converting to hydro driven deck

Discussion in 'Mechanic and Repair' started by BZB_Helpers, Sep 26, 2005.

  1. BZB_Helpers

    BZB_Helpers LawnSite Member
    Messages: 131

    i have aquired a 1972ish Jacobsen out-front 72" mower. the machine runs great except for some issues with the deck. the deck is pto driven to a 90* gearbox that turns the 3 blades via belts. due to the design of the gearbox and the 1970's seal materials, the gearbox leaks oil onto the belts and destroys them($50 a belt). i want to remove the gearbox and install 3 hydro motors on the deck and a pump running off the front of the machine. i was looking through northern tool and found a barnes gear pump that can also be used as a motor, but there are 7 differnet cubic inch sizes. the sizes are .065/1gpm, .097/1.5gpm, .129/2gpm, .194.3gpm, .258/4gpm, .388/6gpm, .517/8gpm
    so if i want three deck motors then i need three .129ci/2gpm motors and a .517/8gpm pump?
    barnes hydro pumps @ northern tool
    anything also besides a tank, strainer, filter, and hoses?
  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Go to NAPA and get new seals for the gearbox and be done with it.
    Is this unit really worth the money and headache to try and re-design ?
  3. steinerguy

    steinerguy LawnSite Member
    Messages: 63

    There are several areas to consider with this change. Part of it being pump effeciency as well as motor effeciency. You lose alot of power through the liquid as well as balancing the flow between the three motors.....and shaft speed or will you still use a belt and pulley to speed up the blade spindle?

    Many things to consider........maybe a newer,better designed gear box....
  4. BZB_Helpers

    BZB_Helpers LawnSite Member
    Messages: 131

    the pump/motors have 95% effeciency. i would like them to be mounted on each spindle instead of using one motor and belt drive. the belt is around $50, how long do they last if no oil is spilled on them?
    i was thinking of putting the motors in series so they would all be the same speed.
  5. betterlawn

    betterlawn LawnSite Senior Member
    from MI
    Messages: 426


    Most hydraulic motors don't take kindly to pressure on the tank port. Nice idea, but it normally won't work. Maybe lawnmower motors are super special - but I doubt it.

    If you have three motors in parallel your speed will be proportional to the load (as you know). If you really want to match speeds than you need a flow divider (gear type or 2x spool type). I see dollar signs and headaches...
  6. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    betterlawn, You hit that nail square on the head. First thing I seen was the dollar signs and headaches and I don't see how it could work properly or efficiently. Besides hit a stump or something and see what happens to a hydro. motor, Bet that belt is cheaper.
    Good thought but way out in left field.
  7. BZB_Helpers

    BZB_Helpers LawnSite Member
    Messages: 131

    would it work if i just used just one pump and one motor, driving the blades with a belt?
  8. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Well, Ingersoll built a hydro. driven deck for their larger garden tractors and worked pretty well so there would be a better chance of that type set-up working. But you still have to figure out which motor will do the job (Power and RPM) You would also need some type of flow valve to engauge and disengauge. Still quite a few bucks and headache to re-design and build.
    I just gotta know why the gearbox couldn't be resealed ? It's been proven a good design on many brand units for longer than you been living.
  9. evan price

    evan price LawnSite Member
    Messages: 28

    I have an old W/B that is hydro deck drive like a brush hog on wheels. Uses a hydro motor to turn a jackshaft and belt drive the spindles. That's so if you hit a stump you don't break a shaft or motor, belt slips. Also both blades stay sort of in synch at speed. THis Is a ditch cutter machine. Can't remember who made it but for some reason David Bradley comes to mind, I have a couple old DB's.
    Remember you need to calculate the hydraulic horsepower needed to turn everything at speed under load, and size pump, hoses and valves accordingly. Also will your motor have enough HP to run pump and drive unit as well? Plus weight of tank, pump, hoses, etc. You need to have enough fluid capacity in the tank to allow for air bubbles to settle out of the fluid and cool off before pumping through again.
    On the other hand wobbleboxes (the farm term for a 90 box) are in every damn thing we use, tillers, mowers, combines, etc. and they work great. Just get new modern seals in it. LOTS cheaper.

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