Tractor "bouncing" ?

[timbrr]

I feel like dodge man hit a solid point on the first reply in this thread, that didn't get answered: What are your tire pressures?

Drop to 10 psi and report back. It's ok to see your front tires squish a bit. You need to use your tire sidewalls as suspension.

Edit: 32psi... thats nuts. I run 10-12 psi.

I just went and checked...

The fronts are Titan "Trac Loader NHS" 10-16.5, inflated to 32psi (with a max of 45, not 40 as originally posted [post corrected]).
The backs are Titan "Industrial Tractor Lug" 420/70-24 R4, inflated to 15psi (with a max of 20psi).

I must admit that I don't know what the tyre codes/numbers mean. Haven't gotten around to learning that yet. I described what I would be doing with the tractor, and the dealer recommended the tyres and pressures. I've just maintained the tyres at the same pressure they were at when I took delivery.

 

[big bubba]

the MX is a relatively small tractor. Kubota tractors are light on their feet anyway. you're going to bounce w/heavy fel loads
3 suggestions: ballast, ballast, ballast the rear 3ph w/brush hog or anything with weight. will be safer on slopes as well

 

[Hay Dude]

NVH?

Noise, Vibration and Harshness.

 

[rScotty]

This sounds plausible.
I'll try that, just to see if it helps, but I don't think constantly switching between 2WD and 4WD is really a practical solution especially when transit times are in the order of 30 seconds. The time lost changing drive mode would almost certainly be greater than the time lost just going slower. The 5100 does not have a way to quickly/easily switch between 2WD and 4WD, unfortunately.

For the loping, it's always a problem with a load in the bucket. The basic way that always works is to reduce the energy input by slowing down. But if you want to go faster before the loping gets out of hand you have to reduce the energy being transferred between the tractor and the FEL. To do that, you add some damping either to the tractor motion or the bucket motion...or both.

Dealing with the tractor first, you reduce the bouncing energy from the tractor by slowing down, reducing tire pressure, and shifting to 2wd.

BTW, since the front tires run at a slightly higher ratio than the rears, there's a lot of torsional energy stored in the 4wd drive shafts when traveling with so much load in the bucket that the front tires can't slip.That takes the form of the drive shaft and transmission windup. So not only for anti-bouncing, but mainly to reduce wear on the whole drive system you DO NOT want to be in 4wd when traveling with a load in the bucket.

Considering the FEL side of the equation, if the pivot pins for loader arms and bucket are tight and unworn, you can reduce the bouncing energy by soaking it up in some sort of damping mechanism. These dampers are called "easy ride" or "comfort ride" systems and there are various types on the market. Some are options when you buy the FEL, and others are aftermarket. All of them work....some better than others. Long's simple & inexpensive aftermarket nitrogen cylinder damping were mentioned by Jeff back in post #11 or #12. They work. Other systems have more complex damping cylinders, cost more, and work better. Some models of Kubota FEL offer a "comfort ride" as an option; that's a factory version of the same thing. All the comfort ride options work by storing energy in roughly the same way in a pressurized accessory cylinder. If your household water is on a well, you have a bladder pressure tank that is stores pressure in a similar fashion.

So with some thought, you could make your own damper with a pressure tank, valve, and some hoses. The picture that Jeff posted on his message shows everything you need to know about how it works.

Most of us just expect the tractor to lope when traveling with a full bucket. The fact is that no matter what you do, they will all lope at some speed on just about any surface. If we have some sort of active ride control like comfort ride we can go 50% faster before it starts to lope, but lope it will.

So what we all do is to reduce front tire pressure, shift out of 4wd, slow down, engage ride control damping if we are lucky enough to have it, and keep the FEL loader pins lubed to reduce the wear.
And sit back to enjoy the ride.
rScotty

 

[oosik]

IMPO - the tire pressures - 32/15 are probably about as close to optimum as you are going to get. Remember - the higher pressure in the front tires keeps them from rolling off the rims when turning with a load in the bucket.

I check the pressure in my front tires 2x annually. Because I do carry HEAVY loads in the grapple I keep them at the max sidewall rating of - 30psi.

I have not checked the actual pressure in the rear tires in over five years. I roll the tractor out on the driveway and inflate until I get a full "V-bar" imprint in the driveway dirt. From the times when I have checked - I would guess it's around 14psi.

Again - the most effective and cheapest way to control bounce - just slow down. Also - don't use 4WD unless you REALLY need it. On hard surfaces - like a well compacted gravel driveway - the tires might not be slipping, like they should. This can/will cause problems with the front driveline components.

 

[k0ua]

But also keep in mind running in 2WD with a heavy load and going down hills can lead to a "wild ride" A total out of control situation where the tractor takes off down hill and you can't stop it. here is what happens: The heavy load in the front bucket "unloads" the rear tires and makes for a lighter ground pressure. This reduces the contact patch on the rears slightly and to make the problem worse the two front tires are "free wheeling" because you are in 2WD,

The drive line is decoupled and normal engine/transmission hold back is not working for those front tires anymore they are free to take off downhill, and the rear tires start to slip on the ground, because remember they are "light". You can hear and feel the slippage. The tractor starts to take off and its picking up speed.

Nothing you can do with the brakes on the tractor will help, because the problem is that there are NO brakes on the front hubs and there is no drive line coupling to the rears where there are brakes because you are in 2WD not 4WD. Pressing on the brakes will activate the rear brakes, sure but the rear wheels are already slipping on the ground so further slowing of the rear tire rotation does absolutely NO good.

The only thing that can save you is to throw out the anchor. You can drop the bucket onto the ground to provide friction, or of you have a ground engagement rear implement like a blade you can drop that to add friction to slow you down. Or you can steer straight, try not to get sideways (will likely cause roll over) and ride it out to the bottom of the hill. Of course going straight to the bottom of the hill, might involve things in your path you don't want to collide with or dangerous path's like running out onto the highway for instance.

So, running with a heavy load in 2WD can be beneficial in some ways, it can also get you killed or injured or total a tractor too if the course involves a steep hill. BE careful. If you haven't taken the "wild ride", and if you live in hilly terrain, you will at some point, and let me tell , you will not soon forget it.

 

[dodge man]

My driveway is paved and about 600 feet long. You can稚 drive 60 mph down it because you would run out of road, but if you could it would feel very smooth. There is just a couple of spots that in my tractor with a full load in the bucket, will get the tractor rocking and bouncing pretty good. We also have a trail through the woods with a couple of rough spots. With out even thinking about I slow down in these spots. I don稚 know the exact speed, but when not driving on pavement, I知 probably going no faster than 5 mph and maybe as slow as 3 mph.

I致e twice had my tractor run away down a hill, both times because I forgot to put it in 4 wheel drive. If you need it off and on, best to leave it in 4 wheel drive.

 

[rgr33]

You don稚 mention whether the tires are filled. When I bought my LS, it bounced around badly, just as you describe. After filling tires with beet juice, the situation improved quite a bit.

Also, As you mentioned, you might need to just Slow down a bit on choppy ground.

 

[timbrr]

You don't mention whether the tires are filled.

The rear tyres are not currently filled with any sort of fluid.

This region is "warm temperate" so we only have a handful of nights that get below 0°C each year, rarely get hail, and never get sleet or snow. The tractor is stored overnight in a shed. There is no danger of anything freezing, so if I do fill the tyres it would be with regular rainwater. A DIY affair, cheap, non-toxic, relatively easily reversible, and no mess.

I wonder if, in addition to adding mass and improving traction and overall stability, whether the 'sloshing' of a fluid in the rear tyres would dampen any harmonics? Probably only to a negligible degree, unless a low-viscosity fluid were used -- and that would create a different set of problems so is probably best avoided.

 

[rScotty]

The rear tyres are not currently filled with any sort of fluid.
I wonder if, in addition to adding mass and improving traction and overall stability, whether the 'sloshing' of a fluid in the rear tyres would dampen any harmonics? Probably only to a negligible degree, unless a low-viscosity fluid were used -- and that would create a different set of problems so is probably best avoided.

With less free air space available for air compression, I suspect that after filling the tires with fluid you lose more air compression damping than you gain by the fluid sloshing. Observations by operators tend to lean toward filled tires giving a slightly rougher ride. Though not by much.

Those comments by K0UA in post #46 about going downhill in 2wd are worth anyone's attention.
Most of us have taken that wild ride downhill with a loaded bucket & 2wd - but only once. It's the kind of lesson that doesn't require repetition.

If our educational system was that efficient, a college education would take about 4 weeks instead of 4 years.
rScotty

 

[mikegatherall]

I found that changing "sensitivity" of hst peddles made a big difference when travelling....change to least sensitive setting and ride was better.

 

[oosik]

Yes - I took the wild ride - only once - right in my driveway. But I was towing my ten ton farm wagon loaded with large rock. Hit the brakes - nothing. Even though the rear tires have 1550# of RimGuard - they skidded real well. I then dropped the bucket. It did not stop me but slowed this catastrophy down so I could control it. Change your shorts - lesson learned.

 

[timbrr]

I found that changing "sensitivity" of hst peddles made a big difference when travelling....change to least sensitive setting and ride was better.

Is that a Mahindra HST feature? My Kubota 5100 only seems to have a "stop" that can be screwed up/down to limit how far the pedal can be pushed down.

 

[rScotty]

Yes - I took the wild ride - only once - right in my driveway. But I was towing my ten ton farm wagon loaded with large rock. Hit the brakes - nothing. Even though the rear tires have 1550# of RimGuard - they skidded real well. I then dropped the bucket. It did not stop me but slowed this catastrophy down so I could control it. Change your shorts - lesson learned.

Isn't that great! Life doesn't offer many of those types of instant learning experiences - happenings so memorable that they are imprinted forever and can be recalled in great detail 50 years later. But the first time you lose control of a tractor going downhill tends to be one of those.
rScotty

 

[rScotty]

Is that a Mahindra HST feature? My Kubota 5100 only seems to have a "stop" that can be screwed up/down to limit how far the pedal can be pushed down.

On the Kubotas with HST+ the sensitivity is adjustable from fast to slow via a knob on the dash. Probably software of some sort. That used to be a feature just for the HST+ transmission, I'm not sure that all HST Kubotas have it.

 

[crashz]

The MX and economy L series do not have that software control.

The adjustment bolt is for pedal travel. The owners manual warns against adjusting those.

 

[kneedeep]

Add weight to rear

 

[Lendsy]

A boat anchor maybe?