Side-slopes: If my B2920 could do it, can my L4310?

[troverman]

I hate mowing side slopes, but unfortunately they are a fact of life for me. I've been mowing a particular jobsite which is listed at 3:1 slope. That may be an average, some areas seem steeper. 3:1 works to to about 19 degrees or 34% grade.

For two years, I've been mowing this slope with a Kubota B2920 tractor and a 4-foot flail mower on the back. I've done it with no loader and no front weights; done it with front weights, and done it with a loader. Definitely some pucker factor a few times, none of it is comfortable, but no incidences.

This year the grass is simply too tall for the B2920...I've tried...so I'm using my L4310 with the same small flail mower.

Would you expect the L-series to be equally stable and safe? It feels more "floaty" during my initial start yesterday. The rear tires are filled; about 550 lbs per tire. It does have a loader on the front, lowered as much as possible.

 

[BAP]

Are you mowing going across the slope or up and down? The safest way to mow a steep slope is to go up and down.

 

[troverman]

Are you mowing going across the slope or up and down? The safest way to mow a steep slope is to go up and down.

I'm mowing across. I'm aware the safest way is up and down. I have always mowed across though. I'm just wondering if the larger tractor will be better, worse, or about the same attempting this job.

 

[OldeEnglish]

If your tires are loaded on both tractors it makes a huge difference for stability.
I have an area that I side slope, it is frightening to do it with a riding lawn mower but amazingly easy with the 2910. We just bought a JD riding mower to mow with instead of the tractor and I'm back to weed wacking a good majority of the slope that I used to cut with the 2910. I've always left the FEL on, but the only thing that matters is what your comfortable with. I would think the larger L tractor would feel even more stable than the B.

 

[troverman]

For some reason this L "feels" a lot scarier than the B on the same slopes. Maybe it's just my inexperience with this larger tractor.

 

[85Hokie]

For some reason this L "feels" a lot scarier than the B on the same slopes. Maybe it's just my inexperience with this larger tractor.

As the tractor gets bigger, the tires/wheels get bigger, with all that - the center of gravity moves higher up too!

Spacers, or moving rear tires outward help a lot, a great deal as a matter of fact!

Whatever you do, do it slowly and carefully!

 

[cerlawson]

With a question like this I have run some physical tests. I park the tractor on the slope. I also park an anchor vehicle up hill. I attach a rope to the test tractor as high up as possible,as on the roll bar. The other end goes to the anchor, as at the trailer hitch with no risk of tipping that over.

Then with a pry bar, such as a 2 x 4, I try to tip the test tractor over, with just a little rope slack. If that "seems OK"and the test tractor is not just balanced on 2 wheels, I go again with a little more slack. Then if all Ok at for sure more tip angle than the slope I put the driver on the seat and see if the first try still is OK.

Try again with front wheels turned, brakes on.

Without this test, I also have observed traction on the steepest part, and losing traction on up hill side shows you are near the point of tipping.

This has worked out for me and no bad results ever.

 

[troverman]

How will I be able to "pry" the tractor to tip when it weighs 5,000lbs or more?

Also, a moving tractor is less stable than a stationary one.

I dunno. This just feels worse to me than the little B2920. It could be because that tractor is considerably shorter.

 

[cerlawson]

Troverman: If you are on a slope that is near critical it won't take much to make it go over. With a lever, you can lift a lot more than your body can without the lever. If you can't move it when it is on the slope, you obviously have no problem.

I also thought about one more test I ran, using two tractors. I connected the rope to the test tractor up high and low on the anchor anchor, with the anchor on a lesser steep slope up the hill. Then drove both along the steeper parts observing loss of traction, etc, driver trying to make it tip by sitting on downhill side of seat and fenders.

With all of this remember the rope will stretch so allow for that.

 

[Utopia Texas]

Just be sure to wear your seat belt while working on slopes and have the ROPs up and locked if they are the foldable type.

 

[cerlawson]

I won't try to convince you of anything but state some physical facts. Moving versus sitting still does not change the location of the center of gravity, thus stability. Hitting depressions or bumps does throw impact up or down to tractor however.

One more item, a mower attached to the belly is a little more safe than hung off the back and has an out-rigger safety effect to some extent. Belly mower not riding on its wheels lowers the center of gravity of the tractor-mower combination also, thus safer when carried along by tractor..

 

[BAP]

Basically, if you don't feel comfortable on the seat of your tractor, then change how you do it. Widen the wheels out or change to mowing up and down. Nobody is going to be able to tell you over the internet if you are safe doing it or not without physically being there and seeing what your situation is. What one person considers tippy is nothing to the next person. If you yourself are not comfortable then I would not keep doing it.

 

[Creature Meadow]

Could you post some pics of your tractor sitting on the slope you are talking about, I'm interested in seeing this?

Thanks,
Jay

 

[skeets]

Im not going to be safety sam here but there are way to many people in the ground from mowing across a slope,,, Seem to many tractors upside down over the years because somebody thought it would be ok. Do as you will, but if I had to back up a grade to cut I would before going across,,just MHO,,, we now return you to normal broadcasting

 

[Grouse Feathers]

These are just basic calculations with these assumptions (swag):
The center of gravity on either tractor is 3” above the axle.
Diameter of ag tires found on the web was 35.5 for the B2920, with 11.2-16 tires.
Diameter of ag tires found on the web was 49.8 for the L4310, with 14.9-24 tires.
Tread width for the B2920 is 37.4”.
Tread width for the L4310 is adjustable 46.5” to 62.4”.
The CG (center of gravity) is ½ of the wheel diameter + 3” above the ground.
B2920 - 20.7”
L4320 - 27.9”
The distance from the center of the tractor to the outside of the downhill wheel is ½ of the tread width +5”.
B2930 - 23.7
For the L4310 to have the same tipping angle would require a center of tractor to the outside of the wheel distance of (B2920 center to outside wheel)*(L4310 CG)/(B2920 CG)=32".
The tread on the L4310 would need to be (32”-5”)*2 = 54”.
I know nothing about the L4310 or how to adjust the rear tread, spacers or turning wheels around?

These are not exact numbers just a good approximation.

 

[skeets]

Sooo your saying that the "L" is or more or less tippy that than "B"

 

[Grouse Feathers]

Sooo your saying that the "L" is or more or less tippy that than "B"

It depends on the width of the rear wheels. At the narrowest setting of 46.5 the L will be more tippy. With the rear tread at 54" they will be the same. At the widest setting on the L of 62.4 it will be more stable.

 

[cerlawson]

I did a google search for the subject and a bunch of comments came up. To add dust in the air, take a look here/ Maybe someone really knows where he C.G. is.

https://www.google.com/#q=Kubota+tractor+.center+of+gravity

Since the center of gravity is not right over the rear axle and likely the wheel spacing of the front tires is less than the rear, calculations based only on rear wheels is likely on the unsafe side.

Also the pivoting of the front axle further is on the unsafe side as compared to no pivot.

 

[cerlawson]

One more. I just now recall something about the subject with a tractor that had a loader. I did some hauling of it with a single axle trailer with tilt bed. I would set the tractor with the CG a little forward of the axle. How did I know that position? Moving it back and forth on the trailer the tilt bed fastener would have a little slop. With that, I easily could know where the CG was. For that tractor with loader it was about 1/3 the way between rear and front axle. Rear tires were filled with fluid also. On that basis ad for a tractor without loader of filled tires it still would be about 1/3 the way, not over the rear by any means. So I parked the tractor, facing backwards with rear tires against the front railing. It's an easy test.

 

[Grouse Feathers]

There are way to many unknowns to do any CG analysis of what slope these tractors can safely operate on, and that was not my intent. My only intent was to compare the stability of the two tractors and to provide some direction on how wide to set the wheels of the L (as wide as possible). I agree cerlawson your test of procedure would give me the most confidence as to operating on a specific slope. However, if someone does not understand your procedure and the engineering principals maybe they should not do your test. I think my analysis points to the width of the L as being a likely cause of the OP's floaty feeling and gives him a good direction on widening the stance of the L.

I am not sure I could ever feel comfortable mowing across slope on a 34% grade. Just like the design tractor unknowns to many hidden terrain lurking in the grass.