Tractor Rollover Myths and Facts

[mars1952]

Hello Everyone:
I have read a great number of posts on this site and I have learned a lot. However, I have also read many posts that give unsafe tractor operation advice based on unsubstantiated conventional wisdom. Frequently a Newbie will post a simple question and the thread will end up being hijacked by more experienced posters that want to express their opinion on another subject, Tractor Rollover is one such subject. I admit that I am guilty of this sin.

In this thread I would like to discuss Tractor Rollover both Rear Rollover and Side Rollover. When you respond to this thread please try to include a link to some evidence that supports your claim. Personal experiences are good evidence but not stories where you knew a guy that knew a guy.

Here are some Myths that I would like to dispel or prove:

1) Pulling from a draw bar below the rear axle eliminates the possibility of a rear rollover.
(I haven't found anything on this yet).

2) Small CUTs do not have enough horsepower to cause a rear rollover when pulling from the draw bar.
This link does not completely prove or disprove this because he was not pulling from a rigid draw bar but the tractor is less than 20 HP and he was pulling from below the axle.

3) Heavy tractors do not need ballast when using a FEL or rear wheel ballast is enough to provide traction and prevent rollovers.
John Deere Handout Scan

4) Attaching a 3PH implement eliminates the possibility of a Rear Rollover.

This happened to me. I was mowing with my JD4300 and MX5 bush hog and the mower caught on a stump. The mower folded up to almost 90 degrees and bent the linkage on the mower (not the tractors 3PH linkage) The front tires came off the ground before I could push in the clutch and the rear wheels lost traction. In this case I was mowing down a steep incline and I had the FEL on the tractor. My point is that the 3PH mower linkage was not strong enough to prevent a rear rollover. If I was on flat ground with less weight on the front of the tractor I could of rolled over. I think that a ridged implement like a box blade could prevent a rollover but I would like to see some proof.
Ferguson System Principal and Theory of Operation

My main goal for this thread is to create a thread that we can link to whenever the subject of Tractor Rollover comes up.

Let the heated arguing begin! (opps, I mean enthusiastic discussion)
Marshall

 

[IslandTractor]

Good idea to start a new thread in the safety sectioin.

First, I would like to borrow an adage from the medical field: Never say never and never say always. When talking about rollovers there are bound to be odd ball exceptions but I think we should focus on finding the principles that should usually be followed.

1) I also looked for "definitive" evidence that using the drawbar eliminates rear rollover. I don't find it but it is very clearly the recommended way to pull based on the physics. "Funny car" tractors are not really relevant. Raising the front wheels a few inches in extreme situations is also not so relevant so long as the rotational force dissipates before the front raises to a level that destablizes the tractor IMO. Maybe others have further evidence.

2) I disagree with the conclusion you draw from the article on the guy who flipped his tractor over using the drawbar. He was climbing a berm which raises the front of the tractor and is essentially a destablizing factor in itself. It is appropriate to warn people that climbing a steep hill while using the drawbar or implement should be done cautiously.

3) no experience to draw on for this

4) Again the issue here is "always or never". Attaching a 3PT implement will clearly lower the risk of rear rollover but one can certainly imagine specific scenarios or find anecdotes that show exceptions.

This thread has great potential. Let's do our best to keep it evidence based and "warm" not "hot".

 

[Bob_Skurka]

Pulling from a drawbar eliminates rollover

1) unknown, presumed to be generally safe and is recommended as generally safe, but nothing is idiotproof and I am often just the idiot who can disprove safety features
​

Small/Low HP tractors can't backflip

2) I believe that a small tractor can tip backwards, it is not a horsepower issue, I believe it is a torque issue combined with a 'condition' issue. For example, a BX1500 in LOW gear range pulling a cart. No problem on flat land. But what happens if pulling up hill, or worse yet, pulling up hill and hitting a rock.

Same tractor, but instead of pulling a free rolling cart, presume it is pulling a box blade that snags a strong root/rock. In low range there is no reason not to believe it will not stand up on its rear wheels, the question then becomes will the implement stop the rollback? See below for that question!

I've scared the heck out of myself on a garden tractor standing it up on the two rear wheels climbing my hills (which is why I no longer use that garden tractor for mowing my hills)

​

Heavy tractors don't require ballast

3) Regarding heavy tractors not needing ballast, that is pure bull-crap. It can be tested with any class of tractor, even Island Tractor's CK20. Ed's CK20 is roughly 1990#. It is also very similar in size to a Kubota B7410/7510 that weigh 1300# (690# or about 45% less weight than the CK20). Still, the Kioti website states 600# of ballast is needed on the CK20. Realize that "heavy" is a relative term, not an absolute term. It is easy to compare a "light" tractor and a "heavy" tractor in any given tractor class/size.
​

Implements prevent Rollback

4) I believe that SOME implements may prevent a backflip and SOME may not, under SOME conditions. I also believe it may depend on the weigth of the tractor that is being used. Again, presume we go back to Ed's CK20 versus a B7510; presume both are hooked up to identical light duty box blades. The light duty box blade may not have enough strength to hold the weight of the CK20, but might have the strength to hold the much lighter B7510.

The CK20, once set in motion, will apply much more kenetic against the implement than that much lighter B7510, presuming they both roll backwards at roughly the same speed. This is not much different than firing 2 bullets at the same speed, a lightweight bullet will have far lower kenetic/terminal energy than a heaiver bullet traveling at the same/similar speed.

Realize both tractors may damage the implement, but all we are trying to do is stop a complete rollback so it would stand to reason that some combination of a lighter tractor and a stronger implement would likely prevent a complete rollback. But a combination of a heavy tractor and a light implement might lead to death?
​

---
​

Now while I used small tractors as examples above, move up to a class 2 frame size and the same principles can be applied. Ditto moving up to even larger tractors/implements.

 

[SPYDERLK]

1) Pulling from a draw bar below the rear axle eliminates the possibility of a rear rollover.

Myth, because it does not stand up under physics as stated. As long as the point you are pulling from is above the point at which your tires apply force to the ground there will be a back tipping moment applied over that distance. If the drawbar is solidly attached, and long, the end where the chain is attached dips toward the ground as the tractor rolls back. This decreases tipover moment as the tractor goes up. If the drawbar is so long as to extend to the rear of the drive tires, the moment from the pull will decrease to zero at some angle of rollback. If this condition occurs after the tractor CG has reached a point rearward of the axle the little tripod formed by the tires and the end of the drawbar is back balanced. Given a flat hard surface and infinite luck - - shut down, climb off carefully and go get your camera!

You cant eliminate the possibility of a back grunt rollover unless the drawbar extends enuf beyond the back of the tires. That distance will vary with tractors.

Where pulling from a fixed drawbar offers a great safety benefit is in a jerk pull. Since the pull point is below the tractor CG some of the tractor weight instantly shifts to the front as the jerk occurs. It shifts back to the rears as soon as deceleration ceases and the tractor could still grunt over - particularly if the drawbar is short. It gives you the chance to be on the clutch tho.
larry

 

[texasjohn]

Display of Stability Data for Safe Tractor Operation has SUPERB video of tractor rollovers of various types

slope
rear pull above axle
rear pull below axle with drawbar
with and without seat belts

It's a MUST SEE.

I like the focus on facts that this thread has, let's try to keep it focused on proven and demonstrated information.

 

[Tom_Veatch]

...
1) Pulling from a draw bar below the rear axle eliminates the possibility of a rear rollover.
(I haven't found anything on this yet).
...

SPYDERLK is correct, this is a myth. A fairly simple analysis shows that a rear rollover WILL occur if:

D > Wl/(r-h)

where:

D = Pull Force on the drawbar.
W = Weight of the tractor (not including the Rear Wheels, axles, etc)
l = Horizontal distance of the Tractor CG (not including the Rear Wheels, etc) forward of the rear axle centerline.
r = Rolling Radius of the rear wheels
h = Vertical distance of the drawbar centerline BELOW the rear axle centerline.

This analysis assumes
a) The tractor is pulling a load on level ground
b) The tractor can develop sufficient torque and the tires can develop sufficient traction to develop the pull force D.

Note that although pulling from below the rear axle does not "eliminate the possibility", it reduces the tendency of a rear rollover to occur. As "h" increases, the value of (r-h) decreases and the critical value of the drag load that would cause a rollover increases at a rate porportional to the square of 1/(r-h). [dD/dh = Wl/(r-h)^2]

The only way to completely eliminate the possibility of a rear rollover is for the value "h" to equal "r". That is, the drawbar centerline would have to be at ground level.

If there is sufficient interest in seeing the details of the analysis, PM me and I'll clean up my hen scratching and send you a copy and/or post the analysis here. Please don't clutter up this thread by posting such requests here. Also, I'm decidedly NOT interested in getting involved in a "Will It Fly" discussion.

edit: In the interest of full disclosure, the "D" value in the above equation is the value at which the "down force" on the front wheels goes to zero and the wheels begin to lift. Whether the tractor would continue into a full back flip depends on the geometry of the connection of the drawbar to the object being pulled.

 

[Soundguy]

I am in general agreement with the others concerning #4.. an implement will help prevent a rear rollover.. For a reference I'll site the reprint 1952 ford 8n owners manual where the 3pt lift is refered to as an added safety feature with respect to a rear implement helping to stall a rear roll over. In the end.. it will go down to circumstance. A big meaty rear implement may be better at supporting the tractor .. etc.

I'm also in agreement with island tractor.. 'never' and always are hard to lock into. strange stuff happens. A tractor with no wheels setting on the ground could roll over backwards if a sinkhole opened up under it.. etc. so NOTHING will make a tractor 'never' rollover.. etc.

Soundguy

Hello Everyone:
I have read a great number of posts on this site and I have learned a lot. However, I have also read many posts that give unsafe tractor operation advice based on unsubstantiated conventional wisdom. Frequently a Newbie will post a simple question and the thread will end up being hijacked by more experienced posters that want to express their opinion on another subject, Tractor Rollover is one such subject. I admit that I am guilty of this sin.

In this thread I would like to discuss Tractor Rollover both Rear Rollover and Side Rollover. When you respond to this thread please try to include a link to some evidence that supports your claim. Personal experiences are good evidence but not stories where you knew a guy that knew a guy.

Here are some Myths that I would like to dispel or prove:

1) Pulling from a draw bar below the rear axle eliminates the possibility of a rear rollover.
(I haven't found anything on this yet).

2) Small CUTs do not have enough horsepower to cause a rear rollover when pulling from the draw bar.
This link does not completely prove or disprove this because he was not pulling from a rigid draw bar but the tractor is less than 20 HP and he was pulling from below the axle.

3) Heavy tractors do not need ballast when using a FEL or rear wheel ballast is enough to provide traction and prevent rollovers.
John Deere Handout Scan

4) Attaching a 3PH implement eliminates the possibility of a Rear Rollover.

This happened to me. I was mowing with my JD4300 and MX5 bush hog and the mower caught on a stump. The mower folded up to almost 90 degrees and bent the linkage on the mower (not the tractors 3PH linkage) The front tires came off the ground before I could push in the clutch and the rear wheels lost traction. In this case I was mowing down a steep incline and I had the FEL on the tractor. My point is that the 3PH mower linkage was not strong enough to prevent a rear rollover. If I was on flat ground with less weight on the front of the tractor I could of rolled over. I think that a ridged implement like a box blade could prevent a rollover but I would like to see some proof.
Ferguson System Principal and Theory of Operation

My main goal for this thread is to create a thread that we can link to whenever the subject of Tractor Rollover comes up.

Let the heated arguing begin! (opps, I mean enthusiastic discussion)
Marshall

 

[IslandTractor]

Implements prevent Rollback

4) I believe that SOME implements may prevent a backflip and SOME may not, under SOME conditions. I also believe it may depend on the weigth of the tractor that is being used. Again, presume we go back to Ed's CK20 versus a B7510; presume both are hooked up to identical light duty box blades. The light duty box blade may not have enough strength to hold the weight of the CK20, but might have the strength to hold the much lighter B7510.

The CK20, once set in motion, will apply much more kenetic against the implement than that much lighter B7510, presuming they both roll backwards at roughly the same speed.​

​

Your hypothetical in interesting but I think there are other factors. For example comparing the light B7510 and the heavy CK20 each with virtually the identical engine power, wouldn't you think the lighter tractor would be more likely to backflip because there is less weight resisting lifting of the front wheels. I'd imagine the lighter tractor with the same power would be more likely to rotate on the rear axle than a heavier tractor.

 

[Farmwithjunk]

The very first condition that must be present to allow a tractor to roll over is an operator that believes it won't (or can't, or shouldn't) roll over.

Saftey devices (or practice's) should be called "safER devices". They don't eliminate the possibility of accidents. They simply REDUCE the likelyhood of accident, OR reduce the severity of injuries as a result of accidents. The concept of "eliminating any chance of accidents" because of saftey features being in place is ALMOST laughable if it wasn't for the fact that it ISN'T a laughing matter.

The best saftey feature ANY piece of equipment can have is an experienced, sober operator with at LEAST a lick of common sense. And that's no gaurantee.

Common sense isn't included with the owners manual. Owner must supply his (or her) own.

 

[Bob_Skurka]

[/indent]I'd imagine the lighter tractor with the same power would be more likely to rotate on the rear axle than a heavier tractor.

I don't know what is 'more likely' but I believe that both will roll backward easily.

It simply boils down to torque. If any tractor has enough torque to pull its front wheels up and roll backwards then it will do so in that type of situation.

Presume the tractor is in low range on the HST or in a low manual gear when this event occurs, it will have a maximum ground speed of about 3 miles per hour. That is not a weight dependant issue it is based on the gears.

Since both the light and the heavy tractor have the same theoretical groundspeed and if both have enough torque to lift the front wheels and rotate the tractor backwards in a backflip, then when the tractor gets to the critical point the heavier tractor has more kenetic energy. At that point the only thing that prevents the tractor from flipping is going to be the strength of the implement.

The best saftey feature ANY piece of equipment can have is an experienced, sober operator with at LEAST a lick of common sense. And that's no gaurantee.

Common sense isn't included with the owners manual. Owner must supply his (or her) own.

Well said.