Mini excavator: why so little HP?

[woof]

I was looking at some specs for mini excavators and was surprised at the HP ratings-10HP for a 2200lb machine? My snowblower is rated 10 HP. Can somebody explain a bit?

Some stats on dozens of models here: http://www.compactequip.com/unbound/exclusive-unbound/12-07-mini-hex.php

[tanky321]

The excavator is run on hydraulics, where as your snow blower is run directly by the engine.

Im guessing thats the reason at least.

[Tractapac]

Another reason might be diesel engines for excavators, vs gas for snow blowers.

[Mondo]

I was looking at some specs for mini excavators and was surprised at the HP ratings-10HP for a 2200lb machine? My snowblower is rated 10 HP. Can somebody explain a bit?

Some stats on dozens of models here: http://www.compactequip.com/unbound/exclusive-unbound/12-07-mini-hex.php

Different methods of arriving at horsepower ratings are used for different types of engines. Small gasoline engines as used in snowblowers are rated differently than diesel engines used in tractors and construction equipment. Even the EPA has a totally different formula for calculating horsepower than what industry has been using for a hundred years. In fact these differences have led to lawsuits against engine manufacturers. :realmad: The result is many small engine manufacturers will not rate their engines in HP anymore. If you look at new equipment using small engines such as snowthrowers, lawn mowers and the like, you will find most are rated only in cylinder displacement as measured in cubic centimeters. This is the only value that cannot be contested (stroke x bore = volume).

Read this at the Washington Post:
Familiar Horsepower Rating No Longer Standard
http://www.washingtonpost.com/wp-dyn/content/article/2008/02/15/AR2008021501732.html

-Mondo

* Figures don't lie but liars figure.

[lugweld]

Mon-

They are actually going back to HP ratings. Briggs and Honda got into a legal tiff about horsepower and went to putting ft. lbs of power on their engines. It just about killed them. Now they are reintroducing revised Hp ratings from what I understand.

[denrep]

I was looking at some specs for mini excavators and was surprised at the HP ratings-10HP for a 2200lb machine? My snowblower is rated 10 HP. Can somebody explain a bit?...

The biggest design factor which allows for lower horsepower engines on equipment is variable displacement hydraulics. With a mechanical drive such as a snowblower may have, the engine needs to be sized to work while outside of it's ideal peak power range.

Variable displacement pumps allows an engine to always run in it's ideal peak power band, while hydraulic pump displacement is varied to suit load and speed requirements. Since less energy is wasted pumping oil that will not be used, and since the engine is working within it's ideal power band, the engine can be more precisely sized.

Good Luck

[boatbuoy]

my case 580k backhoe has a cummins 65 hp engine. oodles of torque but with no revs there is no high hp. hp is torque x rpm divided by 5252 .

[ElGuapo]

Same with these machines Turboed 4-cyl kubota's kind of directly on the sawblade for sawing concrete and tarmac, bridgedecks etc.

http://i40.photobucket.com/albums/e228/ElGuapo77/zagen-betonvloeren-2a.jpg

When these guys put on their earcaps make sure you've instructed them properly. They'll be done in a sec.

[Aquafire]

Here are the basics for operating a mini .
The link was to an online auction. Spam?

[farmall]

Both posts read precisely like copy/pastes. No one writes disconnected posts like that in a forum.

Spam.

[lotechman]

Ironic that horsepower is a marketing ploy invented by non other than Jame Watt. He had to have some way to compare his steam engine to the amount of water that could be pumped using a horse. How else could he sell to mine owners.
It is not a reliable measure because it could be continuous horsepower, intermittent HP or maximum HP. I have seen 400 HP diesels stood twice as high as me and turned a 4 inch propeller shaft. Of course that kind of machine would last for 20 years doing 24/7 if required.

[ironmangq]

Only numbers that really matter and can be directly measured are torque and rpm's. Horsepower is a derived measure and the calculation used to get there is different for the type of motor and whose standards are being used. Torque is always measured the same, no calculations just a raw measurment, same with rpm's. The units might change but their meaning doesnt.
I get into this with my dad all the time, he is always asking how a tractor can do what it does with so little horsepower, I keep telling him to look at the torque specs and gearing.

[sixster]

the thing is diesel engines produce about double the torque at a low rpm

[ASE_MasterTech]

Only numbers that really matter and can be directly measured are torque and rpm's. Horsepower is a derived measure and the calculation used to get there is different for the type of motor and whose standards are being used. Torque is always measured the same, no calculations just a raw measurment, same with rpm's. The units might change but their meaning doesnt.
I get into this with my dad all the time, he is always asking how a tractor can do what it does with so little horsepower, I keep telling him to look at the torque specs and gearing.
I don't see how the two (HP & torque) can compared as one is a measurement of 'work' & the other is a measurement of 'force'..

[PanelDeland]

HP is how fast you hit a brick wall.Torque determines how far it moves.

[killdozerd11]

My father used to call them a hydraulic shovel

they have there place i've run a JD 70D that to me was small
but it was an offset excavator and they had me digging footings up against a retaining wall

[Fat Bastard]

What is Horsepower?

Force, Work and Time
(http://www.vettenet.org/torquehp.html)
If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on.
In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time.

Awhile back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower.

Everybody else said OK. :-)

For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms which define a *twisting* force, such as foot pounds of torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum.

Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.

Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidently, we have done 6.2832 foot pounds of work.

OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement:


Torque * RPM

Horsepower = ------------

5252

This is not a debatable item. It's the way it's done. Period.
The Case For Torque

Now, what does all this mean in carland?
First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.

You don't believe all this?

Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-)

The Case For Horsepower

OK. If torque is so all-fired important, why do we care about horsepower?
Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.

For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-).

On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:

6 HP.

Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.

[Tool Maker]

Well Fat Bastard. Youve surely got your **** together on that. Very interesting. But did you actualy answer your first question?.. Mac

[Fat Bastard]

Well yes I thought I did, in that HP alone or torque alone with out a time factor are meaningless sales dribble.
A sales gimmick to satisfy an ignorant lazy consumer.

Im NOT saying that the OP is ignorant or lazy.

[Tool Maker]

I wasn't actually questioning your very well done explanation. Ive been told that the problem with using torque for any kind of in the field experimentation is that it is an always theoretical definition,, Seeing that the definition of torque is the amount of force it takes to stop a turning object to a dead stop. and cant be accurately measured even with Dynamometer. Its kind of like when is now. Mac

[Fat Bastard]

Oh and I an not the author of the essay on HP and Torque.

[boatbuoy]

I wasn't actually questioning your very well done explanation. Ive been told that the problem with using torque for any kind of in the field experimentation is that it is an always theoretical definition,, Seeing that the definition of torque is the amount of force it takes to stop a turning object to a dead stop. and cant be accurately measured even with Dynamometer. Its kind of like when is now. Mac

WHERE DID YOU GET THAT DEFINITION ? if it were true ,then you cannot by definition tighten a bolt to a specified torque.A force applied at a right angle to a lever multiplied by its distance from the lever's fulcrum (the length of the lever arm) is its torque.

[denrep]

WHERE DID YOU GET THAT DEFINITION ? if it were true. . .
Yeah, the Horsepower Manifesto is full of holes too, but once Fat Bastard said it wasn't his own work, and since this is three year old thread resurrection via spam, I figured why bother.

Good Luck