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  1. #1
    New Member
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    Mar 2007
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    9
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    Texas Hill Country
    Tractor
    PowerTrac PT-425

    Default Terry on using the Treadle

    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

  2. #2
    Veteran Member SpringHollow's Avatar
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    Dec 2006
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    1,693
    Location
    South of Rochester, NY
    Tractor
    Power Trac 1850, NH 2120

    Default Re: Terry on using the Treadle

    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

  3. #3
    Veteran Member
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    Mar 2007
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    1,129
    Location
    Bay Area, CA
    Tractor
    Power Trac PT1445

    Default Re: Terry on using the Treadle

    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

    Quote Originally Posted by 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

  4. #4
    Elite Member SnowRidge's Avatar
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    Jul 2003
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    3,091
    Location
    East Tennessee
    Tractor
    Power Trac PT-425 / Branson 3520

    Default Re: Terry on using the Treadle

    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.

  5. #5
    Platinum Member
    Join Date
    Jan 2004
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    577
    Location
    Tasmania, AU, Bailey, CO
    Tractor
    Kubota F-2880. PT-1845

    Default Re: Terry on using the Treadle

    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
    Tasmania, AU: Kubota F2880 w/60" Front Mower
    Colorado: PT-1845 w/Buckets, ANBO Grapple, Forks, Snow Plow, BearCat Chipper, Hyd winch & Boom, QA-2000 hyd Snow Blower, Foamed tires

  6. #6
    Veteran Member
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    Mar 2007
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    Bay Area, CA
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    Power Trac PT1445

    Default Re: Terry on using the Treadle

    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

  7. #7
    Elite Member SnowRidge's Avatar
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    Jul 2003
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    3,091
    Location
    East Tennessee
    Tractor
    Power Trac PT-425 / Branson 3520

    Default Re: Terry on using the Treadle

    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.

  8. #8
    New Member
    Join Date
    Mar 2007
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    9
    Location
    Texas Hill Country
    Tractor
    PowerTrac PT-425

    Default Re: Terry on using the Treadle

    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.

  9. #9
    Platinum Member RegL's Avatar
    Join Date
    Aug 2003
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    604
    Location
    Northwestern CT
    Tractor
    PT 1430

    Default Re: Terry on using the Treadle

    Quote Originally Posted by 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
    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.

  10. #10
    Elite Member SnowRidge's Avatar
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    East Tennessee
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    Power Trac PT-425 / Branson 3520

    Default Re: Terry on using the Treadle

    Quote Originally Posted by RegL
    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.

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