Risks of lowering the mower rpms?

Discussion in 'Lawn Mowing' started by GarPA, Aug 7, 2003.

  1. GarPA

    GarPA LawnSite Silver Member
    from PA
    Posts: 2,585

    I believe it was AWM who recently mentioned about lowering the rpms to lessen the grass buildup on the mower decks. On a related note, I have a few properties with many planting beds and so I turn down the rpms to lessen the grass being blown into the beds but it still gets in anyway. Its been beaten into my head that we always need to keep the rpms up to get adequate air to these engines that work so hard.

    Just wanted some opinions about whether we risk damage to the engine when we throttle down these mowers for a minute or 2 here and there?? thanks
     
  2. 65hoss

    65hoss LawnSite Fanatic
    Posts: 6,360

    Many times I've run mine at lower than full blast. Most people on realize that the fan cools the motor, but many neglect to realize that the crank generates airflow inside the motor to also help keep it cool.
     
  3. wriken

    wriken LawnSite Silver Member
    Posts: 2,154

    I drop mine down sometimes. I use a syn oil in the motor, change it every 40-50 hours. The syn should also help it run cooler, also have 15-50 mobile 1 in the hyd system. I also have a cooler that mounts on the outside of my hyd filter housing, supposed to extract the heat.
     
  4. geogunn

    geogunn LawnSite Gold Member
    from TN
    Posts: 3,010

    IMHO I believe mower rpm for the sake of the motor is a non issue.

    the motors are designed to run at any speed up to the max rating.

    but for the sake of discussion...as the rpm's are lowered so is the cooling effect of the crank fan, however...so is the heat generating combustion of the engine.

    it always operates within its tolerances.

    GEO
     
  5. redbull

    redbull LawnSite Member
    Posts: 182

    Hold on - 1st are we talking about a 21" HP or a Z or a WB. Todays engine are designed & built to run their best at full RPM. On a Z running one for long periods of time on less than full rpm will not only cause engine problems but also pump & wheel motors. On a HP slowing down the rpm slows down blade speed. On a WB blade speed suffers & if it is a hydro the pump & wheel motors suffer. Slowing one down for a short time (to help keep stuff out of beds) shouldn't have an effect on the engine. But it is not a good idea to run them at less than full RPM
     
  6. geogunn

    geogunn LawnSite Gold Member
    from TN
    Posts: 3,010

    sir--can you back your statment up with proof of what you are saying?

    the point of the original post wasn't to debate lower rpm as it relates to blade speed.

    I must now admit that I have a great deal to learn about this subject if you would please document what you are saying.

    inquiring minds want to know.

    GEO
     
  7. redbull

    redbull LawnSite Member
    Posts: 182

    I feel I can back up this statement by reading the engine/owners manuals (specific the engine manuals) that come with the verious units out there. Most manufactures use the same engines. Or you can contact the manufacture direct. All I said was the engine were designed to run their best (most efficient) at full rpm.
     
  8. geogunn

    geogunn LawnSite Gold Member
    from TN
    Posts: 3,010

    redbull--as for effieiency of rpms, blade speed and cutting, there is no disagreement.

    however, actually you said:

    perhaps you didn't really mean it when you said " less than full rpm will not only cause engine problems but also pump & wheel motors" but you did say it and that is why I questioned your statment.

    in any event, I keep my 14 kaw cranked wide open as much as I can.

    GEO

    GEO
     
  9. redbull

    redbull LawnSite Member
    Posts: 182

    geogunn - you have a fine piece of equipment in that 14kw - they are one of the manufatures to which i was refering
     
  10. geogunn

    geogunn LawnSite Gold Member
    from TN
    Posts: 3,010

    thanks redbull--I'm suprised to hear that. it seems like there oughta be a warning sticker on it somewhere but there isn't.

    my main concern is keeping leaves from gathering around the top fan and cutting off the air flow.

    GEO
     

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