so not to hijack router HP thread

[Randal Stevenson]

In the early sixties, people started changing the way they rated HP. (wasn't alive), But if I remember my older motors that were around, 9 amps was 3/4 hp and 12 amps was considered 1 HP (correct me if I am wrong here guys).

Now they rate them at how much HP they generate the second before the motor fries?

In the last few years, I've seen compressor lawsuits (perceived verse actual running HP), lawnmower lawsuits (now rated I believe as torque (don't need a new mower)), how long till a tool motor lawsuit happens? Better yet, are there actually standards for motor testing, that ALL motors should be rated by?

Kinda a pet peeve of mine, as some of that old arn worked quite well with smaller HP motors (yes I know some of the windings and such were better).

Thanks
Wanting standards.

[Tom Veatch]

...But if I remember my older motors that were around, 9 amps was 3/4 hp and 12 amps was considered 1 HP (correct me if I am wrong here guys)....

Those aren't bad estimates for "real world" conversion of amperage draw (at 110v) to delivered HP considering power factor, heat losses, and other electrical and mechanical inefficiencies.

Some marketing types apparently got into the action (my supposition, no facts/references to back it up) and to make "my" widget look better than "their" widget, started advertising the widgets based on the maximum electrical power the motor would draw rather than the maximum power the motor would deliver at the output shaft. Unethical, dishonest, and downright sleazy in my opinion.

Forget the "Marketing" HP printed on the box or painted on the side of the widget; compare based on the amperage ratings on the motor dataplate. You'll have a better chance of getting a meaningful number.

[glenn bradley]

Shop-vacs will be right behind them if it hits. I just go by amps but speak in manufacturer's HP rating for consistency sake. Used to be the same story with automobile stereos although I believe they now comply.

[Bill Wyko]

I'm in car audio and we needed a standardization for years. We finally got it. When amplifier manufacturers used to over rate their amps i called it the ILS power rating ILS stands for "If lightning Strikes" Sounds like some ILS rating going on in this case.:D

[James Carmichael]

My old Emerson-built Craftsman saw has the "3HP" label on the front, whereas now they at least qualify the claim with "max developed" or "peak".

I searched for one of these old saws on CL for months, and they are very overpriced as a result of the HP claims, IMO. Somebody who doesn't know any better inherits dad's old Craftsman, reads the "3HP" label and think they have something on the order of a Unisaw. A couple got downright onery when I told them their saw wasn't really 3HP.

[Jimmy Newman]

Someone in another recent thread said that the current HP ratings on tool motors are based on the electrical power consumed by the motor with the shaft held at no rotation (I don't know if this is true or not). Said person further pointed out that if the shaft if not turning, the motor is consuming electrical power but is not actually producing mechanical power (This is true). Seems like a BS way to rate motors to me :).

1HP = 745 Watts. Good modern electrical motors actually are often more than 90% efficient. Some are as high as 97-98% efficient. So if you want to figure out the actual HP of a motor, multiply supply voltage by operating amperage during normal use and divide by 745. You should be less than 10% off (off by the inefficiency of the motor, which may be as low as 2-3%).

This happens a lot. A friend of mine is into R/C stuff. He has a helicopter which he claims has a 10HP engine - which is about the size of his fist and runs about 1000W of electrical power (1 1/3 HP). :)

[James Carmichael]

Someone in another recent thread said that the current HP ratings on tool motors are based on the electrical power consumed by the motor with the shaft held at no rotation (I don't know if this is true or not). Said person further pointed out that if the shaft if not turning, the motor is consuming electrical power but is not actually producing mechanical power (This is true). Seems like a BS way to rate motors to me :).


Yep, it's called "locked rotor current", and it is BS.

[David DeCristoforo]

"...it is BS..."

To say the least! I'm no electrical engineer but it shouldn't take one to realize that the "2HP" rating on a dinky router motor is not going be the same as the 2HP you are going to get from that honkin' hundred pound thing that lives inside your table saw base!

[Charles Bruno]

Here are some formulas that might help. I too hate the way tools and compressors motor ratings are advertised.

Horse power for DC motors HP=E x I divided by 746

for AC motors single phase HP= E x I x p.f divided by 746

For 3 phase HP= 1.73 x E x I x p.f divided by 746

For motor and small engine power output or brake horsepower as its called, you can use the Prony brake test. You can Google it if you need to know more or how to do it.

[gary rogers]

So you don`t think the beer can sized motor on my Sears shop vac is really 5 horsepower? I feel ripped off.

[Curt Harms]

So you don`t think the beer can sized motor on my Sears shop vac is really 5 horsepower? I feel ripped off.

:D:D:D

So sue. It's the American way!:rolleyes:. I'll take 10% of any award for making the suggestion.:)

Curt

[Cliff Rohrabacher]

A couple got downright onery when I told them their saw wasn't really 3HP.

Can you blame them? They likely wouldn't know any better - and while trying to sell a thing didn't want to learn. They prolly thought you were just messing with them to knock their price down.

[Cliff Rohrabacher]

a rating like: "Motor 4.0 HP (3.0 kW) S6/40%"
will give you more information than a "peak" rating.
You get to know what the actual output is.

[Ed Blough]

In the early sixties, people started changing the way they rated HP. (wasn't alive), But if I remember my older motors that were around, 9 amps was 3/4 hp and 12 amps was considered 1 HP (correct me if I am wrong here guys).

Now they rate them at how much HP they generate the second before the motor fries?

In the last few years, I've seen compressor lawsuits (perceived verse actual running HP), lawnmower lawsuits (now rated I believe as torque (don't need a new mower)), how long till a tool motor lawsuit happens? Better yet, are there actually standards for motor testing, that ALL motors should be rated by?

Kinda a pet peeve of mine, as some of that old arn worked quite well with smaller HP motors (yes I know some of the windings and such were better).

Thanks
Wanting standards.

Randall
Your not going to get standards. The American public doesn't want standards they want the biggest. The most of the American public has the idea that bigger is better, bigger cars, bigger houses, bigger kids, bigger tools.

No one considers what is needed only how big it is. If you have two tools either will do the job one rated a 3/4 horse power pulling 9 amps selling for $49 and the other with a sticker on it saying 3 hp pulling 10 amps selling for $69 most consumers would pay the extra $20 just to get the biggest one. When in fact the 3/4 horse on is probably over powered for 90% of their projects. Notice also the price is always $49 and $69 never $50 and $70.

The real problem is most in this country has more money than brains, as proven by the price many will pay for a new car and houses, and until that changes you will continue to see totally ridiculous claims made by manufactures on how theirs is the biggest and most powerful.