To Snatch or not to Snatch
(comments on Snatchblock usage and winching - not WENCHING)
This is only to reinforce the body of knowledge already on the forum and to add some personal thoughts to the subject of using a winch with a snatchblock. I refer the reader to the following excellent threads on the Forum:
All you ever wanted to know about Winches and Beer (SILVERDUSK)
Snatch blocks for synth lines? and
http://www.adventure4x4.net/waiting/...ht=snatchblock(HIGHBEAMS)
...and I'm sure I'm missing others that are equally valuable.
Quote:
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(A) "Snatch block" is a specific type of block. A "block" is a "sheave", which is a wheel with a grooved edge to hold the rope or cable, combined with an axle or pin, side plates and a means of attaching it to something, typically a hook or shackle. Blocks are used in "block & tackle" combinations using multiple sheaves and two block assemblies, to increase mechanical advantage. A "snatch block" is a specially-designed block which is used to "snatch" loads or anchors, and is designed so that the side plate can be opened or swung away for the easy insertion of a loop of rope or cable without having to thread a bitter end through the side plates, and can thus be inserted anywhere in the cable without having to remove the load first to change the direction of the cable pull.http://www.dodgepowerwagon.com/glovebox/snatch.html
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I was speaking with a friend who was telling me how he intended to use his newly purchased snatchblock - no he wasn't a forum member- and it concerned me. He didn't buy an FJ, however there are a lot of people new to off-roading who buy FJ's so this may apply to you if you're in that category.
He'd never used one before and hand grand ideas for it's employment. The way he discussed it with me, the snatchblock was cloaked with magical powers and he spoke of doubling or trippling up the snatchblock (can be done with care under some circumstances) in ways that would cause problems for him. So let's just discuss the ABC's.
You are applying a lot of force to the block and the anchor when you are only changing the direction of force for the pull. The amount of force applied to the snatchblock is dependant upon the angle between the incoming line (to winch) and the anchor line (to tree)! The total load on a block can be as much as twice the load applied. The maximum force on the block comes when the two lines are parallel to each other.
Let's assume you're stuck and the angle you need to pull is not "straight". Time for your snatchblock. So you break out your tree saver, rig your line to a large tree and begin to pull. For each pound of winch force applied, the snatch block will be under roughly twice the load, while the line strain will be equal to the line pull. So if you apply a full 9,000 pounds of pull, you are putting 18,000 pounds of stress on the block/anchor. (depending on the angle of pull)
Change the scenario and you now attach the end of the strap back to your rig (double lining). Does this change the dynamics of the situation? Yes. The load on the line is cut in half because two lines are now carrying the load. (makes sense, right?) The load on the lines are now not 9,000 pounds, but 4,500 pounds but the load on the snatchblock is still 9,000 pounds. This is usually the best technique if you don't need to change direction on the line while pulling.
If your winch over-stresses your snatchblock because the snatchblock is not in good repair, you have a potentially dangerous missile that can kill. If you're using a well made, properly rated snatchblock, your electric winch will likely shut off before it overloads the line because of safety features built in. However if it does not, you have a problem.
So take some time to break it out and practice with it under controlled circumstances BEFORE YOU GET STUCK AND NEED IT. That day when you wanted to go on a run and everyone flaked on you and there you are, all dressed up and nowhere to go -- this isn't a bad time to break out all of your rescue gear and just play with it, gently, no stressful circumstances, no emergency. Once you're comfortable with it, you'll be ready to use it effectivly help yourself and your trail buddies.
I think I'll keep the stock rear bumper.
Linear Mode
