Terry on using the Treadle

[baanista]

I have been meaning to ask about something Terry told me when I was in Tazewell back in September. He said that the secret to going up hills was using a light touch on the treadle. The hydraulic wheel motors have their maximum torque at the slowest speed, so the slower you go, the steeper the hill you can go up.

According to Terry, you need to think of the treadle as a speed control rather than a power control. Power is set by the engine throttle on the dash while the treadle controls how fast you go forward or backward.

The problem is that we are all conditioned to equate mashing the pedal with getting more power. But on the PowerTrac, mashing the pedal means give me speed and screw the torque! Thereby leaving PT operators at the bottom of a hill they could have otherwise climbed.

I don't pretend to understand the hydraulics of why it works this way. Since I didn't learn this until after I had demoed the 425, I didn't get a chance to test it out. I hadn't seen this mentioned on the board while I have been following it. Is the secret to getting your PT up a hill or to move a heavy load a light toe on the treadle? Any feedback from the field on this?

Thanks,

David

 

[SpringHollow]

What Terry said to you has been mentioned here and I believe he is correct especially if you are also operating something like the bush hog at the same time.

Ken

 

[ponytug]

This has been mentioned a few times various places.

Yes, Terry is right, and
Yes, it is the preferred method.
​

The variable flow drive pump will develop maximum pressure at low flow, resulting in the most applied torque to the wheel motors. If you mash the treadle one of two things happens;

a) the engine bogs down
b) the relief valve opens.
​

Either way, you aren't helping yourself get up that hill.

Hill climbing is pure horsepower on a hydraulic machine. The more ponies you have, the steeper the hill that you can climb- assuming that you don't lose traction and you use the proper technique.

At 25 degrees, with the brush cutter, and a hot 1445, I'm at the limit. I have to ease up the hill. If I add the draft control, it bogs the engine down, and I'm in trouble.

I'm impressed at the 425 owners who get their machines up 25 degree slopes.

All the best,

Peter

I have been meaning to ask about something Terry told me when I was in Tazewell back in September. He said that the secret to going up hills was using a light touch on the treadle. The hydraulic wheel motors have their maximum torque at the slowest speed, so the slower you go, the steeper the hill you can go up.

According to Terry, you need to think of the treadle as a speed control rather than a power control. Power is set by the engine throttle on the dash while the treadle controls how fast you go forward or backward.

The problem is that we are all conditioned to equate mashing the pedal with getting more power. But on the PowerTrac, mashing the pedal means give me speed and screw the torque! Thereby leaving PT operators at the bottom of a hill they could have otherwise climbed.

I don't pretend to understand the hydraulics of why it works this way. Since I didn't learn this until after I had demoed the 425, I didn't get a chance to test it out. I hadn't seen this mentioned on the board while I have been following it. Is the secret to getting your PT up a hill or to move a heavy load a light toe on the treadle? Any feedback from the field on this?

Thanks,

David

 

[SnowRidge]

The treadle is really a transmission control. All the way down equals high. Almost all the way up equals low. Any position in between is an intermediate "gear."

A tractor is a piece of self propelled power equipment. On power equipment, the throttle is either set to low idle (when not doing work and not being moved) or high idle (or PTO speed on equipment with mechanical PTOs), and the actual engine power is adjusted by the governor. The throttle is really just an engine speed request control, which tells the govenor how fast you want the engine to turn.

The ground speed is set by selecting an appropriate gear in the case of a manual transmission, or appropriate pedal or lever position in the case of a hydrostatic transmission. The ground speed is set at a rate appropriate for the work being done, or slower if comfort and/or safety require it. If the machine does not have enough power to accomplish the work and the selected rate of travel, the engine will bog, and the travel speed must be reduced by selecting a lower gear or reducing the pedal an appropriate degree.

 

[Rip]

The above posts offer a better explanation of how the treadle controls the power and speed of the machine than is found in most of the manuals. The treadle actually controls the position of the swash plate in the variable-displacement (or Tram) pump which is only used for the movement of the machine. If there is no or only light load on either of the other two pumps, then all available engine power is available for movement.

If there is significant PTO load and/or lift arms & steering loads, then engine power must be shared between all of these. Since all pumps are direct driven there is no prioritizing as some more modern machines can to with computerized Power Management or Anit-Stall features.

Something else to check however, to determine if the engine is actually able to put out full power, is the throttle cable. The full stroke of the push/pull cable should move the engine throttle (or governor) lever from low idle stop to max rpm.

In my case, it was only going to about 2/3 max RPM. I was able to play with it and get it up to about 85%, but to get full range I would have to re-make the cable attachment point on the engine governor. I would guess that in typical PT fashion, the throttle cable linkage on many other machines do not achieve full stroke either.

Obviously, this could be a very basic reason that a given machine underperforms other "identical" models and otherwise never lives up to its true potential. Simple to check, and perhaps simple to improve.

Good Luck

 

[ponytug]

Rip,

I guess that is a great reason to fork out for a tiny tach. You would always know if you were able to hit full power. Without a direct drive PTO, knowing the rpms otherwise doesn't have a lot of utility.

All the best,

Peter

 

[SnowRidge]

There are indirect reading tachs, too. One source is Monarch Instrument Company.

There also used to be a contact tach called the "Vibra Tach," which looked sort of like a pencil tire gauge. I don't know if it's still available.

To me, wiring in a permanent tach is a waste of money and time. These aren't race cars. Either high idle is where it's supposed to be, or its not. A quick check with a portable tach is all that's needed to make sure the high speed throttle stop is set correctly.

 

[baanista]

Thanks for the feedback. I like the transmission analogy. I also appreciated the suggestion to make sure your engine was really hitting full rpm.

It doesn't surprise me that this has been brought before on the forum, I either missed it or ignored it. It did strike me as an important thing to keep in mind. Sort of suggests doing the "PT Crawl" when running near the limit of what is possible.

 

[RegL]

I have been meaning to ask about something Terry told me when I was in Tazewell back in September. He said that the secret to going up hills was using a light touch on the treadle. The hydraulic wheel motors have their maximum torque at the slowest speed, so the slower you go, the steeper the hill you can go up.

According to Terry, you need to think of the treadle as a speed control rather than a power control. Power is set by the engine throttle on the dash while the treadle controls how fast you go forward or backward.

The problem is that we are all conditioned to equate mashing the pedal with getting more power. But on the PowerTrac, mashing the pedal means give me speed and screw the torque! Thereby leaving PT operators at the bottom of a hill they could have otherwise climbed.

I don't pretend to understand the hydraulics of why it works this way. Since I didn't learn this until after I had demoed the 425, I didn't get a chance to test it out. I hadn't seen this mentioned on the board while I have been following it. Is the secret to getting your PT up a hill or to move a heavy load a light toe on the treadle? Any feedback from the field on this?

Thanks,

David

This analogy has been used a lot here but after climbing many hills, or trying, I can only say sort of. Here's what I observe.

I can be climbing a progressively steeper hill with the treadle at, say, 1/4 max. At some point, if traction is adequate, the wheel motors will stall. It appears that a wheel motor stalls when the load is enough that the amount of oil entering the motor can leak through and not cause the motor to rotate. It's obvious that the oil can leak through or bypass because with two motors in series you can have one stalled and the other spinning. Now here's where the most torque at low oil flow theory gets a little shaky in my opinion. And let me state that I don't know what I'm talking about, only my experience. If I now increase the flow to the wheel motors,( mash the treadle ) The wheel motors will start rotating again but now the load is being transferred to the engine and it wants to stall. So climbing will be best with maximum amount of treadle that can be applied without stalling the engine.

I think a better hp to weight ratio would give the PT's much better performance on hills, even with the same hydraulics. I'm waiting for someone to drop off a nice 45hp Deutz to put in my 1430.

 

[SnowRidge]

This analogy has been used a lot here but after climbing many hills, or trying, I can only say sort of. Here's what I observe.

I can be climbing a progressively steeper hill with the treadle at, say, 1/4 max. At some point, if traction is adequate, the wheel motors will stall. It appears that a wheel motor stalls when the load is enough that the amount of oil entering the motor can leak through and not cause the motor to rotate. It's obvious that the oil can leak through or bypass because with two motors in series you can have one stalled and the other spinning. Now here's where the most torque at low oil flow theory gets a little shaky in my opinion. And let me state that I don't know what I'm talking about, only my experience. If I now increase the flow to the wheel motors,( mash the treadle ) The wheel motors will start rotating again but now the load is being transferred to the engine and it wants to stall. So climbing will be best with maximum amount of treadle that can be applied without stalling the engine.

I think a better hp to weight ratio would give the PT's much better performance on hills, even with the same hydraulics. I'm waiting for someone to drop off a nice 45hp Deutz to put in my 1430.

On my PT-425, the wheel motors will not stall before the engine. I have never seen it, and I have never seen one motor turning while the other on the same side is stopped, or even turning at a different rate. The wheel motors do not have any bypass valves and certainly aren't leaky enough to bypass oil like that.

So far, the only thing that has limited my ability to climb a slope is all four spinning on steep wet ground, or the engine stalling while trying to climb a tough slope while towing a 6 - 700 lb load.

 

[ponytug]

I agree with RegL. Hill climbing technique is about a light treadle action, but flooring it will definitely bog the engine. I tend to think of Terry's advice the other way around; if the engine rpms start to drop on a hill, back off on the treadle until the rpms pick up again.

On the land around here, with the standard tires, either I lose traction (in which case, backing off on the treadle, and then easing it on again usually cures it). I haven't experienced wheel motor stall, but that may be the effect of the 45 horses.

I'm still trying to work out the wheel motor plumbing, but it looks to me like mine is plumbed with both front motors and both rear motors together, teed off the same port on the pump. Each pair is cross connected to easily allow for a pseudo differential circuit to facilitate turning.

Regardless, having only diagonal wheels on the ground leaves one effectively without power. If during a steep hill climb, diagonal wheels start to lose traction together, the tractor loses (all?) ability to climb, as the low traction wheels spin and drain the flow.

I am sure that there is a hydraulic motor like gizmo that would more or less lock the flow so that the front and the rear wheel motors would get 50% of the flow. This would shred ground in a turn (akin to centrally locking all three differentials in a 4x4), but it would facilitate movement under low traction conditions.

I will say that on steep hills, when the tractor has an issue, I tend to hit the brake first, and then get the motor, and the treadle sorted out before releasing the brake.

RegL: I have to admit to passing on the 1430 because I had concerns about the limits of 30HP on our 25-30 degree hills. That said, except for trying to run draft control on the brush cutter up a hill after a couple hours of cutting, the 1445 has powered straight up my brush slopes, which hit 25-27 degrees for 150 feet or so in a couple of places. It makes it up, but traction is always an issue. I have thought about going back to the turf tires just for the traction.

All the best,

Peter

This analogy has been used a lot here but after climbing many hills, or trying, I can only say sort of. Here's what I observe.

I can be climbing a progressively steeper hill with the treadle at, say, 1/4 max. At some point, if traction is adequate, the wheel motors will stall. It appears that a wheel motor stalls when the load is enough that the amount of oil entering the motor can leak through and not cause the motor to rotate. It's obvious that the oil can leak through or bypass because with two motors in series you can have one stalled and the other spinning. Now here's where the most torque at low oil flow theory gets a little shaky in my opinion. And let me state that I don't know what I'm talking about, only my experience. If I now increase the flow to the wheel motors,( mash the treadle ) The wheel motors will start rotating again but now the load is being transferred to the engine and it wants to stall. So climbing will be best with maximum amount of treadle that can be applied without stalling the engine.

I think a better hp to weight ratio would give the PT's much better performance on hills, even with the same hydraulics. I'm waiting for someone to drop off a nice 45hp Deutz to put in my 1430.

 

[RegL]

On my PT-425, the wheel motors will not stall before the engine. I have never seen it, and I have never seen one motor turning while the other on the same side is stopped, or even turning at a different rate. The wheel motors do not have any bypass valves and certainly aren't leaky enough to bypass oil like that.

So far, the only thing that has limited my ability to climb a slope is all four spinning on steep wet ground, or the engine stalling while trying to climb a tough slope while towing a 6 - 700 lb load.

That's interesting. At anything less than full treadle on my 1430, Wheel motors will stall before the engine. Usually ,if driving forward, the rear motors will stall and the front wheels will start spinning. Here's an experiment. Lift your front wheels off the ground with the loader. Than start operating your treadle and see if the front wheels spin before the rear ones. If they do, oil is passing through the rear wheel motors.

 

[SnowRidge]

That's interesting. At anything less than full treadle on my 1430, Wheel motors will stall before the engine. Usually ,if driving forward, the rear motors will stall and the front wheels will start spinning. Here's an experiment. Lift your front wheels off the ground with the loader. Than start operating your treadle and see if the front wheels spin before the rear ones. If they do, oil is passing through the rear wheel motors.

I have a meeting tomorrow morning. I'll give it a try when I get back.

 

[MossRoad]

I used to grade baseball and softball diamonds by backdragging the LMB with the front wheels off the ground. You can get the front wheels spinning faster than the rears, but not for too long.

Another way to get wheel spin is to turn in reverse on wet grass and then mash the forward pedal. The inside front tire will spin on the grass for a very short while.

 

[SnowRidge]

Here's an experiment. Lift your front wheels off the ground with the loader. Than start operating your treadle and see if the front wheels spin before the rear ones. If they do, oil is passing through the rear wheel motors.

OK, I gave it a try and no go. The off the ground wheels do maybe an eighth of a revolution and stop, and that's it. I assume that is due to hose expansion/ contraction. The rears don't spin, either. They drive the whole shebang forward. The fronts rotate at the same speed once it starts moving.

FWIW, Moss has different wheel motors. His are the "old style," while I have the high torque wheel motors.

Have you looked to see if the 1430 wheel motors have built in bypasses? That might explain things.

 

[MossRoad]

OK, I gave it a try and no go. The off the ground wheels do maybe an eighth of a revolution and stop, and that's it. I assume that is due to hose expansion/ contraction. The rears don't spin, either. They drive the whole shebang forward. The fronts rotate at the same speed once it starts moving.

FWIW, Moss has different wheel motors. His are the "old style," while I have the high torque wheel motors.

Have you looked to see if the 1430 wheel motors have built in bypasses? That might explain things.

Good point on the wheel motor differences between our machines. Could be significant advantage between the PT422 and the PT425, as my 2001 PT425 has the same wheel motors as the current PT422.

 

[Rivco]

Good point on the wheel motor differences between our machines. Could be significant advantage between the PT422 and the PT425, as my 2001 PT425 has the same wheel motors as the current PT422.

And the current PT180.

 

[SnowRidge]

I would like to add that one thing that has always impressed me about my PT-425 is its go anywhere ability, even wearing turfs. The limited slip functionality of the series fed wheels on each side combined with the differential action of the parallel fed sides works superbly. Basically, if at least one of the four wheels has traction, it will go.

I had always assumed all the PT models were like that. Apparently, there are some vagaries.

 

[MossRoad]

Yes. Mine will go most places, too. The engine will die before any reliefs open up on the drive circuit. However, there are just a couple of places on our property that I could use a little more umph that I think the current PT425 wheel motors would provide. However, those places are steep. So, the dying engine is a warning to me that I should stop trying to push the unit into the situation. I back off, re-think and find another way to do it.

 

[RegL]

OK, I gave it a try and no go. The off the ground wheels do maybe an eighth of a revolution and stop, and that's it. I assume that is due to hose expansion/ contraction. The rears don't spin, either. They drive the whole shebang forward. The fronts rotate at the same speed once it starts moving.

FWIW, Moss has different wheel motors. His are the "old style," while I have the high torque wheel motors.

Have you looked to see if the 1430 wheel motors have built in bypasses? That might explain things.

I just went out to do some testing with the 1430 because I was beginning to think I was nuts or something. I tried the test above and behold, I couldn't get the rear wheels to spin either.( fluid is nice and cool this time of year.). Not one to give up, I than placed the bucket against a tree and tried going forward, and thank god I'm not crazy, I dug a couple nice holes with the front wheels and the rears didn't turn. I than added more treadle and the engine wanted to stall. I'm sure with more hp the rears would have broken loose.

I'm thinking that because the 425 is much lighter than the 1430, that maybe it losses traction long before a wheel motor stalls. Another way I proved it, was to operate the parking brakes on the front, applied a little down pressure with a flat bucket to take pressure off the front wheels and backed up the tractor. I've done the same often to reposition the tractor a little on the trailer. Probably not good for it but this tractor has seen a lot worse abuse.