Tractor "bouncing" ?

[timbrr]

When traversing rough terrain, you may have noticed this "bouncing" phenomenon.

I'd fully expect to be bouncing on "rough" terrain. But that's not the case I'm describing, The bouncing occurs on regular terrain. On essentially flat ground (albeit with small amounts of some different types of grasses growing on it). No slopes, no rocks, no ruts.

I can even add sand and build up the track by 10cm or so, smooth it out with the bucket, and the bouncing will return.

A track that can be comfortably traversed at a given speed with a given load with no bouncing whatsoever, eventually can no longer be traversed at the same speed with the same load without bouncing.

 

[jeff9366]

Just wondered what everyone thinks of this new product by W. R. Long. The name is a bit deceptive as it's not something intended to directly improve the "ride" of your tractor, but it dampens the movements of the FEL as you traverse over (uneven) ground. The end result I suppose is that it could reduce the jerky movements of the tractor as you drive it over rough terrain, and help it ride a bit smoother. Their main selling point though seems to be that it reduces the wear and tear on the loader's mechanical joints, and maybe reduces the metal fatigue as well.

I think the theory behind it is good, but it would be nice if they could show a side by side comparison of two identical tractors, one with the system and one without the system, driving over the same terrain. I'm not thinking of buying one, mind you, but the hydraulic dampening technique just peaks my interest a bit. The suggested retail price of the CR10 is $425 and the suggested retail price of the CR20 is $475, if you're interested. :thumbsup:

W.R. Long, Inc. | Tarboro, NC

Kubota dealer installed the Long CR10 on my L3560 with LA805 FEL. Works as advertised. With moderate loads of brush on Debris Forks damping actions eliminate material falling off during transit. Productivity is enhanced.

One hydraulic line had to cross the right loader arm in my ((early)) installation.

With CR10 working, bucket does not pound, burdened or unburdened.

Oak section guesstimate 1,200 to 1,400 pounds. FEL (LA805) lift capacity 1,700+ pounds. I cut large diameter Oak loads to fit in the bucket, near to the tractor, rather than on the forks, where leverage works against stability. Three Point Hitch counterbalance 900 pounds. Much less transient load stress on the tractor with Long's "Comfort Ride" cushion-accumulator installed.

Kubota factory "Shockless Ride" option is available on the Kubota M5660 with LA1154 loader.

Kubota should offer Shockless Ride option on the Grand L series. The proverbial cherry atop whipped cream.

 

[Hay Dude]

When I Road my hay tractors, they will ride perfectly up to about 22MPH, but increase throttle and try to go the full 24.5MPH and they will porpoise wildly front to back. I did find increasing tire pressure helps, but then ride quality sucks in the fields. These 2 tractors have soft ride option on the loaders, and one has a front axle suspension. However, the front axle suspension doesn’t help with the porpoising. It does help in bumpy fields.

My larger tractor, which has a 34MPH road speed, has a front axle and cab suspension, which helps tremendously. It does not bounce front to back.

I think tire brand/quality might also be a factor.

 

[timbrr]

If you insist on operating at the ground speed that causes you discomfort...

My personal comfort is not really what I'm worried about. The MX5100 has Mechanical Front Wheel Drive, so when I'm in 4WD mode the front and back are mechanically coupled. Since the bouncing accentuates the HST/drive-train noise I am mainly concerned about wear and tear on some sort of (obscure) HST/drive-train-related component.

 

[timbrr]

I've noticed when hauling heavy bucket loads over the same path, the bouncing gets worse. I've figured it out, at least for me. First, the 'path' I choose gradually gets smoothed out, flattening the many small bumps and rough ground. That leaves a smooth path but accentuates the slightly larger humps and whoopty-doos. Second, once I get that smooth path I gradually travel at a higher speed compared to the first few trips over it, since the many small bumps are gone and I feel safe.

A pretty accurate description of what happens with me up until this point...

If I can drive the path in mid range, 3rd gear, then I should be able to bump up to mid 4th and save some time, right? Third, I find myself loading larger and larger buckets full after the first couple trips. If 'full' worked, then 'fuller' must be better since it will save me trips, right?

...but I don't go up a gear, or increase the size of loads. They remain constant.

My suggestion... Slow down and enjoy the ride.

Yes, that does stop the bouncing, but it may not be the only solution to the problem.

 

[LouNY]

As others have said the best thing is to slow down.
The various "soft ride" loader additions are designed to dampen the loader oscillations and will do so.
At the speeds you are traveling I'm surprised that you are in 4wd,
one item to be aware of is with the tractor bouncing and loading and unloading the tires is that every cycle will change the
loaded radius of your tires which in turn will affect your front - rear tire balance.
Any tractor with a loader will bounce or porpoise more then the same tractor without a loader, just removing the loader bucket when not needed also reduces the bouncing and stress on the front axle.
The only way to reduce the stress on the tractor is to slow down.
The paved road that we use the most with the tractors has gotten so rough in the tractors that we can't use the highest gears for road hauling, we have to drop down one or two gears and throttle down on the paved road.
The town graded a dirt road the other day and I could actually run faster on that then the paved road for a few days.

 

[timbrr]

Any object has what, in engineering terms, is called a mass-elastic system and a resultany natural frequency that it ç*ºibrates at. The mass elastic system can be mathematically modeled given the stiffness, mass and spring rates of the components and assemblies, and enough computational powers. Wheelbase is one of the factors too.

What痴 happening is that your machine is compacting the earth, causing 途ipples that excite the natural frequency of your tires, and vehicle mass.

Kind of like resonant frequencies in music? Constructive interference then increases the amplitude of motion?

You can change the response by speeding up, slowing down, or changing the air pressure or stiffness of your tires so you aren't exciting the tractor at the natural frequency of its Nass elastic system.

Modifying components of the system (e.g. tyre pressure) would likely alter, rather than eliminate the existence of, such frequency -- correct? If so, then the symptoms would disappear whist the tractor and the track were out of sync. Over time, the track would be remoulded by the new frequency and the symptoms would return, I assume.

If that's the case, and given that most of the tracks are temporary in nature, changing air pressure probably wouldn't be practical as it wouldn't (permanently) solve the problem. Changing transit speed from trip to trip likely would help though. I have noticed that often just changing speed (up or down) subdues the severity of (i.e. 'dampens') the bouncing.

Cars sometimes, in the past, had what was referred to in technical circles as California freeway hop? The story goes that the expansion joints in California freeway pavement were spaced slightly different than most other typical highways. That longer spacing set up many cars structures and suspensions to go into resonance when crossing the expansion joints at the speed limit, resulting in an uncomfortable ride.

Designing cars to a higher mass-elastic stiffness keeps the resonance to a minimum.

So, apart from increasing tyre pressure, is there any way to increase the "stiffness" of a tractor?

 

[ruffdog]

timbrr....I have neighbors that have big end-loaders and also road crews use them, and they will get bouncing on a SMOOTH road surface. I have a feeling that off-road tires are not as round and consistent thickness as on-road tires. If they all start acting in unison, then you get bouncing. Just like them, you just have to slow up, get through it, and try to change the conditions like you have been. The bouncing you describe does seem to happen more on smooth surfaces more.

 

[orezok]

This may not be relevant, but with my B7800, it has a tendency to porpoise when carrying loads in 4 wheel drive. If I switch to 2 wheel, the motion greatly decreases. I guess that the front and rear drives are at a little different road speed causing the rocking as the drive train loads up and then suddenly releases as one axle loses traction.

 

[Gary Fowler]

This may not be relevant, but with my B7800, it has a tendency to porpoise when carrying loads in 4 wheel drive. If I switch to 2 wheel, the motion greatly decreases. I guess that the front and rear drives are at a little different road speed causing the rocking as the drive train loads up and then suddenly releases as one axle loses traction.

I suspect this is exactly what is happening to the sand, the front wheels turn just a little faster so they tend to mound up the loose sand a bit with each pass and eventually this starts the harmonic "loping " so you end up bouncing up and down in the seat. Each time the tires run over the humps they react more and more so you end up with a big up and down, front to back hop. Back dragging to remove the humps results in a smooth ride for a couple trips till the front wheels throw up the humps again.

Try travelling in 2WD if it is safe to do so, ie, not hills to traverse where you might loose rear wheel traction.