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motor selection for power hammer

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One of the advantages that does come from an old style / heavy frame motor is not any magical extra power but simply mechanical...shaft and bearing size. When I first set it up, I had to run my old Blacker on an identical power but smaller spindle motor (Ø20mm (Ø3/4") I think). I could not source a larger frame in that small power. The bearings could not cope with the flat belt and slightly wobbly pulleys and only lasted a year or so. Luckily it lasted long enough to be replaced by the original 3phase one, which had an Ø1 1/2" or Ø1 1/4" shaft, when I had the three phase power connected.

I seem to remember that the power output of infernal combustion engines is measured on a Dynamometer.

Alan

Edited by Alan Evans

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I should have gone into full load current calculations, and that states we would need 60 amp lines installed for proper power for 5 Hp, because of the 140% of the HP rating needed,  I was trying to explain the BS out there to actually help people understand what is needed,  but I should have known better, some people dont want to learn so why do I waste my time trying.  Its fine if you want to believe you have 5 Hp all you want, but do not complain here when it fails to operate your hammer.

Horsepower is not all over the map,  snake oils salesmen are all over when they are telling you this crap.

​Of course I know I cant run the power hammer on the shop vac or chop saw motor. My point was that many things are advertised as much higher hp than truly are capable of. Home depot is not a snake oil salesman, this is just they way these products are marketed across the board. So I understand that your calculations of true hp are correct, if somebody  takes your "horespower is horesepower" statement as straightforward they are not getting a true understanding of what is actually being presented in the market place. 

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Thats 60 amps at 120vac, or 7200 watts. Is that right Steve? Or are you saying 60 amps at 220vac (13,000 watts) after running the numbers i think your talking 220, ( wich gives  nearly twice the power for a 5hp type 2 motor at 50% efficiency). 

Yo do relise that most of this is just an argument over 1/2% difeence in vewpoint?! Lol i respect your oppinion more than your knowledge and skill set Steve (and i trust your knowledge and skills set) 

Truth is, a monday or friday motor may not live up to expectation, wile a motor that all the veriations in specs just happens to lighn up may exede expectations. An older motor (real old) not only suffers from that but as the way they tested its out put may be even have greater veriance. I would expect as much as +/- 5% on a moderm motor and +\-10% on an antiqu (enen if it was build with a heaver case and a larger shaft) i wouldnt go counting on the +, I'd count on the -. 

 

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​Of course I know I cant run the power hammer on the shop vac or chop saw motor. My point was that many things are advertised as much higher hp than truly are capable of. Home depot is not a snake oil salesman, this is just they way these products are marketed across the board. So I understand that your calculations of true hp are correct, if somebody  takes your "horespower is horesepower" statement as straightforward they are not getting a true understanding of what is actually being presented in the market place. 

​Industrial motors have real ratings regardless of what crap stores sell.

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Thats 60 amps at 120vac, or 7200 watts. Is that right Steve? Or are you saying 60 amps at 220vac (13,000 watts) after running the numbers i think your talking 220, ( wich gives  nearly twice the power for a 5hp type 2 motor at 50% efficiency). 

Yo do relise that most of this is just an argument over 1/2% difeence in vewpoint?! Lol i respect your oppinion more than your knowledge and skill set Steve (and i trust your knowledge and skills set) 

Truth is, a monday or friday motor may not live up to expectation, wile a motor that all the veriations in specs just happens to lighn up may exede expectations. An older motor (real old) not only suffers from that but as the way they tested its out put may be even have greater veriance. I would expect as much as +/- 5% on a moderm motor and +\-10% on an antiqu (enen if it was build with a heaver case and a larger shaft) i wouldnt go counting on the +, I'd count on the -. 

 

​Charles; put down the handy pocket guide to electric motors and back away. 

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Lol, bit more than that, Arftist but point well taken. 

Originaly come from the automotive side of things, been years so this has been a bit of a refresher corse (tho some of the heavy reading into magnetic feilds and diffent motor desighns (stuff i andmittadly glosed over when studing for my ASE master certs) was a bit of a slog. I do have more than a passing familiarity with Ac, Dc, 3 phase, high voltage (low and medium aperage) been forever tho. Despite rufling Steves feathers (truely not my aim) it was nice to go digging and refresh my knoledge base. 

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