mechanical advantage.
Justin Hartung Apollo, Pennsylvania
You guys give in too easily. I'm writing in response to Mark Jenkins' letter in the April '06 issue. His letter states that one cannot gain mechanical advantage via one pulley block. He indicates a person lifting a bucket of U-joints through a pulley block attached to the ceiling with a spring scale to measure load. This only considers a three-point winching technique -- the load (bucket of U-joints), the pulley block, and the winch (the person). True, this would indicate no mechanical advantage on the spring scale. If we eliminate one point by connecting the winch to the load, the line load is effectively cut in half. Hang the same bucket from the ceiling, attach both ends of the line to it, and connect the scale to one end of the line. Both ends of the line share the load. Now, a 5,000-pound rig (I drive a fullsize Chevy) only needs 2,500 pounds of pulling force in a minimally stuck situation. Ultimately, a 9,000-pound-rated winch can pull an 18,000-pound load by doubling back to the vehicle. The tradeoff for the gained capacity is recovery speed. By doubling the pulling force, the line speed is cut in half. Correctly utilized, a pulley block may mean the difference between spending the night in a mudhole or making it back to camp.
Eric Linssen Lakewood, Wisconsin
I know I'm one of at least a thousand people who will respond to the letter published in the April '06 issue. Mr. Jenkins forgets that the winch itself acts as a pulley. Imagine the rope is now winding around the pulley rather than going off to the imaginary puller. Therefore, the first illustration [from Apr. '06 OFF-ROAD] is like you hooked to a tree thus pulling whatever the winch's line rating is. The second illustration demonstrates what would happen if you ran the winch cable back to the pulling vehicle, thus doubling your line pull (in theory anyway). I say "in theory" because each layer of the winch cable pulls less weight than the maximum rated line pull rating of the winch.
Aaron ChristensenKirkland, Washington
Editor's Note:
If you have anything you'd like to say to us or ask us, please feel free to write to: OFF-ROAD Magazine, Off-Road Mail, 2400 E. Katella Ave., 7th Floor, Anaheim, CA 92806. You can e-mail us at kevin.blumer@primedia.com.