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Posted by clare on October 10, 2009, 7:39 pm
show/hide quoted text
>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.
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Posted by Worn Out Retread on October 11, 2009, 10:41 am
show/hide quoted text
>>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
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Posted by Worn Out Retread on October 11, 2009, 10:35 am
show/hide quoted text
> 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.
> --
I had an eight horse power MTD blower and for most most jobs it was
perfectly adequate. Now that I want a new blower, I don't want to buy a
machine that has less power than the old one but the published specs are
just plainly designed to confuse the buyer and there are very few web sites
that do much to untangle the mess of misleading information.
If all you are doing is clearing 6 inches of snow off a driveway that is one
thing but when the snow plough comes by and dumps a mess 2 feet deep and 6
feet up the drive, that small snow blower is just not going to get the job
done without nearly blowing its guts out especially if the material to be
cleared has had any great amount of salt added to it making the mess very
dense and therefore heavy and difficult to move.
--
Ron
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Posted by Van Chocstraw on October 10, 2009, 11:57 am
Worn Out Retread wrote:
show/hide quoted text
> 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?
>
They are just trying to pull one over on us by frigging up standard
ratings in the US.
CC's equate more to Cubic Inches. Foot pounds equate to horsepower.
Multiply horsepower by 33,000 to get foot pounds.
It's just another crooked business tactic to screw you over.
See the chart: http://www.geocities.com/MotorCity/Show/3753/convert.htm
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Posted by dpb on October 10, 2009, 12:20 pm
Van Chocstraw wrote:
...
show/hide quoted text
> CC's equate more to Cubic Inches. Foot pounds equate to horsepower.
cc and ci are both displacements, yes.
torque and horsepower aren't the same units at all---
show/hide quoted text
> Multiply horsepower by 33,000 to get foot pounds.
So a 3hp lawnmower has almost 100,000 ft-lb of torque??? Amazing! Them
are some stout crankshafts...
show/hide quoted text
Actually hp*33,000 --> ft-lbs/minute, _not_ ft-lb (as the table shows).
The "per minute" part is significant here.
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>> 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.