Powering 5HP motor

[Josko Catipovic]

Yeah, I was wondering how they got 6 hp out of a sloppy little motor about ther size of an apple.
How DO they come up with that number?

[Mike Henderson]

Yeah, I was wondering how they got 6 hp out of a sloppy little motor about the size of an apple.
How DO they come up with that number?

It's what they call "Peak HP". HP is torque times RPM times a numeric factor. I think they take the torque that the motor generates when it is suddenly very heavily loaded, and just before it stalls (but while it's still rotating at a pretty good RPM). The current through the motor would be quite high at that time, but for a very short time. Of course, this measurement is useless to anyone who uses the motor because what a user is interested in is continuous HP, not peak HP. It's strictly a marketing gimmick.

Most of the universal motors that we (as woodworkers) are concerned with run on 120 volts. So to compare different motors look at the current rating. That doesn't allow for the differences in efficiency but it's a good first check.

Mike

[Frank Pratt]

Yeah, I was wondering how they got 6 hp out of a sloppy little motor about ther size of an apple.
How DO they come up with that number?

However they do it, it's complete falsehood & I can't believe that, with all the regulations covering labeling & advertising, they can get away with it.

[Malcolm McLeod]

However they do it, it's complete falsehood & I can't believe that, with all the regulations covering labeling & advertising, they can get away with it.

Not to be contrary (and certainly not defending the practice), but it isn't a falsehood. As Mike points out the advertised Hp IS true by the 'accepted' calculations - - for about 50 milliseconds. Any longer and the motor would melt, but in this case it apparently meets whatever truth-in-advertising regulations apply.

About all we can do is vote with our dollars: buy something else!

[Frank Pratt]

Not to be contrary (and certainly not defending the practice), but it isn't a falsehood. As Mike points out the advertised Hp IS true by the 'accepted' calculations - - for about 50 milliseconds. Any longer and the motor would melt, but in this case it apparently meets whatever truth-in-advertising regulations apply.

About all we can do is vote with our dollars: buy something else!

Those HP claims are analogous to claiming that a pair of cotton oven mitts are good for 2000*F, which they are; for about 50 milliseconds. Truth is truth & that just ain't it.

[Malcolm McLeod]

Those HP claims are analogous to claiming that a pair of cotton oven mitts are good for 2000*F, which they are; for about 50 milliseconds. Truth is truth & that just ain't it.

I'd buy a different pair of mitts.

[John K Jordan]

Not to be contrary (and certainly not defending the practice), but it isn't a falsehood. As Mike points out the advertised Hp IS true by the 'accepted' calculations - - for about 50 milliseconds. Any longer and the motor would melt, but in this case it apparently meets whatever truth-in-advertising regulations apply.

About all we can do is vote with our dollars: buy something else!

I posted this from ShopVac earlier in this thread (my highlights) - I think it's basically a explanation of why they all lie, under the pretense of helping the consumer. I was told the government made them include this disclosure statement.

"**"Peak Horsepower" (PHP) is a term used in the wet-dry vacuum industry for consumer comparison purposes. It does not denote the operational horsepower of a wet-dry vacuum but rather the horsepower output of a motor, including the motor’s inertial contribution, achieved in laboratory testing. In actual use, Shop-Vac motors do not operate at the peak horsepower shown."

JKJ

[Frank Pratt]

"**"Peak Horsepower" (PHP) is a term used in the wet-dry vacuum industry for consumer comparison purposes. It does not denote the operational horsepower of a wet-dry vacuum but rather the horsepower output of a motor, including the motor’s inertial contribution, achieved in laboratory testing. In actual use, Shop-Vac motors do not operate at the peak horsepower shown."JKJ

This makes me laugh. In a vacuum, the motor's inertial contribution has absolutely no benefit. I does in my little Lamello though, which is kinda under powered. When cutting a slot in hardwood end grain, I have to let the motor spin right up before plunging in. Otherwise it just bogs down. But in a vacuum, no way.

[Mike Henderson]

In any case, comparing shop vacuums by HP seems like the wrong thing to look at. I'd be more interested in air flow and noise.

Mike

[Van Huskey]

In any case, comparing shop vacuums by HP seems like the wrong thing to look at. I'd be more interested in air flow and noise.

Mike

The most useful specs would be a fan curve and a sound pressure level reading at a given distance while including what weighting and in what Pi space it was measured in. The reality is unless the figures are controlled by a regulating body there is no penalty except for bad PR for fudging and few consumers are going to bother to understand and interpret fan curves and aren't capable of comparing SPLs unless they are standardized. In a very rudimentary way, the current HP ratings actually work, they give a low information consumer and an easy way to compare vacuums and in a very general sense, it works.

[Michael Weber]

Used to sell audio equipment in the late 60's and early 70's. Over time power output ratings went from Watts to "Peak Watts". Then "Peak to Peak Watts". Finally something dreamed up called "instantanious Peak to Peak Watts. Small single output transistor amps were being marketed as having 100 Watts or more per channel. And so it goes.

[William Fretwell]

I have 3 shop vacs, power was not even a consideration. If they have silly small wheels that look like they will break, they WILL break (usually at the mounts). Listen to it in the store some are horrendously noisy. A commercial vacuum store will have a good one for $200. My Hilti is compact for job sites, has expensive filters up to HEPA for hospital jobs but back flushes them every few seconds so they last ages. It’s wheels will never fall off!
My main criteria would be wheel size and mounts followed by noise.