Author Topic: Harbor Freight achieves perpetual motion device  (Read 1419 times)

230RN

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Harbor Freight achieves perpetual motion device
« on: June 25, 2017, 10:19:24 PM »
Harbor Freight is advertising an electric pole saw and they say it is 1.5 horsepower and draws 7 amps.

Hm. 7  amps X 125 volts = 875 watts.

Hm. 875 watts  Ã· 746 watts per horsepower = 1.17 horsepower.

Hm.  1.5 horsepower advertised  Ã· 1.17 horsepower by the numbers = 128% efficiency.

Apart from mere "advertising hype" and pure "typographical error," can anyone see how they could make such a technical mistake in the arithmetic?

???

I've got a cortex vortex over how they could screw up this one, even using Occam's razor and just saying "it was a boo-boo."

I've been a little off my stride lately, but that one kind of leaped out at me.  I know I'm going to feel like an idiot when someone points out my error in thinking.  :facepalm:

Terry

REF:
Page 6, middle right, their "Super Coupon, June 2017, Issue 8724-2," but you can take my word for it: "7 Amps, 1.5 HP."
« Last Edit: June 25, 2017, 10:43:09 PM by 230RN »

zxcvbob

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Re: Harbor Freight achieves perpetual motion device
« Reply #1 on: June 25, 2017, 10:49:40 PM »
1.5 HP is its maximum power output.  It can't sustain that for very long but it can achieve it. 
7 amps is what it pulls under no load.  HTH
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Nick1911

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Re: Harbor Freight achieves perpetual motion device
« Reply #2 on: June 25, 2017, 10:53:40 PM »
Honestly, many motor ratings on consumer products are vastly over-inflated.

I have a shop vacuum that advertises on it, 5 peak horsepower.  That plugs into a 120V receptacle using a length of 16awg cord....

The CPSC finally started coming down on small engine manufacturers for the same reason.  Now you'll only find CC's of displacement listed on a small engine.

zxcvbob

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Re: Harbor Freight achieves perpetual motion device
« Reply #3 on: June 25, 2017, 10:57:37 PM »
Honestly, many motor ratings on consumer products are vastly over-inflated.

I have a shop vacuum that advertises on it, 5 peak horsepower.  That plugs into a 120V receptacle using a length of 16awg cord....

The CPSC finally started coming down on small engine manufacturers for the same reason.  Now you'll only find CC's of displacement listed on a small engine.

I was part of a class action settlement a few years ago on air compressor ratings.  We won the case, but I didn't get a damn thing.  Not even a worthless coupon.  I assume the lawyers made $millions.
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230RN

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Re: Harbor Freight achieves perpetual motion device
« Reply #4 on: June 26, 2017, 01:43:00 AM »
I thought maybe they were screwing up with power factor or something, but that seems to work out backwards.  You'd need even more (measured, lagging) current to develop 1.5 HP than 7 amps.  Getting kinda rusty on this stuff, though.  I no longer do it on a day-to-day basis.

Sounds ike that's the no-load value, though, as mentioned.  Also sounds like a "hyoe," as also mentioned.
« Last Edit: June 26, 2017, 01:56:36 AM by 230RN »

Fly320s

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Re: Harbor Freight achieves perpetual motion device
« Reply #5 on: June 26, 2017, 09:09:25 AM »
Honestly, many motor ratings on consumer products are vastly over-inflated.

This.

Those ratings are only accurate on brand-new, lab tested equipment.  Nothing in the real world comes close.  That applies to cars, planes, boats, women, tools, lawn mowers, and everything else.
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bedlamite

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Re: Harbor Freight achieves perpetual motion device
« Reply #6 on: June 26, 2017, 10:51:35 AM »
Sometimes called ILS power ratings. If Lightning Strikes.
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230RN

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Re: Harbor Freight achieves perpetual motion device
« Reply #7 on: June 26, 2017, 07:30:05 PM »
Sometimes called ILS power ratings. If Lightning Strikes.

 :rofl:

I guess that's the case.  I got "triggered" by the advertised numbers, though.  Even without a calculator, they didn't "look" right...

"Hmmmm.  Seven times one hundred equals seven hundred watts.  That's even less than a horsepower.  Oh, wait, seven times one hundred ten is seven hundred and seventy watts... still not even close."

Terry reaches for one of the many calculators around the house, each one parked near a gun, all for instant access....

"Hmmm... that's for DC, though.  I wonder if they screwed it up with power factors... let's see, a running motor ought to have about an 0.80 PF..."

At about that point, I realized how rusty I was on that stuff.  I just wanted to know how they could make that mistake and decided to consign the problem to the hive mind here.

Terry
« Last Edit: June 26, 2017, 07:51:13 PM by 230RN »