Has this happened to you?

[jmc]

JMP1320,

In the log incident, the FEL load was just high enough to clear unanticipated obstacles and the instability was wanting to cause the tractor to roll, rather than tip about an axle. I had a box blade on the back.

Yeah, I liked that 1920 in some ways more than the Kubota L4330 I replaced it with. I don't miss that non-syncro tranny, though.

John

 

[JMP1320]

That is very strange, I have never heard of such a thing happing with weight on the back

 

[roxynoodle]

It seems to me tractors can flip sideways rather easily. My incident happened as I was going forward down a small hill with nothing in the loader and the loader low to the ground. I believe I went up on an anthill on the left side or into a dip on the right side and next thing I knew I had a tractor very, very close to rolling over sideways (left front wheel was at least a foot off the ground). I had to debate whether to try to bail or try to fix the situation. I was able to reverse and change course and all worked out fine. I learned though that tractors can flip! So if you are moving loads of any kind, particularly something long like a log that can become easily unbalanced, you need to be alert at all times for a possible problem. Obviously some tractors are more stable than others, too. Both of mine are narrow compared to their amount of clearance (high center of gravity).

 

[dynasim]

If it is fwd, and the back is light(essentially, the tractor is balanced over the front axle), the torque on the front drive shaft will cause the tractor to rotate. The front axle is on a pivot, and the torque of rotating the front tires must be counterbalanced by the back wheels. If the back wheels don't have any force on them, the tractor will rotate axially.

Of course, this is only relevant if you have a fwd.

Chris

 

[greenedeere]

If the log is not centered then the frame and axial torque will cause a lateral flex like a drag car until it reaches a point of balance or no return, thank goodness we have pucker factor and wussing out as a first reaction to backer down.Don't know if this is your proplem or not but this happened to me on same tractor and almost same conditions.I kept on re-enacting over and over and came to this conclusion.I never felt like I was going to flip just a strange and unusual situation for me.If you feel as though a chip has been knocked off your shoulder may I say I have somewhat the same feeling from time to time from some comments and remarks made but like I've found most of the time a mis-diagnosed, or quick reply can be mistaken as hurtful when in most cases it is really not meant to be. IMHO only.

 

[KICK]

Soundguy was not too tough on you. QUOTE]


its better he was tuff on you than the tractor was on you.

tractors and loads can break your bones,but words can never hurt you.

 

[Gryantaylor]

At the risk of getting a little "tough love" myself. I've had a similar experince with a JD 855. I was using the FEL to move sand out of a large ditch. I would drive straight down the ditch so the tractor was level side to side. Fill the bucket (which was way to big for that little tractor) full of sand and back out. More then once (let the tough love begin) when I reversed up the hill one of the rears would start to lift. I quckly stopped and dropped the bucket which was less then a foot off the ground, emptyed a little sand and tried again.

What I think was happening:
1. The weight in the FEL made the rear very light (to spite the BB I had for counter weight)
2. When you back up a hill the center of gravity is shifted further forward taking more weight off all ready light rear wheels
3. The front tires (4wheel drive) have to exert more torque to move the tractor up a steeper hill. That rotation further lightens the rear.

1,2,3 combine to cause the rear to just start to lift (CG just over the front tires). Since the front end is not fixed the front tires don't provide any initial resistance to tipping sideways, and the rears both have effectivally zero weight on them any minor inbalances in the tractor (load just barly off to one side, ground not perfectly level, engine torque, steerwheel off to one side or the other, etc. etc. all forces that usually don't make a big diffrence) cause one wheel to lift just before the other. Some tractors may naturally have slightly more weight on one side e.g. an extra gallon of fluid in one tire etc. that makes the same wheel lift consistantlly. In my example it was the right rear that always came up first.

If the above theroy is correct and someone lacked the "pucker factor" to stop quickly whne the first tire lifted off the ground eventually the front pivot would hit a stop and both rear tires would leave the ground, the tractor would then pivot on the front tires until the FEL hit the ground.

Numerous factors would control weather the tractor would rest on the FEL and front tires and stop or flip sideways. Personally I don't care to find out. Just one tire in the air is enough to need to change my shorts.


So thats my theroy, let the debating begin.

 

[jmc]

You guys may be on to something regarding a light rear end in combination with the front axle not being able to resist the reaction torque unti it hits its stops. Still, I've pushed that tractor hard in both forward and reverse under various loading conditions and it only happened in reverse. If your theory is true, then a heavy load in the fel, with little or no ballast, should tip it going forward as well. It could very well do that, its just that I usually have enough ballast when pushing hard going forward and therefore, never experienced it. Thanks for your input.

John

 

[jmc]

I believe I went up on an anthill on the left side or into a dip on the right side

roxynoodle,

Been there, done that, but never quite as harrowing as yours. These incidents were with the tractor flat from side to side, weird phenomenon, and that's why I asked about it.

Thanks,
John

 

[Gryantaylor]

You guys may be on to something regarding a light rear end in combination with the front axle not being able to resist the reaction torque unti it hits its stops. Still, I've pushed that tractor hard in both forward and reverse under various loading conditions and it only happened in reverse. If your theory is true, then a heavy load in the fel, with little or no ballast, should tip it going forward as well. It could very well do that, its just that I usually have enough ballast when pushing hard going forward and therefore, never experienced it. Thanks for your input.

John

I think its more likly to happen in reverse because of the moment (rotational force) the front tires exert on the tractor in reverse help to lighten the rear. When traveling foward the moment is reversed and it actually helps (however small) push the rears down.
If that doesen't make since picture the front tires frozen in ice (pretent they won't break loose) if the tires were to stay fixed and the tractor tried to backup how would the tractor rotate around the front tires. What would happen if the tractor tried to go foward, which way would the tractor rotate then.
A steep hill is similar to the ice example in that it requires more torque to move the tractor.

On a related note, if your traveling forward and need to stop quickly with a heavy FEL and too little ballest. the rotational force of the front tires can cause the rears to lift. Once I was carrying a bucket of dirt down the driveway when a dog ran out in front of me. Let off the HST and hit the breaks. Next thing I knew the tractor was sitting on the FEL and the front tires. (good thing the FEL was only about 1' foot off the ground.