What's pitch got to do with it?

Discussion in 'Lawn Mowing' started by Envy Lawn Service, Jun 18, 2004.

  1. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Posts: 11,062

    That 1/4" deck pitch number... what's that got to do with striping?

    Did that just become the standard because someone said so?
    Is that automatically accepted for all deck types and sizes?
    Does anyone run level anymore?
    Anyone run a different pitch?

    Has anyone ever actually adjusted to 1/4" pitch and seen a dramatic change/difference it striping?
    What about cut quality?

    Just real curious....
     
  2. dishboy

    dishboy LawnSite Platinum Member
    from zone 6
    Posts: 4,318

    I run at 1/8 pitch because I want as flat as cut as possible, I strip with a roller and proslide.
     
  3. saw man

    saw man LawnSite Bronze Member
    from utah
    Posts: 1,021

    The pitch of the deck (not sure why on striping) delt more with mulching. Honda had a mower out with the pitch already set, so the front would be higher than the rear.
    The reason for this is to push gras up front where there is more cleareance. Therefor making it a better mulcher, because it would pick the grass up again and cut it.

    Hope i understood your question right.
     
  4. Tonyr

    Tonyr LawnSite Bronze Member
    Posts: 1,973

    Hi Envy,

    My owners manual for my Toro Z588E says 1/4 to 3/8'' is the pitch range, I'm close to 3/8 off memory (8mm or so)

    As far as sriping goes I can't comment as my work isn't on good enough lawns to stripe properly.

    BUT, since using RAPTOR blades I do have defined stripes for our conditions anyway.

    I always thought pitch was deck breathing for lift and grass processing etc. but to what degree certain amounts of pitch give I dunno.
     
  5. laborador

    laborador LawnSite Member
    Posts: 148

    So for mulching only you should have the pitch lower in the back not front and by how much. Thanks
     
  6. specialtylc

    specialtylc LawnSite Bronze Member
    Posts: 1,656

    The purpose of the deck being pitched down a quarter inch is so the back of the blades are not in contact with the grass. This reduces the required horsepower to run the blades, and it makes the grass discharge from the deck better. As the grass is thrown out from the front of the deck. As an example try mowing in reverse and as you all know the grass clippings dont flow out the deck very well. Even your 21 in. push mowers are pitched down in the front, check one and you will see.
     
  7. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Posts: 11,062

    The extra load I can understand and I feel it slightly. But I guess I would have noticed that more if I had less HP.

    But what about say 1/8" isn't that enough to reduce load?

    About the discharge part... you have me wanting to take the mulch kit off and play this weekend...
     
  8. Sam-Ohio

    Sam-Ohio LawnSite Senior Member
    from Ohio
    Posts: 304

    The slight foreward tilt to a rotary mower deck is done to save horsepower, and to reduce clogging and matting inside the deck. It will also give a much better shear to the grass blades and reduces exploded tips on the grass.

    If a rotary mower deck is adjusted with the front slightly higher than the rear of the mower, and of course the blades arc are then a bit higher in front, so the grass is cut off at say 31/4 inch high at the front of the mower, then as the deck travels on across this grass and it finally gets under the rear edge of the deck , here comes the blades again , and the blade is cutting at the lower 3 inches on the backside of its swing. This means that the grass gets mowed again [just 1/4 inch] but it really kills your power to mow off say 60 inches of grass in front and then mow another sixty inches of the same grass again just as it exits the rear edge of your deck.

    The second bad thing that happens is that the clippings are cut and thrown out the chute by the swing of the blades at the front end of the mower, but the grass that gets a second cutting at the rear of the blade arc is all tossed the WRONG WAY. This grass is all blown over into the closed in left rear corner of the deck, where it matts and sticks to plug up your deck, it then falls out as wads and clumps of finely chopped grass. The lawn then begins to look like a goat puked all over it.

    The third bad thing that can happen from reversed pitch on a mower is that grass blades that are cut off at the very tip end of the blade [last 1/8 inch] will often explode the leaf tip of the grass. This is especially a problem with Kentucky Blue grass.
    If you look closely at the grass tips, they will look like the end of a bull whip that has been cracked till it's shredding. The grass will then get a yellow unhealthy look all over the lawn, not the deep green vibrant appearance you want after you have mowed it. This damage can happen even from a mower that is set dead level. The blade RUBBING the grass tips can explode the grass leaf tip. This is why they recomend a 1/8 to 1/4 inch foreward tilt to all rotary mower decks - so that the blades on the back side of the swing never touch or cut the grass at all. If you set your deck correctly with just a touch of foreward tilt , then all these problems just go away !!!
     
  9. Envy Lawn Service

    Envy Lawn Service LawnSite Fanatic
    Posts: 11,062

    Ok, so would the proper amount of pitch depend on the actual blade length? Like a 61" deck with 21" blade lenght would actually have a bit flatter blade pitch than a 48" w/shorter blades.

    Think of it as an amount of rise in run, like a house roof....
     
  10. One Timer

    One Timer LawnSite Member
    from iowa
    Posts: 17

    Just think this guy did a mower review, and he doesnt know what pitch is all about
     

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