ShaneLogs
Addicted to ArboristSite
The "Great Timber" name on the trailer sorta cracked me up, given the circumstances...
Haha! I just now see that on the trailer
The "Great Timber" name on the trailer sorta cracked me up, given the circumstances...
Lack of proper mindset, if he was on his game, there wouldn't be that mess.
I have had my marginal days, I had the self knowledge to pull myself out of the game.
As a certified arborist and also a tree climber for the last ten years, there is one thing that has not been really said is that you get what you pay for. The reason the guy with the chainsaw and a pickup truck is so cheap and the guys with the credentials and know what they doing cost more is that you get results like this one. Also any chainsaw has sight lines on them for felling if this guy had known this he would have seen that he was way off and could have made a minor correction. Not sure why there was no back cut but essentially he almost looks like he made a snapped cut on the tree which allowed the tree to go in any direction it wanted no matter what he did. The only thing that could have helped the situation could have been to put two relief cuts below the notch because in the picture it looks like he spun the tree which is a typical thing in a pine tree without putting those relief cuts on the tree. One way to look at this situation is that no one was hurt and property can be replaced and hopefully another guy has learned to leave tree work to the professionals.
80% huh? My 3500 Dodge weighs in at 7200 lbs. Are you saying I should only be able to pull 80% of that? My Teton fifthwheel loaded with water food, and just everything you would carry with you, comes in at 16,500. Now I know it has wheels but still it is a load. If the winch on the front was using a double line that would be 16,000 from an 8000 lb winch. How would that figure in?
Hardpan,
<snip>
Lastly, IME other than preloading the rope, usually the pull is only for a fraction of a second and the effect is simply to put gravity and the hinge to work. Ron
Personally I have a 3100 pound 4WD tractor. I want a rope to hook to a stationary object like a tree and pull until the tires break traction before the rope breaks and approaches me at 200mph. Maximum pull is the only one we can really measure. What is the minimum rope rating I should use?
(We'll see how badly the engineers tell me I botched this later :msp_biggrin
Wheels are no small matter.
Tires locked up, on pavement, will have a coefficient of friction of about 0.8.
Tires turning freely, on pavement, will have a rolling coefficient of friction of about 0.015.
If I'm remembering my math right:
16,500 x 0.015 = 247.5 pounds of force to move the trailer. I could do it with a hitch dolly...but your Dodge will be able generate enough momentum to get to road speed.
Lock it up solid so the wheels don't turn, it'll take 16,500 x 0.8 = 13,200# to drag the trailer somewhere.
Reverse it, you have a 7200# Dodge, with the tires not moving (brakes or you're applying power equal to the pull), 7200 x 0.8 = 5,760#. That's the most "break out" power you'll have. If you try a straight pull that trailer with the locked up wheels from a dead stop, your Dodge will spin it's wheels.
Now that's on pavement. Ice, gravel, grass will all different values.
Now, if you're moving momentum comes into play...and speed adds up fast.
You also might try to get torque working on your side -- and I'm not talking engine torque. Rather then trying to straight pull that dead load trailer, come in at an angle. For example's sake, let's figure you have a *really* long trailer hitch and can line up 90º to the tongue. Now let's figure your trailer wheels are 14' behind the ball. 5760# of breakout force x 14' = 80,640ft-lbs...betcha that'll twitch it free...now that you have some momentum you might be able to keep the load moving (though my math skill start to break down trying to do those calculations )
It's not just trucks. Watch people who pull competively with animals. As the loads get heavy, you'll see horse teams always use momentum to get a load started and some times twitch it too. Oxen folks don't use momentum to start loads, but they'll always twitch the heavy ones by starting to pull a bit off then straighten themselves.
In the case of pulling the top of a tree we have a few things going on.
Basically while you're pulling the tree, the tree is pulling you UP. The torque we used horizontally to twitch the trailer is now working vertically to pull you up and reduce the amount of weight on the wheels, thus reducing how hard you can pull before the tires spin or get dragged.
My physics is way too rusty to try and figure out the force and vector math though
Conversely, if you can pull something lower then your hitch that will increase your traction, though you might hit a point of diminishing returns as your front end comes up (not really sure all the math involved at that point!)
Since 5,760# is how much it takes to move your Dodge on pavement with the wheels locked up, if you really want to push that 8,000# winch to it's limits you best have some good wheel chocks to keep your truck from being dragged.
Did I make this clear as mud?
(Engineer / Physics types please tell me I didn't screw it too much )
In a nut shell. If we use a rope whose tensile strength is equal to the weight of the pulling vehicle we will have 25% more rope than we need in a level, slow pull but since the rope will also have a vertical pull when tied up in a tree then the "lift" of the rope will reduce our pull ability to even less than the 0.80 coefficient. Of course one jerk will turn it into a working load and a much larger rope is needed. Add a threat to people and property and the sky is the limit. Maybe that is why the pros use the big expensive rope. Ya think? It sounds like the rope requirements differ greatly between the locations of woods and crowded residential areas. Great discussion. Thanks to all.
Enter your email address to join: