Hydraulic Horsepower

Discussion in 'Heavy Equipment & Pavement' started by GMUGNIER, Dec 11, 2005.

  1. GMUGNIER

    GMUGNIER LawnSite Member
    Posts: 61

    Hello all - I am new to this forum but I previously posted a request for information on drum cutters - haven't gotten much back yet as far as different brands and reviews of each other than the Fecon - but several members posted that the ASV 100 had more horsepower and would outperform my 287B hi-flow - well I did some calculations and have determined that the ASV has less hydraulic horsepower than my cat - 66 on the ASV100 hi-flow as ocmpared to 69 on my 287B hi-flow - the calculation that i used is - Hydraulic Horsepower = your flow x your pressure x .90 divided by 1714 = answer based on this info - i guess the ASV might have more engine horsepower but when it comes to actual attachments the Cat seems to outperform - all comments will be appreciated

    Thanks
     
  2. ksss

    ksss LawnSite Fanatic
    Posts: 7,131

    Loftness has a chart that shows Hyd. Hp for practically every skid steer made.
     
  3. GMUGNIER

    GMUGNIER LawnSite Member
    Posts: 61

    I guess that further confirms the CAT for more Hydraulic horsepower - Does anyone know if this is a accurate method of determining the usability of attachments?
     
  4. muddstopper

    muddstopper LawnSite Silver Member
    Posts: 2,342

    One thing you left out of your equation is the hp needed to produce the flow and psi your equipment needs. You might have a system that will pump 20gpm at 1500 psi but if the motor wont pull the pumps at that flow and psi then your figures are mute. Here is a link to some more information and online calculators you might find helpful. http://www.surpluscenter.com/techhelp.asp?UID=2005111814244042&catname=hydraulic
     
  5. StoneStacker

    StoneStacker LawnSite Member
    from OR
    Posts: 47

    Gus,

    I think you're on the right path here. I had lunch with the local CAT salesman from Peterson CAT about 3 months ago, and we talked about this same topic. It's important to know that there is a big difference between calculated hydraulic hp, and useable hyd. hp. The reason we talked for about an hour on this subject was due to some figures he had given me that stated that the CAT machine put out more hyd. hp than any competitor. The formula that he used was the same as yours, but it didn't have .90 in the equation (does anyone know what this is for?). Using his equation he said that they put out 79 hyd. hp. I asked him how a pump could put out more hp than the engine could produce net. He said it couldn't and that the equation only provides calculated hp's. I think this is where engine hp comes into play. Besides having to drive the auxillary hydraulic pump, it also has to drive the hydraulic transmission, the A/C compressor, etc. I think that this is where a larger displacement engine with more net hp is an advantage. As I said in an earlier post, I think you will get good use out of your 287, but I just can't see where it would provide more useable hydraulic hp than a machine with more net engine hp. Especially in applications where the machine is climbing, turning, raising the loader arms, running A/C, etc. I hope someone with more hydraulic system knowledge posts on this topic.
     
  6. Tigerotor77W

    Tigerotor77W LawnSite Bronze Member
    from Germany
    Posts: 1,892

    I'm taking a guess here, but the 0.90 may be for the efficiency of the pump setup. Cat's leaving the efficiency at 100% (1.0) is setting the playing field even for all makes -- if everyone *could* produce with no losses, and barring engine power, Cat's XPS has the highest flow out there.

    I have no clue when it comes to hydraulics... I'm working at it. :)
     
  7. muddstopper

    muddstopper LawnSite Silver Member
    Posts: 2,342

    The .90 is pump efficiency but even .90 isn't realistic. A completely new pump and hydraulic motor setup might come close to that but .80-.85 is more real world. There are a lot of variables in computing the actual efficiency, engine hp and torque range also play a part. Which is why I mentioned in my previous post that the stated flow and psi is a relationship of the engines ability to actually operate that pump and hyd motor combination in its intended range. A hydraulic pump has to turn a certain amount of rpms to produce the advertised flow and pressure under constant load. If that rpm range is in the correct torque range of the engine then the pump should be able to maintain the flow and pressure. If the rpms don't match the engines hp/torque curve the engine might struggle to maintain a constant rpm for constant flow and pressure. Temperature of the oil and even the type of oil also effect flow and pressure and the hp needed to create that flow and pressure. Most manufacturers should have engineers that have all those variables calculated into their published material. Al tho published information can be skewed by simple things like stating 100% pump efficiency when in reality the machine is only 90% or less. Even tho the 100% might be accurate under ideal conditions.
     
  8. StoneStacker

    StoneStacker LawnSite Member
    from OR
    Posts: 47

    Thanks for the posts guys. It has helped allot, but I'm still intrigued at how a manufacturer can claim 78.3 hydraulic hp when the net engine hp is only 78hp. I guess I could see a pump producing the "same" hydraulic hp as the engine in a perfect world, but that would be without having to supply engine power to drive the machine, operate the loader, and drive any compressor if it was using one. All of these functions require hp from the engine so I'm still curious about that.
     
  9. ksss

    ksss LawnSite Fanatic
    Posts: 7,131

    Actually the 95XT/465 CASE with the 5000 PSI high flow system is still the number one skid steer on the market for highest hydraulic hp. I have talked to many of the different brush cutting manufacturers and most that I talked to used this machine to spec. their cutting attachments. It is important to look at more than engine HP when specing a skid steer for this type of work. I learned from talking to these guys that the Gehl 7800-10 which I thought would be great in these types of applications actually has major over heating problems. Looking at the spec. sheet your would think it would do well with 115 hp and 40 gpm but with these high stress applications how well they are designed is equally important to the numbers they post.
     
  10. Tigerotor77W

    Tigerotor77W LawnSite Bronze Member
    from Germany
    Posts: 1,892

    StoneStacker: once again, I'm taking potshots, but I believe the reason for the "excess" power comes from the calculation itself. Power is work per unit time, and somehow in that flow (volume per unit time) and pressure (force per unit area), you get a unit of power. This unit of power, although still the same as horsepower or watts, may not be technically correct. Perhaps it's more of a "gross" horsepower for the entire hydraulic system -- not counting parasitic losses in the pumps, lines, or valves. I'll try to dig into this a bit more, but it may be a full year before I can answer this (fluid mechanics is next fall for me).

    kaiser, you are right -- the 90XT and 95XT had the highest hydraulic horsepower ever (around 88.5). However, the 5,000 PSI system doesn't seem to be offered on the 400 series.
     

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