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need mower for wet soggy lawns

Discussion in 'Lawn Mowing' started by GrassmasterB, Jul 1, 2005.

  1. GrassmasterB

    GrassmasterB LawnSite Member
    from Florida
    Messages: 201

    hopefully this month i will be upgrading to bigger mower. currently using a 36 wb, 26", and a 21". while working in an upscale neighborhood, after a weeks worth of heavy rain every afternoon, i was forced to use my 21" on several lawns as my 36 ruts badly. i noticed while there several companies using standers with a lot of success. are the standers better at handling wet lawns than a ztr? whats the top speed of a stander?
  2. HK45Mark23

    HK45Mark23 LawnSite Member
    Messages: 200

    If you want to know the impact that a mower will have on a lawn it is simple.

    Take the contact patch of the front and back tires and find the aria in inches. Divide the weight by the inches contacting the ground. This will tell you the pounds per sq. in.

    Basically you will find no matter what that if you can’t walk the yard then you can’t mow it.

    Key for this example
    X = Total mower weight, in this case 1,657 lbs. and is representative of the Exmark LaserZ XP
    L = length from the front of the tire to the back where it contacts the ground, most are about 8”
    W = width of the tire from outside to inside or left to right, most are about 12”
    Y = lbs per sq in.
    ( ) = perform this function first
    • = multiply

    X ÷ (L • W) • 2) + (L • W) • 2) = Y
    ^ Front tires + ^ Back tires

    In order to work this formula you first find the width of the tire then the length that contacts the ground.

    So find the L • W of contact patch for the castors then double it to total both castors.
    Then find the L • W contact patch for the drive tires then again double it to equal the aria for the two drive tires.

    Lets say that the drive tire is 12” wide and deforms under weight to allow 8” to contact the ground. This means you would have 12” • 8” = 96”. That is for one tire; again double that for two tires to equal 192”.

    Now for the front casters, they are about 6.5” • 3” = 19.5” • 2 = 39.

    Add these together to get total square inches of contact patch. 192” + 39” = 231

    Then all you do is divide the weight by the total contact patch in and you will have the weight per sq. in.

    1657 ÷ 231” = 7.17 lbs. per sq. in. This is approximately the lbs. per sq. in. for the Exmark LaserZ XP it is the heaviest one Exmark makes. This was the diesel model with the large deck.

    In order to put this in perspective I weigh a whopping 120 lbs. and have a contact patch bare footed of about 16.5” per foot to make 8.78 lbs. per sq. in. when standing on one foot.
    As you can see the full size Exmark LaserZ XP weighs less than me per sq. in. when walking.

    X ÷ (L • W) • 2) + (L • W) • 2) = Y
    (12” • 8”) = 96” • 2 = 192”
    (6.5” • 3”) = 19.5” • 2 = 39”
    192 + 39 = 231
    1,657 ÷ 231 = 7.17
    ^ is X ^ is Y

    Y = 7.17 lbs. per sq. in.

    Really if you want to damage you customers turf less then get the lightest machine per sq. in.

    All of these are estimates only. I generated these estimated based on information in the brochures. In reality you would need to measure the actual foot print for every machine in person to get totally accurate numbers.

    Walker Kubota D722 = 2.35
    Exmark LaserZ XP = 7.17
    Exmark Metro 26 = 5.84
    John Deere JX 75 = 6.7
    And I = 8.78

    As you can well see I am heavier than any one of these large mowers and have the potential to cause more damage walking a yard based on weight than the mowers if the ground is soft.

    Of course you must take in account driving styles and that a Z turn can damage turf if you are not careful when you turn. The real deal is how heavy is it per sq. in. This will determine the true effect it could have on the turf.
  3. HK45Mark23

    HK45Mark23 LawnSite Member
    Messages: 200

    I see that a few things moved around. The arrows are suppose to be pointing at (L • W) to refer to one being the front tire and the other being the back. And the other one 1,657 ÷ 231 = 7.17
    231 is X, and 7.17 is Y

    Hope that is more clear.
  4. John Gamba

    John Gamba LawnSite Fanatic
    from ct
    Messages: 10,812

    Put spacers on the rear hubs and then you can put wider tires on your 36 when needed.

    You will have no trim side when doing it.

  5. The mayor

    The mayor LawnSite Senior Member
    Messages: 592

    You could try a hover mower. I don't have one, nor have I used one. With no wheels you won't have to worry about ruts.
  6. brucec32

    brucec32 LawnSite Platinum Member
    Messages: 4,403

    I am assuming you are mowing the St. Augustine so common there. The rutting is a function of ground pressure of the tires on the 36". Is it a hydro? Some of them are pretty heavy. A bigger deck version might up the tire size enough to lower ground pressure. I have found that my belt drive 44" toro makes a good wet area mower because it's relatively light in comparison to the tire size.

    St. Aug is mowed tall and your wheels can push it over into muddy soil underneath, leaving a rutting effect when it's really just the blades getting dirty. I don't know what the cure for that would be.

    I have heard of some problems with rutting on smaller standers (36/32) I think they widened the rear tires for that reason this model year. But obviously anything you add your weight too will probably be worse than a wb unless the tires get bigger too.

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