Horse power, horse hockey

You are quite welcome.

Have you been reading any Sears advertisements by chance?

RonB

I'm going to take the motor off of my shopvac and put it on my tablesaw. Not only is it more powerful, it's smaller! Technology is wonderful.

Since HP is the result of a calculation that includes RPM, bizarre ratings can occur.

Dave

My God! How did you know?

Sears has had more ways to sidestep specifications and other features than any distributor I can recall. Remember 'starting horsepower'? That is probably what started their credibility gap with us older farts. You never know what they are talking about.

RonB

If you're measuring electrical input power, then I've got a 4 horsepower kitchen toaster, and that doesn't even move. If you allow electricity wasted as heat into the calculation, then you can get some perverse measurements. As vacuums move a lot of air that they also use for cooling, they're usually designed to be woefully inefficient in the search for cheap power. It might even _be_ mechanically quite powerful

- some of them are, despite their small size and weight.

My table saw is not only rated at 3HP, that's real 3HP at almost any speed, without risk of burning out.

Me too. Perhaps you should understand more about horsepower ratings.

The purveyors of this stuff rate motorins things like the Shop Vac as the product of the maximum amperage times the maximum voltage. And, they don't worry about such niceties as temperature rise.

However, motors for machinery such as table saws are rated at the average power (which is 1/2 of what the above calculations show) and for an intermittent load. This load results in a temperature rise of 60F above ambient temperature. Thus, machinery motors are conservatively rated whereas those other are wildly optimisticall rated.

Jim

"RonB" wrote in news:_NDQg.1487$Go3.1277@dukeread05:

From RepairFAQ.orgs humour page: About Sears Shop Vac HP Ratings (From: Kevin AstirCS "1U" KO0B ( snipped-for-privacy@aquilagroup.com).) I note that air compressor manufacturers have taken after the vacuum sweeper folks, and are re-inventing the horsepower. Imagine, 6HP at 15A, 115VAC!

(From: sam).

Have you seen Sears shop vacs lately? I think they are also up to 6 HP. Every week or so, they seem to come out with one that is a little higher in their HP ratings - I guess internal cold fusion or something.

(From: Pin 2 Hot ( snipped-for-privacy@io.com).)

Let's see, RPM X Torque = Horsepower.

Thus: No-load RPM X Locked-rotor Torque = Sears Horsepower

Notes:

1. testing done at 177V DC, equal to peak of 120V AC (AC-DC motors).
2. Sears Horsepower: How "hoarse" you get trying to talk over one of their shop-vacs while it's on.

Or maybe it's got something to do with vacuuming performance out at the stables.

Source (again) RepairFAQ.org's humour page.

So, looking at realistic HP ratings (not shop vac sensationalized values), my table saw is a 230 volt, 3hp motor. My router is a 120v

You shouldn't. On a 120 volt, 15 amp circuit, even 2.5 horsepower is impossible.

I might put mine on the wife's blazer *g*

Mac

From what Jim said, if I understood it, the table saw could actually max at maybe 6 hp...

Mac

Joe

hello,

formula: HP = T * RPM / 5252 (T in lb/ft). Thus T = (HP*5252)/RPM

Let us assume that the peak HP is at 4000 RPM (induction engine), this means that to generate 3 HP, the ST will need around 4 lb /ft of torque. with a 10 " blade (5" radius), this mesures to 9.5 lbs at the teeth...

same calculation: .7 lbs /ft of torque on the router, with a 1/2 radius bit, this is 17 lbs of pressure at the teeth...

yep, directly proportional... note, it is easier to make a fast spining engine have high power than a slow spining engine as less power torque needs to be generated...

the overall weight of the cutter is negligeable compared with the weight distribution (ie: how far from the axis is the weight).

note, 1 HP = 745 W and 1 W = 1 V*A so if your tool is rated to draw up to

cyrille

Good point, Joe... I don't think our 400 watt invertor would run it.. lol Mac