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  1. #1
    Epic Contributor jinman's Avatar
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    Feb 2001
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    Texas - Wise County - Sunset
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    NHTC45D, NH LB75B, Ford Jubilee

    Default The Tortoise & Hare (not Aesop's version)

    Those of us with Class III HST Boomers (TC35D/40D/45D and derivatives) have a wonderful Rabbit-Turtle switch to electrically shift our HST transmissions. Those of us with FELs have a switch on the right fender and another one on the Joystick. Both switches are in parallel and do the same functions, but the fender switch also has lights to indicate whether the transmission is in Rabbit or Turtle mode.

    Since becoming a member of TBN, I've noticed through the years that the functioning of the Rabbit-Turtle circuit is often mysterious to many and a point of frustration. Many/most of the malfunctions are related to broken or disconnected wires, but occasionally there have been malfunctions of switches and relays that control the switching in this circuit.

    It's been cold the last couple of days in Texas. Since I don't have any snow to plow (lucky me ) and I'm a little bored, I've decided to try to dispel some of the mystery around the operation of the Rabbit-Turtle circuit. I guess if I have to have an excuse, I'd say that the years of being an instructional designer are driving me to do this thread even though I'm in retirement.

    The attached five (5) illustrations are in order of when you turn the tractor on through switching to Rabbit and back to Turtle. I think the descriptive text and illustrations are self-explanatory, but I'll be happy to answer any questions. These are very simplified illustrations that do not have a bunch of details like schematics. I hope they help to explain the operation of the circuit for those who haven't taken the time to figure it out in detail. As always, feel free to challenge me or discuss your interpretations. Enjoy!
    Attached Thumbnails Attached Thumbnails The Tortoise & Hare (not Aesop's version)-rabbit-turtle1.jpg   The Tortoise & Hare (not Aesop's version)-rabbit-turtle2.jpg   The Tortoise & Hare (not Aesop's version)-rabbit-turtle3.jpg   The Tortoise & Hare (not Aesop's version)-rabbit-turtle4.jpg   The Tortoise & Hare (not Aesop's version)-rabbit-turtle5.jpg  

    Jim


  2. #2
    Super Member
    Join Date
    Apr 2000
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    7,914
    Location
    Shingle Springs California
    Tractor
    New Holland TC40D

    Default Re: The Tortoise & Hare (not Aesop's version)

    Nice slides!

    Do you know, from the transmission, how the tortoise/rabbit function works? Does an acuator shift ranges in the tranny or something?

    I wonder of the compl;ication of having the range lever, then a secondary range with bunny/turtle.
    RobertN in Shingle Springs Calif

  3. #3
    Epic Contributor jinman's Avatar
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    Texas - Wise County - Sunset
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    NHTC45D, NH LB75B, Ford Jubilee

    Default Re: The Tortoise & Hare (not Aesop's version)

    Robert, the solenoid is attached to a hydraulic spool. When that spool is shifted, it uses pressure from the HST charge pump to shift the motor's swashplate between 15 degrees (turtle) and 9 degrees (rabbit). The lower motor angle (rabbit) provides higher speed with less torque. The HST pedal changes the pump's swashplate and the rabbit-turtle solenoid changes the motor's swashplate. I don't know of any other tractor manufacturer with this dual-mode type HST.
    Jim


  4. #4
    Gold Member RADIUM's Avatar
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    Jul 2005
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    296
    Location
    NY
    Tractor
    NEW HOLLAND 2420

    Default Re: The Tortoise & Hare (not Aesop's version)

    Excellent as always :-) I wish you did this about three years ago when I owned my 40, I always wondered how it worked I just remembered as always being a great feature that really works when you have a load of dirt and you didn't want to shift to a lower range. While we're on the topic of hydrostatic transmissions does anyone know why they don't offer a TC 55 or 4060 for that matter whatever they're calling today with HST transmissions? Check out my video snow blowing in the new video forms take care

  5. #5
    Elite Member JC-jetro's Avatar
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    Jul 2006
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    3,096
    Location
    Kansas
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    Ford 1700, Kubota MX-4700

    Default Re: The Tortoise & Hare (not Aesop's version)

    Right on Jim

    I don't even have an HST but certainly will keep a copy for future and a good read for now.

    JC,
    Ford 1700, 2wd.
    Kubota MX-4700DT, Gear transmission with LA 884 loader, Q/A and HD bucket.
    60" Woods Rotary Cutter, home made (3-pt boom and a Row Hipper) ,King Kutter( 5 ft Tiller,Middle Buster,Single Row Cultivator,Carry-all, 5 ft blade, 6 ft Landscaping Rake ,30" Dirt Scoop and a 4'x4' Drag Harrow)

  6. #6
    Silver Member
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    May 2008
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    230
    Location
    Plymouth, MA
    Tractor
    Ford F6640SL Ford F5000 NH 3050 CVT Ford 2110 JD555B

    Default Re: The Tortoise & Hare (not Aesop's version)

    Great Slides Jim Hope you don't mind that I copied them for later use.

    What do you know about pedals getting sluggish at 2500 rpm. Sometimes I have to press the reverse pedal to get the tractor to slow and stop. This is new and appears to be gettting slowly worse on our TC45DA.

    Jack

  7. #7
    Epic Contributor jinman's Avatar
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    Texas - Wise County - Sunset
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    NHTC45D, NH LB75B, Ford Jubilee

    Default Re: The Tortoise & Hare (not Aesop's version)

    Jack, you can lubricate the roller on the "B" shaped plate and adjust the return spring. Some of the later models (TC45DAs) have a heavier return spring to ensure the pedals return to neutral. If you were at low rpm, I'd tell you to bump it up, but you asked about 2500 rpm and the return spring adjustment or larger spring is your best approach.
    Jim


  8. #8
    Silver Member
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    May 2008
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    230
    Location
    Plymouth, MA
    Tractor
    Ford F6640SL Ford F5000 NH 3050 CVT Ford 2110 JD555B

    Default Re: The Tortoise & Hare (not Aesop's version)

    Thanks Jim

    Jack

  9. #9
    Silver Member
    Join Date
    Sep 2006
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    104
    Location
    North Carolina U.S.A.
    Tractor
    TC40D

    Default Re: The Tortoise & Hare (not Aesop's version)

    Great info Jim, thanks.
    Fred Henry

    Over worked, under paid!

  10. #10
    Epic Contributor jinman's Avatar
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    Texas - Wise County - Sunset
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    NHTC45D, NH LB75B, Ford Jubilee

    Default Re: The Tortoise & Hare (not Aesop's version)

    Quote Originally Posted by Jackfr View Post
    Thanks Jim

    Jack
    Jack look at this diagram. Item 16 is the spring and item 1 is the nut you adjust to make it tighter.
    Jim


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