Page 1 of 5 1234 ... LastLast
Results 1 to 10 of 44
  1. #1
    New Member
    Join Date
    May 2012
    Posts
    3
    Location
    Ogdensburg, NY
    Tractor
    kubota b7510

    Default What does horsepower actually mean?

    I can't seem to find a good online answer and asking a mechanically minded friend only confused me more. So here goes a dumb question...


    What does horsepower actually mean? Not the definition according to James Watt (how much a horse can move) but something that explains what it actually measures.

    My confusion comes from having a john deere lawn tractor with 23 horsepower (that actually doesn't have the ability to really pull something) and a kubota tractor with 21 horsepower that can actually do relatively heavy work. Obviously horsepower doesn't explain the difference between these two machines.

    thanks -- tim

  2. #2
    Super Star Member murphy1244's Avatar
    Join Date
    Nov 2011
    Posts
    17,256
    Location
    Ohio
    Tractor
    Kioti DK-40, MF-135, Ventrac 4500Y

    Default Re: What does horsepower actually mean?

    1 HP= 33,000 foot lbs per minute. foot lbs = amount of energy required to raise 1 lb weight a distance of 1 foot.

  3. #3
    Super Star Member murphy1244's Avatar
    Join Date
    Nov 2011
    Posts
    17,256
    Location
    Ohio
    Tractor
    Kioti DK-40, MF-135, Ventrac 4500Y

    Default Re: What does horsepower actually mean?

    Quote Originally Posted by TimNY View Post
    I can't seem to find a good online answer and asking a mechanically minded friend only confused me more. So here goes a dumb question...


    What does horsepower actually mean? Not the definition according to James Watt (how much a horse can move) but something that explains what it actually measures.

    My confusion comes from having a john deere lawn tractor with 23 horsepower (that actually doesn't have the ability to really pull something) and a kubota tractor with 21 horsepower that can actually do relatively heavy work. Obviously horsepower doesn't explain the difference between these two machines.

    thanks -- tim
    The weight of the machines is where the torque can be applied.

  4. #4
    Elite Member dodge man's Avatar
    Join Date
    Oct 2008
    Posts
    3,940
    Location
    West central Illinois
    Tractor
    Kubota BX2350

    Default Re: What does horsepower actually mean?

    The kubota tractor has more torque, is why is seems to have more power.

    I'll give two extremes of engine design. Take a 1000 cc motercycle engine that is very high performance, its probably 4 cylinders, and makes something over 100 horsepower. Take a 1000 cc engine in a Kubota tractor. It probably makes something like 23 to 25 horsepower. The difference is how it makes that horsepower. The motorcycle engine makes it peak power at probably something close to 10,000 rpms, the tractor engine at something like 2800 rpms.

    Can you picture a engine in a tractor that you have to crank over 8000 rpms? In theory, it would work, but I don't think it would last long. How about a 3 cylinder diesel in a motorcycle? It would work, but not well.

    The truth is, torque in a high load, low rpm engine is more improtant, but they still rate just about everything in horsepower.
    Dave,
    BX2350

  5. #5
    Platinum Member
    Join Date
    Oct 2008
    Posts
    772
    Location
    Piedmont Triad, NC
    Tractor
    Didn't intend to have a Deere fleet - it just happened 310C, F915 & 5200

    Default Re: What does horsepower actually mean?

    Quote Originally Posted by TimNY View Post
    I can't seem to find a good online answer and asking a mechanically minded friend only confused me more. So here goes a dumb question...


    What does horsepower actually mean? Not the definition according to James Watt (how much a horse can move) but something that explains what it actually measures.

    My confusion comes from having a john deere lawn tractor with 23 horsepower (that actually doesn't have the ability to really pull something) and a kubota tractor with 21 horsepower that can actually do relatively heavy work. Obviously horsepower doesn't explain the difference between these two machines.

    thanks -- tim
    Let me try ... The deere and kubota are rated at X horsepower at the output shaft of their engine. The HP is a calculated number based on the speed of the shaft and the torque produced. example... Deere motor turns at 33,000 RPM but only produces 1 foot pound of torque. ( a foot pound is the force applied on a lever ) So it's rated at one horse power.

    The kubota motor turns at 1 rpm but produces 33,000 foot pounds of torque. It too is rated at one horsepower.

    Pulling ability requires traction and the ability to convert the turning of the engine shaft to the drive wheels. ( I'll wager that the kubota is heavier and has lower gearing to the wheels.) After that, more horsepower just lets you go faster.

  6. #6
    Elite Member schoolsout's Avatar
    Join Date
    Feb 2011
    Posts
    4,362
    Location
    Awendaw, SC
    Tractor
    Massey Ferguson 1533

    Default Re: What does horsepower actually mean?

    Torque gets loads moving
    Horsepower keeps loads moving

    simple answer we use in the trucking industry
    __________________________________________________ _______
    "The greatest shortcoming of the human race is our inability to understand the exponential function." -
    Prof. Al Bartlett

    Any person is entitled to their own opinion, but not to their own facts and outcomes. So one may believe as they will, but will be held accountable by the numbers for their beliefs. At the end of the day, life is a school of probability. Jesse via Jesse's Cafe Americain

  7. #7
    Member
    Join Date
    Oct 2011
    Posts
    34
    Location
    Boise, Idaho
    Tractor
    Ford 800 OC-3

    Default Re: What does horsepower actually mean?

    Horsepower is a measure of power in the mechanical world much like watts is a measure of power in the electrical world. Horsepower is the product of torque and rpm. Torque is the twisting force and the rpm, how rapidly you can perform this twisting force, determines the power (horsepower). If you lift 550 pounds 1 foot in 1 second you have produced 1 horsepower. If you have a model airplane engine that turns at 10,000 rpm and with suitable gearing it is coupled to a winch and it manages to raise 550 lbs, 1 foot, in 1 second it produced at least 1 horsepower (more, unless you have a no friction perfect gearbox on your winch). A 1725 rpm electrical motor again with suitable gearing connected to the winch lifting 550 lbs, 1 foot, in 1 second also produces 1 horsepower. Obviously torque from the model airplane engine is much lower than the torque on the electric motor, much like the difference between the 20+ hp lawn tractor engine and the 20+ hp compact tractor.

    Then there are muddling factors like gross hp ratings vs net hp ratings. The garden tractor manufacturer may have quoted a gross hp output at the flywheel, where as the FEL may have quoted net hp at the draw bar or PTO. It was this marketing nonsense and liberties that created the Nebraska testing laboratory in the early days of ag tractor manufacturing. Add to that the durability factor i.e. how long can that engine generate that 20+ hp and not self destruct, and things get rather confusing.

    As a kid growing up we would see that the Chevy 283 V8 was rated at a 195 hp. Yet my dad's 400 cubic inch IH 856 was only 100 hp. What's up with that? One thing, the rpm at which those horsepower outputs had occurred, another how long can you keep that up?

    Yes I am sure that the 283 V8 installed in a tractor suitably geared to the transmission would indeed pull 100 possibly 150 horsepower but I daresay that a few days of pulling the field cultivator would leave you with a smoking ruin of an engine, as sustaining the power output to put a 100+ draw bar horsepower on the field cultivator would overstress pistons, valves, etc. to point of failure. If you ballasted the 20+ hp garden tractor sufficiently you could pull that scaled down land plane almost as well as the 20+ hp Kabota. But the Kabota will be doing it long after the garden tractor shucked a rod or blew a transmission.

    gordon

  8. #8
    Veteran Member
    Join Date
    Dec 2009
    Posts
    1,895
    Location
    S. W. Virginia
    Tractor
    Kubota B3200, Ford NAA, IH 454D, Case 1845C

    Default Re: What does horsepower actually mean?

    Its actually a very simple measurement.

    HP = (Torque x RPM)/5252


    So your lawn tractor may only have 34lb-ft of torque since it's rated at 3600rpms.

    A 21hp tractor rated at say, 2200 may have roughly 50lb-ft. As related to work ability, not only does the tractor have more torque but also more gearing and weight.
    Kubota B3200
    Ford NAA Jubilee
    International 454D
    Case 1845C skid steer
    JD 265

  9. #9
    Elite Member Bob77064's Avatar
    Join Date
    Sep 2011
    Posts
    3,972
    Location
    KY @ TN line
    Tractor
    2011 LS R3039

    Default Re: What does horsepower actually mean?

    Torque is power or twisting effort. Horse Power is more like speed.

  10. #10
    Elite Member J F's Avatar
    Join Date
    May 2012
    Posts
    4,174
    Location
    North of Atlanta, GA
    Tractor
    ShovelandBarrow

    Default Re: What does horsepower actually mean?

    Kudos to the guys explaining it...I was having the same "wonderings" the last couple of days upon discovering this site "My riding mower has suchandsuch HP...".

    Didn't quit make sense in my uneducated mind, so thanks for the explanations, and to the op for asking.
    ____
    Jay

Page 1 of 5 1234 ... LastLast

Similar Threads

  1. Horsepower hours per gallon- help me understand
    By Kaliburz in forum Oil, Fuel & Lubricants
    Replies: 83
    Last Post: 02-19-2014, 02:38 PM
  2. 25 horsepower vs. 30 horsepower
    By powhatanpete in forum Kioti Buying/Pricing
    Replies: 4
    Last Post: 07-31-2005, 01:26 PM
  3. Engine Horsepower: Rule of Thumb
    By duane in forum Owning/Operating
    Replies: 11
    Last Post: 06-20-2005, 03:39 PM
  4. Engine horsepower or PTO horsepower?
    By porky1 in forum Attachments
    Replies: 3
    Last Post: 11-19-2004, 11:27 AM
  5. Horsepower? Gas vs. Electric Motors
    By Spencer in forum Related Topics
    Replies: 11
    Last Post: 05-16-2003, 08:30 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
© 2014 TractorByNet.com. TractorByNet is a registered trademark of IMC Digital Universe, Inc. Other trademarks on this page are the property of their respective owners.