pulling force of a B2920

[tractchores]

I was wondering if anyone ever estimated the pulling force of their tractor. I'm trying to size some rope / chain / cable for pulling trees (i.e. putting pressure on them as they are cut to get them to fall in the right direction). I have 5/16" chain now, which is labelled as having a working load of 4,700 lbs. I pulled on a tree on a level surface with great traction (paved and I have loaded turf tires) and spun all 4 wheels without breaking or stretching the chain. The shock load of going forward and being stopped by the chain also did not effect the chain. I"m not sure if my chain has a max load of 4700 lbs or something greater.

I'd like to get a chain / cable / rope that is far greater than the pulling strength of the tractor so that I cannot break it and create a dangerous situation. Anyone have any ideas what the largest pulling force a tractor of this size can apply is?

 

[oldballs]

I'm no tree expert, but.......it's my understanding that a rope...cable...chain etc. is used to simply guide the fall of the tree; not literally pull it down. A chain long enough to do the job would be too heavy in my estimation. I use 3/4 inch nylon rope that has a "work load limit" of 1,420 lbs. I've had no rope failures using my F-250 as the power source. On some ocassions I use the bucket of the B2620 to push an easy one over. I doubt that a B2920 could break any decent size rope..cable or 5/16chain....:2cents:

 

[locknut]

Breaking strength on that chain is very high.You won't break it unless you take a running start with a lot of slack,hooked to something totally unmovable.

http://www.1st-chainsupply.com/chain/SpecsCh70.pdf

 

[Sysop]

Most chains are underrated for wear and abuse. 4700 pounds "work load limit" basically means with 4700 pounds hanging, it will never stretch or break. The actual point that it will stretch or break would be significantly higher depending on the type of force put on the chain (jerking, binding, etc.). A chain made to work with 4700 pounds of weight would likely take up to 6000 pounds of hanging weight before any stretching occurs, and a break weight would likely be closer to 10k. I've seen what it takes to stretch an old "unrated" 5/16" chain, and 10k isn't even touching it...

Before the safety police jump in, none of this is any sort of recommendation to overload a chain or anything else; my point is only that "working weight ratings" are underrated to allow for the typical wear and uses for such things.

I would agree that a B2920 will never break a 4700# rated chain without adding a lot of weight to the tractor. At 30ish horsepower, I think there is the power to break such a chain, but at 1500ish pounds, it'll never put enough of that power on the ground...

 

[tractchores]

Thanks, that is an eye opening link to the strength, i had no idea breaking force was 18k lbs. i'm looking to get some rope so i can use pulleys, i was looking at 8,000 lb breaking strength on that. Think that will be a safe enough margin?

 

[SPYDERLK]

My 12K# 7520 setup will stretch a 5/16 Grade 43 chain but will not stretch the Gr70 - which is the one rated for 4700 working load. This is steady pull w/o intentional jerking. Inevitable jerks are what the ~ 4X breaking strength safety factor covers.
larry

 

[TomSeller]

Remember, you do NOT want to pull hard on a tree that is being cut. As stated above, you want to GUIDE it. Pulling too hard could create a very dangerous situation for the person behind the saw. Effectively making the tree into. to a "leaner" which could barber chair on the cutter.

 

[milkman636]

My memory seem to recall that the safe working load of chain is typically about 1/4 of its breaking strength.

But being a boater, I've used 150' anchor ropes and a come-along to pull trees in the direction I want them to fall. Leaning an extension ladder up against a tree can get you high enough to apply some real good leverage without needing tons of force. Using my tractor as the anchor point also allows me to stretch the ropes before tugging any with a come along. If I need more pull I can walk over to the tractor and work the come along without even putting the saw down, all while staying out of the tree's fall path.

 

[xring100]

If your not jerking the chain just a dead pull then you could guesstimate your tractive effort on level ground by knowing the operating weight and mu level Ag tires have about 0.7 mu on hard pack or gravel. Meaning if your rig weighs 4000 lbs you can only pull about 4000 lbs .7 = 2800 lbs is the maximum cable tension you could hope to sustain. However if your jerking it loads go through the roof and i would switch to a snatch strap. As you don't want to be on the receiving end of a broken chain or cable

 

[tractchores]

Thanks. In pulling configuration the machine is probably 3500 lbs, the BH almost doubles the weight. I usually tense it up, make a partial cut then pull to get the tree to pivot on the hinge if it's a bad leaner then make the final cut when it's leaning the right way. It does load the tree a bit, so safe positioning is huge.

The biggest forces will be from skidding or from pulling a leaner's butt end out to get it on the ground.

 

[xring100]

No problem

 

[TomSeller]

You don't need much to guide a falling tree, but you must get it guided at the star of its fall. Have it in a fairly tall gear to keep the rope/chain/cable tight as it goes.

 

[s219]

For tree work with a tractor, I prefer 5/8" or 3/4" Samson logging rope:

Samson Stable Braid Rigging Line, Double Braid Bull Rope

Size depends on the load rating you think you need, and the size of pulleys you're looking at (many handle 5/8 or 3/4 rope). I have a 150' length of 5/8" right now, and it gets frequent use. I use an old gym bag as a stuff sack to prevent tangles.

Rope is often preferable to chain for tree work because of ease of use (guiding through/around branches, other trees, etc) and the ability to tie various knots. Just remember that knots reduce strength. A bowline knot is very handy for logging type of stuff and you can always break t back open even after a high tension pull. You can also splice these types of ropes and put in eyes, with no loss of strength.

Generally, my shackles, links, and pulleys are rated lower than my rope, so they'd end up breaking first. I have a selection of them, and pick accordingly. Also handy is some sort of tree sling. When setting a pulley on an adjacent tree, you want something to safely spread the load.

With a 150' rope and a pulley, I can handle most any tree-work situation and keep the tractor well out of harms way. The ability to reverse direction or change direction of a pull is a big help.

 

[94BULLITT]

I was watching antique tractor pulling on TV one night. The winner was the guy that could pull the most percentage of the tractors weight. Most of the tractors only pulled 75%-80% of their weight. The winner pulled 135% of his weight IIRC. The tractor probably had some stuff done to it to pull that much. I think you would be safe to think your tractor will pull 100% of its weight. When you are looking at ropes, chains etc. look at the WLL, the working load limit. That is what is important. When you use a rope and tie a knot you can loose 35-50% of the ropes strength.

 

[sd455dan]

If your not jerking the chain just a dead pull then you could guesstimate your tractive effort on level ground by knowing the operating weight and mu level Ag tires have about 0.7 mu on hard pack or gravel. Meaning if your rig weighs 4000 lbs you can only pull about 4000 lbs .7 = 2800 lbs is the maximum cable tension you could hope to sustain. However if your jerking it loads go through the roof and i would switch to a snatch strap. As you don't want to be on the receiving end of a broken chain or cable

Might Check the manual -some tractors actually have the tractive force @ a % of slippage listed in the manual, in my Rhinos case it's just over 13,000lbs. @ 15% slippage, and after breaking two 10k (rated straps i don't doubt it)... and the Ford is just over 6500lbs. IIRC from nebraska test data... those #s are with factory weights.

 

[tractchores]

Thanks everyone. I'll check the manual. I ordered some amsteel blue and shackles rated a bit less than the rope. The rope is 1/4" rated at 8k lbs, with a working load of 4k. we'll give it a shot and see how it works. I will probably keep using my heavy chain for rocks and skidding so i have the greater strength and don't tear up the rope. I'll post on how it works out! Are their knots that reduce strength less? I have spliced eyes so will try to use those most of the time.

 

[Gary Fowler]

I don't think you could break a 1/4" chain with a 2920, you just don't have the weight to get the traction. When pulling on a tree with the chain up high, it naturally wants to lift up the tractor also, assuming you are pulling from the drawbar as you should be. I had a 5/16" chain hooked to my 8500# tractor trying to pull out a loaded dump truck a year or so back and pulled the drawbar bracket off the tractor but didn't damage the chain. All four tires had dug holes down over a foot and then started lunging (basically a snatching action)which is what broke the drawbar bracket before I could get my foot on the clutch.
Besides the amount of traction, you don't need much force to guide / pull over a tree when cutting it. Too much force and you may snap the tree trunk which happened to me once trying to pull one out from in the branches of a neighboring tree.

 

[bigdeano]

I did drawbar pull tests a while ago using a hyd cylinder with a pressure gauge. Test was done on damp grass. My 4x4 pickup with all season tires weighs close to 5000# and pulled 3500# when the wheels spun. My 2wd tractor with R1's weighs 6000# with loader and pulled 5250# when it spun. I had the 3ph at 18" off the ground to transfer weight to the rear. The truck tires just spun on the grass, the tractor kicked the sod out the back.

I set up my video camera looking at the gauge to capture the max reading.

 

[94BULLITT]

Thanks everyone. I'll check the manual. I ordered some amsteel blue and shackles rated a bit less than the rope. The rope is 1/4" rated at 8k lbs, with a working load of 4k. we'll give it a shot and see how it works. I will probably keep using my heavy chain for rocks and skidding so i have the greater strength and don't tear up the rope. I'll post on how it works out! Are their knots that reduce strength less? I have spliced eyes so will try to use those most of the time.

Factory spliced roped does not hurt the strength of the rope. Here is some info on knots and how they reduce the strength of ropes. http://www.neropes.com/Resources/sail_reprint.pdf Since you have a nice rope and a chain you may also want to get a tow strap.

 

[tractchores]

I don't think you could break a 1/4" chain with a 2920, you just don't have the weight to get the traction. When pulling on a tree with the chain up high, it naturally wants to lift up the tractor also, assuming you are pulling from the drawbar as you should be. I had a 5/16" chain hooked to my 8500# tractor trying to pull out a loaded dump truck a year or so back and pulled the drawbar bracket off the tractor but didn't damage the chain. All four tires had dug holes down over a foot and then started lunging (basically a snatching action)which is what broke the drawbar bracket before I could get my foot on the clutch.
Besides the amount of traction, you don't need much force to guide / pull over a tree when cutting it. Too much force and you may snap the tree trunk which happened to me once trying to pull one out from in the branches of a neighboring tree.

Interesting. I use 5/16" chain now, so no chance of breaking that. I hadn't considered the breaking strength of the draw bar, I'll have to be careful with any lunging or other jerking type action. The only time I'd be applying full force is the same situation as you mention when a tree is hung up. Definitely need to proceed with caution in those scenarios!

I did drawbar pull tests a while ago using a hyd cylinder with a pressure gauge. Test was done on damp grass. My 4x4 pickup with all season tires weighs close to 5000# and pulled 3500# when the wheels spun. My 2wd tractor with R1's weighs 6000# with loader and pulled 5250# when it spun. I had the 3ph at 18" off the ground to transfer weight to the rear. The truck tires just spun on the grass, the tractor kicked the sod out the back.
I set up my video camera looking at the gauge to capture the max reading.

Very interesting! I'm tempted to try and get a force gauge and do an experiment. I can't imagine that even with 4wd I'm going to be even close to what your tractor pulls given the weight.

Factory spliced roped does not hurt the strength of the rope. Here is some info on knots and how they reduce the strength of ropes. http://www.neropes.com/Resources/sail_reprint.pdf Since you have a nice rope and a chain you may also want to get a tow strap.

thanks I'll check this out. I got a 20k lb tow strap already and have been using it to loop around live trees for the come-along to prevent bark damage. I just ordered some pulleys as well, which will let me stay out of the 'fall line'.