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  1. #21
    Platinum Member
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    Oct 2004
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    789
    Location
    New Holland, PA
    Tractor
    Power Trac 425

    Default Re: PT425 vs. PT1430 Mystery?

    Man, my head hurts... I'm only an electrical engineer; I can't understand this stuff... [img]/forums/images/graemlins/confused.gif[/img]

  2. #22
    Veteran Member Charlie_Iliff's Avatar
    Join Date
    Jun 2001
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    1,896
    Location
    Arnold, MD
    Tractor
    Power Trac PT1845, John Deere 2240, John Deere 950, John Deere 755, Jacobsen Turf Cat II

    Default Re: PT425 vs. PT1430 Mystery?

    <font color="red"> then the second part of your assumption is wrong. </font>
    Too strong a statement, of course, but I was writing it late at night (for me [img]/forums/images/graemlins/crazy.gif[/img])
    If 30 hp wasn't enough to hold the mower rpm and turn the wheels, then both will slow. As they slow, the gasoline engine will fall farther away from its power peak than the diesel, and thus slow more. So, what you described may be exactly what happens. After slowing, the diesel will deliver more power than the gas engine -- but no longer 30 for either..

    I think the only point I really am trying to make is that the potential work of the machine is determined by available power, which is torque times speed, not torque alone. 30 horsepower machines will do equal work, provided they are geared to deliver the whole 30 hp. If not at the power peak, 25 hp will beat 19 every time.

    It's not the temperature, it's the humidity. [img]/forums/images/graemlins/grin.gif[/img]

  3. #23
    Bronze Member lowellw2's Avatar
    Join Date
    Apr 2002
    Posts
    86
    Location
    Driftwood, TX
    Tractor
    Kubota BX24

    Default Re: PT425 vs. PT1430 Mystery?

    Charlie -- My head hurts also... but thanks. As an old tired attorney, I sure wish I had you as a witness to explain these type of things. Good job. That explains why my kubota B7100 with about 16hp hangs in there much better than my 25 hp gas powered lawn tractor when things get tough. Gotta get one of these PT things. I figure a 425 will do most of what I need. The 1430 would do everything, but the bigger size could be a problem. 25hp vs 30hp is no big deal. I'm only 5-8 but I can do generally what a 6 footer can do. It just takes a little longer. [img]/forums/images/graemlins/cool.gif[/img]

  4. #24
    Epic Contributor MossRoad's Avatar
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    Aug 2001
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    22,519
    Location
    South Bend, Indiana (near)
    Tractor
    Power Trac PT425 2001 Model Year

    Default Re: PT425 vs. PT1430 Mystery?

    No one's taking up the beer analogy challenge. [img]/forums/images/graemlins/tongue.gif[/img]

  5. #25
    Gold Member
    Join Date
    Apr 2002
    Posts
    406
    Location
    Dexter, MI
    Tractor
    BX-2200

    Default Re: PT425 vs. PT1430 Mystery?

    Just to add a too Charlie's excellent definition of HP/Torque discussion.

    The term that is often used to compare engines is Torque rise. Often diesels have more torque rise than small air cooled gas engines such as the Kohler or Robin. This torque rise allows the diesel to produce more power over a broader range than the small peaky air cooled gas engine. Some of these air cooled gas engines have little or no torque rise when you look at the torque curves. The torque rise on the torque curve is when you start at the engines maximum operating RPM and work backwards to 0 rpm. Does the curve go upward and for how many rpm? The slope in this direction and RPM range determines it torque rise. A peaky type engine's torque curve will rise for a few hundred rpm and then fall off, were most diesels will rise for most or at least 1/2-2/3 thds of it's rpm range and then fall off.

    Here's another way at Moss's blaaa or vroooom. The diesel starts into the grass, it begins to bog down but there is available torque left, so the engine slows somewhat, but torque is rising so there's HP there to keep it going. The gas engine hits the grass and the rpm slows down, during this slow down torque was rising, but then it passed over it's peak torque because it's power/torque band is narrower. Now its sliding down the back of the torque curve and theres no recovery until you slow down or stop and let the engine build rpm again and let it get to the right side of the peak on the torque curve.

    Tim


  6. #26
    Veteran Member Charlie_Iliff's Avatar
    Join Date
    Jun 2001
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    1,896
    Location
    Arnold, MD
    Tractor
    Power Trac PT1845, John Deere 2240, John Deere 950, John Deere 755, Jacobsen Turf Cat II

    Default Re: PT425 vs. PT1430 Mystery?

    <font color="red"> an old tired attorney </font>
    I, too, am one of those. I think some of the thoughts above are based on times when I've had to try to tell my expert witnesses in products cases what I wanted them to say. But that's for some other forum. [img]/forums/images/graemlins/grin.gif[/img]

    I had a B7100 HST, along with a gaggle of various-size John Deeres, gas &amp; diesel, and gas Farmalls. Because of its configuration and flexibility, my PT 1845 will out work any other machine I've ever used. I've watched Hans Luginbuhl's 425 do amazing things, as well. I've seen a complaint here and there on this board, but its a rare PT purchaser who has regretted the decision.
    As a bit of a challenge: Pick a project that you might want to do and see if someone doesn't explain pretty quickly why a Power Trac is a better machine for the job than _________________.
    After all, this is the Power Trac Forum. [img]/forums/images/graemlins/tongue.gif[/img]

  7. #27
    Veteran Member FOURTEEN's Avatar
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    Jan 2004
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    1,028
    Location
    Efland - Triangle of North Carolina.
    Tractor
    2004 Power Trac PT-425

    Default Re: PT425 vs. PT1430 Mystery?

    </font><font color="blue" class="small">( No one's taking up the beer analogy challenge. [img]/forums/images/graemlins/tongue.gif[/img] )</font>

    Here goes:

    Horsepower is alcohol.
    Speed is volume.
    Torque is proof.

    All these drinks have the same alchohol:
    1 pint of 80 proof Vodka.
    1 quart 40 proof Whiskey.
    1 gallon of 10 proof Wine.



    A 100HP truck has high torque at low peak RPM. A 100HP car has medium torque at medium peak RPM. A 100HP motorcycle has low torque at high peak RPM.

    They all have 100HP, and will do the same amount of work (weight times speed). The truck moves heavy weight at slow speed. The car moves medium weight at medium speed. The motorcycle moves light weight at high speed. With no change in weight, if you geared the motorcycle engine to drive the truck, or the truck engine to drive the motorcycle, they would perform the same because you would still have 100HP to use in each.

    The hydraulic pump should be designed for maximum output at a given input torque and speed. Higher speed with lower torque when used with a gas engine, and lower speed with higher torque when used with a deisel. At rated RPM, 25HP is 25HP!

    PS: My Kohler technician, who has been servicing Kohler engines for over 50 years, told me that the 25HP Kohler engine in the PT-425 is designed to always run at full throttle for proper cooling and longer engine life.
    [img]/forums/images/graemlins/grin.gif[/img]

  8. #28
    Epic Contributor MossRoad's Avatar
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    Aug 2001
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    22,519
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    South Bend, Indiana (near)
    Tractor
    Power Trac PT425 2001 Model Year

    Default Re: PT425 vs. PT1430 Mystery?

    NOw I Getsssh ITT!!! (hic) Oooo, I feeeel woooozy [img]/forums/images/graemlins/crazy.gif[/img]

    (I run my Kohler at full RPM because I like the noise [img]/forums/images/graemlins/grin.gif[/img])

  9. #29
    Bronze Member
    Join Date
    Oct 2004
    Posts
    50

    Default Re: PT425 vs. PT1430 Mystery?

    </font><font color="blue" class="small">(
    (I run my Kohler at full RPM because I like the noise [img]/forums/images/graemlins/grin.gif[/img]) )</font>

    I run my Kohler quietly, in my dreams, because I don't have one, yet... [img]/forums/images/graemlins/ooo.gif[/img]

  10. #30
    Platinum Member
    Join Date
    Jan 2005
    Posts
    628
    Location
    SW Virginia
    Tractor
    PT425

    Default Re: PT425 vs. PT1430 Mystery?

    Another possibility: I recently noticed that the Robin 25 hp engine is rated at 25 hp *peak*, and 18 hp *continuous*. I believe other gasoline engines are rated the same way, and wonder if diesel engines are rated by continuous hp. If so, it would explain some of the difference in real world working power.

    Gravy

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