RPM’s & hydro stress while working land.

[Hd883chopper]

Hi folks,
Just wondering what the more experienced tractor operators would say here. I was plowing today with my L4330 4x4 w/ FEL and at I had it idled up to about 2400 RPM’s. Once plowing and working it would drop to about 2200 RPM’s.
My foot pretty much had the floor pedal mashed 90% of the time. This is about as hard as I work this machine but she was definitely working.

Here are my questions, should I be idled higher so I’m not flooring the pedal as much? In other words, does it matter if I’ve got the pedal pegged to the floor or should I just give the engine more power?

What is the ideal RPM range when plowing, tilling or any other heavy work?

I can hear the hydrostatic transmission whining a little under this load. Is this normal? I’m always concerned that I’m stressing the hydraulics and will damage something. Since I’m not operating the PTO with this scenario, I know it’s all transmission stress.

Thank you,
HD

 

[bmblank]

You should not be flooring the pedal. On a hydro, the pedal is not a normal accelerator. The harder you press the pedal, the higher "gear" you are in. It's a little counterintuitive, but when the tractor starts to bog down, you have to remember to back off on the pedal. Slow down a bit and your RPMs won't drop so much.
That being said, a little RPM drop when you're working it pretty good, like plowing, is not out of the question. I guess I don't really know to what extent; I don't pay so much attention to the RPMs, I just use my ears.
I was using my disc the other day and for the most part I was running it somewhere in the 2000-2500 range.

 

[NCL4701]

A couple of things:

Unless it was in High range, which is unlikely being you actually got the plowing done, I don’t think you did anything abusive. Someone may know something I don’t, but I don’t see that damaging your tractor.

I’m also assuming you didn’t have it in Low range based on the reduction in engine RPM. Honestly don’t know if the 4330 is just 3 range or if it is the 3 range with high/low in each range for a true total of 6. It doesn’t really matter much for purposes of answering your question.

Personally, I will push my machines hard but I do prefer to have them working where they are happy, particularly for some lengthy chore such as mowing or plowing. I would either drop a range or back off on the pedal until the rpm loss on the engine was nominal. I’d also want the pedal to be at least 50% or more to get enough flow through the hydraulic motor in the HST to cool properly. Between messing with the ranges, pedal position, and throttle position, I’d try to find a spot where the tractor is happy and I am too.

WOT and full pedal is not abuse on a diesel HST. WOT and full pedal resulting in rpm loss sustained for a long time implies consideration of backing off the pedal a bit or range reduction, but the rpm loss you report doesn’t suggest abuse.

Just my opinion.

 

[Hd883chopper]

You should not be flooring the pedal. On a hydro, the pedal is not a normal accelerator. The harder you press the pedal, the higher "gear" you are in. It's a little counterintuitive, but when the tractor starts to bog down, you have to remember to back off on the pedal. Slow down a bit and your RPMs won't drop so much.
That being said, a little RPM drop when you're working it pretty good, like plowing, is not out of the question. I guess I don't really know to what extent; I don't pay so much attention to the RPMs, I just use my ears.
I was using my disc the other day and for the most part I was running it somewhere in the 2000-2500 range.

Thanks for that info. I have heard in some circles that pushing the pedal down further when under a load is counter productive. Unsure why this is but I noticed NCL4701 indicated that it was fine, so differing opinions I guess.

Sounds to me like your advice is to idle the machine up a little more so that I don't feel the need to bury the pedal. And slow down some. Just a side note, I was in Low gear during this process.
Thank you

 

[Hd883chopper]

A couple of things:

Unless it was in High range, which is unlikely being you actually got the plowing done, I don’t think you did anything abusive. Someone may know something I don’t, but I don’t see that damaging your tractor.

I’m also assuming you didn’t have it in Low range based on the reduction in engine RPM. Honestly don’t know if the 4330 is just 3 range or if it is the 3 range with high/low in each range for a true total of 6. It doesn’t really matter much for purposes of answering your question.

Personally, I will push my machines hard but I do prefer to have them working where they are happy, particularly for some lengthy chore such as mowing or plowing. I would either drop a range or back off on the pedal until the rpm loss on the engine was nominal. I’d also want the pedal to be at least 50% or more to get enough flow through the hydraulic motor in the HST to cool properly. Between messing with the ranges, pedal position, and throttle position, I’d try to find a spot where the tractor is happy and I am too.

WOT and full pedal is not abuse on a diesel HST. WOT and full pedal resulting in rpm loss sustained for a long time implies consideration of backing off the pedal a bit or range reduction, but the rpm loss you report doesn’t suggest abuse.

Just my opinion.

Hey, thanks for the info. I actually did have it in Low gear. This machine has a High, Mid and a Low. I was told once by the dealer that I should be in Low when working the loader and generally working the machine. Med or High is fine to move a full loader of sand from A to B but when digging in or working the PTO hard, use Low only.

I'm new to the hydro transmission and I just don't want to break it haha. Guess I'm used to my old International with a shifter for the transmission. The only thing that would woe down when working was the motor if it too tough.

Good point on cooling the HST with at least 50% pedal, I'm usually running at least that.

As far as RPM loss, it only happened when the load got pretty tough. Either the plow was digging more or tires caught more traction for a moment. I was more concerned with the whining noises from the hyd pump. Do you all hear that noise when working? It's different from the engine noise, just wondering.

Thanks NCL.

HD

 

[bmblank]

Yeah, that sounds totally normal. The great thing about the hst is that you can feather how hard it's working without backing off completely. When it starts bogging down a bit, just back off the pedal a little to make sure it keeps the RPMs up.

Just remember, the pedal is controlling the transmission, not the engine. When the treadle pedal is in the middle, it's in neutral, when you barely push it down, that's like putting it in a real low gear. The harder you push, the higher your gear ratio will be.
Driving along and it starts bogging down, release the pedal a little bit and it is like down-shifting, except you have infinite "gears" and you don't lose all your momentum in having to push in the clutch.

 

[NCL4701]

Hey, thanks for the info. I actually did have it in Low gear. This machine has a High, Mid and a Low. I was told once by the dealer that I should be in Low when working the loader and generally working the machine. Med or High is fine to move a full loader of sand from A to B but when digging in or working the PTO hard, use Low only.

I'm new to the hydro transmission and I just don't want to break it haha. Guess I'm used to my old International with a shifter for the transmission. The only thing that would woe down when working was the motor if it too tough.

Good point on cooling the HST with at least 50% pedal, I'm usually running at least that.

As far as RPM loss, it only happened when the load got pretty tough. Either the plow was digging more or tires caught more traction for a moment. I was more concerned with the whining noises from the hyd pump. Do you all hear that noise when working? It's different from the engine noise, just wondering.

Thanks NCL.

HD

Yeah, the harder you push it the more it whines. I’ve heard some say the whine is pretty loud on some of the smaller 01 L’s and not so much on the Grands. I haven’t noticed high decibel whine out my L4701 but as a general thing it whines louder the harder you’re pulling with it. I haven’t plowed with the Kubota, but skidding a big log that’s pushing its limits in any range or running up a hill in High range it will make some noise. Wouldn’t be concerned.

Like you, my prior tractor experience was on older machines that had simple gearboxes, clutch, and shift lever on top of the transmission just sliding gears with forks. Took some getting used to what the normal sounds for the new Kubota HST are.

 

[foobert]

This is a great question. It might help to think about what a hydrostatic transmission is:

1) A dedicated variable displacement, reversible flow hydraulic pump​

2) a hydraulic traction motor (typically fixed displacement)​

The pump and motor are hydraulically connected via 2 oil passages that also have a pressure-relief to keep things safe.

If we ignore system losses (bypass leakage, hitting pressure relief, etc), traveling at a constant speed in whatever range you've selected requires X gallons/min of oil flow into the traction motor regardless of the load being applied (up/down hill, plowing, or just cruising) -- in other words, the traction motor output RPM is directly proportional to oil flow into it.

There are 2 variables to create that X g/m of oil flow:

1) modulate the displacement of the pump (push the pedal more/less)​

2) modulate the input RPM of the pump (adjust the engine revs with the throttle)​

Maxing out the pump's displacement (pushing the pedal to the floor) causes the pistons in the pump to utilize their maximum stroke during each revolution. It's designed to do this, so, no big deal (in fact -- the traction motor is a simplified likeness of the pump with its displacement "pedal" permanently "maxed-out").

Now, if you are still reading, maybe we should talk about power transfer:

Rotational power is: Torque * RPM​

Fluid power is: Pressure * Flow​

When you drop the plow into the ground and increase the load, in order to maintain a constant travel speed (ala, same flow into the traction motor), the pressure must go up. This makes it harder for the engine to turn the pump and loads the engine up and the engine torque goes up more than engine RPM drops because the injection pump increases fueling (else, the engine stalls). Since the engine is at a bit lower RPM, to keep constant speed we press the HST pedal more to compensate. If you started out at reduced engine RPM (low/mid throttle), your HST is not working hard at all simply because engine power is already lower than design rating. Again -- maxing out the pedal is no big deal in this case.

Now, suppose you have a heavily ballasted tractor and you are trying to pull an immovable object. Ya giv'r hell at wide-open-throttle and mash the HST pedal to the floor! You have so much traction the wheels don't even spin. In this regime, you are very much stressing the HST pump as it is pumping maximum flow rate at maximum pressure -- all the flow is going to the pressure relief valve. All of the engine power is transferred directly into the hydraulic fluid as heat. Not good!

Oil flow creates heat (not pressure). Now that we understand the relationship of oil flow vs speed (for the same H/M/L range), hopefully we can now see the chosen engine RPM isn't the first-order cause of HST heat generation -- it's actually the chosen operating speed. How you achieve that speed (low engine RPM and high HST pedal vs high engine RPM & low HST pedal) is all the same. Thus, the notion that HST pedal % keeps things cool is incomplete. If you want a cooler HST, go slower (or stop!) is the real answer, and avoid applying the maximum rated torque output of the traction motor (i.e. hitting the pressure relief at high engine power where more pedal doesn't increase the speed more).

If you've made it this far, I hope that helps understand what's happening.

 

[NCL4701]

This is a great question. It might help to think about what an hydrostatic transmission is:

1) A dedicated variable displacement, reversible flow hydraulic pump​

2) a hydraulic traction motor (typically fixed displacement)​

The pump and motor are hydraulically connected via 2 oil passages that also have a pressure-relief to keep things safe.

If we ignore system losses (bypass leakage, hitting pressure relief, etc), traveling at a constant speed in whatever range you've selected requires X gallons/min of oil flow into the traction motor regardless of the load being applied (up/down hill, plowing, or just cruising) -- in other words, the traction motor output RPM is directly proportional to oil flow into it.

There are 2 variables to create that X g/m of oil flow:

1) modulate the displacement of the pump (push the pedal more/less)​

2) modulate the input RPM of the pump (adjust the engine revs with the throttle)​

Maxing out the pump's displacement (pushing the pedal to the floor) causes the pistons in the pump to utilize their maximum stroke during each revolution. It's designed to do this, so, no big deal (in fact -- the traction motor is a simplified likeness of the pump with its displacement "pedal" permanently "maxed-out").

Now, if you are still reading, maybe we should talk about power transfer:

Rotational power is: Torque * RPM​

Fluid power is: Pressure * Flow​

When you drop the plow into the ground and increase the load, in order to maintain a constant travel speed (ala, same flow into the traction motor), the pressure must go up. This makes it harder for the engine to turn the pump and loads the engine up and the engine torque goes up more than engine RPM drops because the injection pump increases fueling (else, the engine stalls). Since the engine is at a bit lower RPM, to keep constant speed we press the HST pedal more to compensate. If you started out at reduced engine RPM (low/mid throttle), your HST is not working hard at all simply because engine power is already lower than design rating. Again -- maxing out the pedal is no big deal in this case.

Now, suppose you have a heavily ballasted tractor and you are trying to pull an immovable object. Ya giv'r hell at wide-open-throttle and mash the HST pedal to the floor! You have so much traction the wheels don't even spin. In this regime, you are very much stressing the HST pump as it is pumping maximum flow rate at maximum pressure -- all the flow is going to the pressure relief valve. All of the engine power is transferred directly into the hydraulic fluid as heat. Not good!

Oil flow creates heat (not pressure). Now that we understand the relationship of oil flow vs speed (for the same H/M/L range), hopefully we can now see the chosen engine RPM isn't the first-order cause of HST heat generation -- it's actually the chosen operating speed. How you achieve that speed (low engine RPM and high HST pedal vs high engine RPM & low HST pedal) is all the same. Thus, the notion that HST pedal % keeps things cool is incomplete. If you want a cooler HST, go slower (or stop!) is the real answer, and avoid applying the maximum rated torque output of the traction motor (i.e. hitting the pressure relief at high engine power where more pedel doesn't increase the speed more).

If you've made it this far, I hope that helps understand what's happening.

Long term that’s the only real problem I have with HST v gear although HST is much better for my usage of the tractor. It’s a bit of a balancing act between range selection, engine RPM, and pedal position to keep everything in the system happy. I don’t think it’s so sensitive you have to get all wound up about it but it’s still something to be cognizant of. Gear, you just pick a gear and go. If you need more speed pick a higher gear; more torque, lower gear. Gear is more intuitive, at least for me.

 

[NHSleddog]

What RPM is too general of a question because each tractor/motor pairing are going to have a different range. Run it high enough to keep it from "lugging". In my case on the B2650 it is just a hair over 2450 to get about 550 PTO RPM. I run a tick over 540 and the power seems to be best there. AAGR the torque curve on the engine should place its max torque output around 540 PTO RPM (engine RPM will vary by motor/setup).

Unless I am working around people or just want to go really slow, I rarely use low range. LOW range on the B2650 digs holes with the tires like no tomorrow. I get better faster easier full buckets in MED range. This will also depend on the model as they all have varying speed ranges. The same goes for the box blade, I get the most effective pulling in MED range. In low range before I can even fill the box all the way the tractor will stop moving forward and spin the tires, in MED the ground speed/traction are well paired.

 

[Hd883chopper]

This is a great question. It might help to think about what a hydrostatic transmission is:

1) A dedicated variable displacement, reversible flow hydraulic pump​

2) a hydraulic traction motor (typically fixed displacement)​

The pump and motor are hydraulically connected via 2 oil passages that also have a pressure-relief to keep things safe.

If we ignore system losses (bypass leakage, hitting pressure relief, etc), traveling at a constant speed in whatever range you've selected requires X gallons/min of oil flow into the traction motor regardless of the load being applied (up/down hill, plowing, or just cruising) -- in other words, the traction motor output RPM is directly proportional to oil flow into it.

There are 2 variables to create that X g/m of oil flow:

1) modulate the displacement of the pump (push the pedal more/less)​

2) modulate the input RPM of the pump (adjust the engine revs with the throttle)​

Maxing out the pump's displacement (pushing the pedal to the floor) causes the pistons in the pump to utilize their maximum stroke during each revolution. It's designed to do this, so, no big deal (in fact -- the traction motor is a simplified likeness of the pump with its displacement "pedal" permanently "maxed-out").

Now, if you are still reading, maybe we should talk about power transfer:

Rotational power is: Torque * RPM​

Fluid power is: Pressure * Flow​

When you drop the plow into the ground and increase the load, in order to maintain a constant travel speed (ala, same flow into the traction motor), the pressure must go up. This makes it harder for the engine to turn the pump and loads the engine up and the engine torque goes up more than engine RPM drops because the injection pump increases fueling (else, the engine stalls). Since the engine is at a bit lower RPM, to keep constant speed we press the HST pedal more to compensate. If you started out at reduced engine RPM (low/mid throttle), your HST is not working hard at all simply because engine power is already lower than design rating. Again -- maxing out the pedal is no big deal in this case.

Now, suppose you have a heavily ballasted tractor and you are trying to pull an immovable object. Ya giv'r hell at wide-open-throttle and mash the HST pedal to the floor! You have so much traction the wheels don't even spin. In this regime, you are very much stressing the HST pump as it is pumping maximum flow rate at maximum pressure -- all the flow is going to the pressure relief valve. All of the engine power is transferred directly into the hydraulic fluid as heat. Not good!

Oil flow creates heat (not pressure). Now that we understand the relationship of oil flow vs speed (for the same H/M/L range), hopefully we can now see the chosen engine RPM isn't the first-order cause of HST heat generation -- it's actually the chosen operating speed. How you achieve that speed (low engine RPM and high HST pedal vs high engine RPM & low HST pedal) is all the same. Thus, the notion that HST pedal % keeps things cool is incomplete. If you want a cooler HST, go slower (or stop!) is the real answer, and avoid applying the maximum rated torque output of the traction motor (i.e. hitting the pressure relief at high engine power where more pedal doesn't increase the speed more).

If you've made it this far, I hope that helps understand what's happening.

Great write up! Thx for taking the time to do that. I actually read it 3x lol. It seems like (as NC also mentioned) there seems to be a balance between the pedal, the throttle and the gear chosen. I do feel better now about how I’ve been working this machine.
Low gear keeps me on my row, 2500 rpm’s gives me all the power I need but makes the hst whine some bit apparently that’s normal. My pedal is probably 80% down.

thanks again!
HD

 

[Hd883chopper]

Long term that’s the only real problem I have with HST v gear although HST is much better for my usage of the tractor. It’s a bit of a balancing act between range selection, engine RPM, and pedal position to keep everything in the system happy. I don’t think it’s so sensitive you have to get all wound up about it but it’s still something to be cognizant of. Gear, you just pick a gear and go. If you need more speed pick a higher gear; more torque, lower gear. Gear is more intuitive, at least for me.

Thanks for the input. Glad we have a place like this to get educated.
HD

 

[Hd883chopper]

What RPM is too general of a question because each tractor/motor pairing are going to have a different range. Run it high enough to keep it from "lugging". In my case on the B2650 it is just a hair over 2450 to get about 550 PTO RPM. I run a tick over 540 and the power seems to be best there. AAGR the torque curve on the engine should place its max torque output around 540 PTO RPM (engine RPM will vary by motor/setup).

Unless I am working around people or just want to go really slow, I rarely use low range. LOW range on the B2650 digs holes with the tires like no tomorrow. I get better faster easier full buckets in MED range. This will also depend on the model as they all have varying speed ranges. The same goes for the box blade, I get the most effective pulling in MED range. In low range before I can even fill the box all the way the tractor will stop moving forward and spin the tires, in MED the ground speed/traction are well paired.

Thx. After reading these posts, I’ll be less apprehensive to use the Medium gear when working. Thx.

 

[bmblank]

Thx. After reading these posts, I’ll be less apprehensive to use the Medium gear when working. Thx.

I'd say mine is in Med about 90% of the time. I put it in hi if I'm running down to the end of the private road to get the mail and I put it in low if I'm bogging down without pushing the pedal much.
It sounds like you were using it as intended.
Just remember, too... It's a tractor. It's kinda like a farm truck. It's not meant to be babied.

 

[Hd883chopper]

I'd say mine is in Med about 90% of the time. I put it in hi if I'm running down to the end of the private road to get the mail and I put it in low if I'm bogging down without pushing the pedal much.
It sounds like you were using it as intended.
Just remember, too... It's a tractor. It's kinda like a farm truck. It's not meant to be babied.

Thanks for the info. You know, I had a neighbor a few years ago that had an old JD and he let me use it to spread some rocks on my driveway and dirt mounds I had hanging around. He told me to be smart about it but "don't be afraid to work the damn thing, it's a tractor, it ain't gonna collapse on you." haha.

Pretty much what you said.
Thanks.

 

[bird dogger]

Don't forget your tractor's temperature gauge is also a great indicator of whether the tractor is being under/over worked. Unless you see the indicator climbing well above midrange you most likely aren't overworking the tractor.

 

[Hd883chopper]

Don't forget your tractor's temperature gauge is also a great indicator of whether the tractor is being under/over worked. Unless you see the indicator climbing well above midrange you most likely aren't overworking the tractor.

That’s a good point and yep I keep an eye on that gauge. Do you use Kabota coolant or another premium brand?

 

[bird dogger]

That’s a good point and yep I keep an eye on that gauge. Do you use Kabota coolant or another premium brand?

Yes, I just use a good premium brand that I have on hand for the other vehicles, motors. The B2650 only takes about a gallon of mix. It was just changed per the maintenance schedule and came out as clean as could be. Seemed a little silly to change it but at only a gallon of mix there's no point not to.

 

[Orange man hero]

You should not be flooring the pedal. On a hydro, the pedal is not a normal accelerator. The harder you press the pedal, the higher "gear" you are in. It's a little counterintuitive, but when the tractor starts to bog down, you have to remember to back off on the pedal. Slow down a bit and your RPMs won't drop so much.
That being said, a little RPM drop when you're working it pretty good, like plowing, is not out of the question. I guess I don't really know to what extent; I don't pay so much attention to the RPMs, I just use my ears.
I was using my disc the other day and for the most part I was running it somewhere in the 2000-2500 range.

Great write up here. I'm cutting some small hills down to size with my LX26 10 IT is slow going as there are a lot of glacial rocks up to a foot in diameter and down deep the ground is still frozen. I operate at around 1400 rpm in low gear. The blade of the bucket hangs up on the rocks constantly and feel that the bucket gets a lot of stress from this??? Is this enough rpm? Engine does not seem to bog down. Most of the time I am cutting the hill down to make this road the tractor is going dead slow. More rpm just seems to put more stress on the loader as I probably would be better off with a small cat.

 

[Old_Paint]

You'll smell it if you're doing something wrong, particularly if you're checking the oil before each use.