> I also know how they overrate the volume by basing it purely on the
> displacement- my question is, where do they come up with the hp
> rating? The
> only explanation I've found that would let them make the claim
> would be from
> the gearing between the motor and the compressor on the direct drive
The problem with that is that gearing cannot produce power. A 2:1 drive for
example, give twice the torque but half the speed, and the horsepower is
torque times speed so it remains the same (less whatever is lost in the
gears).
The only reasonable explanation I've heard for compressor "hp" figures is
that they measure an instantaneous peak torque (which I'd guess is something
like 30 degrees BTDC on the pump) and then multiply that times the average
shaft speed. IMO a more likely explanation is that they are simply lying.
Since "everyone does it" and there's no legal body forbidding it ...
> And one other thought- duty cycle is important too along with volume, just
> like with a welder, especially with 110 as compared to 220. These newer
> direct drives run faster and hotter than a belt drive 2 cycle and
> since they
> can't deliver as consistent a volume will toast off a lot faster since
> people (myself included) just keep running without letting 'em cool down.
Good point, I hadn't realized they couldn't be run continuously. Mine's a
belt drive, and although it's efficiency drops off when it gets hot, it does
just keep chugging along. Especially since the cut-off has failed closed
<g>
Randall
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