Calibration idea for a PG that just might work

Discussion in 'Pesticide & Herbicide Application' started by FERT-TEK, Feb 5, 2007.


    FERT-TEK LawnSite Bronze Member
    Messages: 1,035

    This might be my most hair brained idea to date but it just might work.

    Below you will find the recommended method of calibrating a PG.
    My hair brained idea is, take the manufacturers amount of product per 1000 sq/ft and add it to the permagreen hopper. Note you should first run that product through the machine so there is some residual on the bottom of the "empty" hopper (see step 6). Add the recommended product for 1000 sq/ft, then park the machine on a large tarp, raise the sides to catch the product dispersed, run the machine up to 3500-3700 RPM's, open the gate for the recommended time it takes to cover 143' or 1000sq/ft (approximately 20 sec), weigh what you collected and adjust your rate dial accordingly. This way you are not experimenting in a parking lot or on yours or a customers lawn.

    1 Verify that high RPM’s are between 3,500-3,700. Adjust if necessary.
    2 Mark off a test course of 143 feet. This represents 1000 sq. ft.
    of turf as you are effectively covering 7 feet with each pass.
    3 Shift into High (H) gear, and time yourself over the course.
    Do the test several times to get an average elapsed time.
    4 At 3,600 RPM’s, the elapsed time should be approximately
    20 seconds. In that time you want 1000 sq. ft. of granular product
    to fall through the hopper.
    5 Using a postal scale, weigh 1,000 sq.ft. of product and add it to the hopper.
    6 With the machine running, record the time it takes to empty
    the hopper. NOTE: the 1st test is not accurate because some of the
    fertilizer will be left in the bottom. Start recording with the second test.
    7 If that time is less than your elapsed time, rotate the spreader
    rate dial (FIG. 6-1) to a lower number. If that time is longer than the
    elapsed time, select a higher number. Retest and adjust as needed.
    8 After rate adjustment is complete, record your 1st, 2nd, and 3rd hole settings
    as measured with your calibration gage. Repeat the pattern distribution test
    and adjust if necessary.
    9 Repeat the entire process for Low (L) gear.
  2. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,796

    I love hare-brained ideas--however--your idea is good. But I wonder--do you actually have to have the machine running when you do the test? Will it work almost the same without the agitation? Can you work the impeller back and forth to simulate agitation and thereby reduce the mess--of fertilizer spread everywhere?
    -- Also I question the idea in the official calibration directions. For 1000 sqft They say to measure 143 feet long and only 7 feet wide, as that is the effective covered width. Does Permagreen mean that you should operate the machine with a distance between swaths of 7 feet measured center to center? That would mean that the wheel track to wheel track distance would be only 4 feet.
    -- Myself I try to operate at 11 feet swath width, which is 8 feet wheel to wheel distance. Machine is 3 feet wide. 3 feet plus 8 feet is 11. In a lawn 55 feet wide, I would make 5 passes.
    -- It is difficult for me to turn the machine around at the end if I try to get the swath any tighter than 8 feet. Although, on cement i can turn around in my 10 feet driveway.
    Or am I doing this wrong--are you supposed to stop or slow way down at the turnaround so you can make a tighter turn?

    FERT-TEK LawnSite Bronze Member
    Messages: 1,035

    Each pass is supposed to apply 1/2 the recommended product so when they overlap you have 100% coverage and no streaking. I space my passes so the product reaches the wheelmarks of the last pass. never measured it though. Below is PG's recommended spacing

    The Ride-On uses a double overlap spread. For most products, turn every 7 feet so that on the next pass the fertilizer
    reaches approximately back to the center of your last wheel marks. This method prevents striping the lawn, and allows
    the 11’- wide spray pattern to overlap at the edges for complete coverage. The fertilizer is applied at one half rate with
    each pass.
  4. sclawndr

    sclawndr LawnSite Senior Member
    Messages: 326

    Yes, sorry to say you're doing it wrong. Any broadcast spreader throws 100% of the rate forward, 50% of the rate to the left and 50% of the rate to the right. This is why the pattern is 7 ft - when you turn around the left and right 50%s hit the first left and right 50%s to make 100%. As for pattern, don't try to go back and forth in most cases. You should work a counterclockwise spiral pattern - basically go in tighter and tighter circles until you're standing in the middle of the area. You'll find it easier to see your wheel tracks and get the overlap correct. This pattern also means you don't have to slow down to try to turn around too tightly until the last pass. And last, don't overload the PG - if you're doing a small yard, don't put 100 pounds of fert in the hopper - it just makes it heavier to turn.

    DUSTYCEDAR LawnSite Fanatic
    from PA
    Messages: 5,132

    i like it so far

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