"Snag" wrote in
:
And a new, versus old blade won't make any particular difference

Uh , Bill , it most assuredly WILL make a difference . New sharp
blades
take a lot less power to cut than old dull blades . I work full time
in a commercial millwork shop , and we can really tell the difference
when the blades start to drag from dull teeth .
Dave , you'll want to be sure the 2X4's don't warp and bind the
blade ,
that'll raise all kinds of hell with that setup .


I think the point of his statement, and mine was that the motor startup
would likely be the pass/fail point of this setup and the blade makes no
difference at that point. Once it is running the blade condition will
contribute to the overall current draw but a test before buying a new
blade would tell if the entire endeavour has even a chance to work. A
5hp motor even single phasing without any help from the rotary can
surely rip construction lumber, once it is up to speed.

As a real world data point I coincidentially needed to rip some 2x
lumber on my Uinisaw so I popped open the starter and stuck on my clamp
meter.

SINGLE phase 3 hp motor, 240 volt input. Motor full load amps label
spec is 12.3
Blade is a thin kerf 24 tooth, probably average sharpness from having
been used for light duty reno work on mostly clean old lumber.
Wood was old, some more completely dry reclaimed construction grade
lumber of an unknown spruce/pine species.

Measured current while ripping was about 8 amps, climbing to about 10 if
I pushed a little too fast. Given about 80% motor effiency for
calculation purposes I figure the input to the blade was near 2 HP, give
or take.

Based on all that I think the OP's setup will in fact be capable of
performing the task, provided it can even start the motor unloaded.

Lacking a clamp on amp meter to monitor the input current I would ensure
the rotary converter had some form of overcurrent protection before
using the setup for any length of time. The saw should have it's own
protection for all three legs built into the starter, assuming it has
one. At 5 hp it should.