Newbie- Understanding the horsepower of a machine.

[Verfur]

i think it may have bin mentioned above some where, but what the heck I chip it back in.
There are 3hp peak and then there is 3hp cont. most 3hp peak are raely only 2hp.

Also dont forget about the gear ratio and all the other junk the poor little motor may be turning as well.

Now there is this dang new hp ratings an lawn mowers so a 3.5 hp briggs says it has a peak of 5 hp (its all in the sale) same with air compressors a 5hp compressor will draw at least 15-20 amps on 220v so I guess they have magic motors on a 120v 5hp compressor then... haa lol

[Caprirs]

How is the speed controlled on the manual lathe? Changing gears or a VFD? If using gears to achieve the 800rpm, then the motor is always turning it's rated speed of (typically) 1725rpm or 3450rpm. That means the motor always turns at the same speed until you start to stall it. As the load increases, the motor draws more amperage trying to maintain rpm which increases the torque and thus the horsepower.

On the other hand, a variable frequency drive will have only half the horsepower when running at half the rated rpm. Huge difference compared the the gears. In fact, one of the biggest advantages of using a gearbox is to get the maximum horsepower over a wide range of rpm.

CNC machines use overwhelmingly fancy VFDs. By using circuitry, they create an artificially flat power curve over a wide range.

[MidFloridaTech]

AHHHHHHHHHH! Thank you for these last couple of posts its all very clear now. Both the lathes in question were geared head lathes. Still not sure why the power was so different, but I will chalk it up to being an older lathe.