Is 50 HP really 50 HP?

[buickanddeere]

I have a few big Craftsman shop vacuums that range from 4.25 to 5.5 horsepower, and I have wondered the same thing: How a little electric motor can possibly develop that much horsepower. I have an older Craftman push mower with the 190cc Briggs engine and it was rated about 5.5 or 6 horsepower...might be over rated itself but...which motor do you think has a more honest power output rating?

Torque rise , real power, intermittent over load capacity and the operation characteristics of various prime movers are not well understood .

 

[SPYDERLK]

If thrust truly was measured in ft-lbs, that would imply there would be a time factor. How fast it can move XXXXX pounds that 1-foot. Thus it would be easy to convert to HP for comparison reasons.

HP and thrust cannot be compared. Its apples to oranges. Thrust is just the max ability to push something. 8500 pounds in the case of the F9F. If that jet weighed less than 8500#, it would have the ability to fly and accelerate vertically.

HP has the TIME element. How fast a force can be applied. Different measurement all together. Like trying to convert inches to gallons or something.

I have often wondered how to get out of the quandary that an engine producing constant thrust [by throwing stuf backward] produces increasing HP as speed increases. :confused2: ... It must be the increasing energy stored in the motion of the carried fuel mass.

 

[SPYDERLK]

Who could blame one for believing nothing anymore. I once saw a shop Vac with 5 (or was it 6) HP sticker. It had 110 volt 15 amp plug. You can figure about 737 watts per horsepower. You can get about 1700 watts from a normal outlet so how did they get 5 or 6 hp? Maybe it had a free energy collection system.

Anything to fool and fleece the consumer.

Iv always used 746 watts per HP conversion. ... I think they use max inrush as the motor starts ??? or maybe current at near stall for that 5 - 6 figure. Its consuming the electrical HP, but surely not producing the mechanical HP.

 

[LD1]

Why would you need to get out of the quandary?

HP is a function of force and time

more force = more HP
more speed = more HP

Many people forget the time aspect. You can apply a LOT of force (thrust or torque) to something and until it moves, you cannot have the time aspect, thus have no HP. With a conventional engine, to make whatever its operating go faster, we use gearboxes. Which proportionally effects torque. 2x's faster means 1/2 the torque. So frictional losses aside, HP remains constant because 2 x 1/2 = 1.

With thrust, weather it be a boat or jet, there are no gearboxes for what is being "thrown out the back". So the faster you go, the more HP.

 

[LD1]

Iv always used 746 watts per HP conversion.

metric HP?

Did some reading, seems its something newer? 75kg m/s. Which works out to 736w

Bad enough to have metric and imperial measuring systems.....just imagine how messed up things would be if there were metric and imperial units for time too:confused2:

 

[Industrial Toys]

When I grew up, I seem to remember your standard B&S equipped push mowers were either 2.5 or 3.5 HP. Now, I see them at 6.5 HP and don't get the impression that they are twice the power of the old machines. Too bad when what should be a technical spec becomes a (bogus) sales feature.

Kind of like the stupid PU truck wheel size war. I was perfectly happy with 15" (afordable) wheels!

 

[LD1]

Kind of like the stupid PU truck wheel size war. I was perfectly happy with 15" (afordable) wheels!

Hate the big wheels myself. Like the 20" crap on 1/2 tons All for looks and show.

The trend to 16's and 17's on 3/4 and 1-ton trucks though I think alot has to do with clearing bigger breaks to stop the heavier loads they are rated to tow.

 

[mike69440]

I hardly ever use the PTO on my tractor. I bought a B7100 to do my mowing, so now the PTO on the L3240 never gets used. I work my tractor hard, much harder than the average TBN member. My primary use is the loader and a distant second is the backhoe. My tractor has 715 hours and I have used the PTO for less than 20 of them. How does this make it a glorified lawn mowers?

That little B7100 has a lot of torque rise as it backs up on the curve. makes the 16 NP net 17 hp gross seem like a lot more. My new Max28 does have more power, but with a torque curve more like gas engine than diesel, so it does not seem like it has 28 HP.

 

[mike69440]

Who could blame one for believing nothing anymore. I once saw a shop Vac with 5 (or was it 6) HP sticker. It had 110 volt 15 amp plug. You can figure about 737 watts per horsepower. You can get about 1700 watts from a normal outlet so how did they get 5 or 6 hp? Maybe it had a free energy collection system.

Anything to fool and fleece the consumer.

Of course tit is true that a shop vac motor can produce 5 (whatever HP)

It can, but never will as the impeller does not load it that much.

If you hook a shop vac motor to a 50 Amp 120V fused supply and connect it to a dynamometer and then load the motor to its break down torque, it will make lots of hp.
For a few seconds anyway, till the windings cook and it burns down your shop.

The electric motor will produce 2 to 2-1/2 times its continuous duty power rating.

Continuous duty power rating might be 1-1/2 to at best 1-3/4 hp, as that is all you can ever get out of a 15 A 115 outlet.

1 hp = 746 watts, x Motor eff. (Use 90%)

 

[mike69440]

Another frustrating aspect is that most brands also take the same engine, and tweak the fuel delivery amount to add or subtract HP, then charge you more for the higher HP. For example, the 1.8L Turbo'd diesel in the Kioti NX4510, 5010, 5510, & 6010 all use the identical engine, and the HP numbers are changed with fuel & computer settings. The 3.0L diesel in my Massey 1652 is identical for the 1655 & 1660, but these are all naturally aspirated, and is literally adjusted only by a fuel pump setting (very easy to adjust the set screw on these).

Kubota, LS ... They all do this.

http://www.tractorbynet.com/forums/...39070-boosting-power-l4610-possibly-just.html

After turning up the fuel, mine does stink a little if you have it at full load for awhile. Certainly it is not "rolling coal" like some jerks who mess with their pumps.

I suspect a turbo motor really respond to more fuel. Remember a little more is usually enough.