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checking doubles and single blde rpm

Discussion in 'Lawn Mowing' started by awm, Jul 30, 2002.

  1. awm

    awm LawnSite Gold Member
    Messages: 3,354

    this by that great master mechanic aw.
    checked max rpm with doubles
    high lift gator comb. max at 3860.
    blades engaged . same check w high lifts only 3860.. surprised me a bit.
    by the way im talkin a 20 kohler command.
    another surprise max rpm without bldes engaged 3750. ???
    also checked 141/2 briggs max rpm 3650 turned all the way up. engaged bld
    3250. turned it back to 3350 which is what i started with unengaged.
    engaged 3250.
    now this leaves me knowing one thing for sure . that i dont understand all i know about these things:)
    guess the main result is that doubles
    didnt slow the rpm. of course it would have more affect in cut ,as u have a lot more blade contact with the grass.
    hope somebody finds this info worth while.
  2. FrankenScagMachines

    FrankenScagMachines LawnSite Platinum Member
    from IN
    Messages: 4,739

    Interesting results....
    It's all in the governor's on the engine. The Kohler over compensates for the load (thats why they're so much better than a Briggs, Tecumseh etc.) so that it is actually faster under load (more power) so it won't bog down as easy. The Briggs has a crappy guv'ner on it so it doesn't take as much, proportionally, to bog it down.
    The governor in a Kohler is much quicker and picky-er than a Briggs.
  3. yardboyltd

    yardboyltd LawnSite Senior Member
    Messages: 323

    The double blade rpm sounds about right because two blade have twice as much intertia as one. Meaning it takes more power to get the blades up to speed, but not much more to keep them running.
  4. vipermanz

    vipermanz LawnSite Bronze Member
    Messages: 1,773

    exactly , if i wanted to, some physics and math might make it look more technically orientated:)
  5. scott's turf

    scott's turf LawnSite Senior Member
    from NH
    Messages: 949

    You will need more power to spin doubles do to the friction with the air. The higher lift bleades the higher the resistance. Most of the enigines that we currently have enough hp to over come this.

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