will this damage? hitch ball to drawbar

Woodsman_Pete · Dec 28, 2005

If you don't have a slip hook, you can make a choker hitch by doubling the free end back over the main line coming from the hitch and hooking back into itself; the harder you pull the tighter the chain grabs in to the log; i.e. choking it. I grew up on a small farm where we did most of our daily chores with 2 cylinder John Deeres. We have had good luck skiding logs with both the draw bar and the 3ph... If the ground is frozen the logs would slide right along, if it was soft, a little lift with the 3ph worked well to keep the butt from digging in. We also had a couple of 2 cylinders "reserved" only for tractor pulling contests, I can attest that a load hooked to a draw bar will most certainly raise the front end off of the ground. Infact, our tractors would get the best bite on the track with the front wheels up about 2 feet and using the individual brakes to steer. I'm also a civil engineer, I know and trust the basic free body diagram that you guys are using, but it is being applied some what incorrectly, a basic free body diagram showing the forces is correct for an object at rest, but there are other factors to consider for an object in motion (dynamics) such as friction, HP, wheel size, momentum and probably a lot more which I'm forgeting right now (lots of calculus... wasn't my favorite class). Anyway, for some proof of axle rotation of a tractor in motion with draw bar forces go to the fair this summer or catch some NTPA events on cable...

good luck and grab a bucket full of dirt...

pete

XmasTreeGrower · Dec 28, 2005

I have read through the theoretical discussion of flipping your tractor when skidding logs from the drawbar, and I can assure you it can happen, since I managed to roll my Kubota over last summer doing just that.

Here was the scenario: I was skidding a 20" butt end pine log, hooked as tight and low as possible to the drawbar, at a very gingerly pace, snaking the log through some tight quarters. I had to make a tight down hill right hand corner turn, and failed to see an old hidden stump that was in the path of the pulled log. The butt end of the log caught the stump, instantly stopping forward motion. The 4wd HST Kubota just kept pulling, "rotating" the tractor around that fixed point, and pulled the tractor over on it's right side before I could get to the clutch, or fully release the HST pedal. All of this happened in far less than one second at less than a walking pace!

I remember two thoughts during this incident. One, as the tractor was going over I couldn't believe the kubota was getting enough traction to pull itself over, I was thinking "Why aren't the tires slipping like any normal vehicle would?" Secondly, as I was now hanging downhill sideways from my normal seating position, with an overturned tractor, the lighbulb came on that this how people get killed in farming accidents. Despite taking precautions, it had happened to me! I thanked the Lord for the modern ROPS tractor and seatbelts, which I did have on. I thought about how very different the outcome could have been if I had done the same with my old 8N.

Some hard learned lessons; skid logs too low, risk hanging the log up on unforseen hazards. Raise the drawbar too high, and you risk being above the axle centerline. Either way you can rotate a tractor given the wrong set of circumstances! Be very wary, keep your foot on that clutch pedal, and don't try skidding on a non-ROPS machine.

BTW, no damage whatsoever to the drawbar, hitches, chains, or tractor. The operators however are made of far more fragile parts!

Be careful out there.

Thanks
Bill

Toolguy · Dec 28, 2005

XmasTreeGrower, Did you have the differential lock on when the tractor turned over? I don't doubt the fact that you rolled the tractor, but I can't imagine why the left rear tire did not spin and allow the right rear tire to stop when the weight was transferred to the right tire. Sure sounds odd. It must of had something to do with turning. Glad you're OK.

Toolguy · Dec 28, 2005

Woodsman Pete, Alright, I'm glad someone finally mentioned tractor pulling! I did that a lot years ago at the local fairs with our 850 Ford and our 3020 John Deere. Lots of fun. I did quite well, too if I may brag a little. As you know the key to winning is getting the tractor balanced perfectly. That is, adjusting the weight bias front to rear and the drawbar lenght so that the front end is "light". This allows the most weight transfer from the sled to the rear wheels. I did a few weight transfer pulls on dirt, but most of the pulls in my area were "dead weight pulls" on concrete slabs. I don't know if anyone pulls that way any more. Back in the '60s & early '70s they were quite popular with the Farm Stock tractors. Pretty tame compared to the "Modifieds" and "Super Stocks" that became so popular. I saw some tractors pull some pretty big loads and never saw one flip. The most I ever pulled with the Ford, which weighed in at 4000 lbs. was 13,500 lbs or almost 3.5 times it's own weight. That thing was really hooked up that day!

XmasTreeGrower · Dec 28, 2005

Diff lock was not on. I would have expected the tractor to react as you suggested, spinning the least traction tire. Didn't happen: that sucker just kept pulling!

I was running across a mild downhill slope, turning downhill, on a short wheelbase tractor with a relatively high center of gravity, all contributing factors I am sure.

Just takes an instant for all of the "wrong" circumstances to come together, and everyting to go south.

Thanks
Bill

Marlowe · Dec 28, 2005

Wow! Lots of good and interesting discussion regarding towing here. I'm sure the original fellow has all the answers he needs, just thought I'd tell a short story of how I did it a couple of days ago.

The day after Christmas I spent the morning wrapping up a few loose ends on the foundation rebar for my new house. That afternoon I had a few hours left so I decided to clear a bit more of the clutter such as roots and stumps, and level dirt as I could get to it. My tractor has a FEL and a box blade attached. I've got a trailer hitch ball attached to both the front bucket and the box blade for convenience. I've got lots of trailers to move around at times. The smaller stumps I usually scoop up with the front bucket, or simply push them into a pile out of the way, but I had this one big ole stump that I'd put off as long as I could stand it. I backed up to it and attached a chain, then wrapped the other end around the ball on the box blade. I tightened up gradually then let out the clutch when the chain was tight. The front wheels came off the ground, surprising me, but the clutch was depressed as a reaction. The wheels couldn't have been more than eight inches off the ground, but still, it gave me a start. I lowered the box blade reducing the downward pull on the back of the box blade and started over. This simple adjustment kept the wheels on the ground, but the straighter pull made the stump harder to drag since I eliminated the lift on the stump. My engine started to bog down and I shifted into the mid range to take the pressure off the engine. All was fine as I slowly drug the stump to my pile.

Could my tractor have gone over if I hadn't pressed the clutch back in? Maybe, but I doubt it. The box blade hangs out the back of the tractor a couple of feet, sort of like a wheelie bar on a dragster. If the front end came up high enough, the blade would hit the ground removing the weight of the blade from the back end behind the pivot point of the rear axle, effectively making the front end heavier, while reducing my traction on the rear probably resulting in wheel spin.

Would I trust all that to happen? Not on my life. I'll keep my foot on the clutch and I couldn't even make myself not depress the clutch when the tractor starts to lift. Manure happens, you know, when we least expect it.

Toolguy · Dec 28, 2005

"turning downhill". That makes sense. I can see how that would happen now. Gravity was not your friend that day. Your post may just save someone from having that unfortunate experience. I know I will remember that one. Thanks.

rdsaustintx · Dec 28, 2005

( I'm also a civil engineer, I know and trust the basic free body diagram that you guys are using, but it is being applied some what incorrectly, a basic free body diagram showing the forces is correct for an object at rest, but there are other factors to consider for an object in motion (dynamics) such as friction, HP, wheel size, momentum and probably a lot more which I'm forgeting right now (lots of calculus... wasn't my favorite class).)

Pete, my degrees are in mechanical. FBD's work in dynamic systems too. The difference in statics (or a dynamic system in equilibrium) is that sum of all forces and moments has to equal zero (Newton 1). If they don't sum to zero you can still analyze, but it's accelerating and Newton's 2nd rules. I remember meeting a lot of civils and architecturals in statics, but they all went away in dynamics. /forums/images/graemlins/frown.gif

I totally agree the amount of simplifying assumptions might be deadly when playing on a tractor. Or a space shuttle for that matter. /forums/images/graemlins/blush.gif

RDnT

Marlowe · Dec 28, 2005

I aced calculus, but when one or more of my tractor's tires comes off the ground, I can't remember any of it. /forums/images/graemlins/shocked.gif

Tom

California · Dec 29, 2005

( FBD's work in dynamic systems too. The difference in statics (or a dynamic system in equilibrium) is that sum of all forces and moments has to equal zero (Newton 1). If they don't sum to zero you can still analyze, but it's accelerating and Newton's 2nd rules. -rdsaustintx )

Not sure I understand the fine points there, but I think that also implies that a stickon tiltmeter isn't as useful as it seems.