Help...shoudnt the tires spin ???

[SPYDERLK]

But I want to point out that this is not an INHERENT limitation of HST. Beef up all your hoses and fittings and stuff, set the relief higher, and you could snap an axle off the same as you could by abusing a geared tractor. If you engineer the drive train of a geared tractor just barely strong enough that it won't be broken by sudden, full-stop traction against its engine running at full tilt...and you design the HST system of its otherwise twin brother to relieve just before breaking the other drive train components also, then they could put exactly the same maximum torque to the ground.

As you imply, we implement the relief because we don't want users approaching and exceeding the limit without feedback. So instead of suggesting that HST systems are deficient, what you're really saying is that both can put the maximum safe reliable torque to the ground, but that a geared tractor will let you go beyond that and break it if you want. To CobyRupert I'd say I'll take the infinitely variable ratio and the built-in protection, thanks.

"Stuff" includes pump and hyd motor that, due to the automatic protection relief, have been designed close to the original specific torque point.

A gear typically has a large performance margin to start with. Try nearly tripling the weight of an HST tractor and see if it will spin the wheels with AGs on good ground. A gear will.

 

[Jhiphop72]

"Stuff" includes pump and hyd motor that, due to the automatic protection relief, have been designed close to the original specific torque point.

A gear typically has a large performance margin to start with. Try nearly tripling the weight of an HST tractor and see if it will spin the wheels with AGs on good ground. A gear will.

Exactly... When was the last time you saw a HST win a tractor pulling contest???

 

[peter3759]

I'm not interested in winning a tractor pull but I know I can move faster with a lot less effort when moving dirt and other various tasks with my hydro! If I needed every ounce of power to the ground with everything I did then I MIGHT consider a gear tractor but I don't! I moved a lot of dirt today and just thinking about all the clutching I would of done on a gear makes my knee hurt! For all of you who are masters at a gear tractor that's awesome because it's becoming a dying art but for me and MY applications hydro I went and I'll never look back!

 

[Woodshaver]

Everyone, let go of the past, gears are good but things change . Embrace new technology when it makes things more productive and easier.

 

[dfkrug]

But I want to point out that this is not an INHERENT limitation of HST. Beef up all your hoses and fittings and stuff, set the relief higher, and you could snap an axle off the same as you could by abusing a geared tractor. If you engineer the drive train of a geared tractor just barely strong enough that it won't be broken by sudden, full-stop traction against its engine running at full tilt...and you design the HST system of its otherwise twin brother to relieve just before breaking the other drive train components also, then they could put exactly the same maximum torque to the ground.

True, it is not an inherent limitation of HST; you can make an HST tractor of the same size/weight/hp deliver the same torque to the rear wheels as an equivalent gear tractor. Won't go as fast up a hill, but that's a power and efficiency issue.

A tractor's designer can play with not only the RV pressure and final drive gear ratios (incl tire diameters), but also the volumes of the HST pumps and motors.

This issue has been dealt with in several other threads, but I have had the 3 distinct design variations of an HST tractor:
> goes to relief
> spins tires
> bogs engine

while my gear CUTs all either:
> spins tires
> bogs engine
no gear tractor should ever slip the clutch

All situations are in excellent traction (hi weight, AG tires, great surface) in lowest range at full engine speed.

IMO, the designer should shoot for the "spins tires" condition for all CUTs up to a weight of at least 2x naked weight in high traction conditions. Maybe even higher.

The fact that some of my gear tractors have failed to do that (bogging engine) implies that even the designers of gear tractors sometime fail to make the "correct" tradeoffs.

My own tractor is a little deficient (RV opens), but I can live with the rare conditions that cause that.
I am almost up to 2x naked weight as well (6000#).

I have never had any Deere HST ever fail to spin tires, BTW.

 

[SPYDERLK]

I'm not interested in winning a tractor pull but I know I can move faster with a lot less effort when moving dirt and other various tasks with my hydro! If I needed every ounce of power to the ground with everything I did then I MIGHT consider a gear tractor but I don't! I moved a lot of dirt today and just thinking about all the clutching I would of done on a gear makes my knee hurt! For all of you who are masters at a gear tractor that's awesome because it's becoming a dying art but for me and MY applications hydro I went and I'll never look back!

Yes! Id sure love to have a 14K# HST tractor platform for loader work. The advantage in control is huge. The only time Id miss the gear is if there ever came a time the wheels wouldnt spin.

 

[SPYDERLK]

All situations are in excellent traction (hi weight, AG tires, great surface) in lowest range at full engine speed.

IMO, the designer should shoot for the "spins tires" condition for all CUTs up to a weight of at least 2x naked weight in high traction conditions. Maybe even higher.

The fact that some of my gear tractors have failed to do that (bogging engine) implies that even the designers of gear tractors sometime fail to make the "correct" tradeoffs.

My own tractor is a little deficient (RV opens), but I can live with the rare conditions that cause that.
I am almost up to 2x naked weight as well (6000#).

I have never had any Deere HST ever fail to spin tires, BTW.

Did that gear tractor have a rather high 1st gear, or the conventional 1 to 1.5 mph? All the ones Iv ever encountered with the 1.5 low will hold a spin at about 1K engine speed. That would be about 0.6 mph wheel rate.

 

[4570Man]

I am running over double naked weight on the L3240 HST. I can still spin the wheels even on asphalt. A gear tractor could spin the wheels faster, but please explain how a gear could pull any harder. The old F2550 gear could spin the wheels idling in first or second gear. Running 2500 rpm it would spin in 5th gear. I don't care how much faster a gear tractor can spin the wheels I'll take a HST every time.

 

[SPYDERLK]

I am running over double naked weight on the L3240 HST. I can still spin the wheels even on asphalt. A gear tractor could spin the wheels faster, but please explain how a gear could pull any harder. The old F2550 gear could spin the wheels idling in first or second gear. Running 2500 rpm it would spin in 5th gear. I don't care how much faster a gear tractor can spin the wheels I'll take a HST every time.

No advantage to a fast spin as far as force delivery. In a gear to gear comparison it would give an idea of the surplus power available. ... But comparing between types it would be very hard to judge due unknown hyd losses.

I am impressed at your 2x spin on asphalt - particularly if 4wd and you have R4s that are not overinflated, and asphalt that has good exposure of grit. Still, from test measurements I have done with R1s on good ground I find they have a traction coefficient of 1 or a little more in that application. I dont think tractor rubber on pavement can meet that number. But R4s would be a little better there than R1s.

 

[4570Man]

I was pushing a wood pile that was right on the edge of the driveway. The tractor was in 4wd, but the front wheels were off the driveway on dirt. I have R4 tires on the tractor.

 

[k0ua]

I remember spinning 3 tires on my last tractor ( the Kubota) in LO range on Asphalt when trying to pull over a tree. I haven't tried it with the Kioti. Both have R4's, both 3 speed Hydro's, This included rear ballast, and a downhill pull.. Any hydro should be able to spin tires in LO range. Med, may be iffy, depending on many factors, and HI is no way. At least that is been my experience.

 

[oldpilgrim]

I don't care how much faster a gear tractor can spin the wheels I'll take a HST every time.

yup,

and with my HST with FEL, BH and loaded tires, I always break traction. I've never noticed a relief valve kick in. I'm running about 2 1/2 times naked weight.

 

[dfkrug]

Did that gear tractor have a rather high 1st gear, or the conventional 1 to 1.5 mph? All the ones Iv ever encountered with the 1.5 low will hold a spin at about 1K engine speed. That would be about 0.6 mph wheel rate.

I have had Kubota L2550DTs that would bog the engine rather than spin tires on dirt just soft enough for the
AGs to bite deeply. This was with a backhoe mounted and using the FEL to push into a giant pile. On pavement,
which is not as good of a surface, I could always spin them.

This tractor has a very low 1st gear.

Another Kubota, this time an HST B21, would bog the engine in Low range even with R4s. Hoe mounted. The
B21 is very low on power, and, as they get older, they often have less hp. This one had 2400 hours. Note
that not all tractors as they age lose power. If rings/cyl get worn they might lose some compression (less hp),
but they also loosen up and have less internal friction losses.

Once you break loose the tires, less power and force is needed to maintain (or speed up) the spin.

Those with gear tractors pushing their FEL into a huge pile of materials should avoid feathering
the clutch to increase torque to the rear wheels. Clutches are a huge job to replace....I
just did one on an L2550.

 

[4570Man]

yup, and with my HST with FEL, BH and loaded tires, I always break traction. I've never noticed a relief valve kick in. I'm running about 2 1/2 times naked weight.

Me too. Naked weight is 3,139 with everything on it it weighs 8,500. The only time I couldn't break traction was when I failed to release the parking brake. With the backhoe removed I can break traction in medium.

 

[oldpilgrim]

Me too. Naked weight is 3,139 with everything on it it weighs 8,500. The only time I couldn't break traction was when I failed to release the parking brake. With the backhoe removed I can break traction in medium.

I should have mentioned my gear range is in medium range as well.

 

[SPYDERLK]

I have had Kubota L2550DTs that would bog the engine rather than spin tires on dirt just soft enough for the
AGs to bite deeply. This was with a backhoe mounted and using the FEL to push into a giant pile. On pavement,
which is not as good of a surface, I could always spin them.

Those with gear tractors pushing their FEL into a huge pile of materials should avoid feathering
the clutch to increase torque to the rear wheels. Clutches are a huge job to replace....I
just did one on an L2550.

Thats pretty amazing. Our L2550 with loaded AG tires, 1500# power brush as counter weight, and the loader carrying all it will pick up, will spin 4wd with diff locked effortlessly in low range 1st at low idle. The engine barely loads.
,,, 1st is very low as you said - it tops out at under a mph. I only use it to go/spin as slow as possible ... about 1/3 mph so I dont have to feather the clutch . The lowest I ever go for max tractive force available is low range 3rd.

 

[4570Man]

I have had Kubota L2550DTs that would bog the engine rather than spin tires on dirt just soft enough for the AGs to bite deeply. This was with a backhoe mounted and using the FEL to push into a giant pile

Yours must be defective. My Grandpa used to have one. It had a loader, loaded R1 tires and a backhoe. It would effortlessly spin the wheels on dirt with the engine idling. With the engine turning about 2500 rpm it would slip the wheels in 5th gear.

 

[SPYDERLK]

Yours must be defective. My Grandpa used to have one. It had a loader, loaded R1 tires and a backhoe. It would effortlessly spin the wheels on dirt with the engine idling. With the engine turning about 2500 rpm it would slip the wheels in 5th gear.

Well, that matches mine on the low end. Fifth/hi range1st gear however can easily be over ridden by good traction conditions.

 

[xtn]

"Stuff" includes pump and hyd motor that, due to the automatic protection relief, have been designed close to the original specific torque point.

A gear typically has a large performance margin to start with. Try nearly tripling the weight of an HST tractor and see if it will spin the wheels with AGs on good ground. A gear will.

Sure. My point is that a lower capability may be TYPICAL of production hst tractors, but it isn't INHERENT in the design of hst systems. An hst system can be designed to deliver whatever torque delivery specifications you might request. It is incorrect to generalize that hst systems have some inherent deficiency that prevents them from ever matching the torque delivery of a geared system.

 

[dfkrug]

Yours must be defective.

I don't think so. My 1st tractor was an '89 L2550DT, purchased along with 2 others
from a rental company. I still know where 2 of them are, owned by friends. One
has a hoe on it.

It is not as easy as you might think to duplicate ideal traction conditions. High
weight plus soil that allows the deep AG lugs to fully embed, front and rear.
Simultaneously pushing into an immovable pile, and lifting with the FEL at the
same time.

Of course, lifting at the same time as pushing does use some of the engine's
power, which takes away from motive power.

I could never bog any of the L2550s without the hoe mounted or on pavement.
Never. Always spin the tires.

Finally, this is a pre-EPA tractor with about 2000hr, and all 3 had significant
blow-by, readily visible from the hose that hangs at the bottom of the engine.
Clearly, less power was available vs. new.