wrote in message
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On Sat, 10 Oct 2009 10:04:18 -0500, dpb wrote:

Worn Out Retread wrote:
I am looking for a new snow blower and have discovered that the power
rating of the engines are no longer in "Horse Power" but in "Foot
Pounds" if given at all. Sometimes all that is given is the CC's of the
engine.

Even the people selling these machines don't know what the "Horse Power"
ratings are so that old geezers like myself can understand what is going
on. Does anyone have any general rules regarding the conversion of Foot
Pounds or CC's to Horse Power?

Unfortunately, not at all precisely, no...thanks to the dam lawyers

One can _VERY_CRUDELY_ estimate hp at about 60-70% of torque.

The relationship I recall (I'd have to go off and think again to
re-derive the denominator) of hp ~ torque (ft-lb)*rpm/5250 which boils
down to the above since most ratings are at 3200-3600 rpm.

Unfortunately, that's about best one can do other than simply try to
find similar engine w/ known rating and compare based on displacement.
Problem there is that tune and emissions requirements, etc., make that
comparison as variable as the above.

Earlier Northern Tool catalog still listed an unofficial "old hp rating"
as well but I just looked and the last one doesn't. Now I'm hoping I
didn't throw the old one away and lose that cross-reference.

All in all, it sucks to guess how to compare even worse than before when
ratings could be tweaked--at least you knew what Sears was doing w/
"peak" or "instantaneous" horsepower; the torque ratings might be
absolutely accurate but they're still nearly useless as a comparison to
previous ratings and certainly there's not even the same measure used if
only provide displacement in one and torque in another.


Multiply the old rating X 5252 and devide by 3600 and you have the
torque rating of the old engine to compare. Virtually all of the old
engines were rated at 3600 rpm.

So that works out to be approximately 70% of the rated torque if rated in
foot lbs. which would be easily calculated while browsing different models.
Someone else gave some equivalents of torque and horse power and the figures
pretty well agreed with what you have given.

Thanks

--
Ron