Detoured from the "Damage from accidents !!! " thread...
i use a truck confidentally to pull trees over (sometimes put through a 3/1); sometimes lift limbs-then lower thru a PortaWrap on the hitch; sometimes pretightening a line with the truck, then lower the same way through a PortaWrap. But, i really hear you guys about overdoing it!
That is what i meant by "carefully metered force"; the points about proper timing for its application are very important too. Eye see a truck as one type of portable power and anchor; that can be safely used with discretion. One, point is we never really max out the truck, have it sliding sideways, burning rubber or anything. Just to apply overwhelming force at the right moment. Just like all are ropes are so much stronger than we need, we always keep the RPM's low. So we would have all that force in reserve, if we need it; without wearing out the guys, or possibly with less of them! i look at the truck as a tree-mendous amount of power; that we are only going to use a small metered amount of, with plenty of reserve.
The first thing i look at; is 'how much force do i need?'..... 'How off balance is the tree?'; and then 'how much leverage do i have already?'.
i look at how the weight is distributed in the tree, ie. how much lean am i fighting, and is the weight of lean high or low that i am fighting. i see the point between the cut and the pulling point as a lever. The higher the weight is leaning backwards, the more leverage it has against me; the more force i need. Lower, weight leaning backwards is easy to get leverage on. i look at the attatchment point of the limbs to determine this height/leverage point of that weight, and then subtract equivalent weight leaning forward at its attatchment points; judge what has leverage on what etc. Though a lot of times, we use a truck on things we don't have to. Just when we would like more positive steering and slower drop; by pulling the tree earlier in the backcut; with a 'meatier' hinge, to usher it down. Thereby keeping the tree more 'polite'; on it's fall; into wide facecut. That wide mouth facecut gives the system the mechanical instruction for the tree to hang on longer to the stump; until the faces slam together; committing that all that leveraged, moving force to stop or tear off, as it can't move anymore.
i seek to maximize the leverage into the system by putting the line in the tree as high as possible. i think tracing the line down the back of the tree; instead of just a running bowline up to the top, gives it more bracing; thereby you can confidentally put it into the tree higher, for more leverage. Also, it applies the force in a cocked back position, pushes the tree from the back, and also allows for second guessing your (or someone else's) choice of where it is in the tree. Dropping the cut as low as feasible, also; increases leverage; i like staying in an upright 'running' position - just in case!
i also think that the bend in the red rope at the top; before it comes down to the clove hitch 'wants' to straighten out; the more line tension there is; thus putting some some diffrent kind of force into it too. But, i can't prove or site exactly why.
We also, wedge from the back; using the longest wedge possible. If, a wedge takes a longer distance to give you the same amount of lift; it will put more pressure on the lift of the tree (if your pounding it in tight). Taht's the Mechanical advantage, of that longer distance to achieve; funneled into the same space. A lot depends on the moving machine here, ie. the hinge. So it must be just write. Any rot, 'cat facing', knots, dryness, species, temp etc. that would effect the strength or flexability; could effect the outcome. Good wood, with the face cut almost half way in (scheduling the hinge to be at the widest part of the tree); and walk the hinge down to a point of failure and ease it down with overwhelming force. With the most amount of strong, flexible hinge ushering it down with the most control.
Then, after all else is maximized; we dribble some of the truck force on top at the right moment. Usually a well centered pull, unless we are trying to get some kind of tourqed pull or something. Knowing we could wear the truck out, before we even had enough backut to free it to to fall, might be able to break the rope, mabe even snapping the tree backwards at the same time! We just don't! We just carefully use that mule and anchor and save ourselves, and have more backup force in case something goes wrong! And with a 3/1 on it; you have massive power available; with a lil run; you just very carefully meter it in confidentally, after surveying just what you need when; and realizing you could overdo it at any time, and have plenty of power to get you out of trouble, or into it!.