Why 21 inch?

Discussion in 'Lawn Mowing' started by MOturkey, Jul 28, 2007.

  1. MOturkey

    MOturkey LawnSite Silver Member
    Messages: 2,781

    OK, one of the great mysteries of the universe. Why are the bulk of "push" mowers 21 inch cut? I know there are other sizes, but are not all that common, compared to the 21. Just curious if anyone knows why 21 instead of 23 or 24 1/2?
  2. Mr Priceless

    Mr Priceless LawnSite Senior Member
    Messages: 412

    i would ASSume it has to do with balancing blade tip speed with safety...

    too short and the blade tip isn't nearly fast enough to cut clean at an already slow pace

    too long and the blade tip RPM can be dangerous flinging an unsuspecting sharp object through the cheapa$$ thin metal (or aluminum) cutting deck and causing damage or harm, and may cause more stress on the engine for having to lug around a 10 pound blade at the desired speed.

    That's just my guess:)
  3. Vikings

    Vikings LawnSite Bronze Member
    from canada
    Messages: 1,657

    A quick 36 has 3 short blades under the deck while my Toro 36 has two.
  4. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Messages: 2,613

    My guess is that at whatever the governed speed of the engine on a 21'' mower is be it 3200 3600 rpms at that speed the blade tip speed is 18000fps. Just a guess.

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