Bucket Force and Arm Force

Discussion in 'Heavy Equipment & Pavement' started by RockSet N' Grade, Oct 6, 2007.

  1. RockSet N' Grade

    RockSet N' Grade LawnSite Silver Member
    Posts: 2,454

    I am comparing machine specs. I know this has been talked about before, but I still do not completely understand. Machine #1: Max bucket dig force: 15,311. Machine #1:Max arm dig force: 7507. Machine #2: Max bucket dig force:10,900. Machine #2: Max arm dig force: 8150. So for me alot of questions arise: Is there a formula to calculate these two numbers to come to a variable to fairly compare different machines? Is there a universally accepted method to calculate bucket dig force or do different manufacturers calc it differently? I am trying to level the playing field here on the published spec sheets from different manufacturers and have not been able to get the straight scoop.
     
  2. ksss

    ksss LawnSite Fanatic
    Posts: 7,129

    Tigerrotor knows this stuff better than most and hopefully will correct me if I am wrong. The bucket breakout (excavators) is rated with a bucket of choice which is usually a bucket that has a short tip radius for max power. The arm dig force or sometimes called crowd force is the force generated by crowding the arm toward the machine. Some machines have higher bucket breakout and less crowd force. Other OEMs go the other way. As a result some machines are better bucket diggers than others. High crowd forces I think are an advantage in trenching allowing you to fill the bucket easier while pulling a level plane. If you compare the bucket and arm crowd force of different machines you will see what I mean. TK machines seem to be more bucket diggers as their bucket breakout forces are higher. Bobcat seems to be more of an arm digger as their crowed forces are higher.
     
  3. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Posts: 9,544

    What KSSS says is true I noticed it running 3 different brands of excavators the Komatsu seemed to have the most crowd force the machine would always want to stand on its nose when you hook a rock and start pulling.

    The Hitachi seemed to have the best of both worlds and the Deere you really had to work the bucket.

    It is interesting to see that Takeuchi has a higher bucket force that may explain the reason why one of the local utility companies prefers Takeuchi minis. They dig alot of power pole holes in a year and with power pole holes your digging a hole where your taking a scoop and lifting it out.
     
  4. Tigerotor77W

    Tigerotor77W LawnSite Bronze Member
    from Germany
    Posts: 1,891

    KSSS isn't telling any lies with his analysis of breakout force.

    I'd say that Cat is also a stick-digger -- the speed that I could "stick-load" a 305C CR's bucket impressed me to no end. I never even had to work the stick; it would just move the material.
     
  5. RockSet N' Grade

    RockSet N' Grade LawnSite Silver Member
    Posts: 2,454

    I understand the above posts and possible qualities of both. I was hoping Tigerotor that there may be a calculation that could be done with those basic numbers to give a rating to compare machines that the guys who design these things use to compare" theirs " to the competition.
     
  6. SiteSolutions

    SiteSolutions LawnSite Bronze Member
    Posts: 1,114

    I thought the Deere was made by Hitachi?
     
  7. Tigerotor77W

    Tigerotor77W LawnSite Bronze Member
    from Germany
    Posts: 1,891

    RockSet: mmm, I think I understand your question. Sorry about that.

    The issue with comparing the actual numbers is, as KSSS pointed out, that a manufacturer may use different buckets to get those numbers. There is no standard "SAE bucket" for each size-class of machine for the manufacturers to use, so even though the calculations used to arrive at the numbers are likely similar, there isn't a way to guarantee that the actual numbers involved are comparable.

    There isn't a quick way to calculate the combined force of the bucket and stick forces. You can add them vectorally, but this is no easy process... it'd be a very ugly equation, most likely, with several terms.

    Cat_excavator.jpg
     
  8. ksss

    ksss LawnSite Fanatic
    Posts: 7,129

    To complicate matters, by adding a quick coupler you also lessen your breakout numbers (there are coupler OEMs that claim their coupler does not affect the breakout force). Also the buckets that are used to achieve max. breakout are not necessarily that are the most productive for excavation. All the more important to demo a machine with the configuration that you are likely to use it under. The distance from the tip of the teeth to the top of the bucket is the key. The shorter the distance the more power, of course this typically means less capacity.
     
  9. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Posts: 9,544

    SiteSolutions the machines are before Hitachi and Deere were sleeping with each other. I'am not the only one that noticed the Deere didn't have the crowed force.

    Kobelco machines really have the crowed force or they seem to have. The one of the contractors has a couple Kobelco hoes and watch them work you pull the stick in towards the machine and it drags the machine.
     
  10. RockSet N' Grade

    RockSet N' Grade LawnSite Silver Member
    Posts: 2,454

    Tigerotor........thanks.....So, the bottom line as I see it, is there is no set standard and you can arrive at your particular machines numbers any way that you want to. Choose a particular bucket that gives you great numbers, yet is not practical in real application........So published numbers are not necessarily apples to apples.
     

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