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Posted by Ulysses on August 9, 2005, 11:17 am
>
> Ulysses wrote:
> > >
> > > >I bought a new table saw and I can run it on 120 or 220, However,
they
> > > > recommend 220. What does running it on 220 buy me over 120? Thanks
for
> > > > your
> > > > opinions.
> > >
> > > >
> > > Faster starting, less likely to bog down. Same operating cost.
Smaller
> > wire
> > > size. A few Delta saws have a different set of windings and you get 2
HP
> > > instead of 1.5
> > >
> > > Separate circuit is always a plus. When I first go my saw I wanted to
try
> > > it out before hte new line was installed. I hit the switch and the
> > > fluorescent lights went out for maybe 5 seconds until the saw got up
to
> > > speed. Scary. Next day I ran the new line. .
> > >
> > >
> >
> > Just curious because I've never worked in a shop with fluorescent
lights,
> > but is it true that the blade on a saw can appear to be stopped due to
the
> > 60 cycle strobing of the lights?
>
> A tidbit that some people might be interested in:
>
> Fluorescent lights will flicker at twice the AC frequency, which would
> be 120 Hz for North America. You get two cycles of the light
> flickering for each AC cycle because the current flows one way and the
> light comes on, then the current goes to zero and the light goes out,
> and then flows the other way and the light comes on again. The light
> doesn't care which way the curernt is flowing. In theory this happens
> with other light sources such as a regular tungsten bulb, but you never
> see the flicker in a tungsten bulb because the glowing filament doesn't
> cool off quick enough to see any flickering.
>
> A calibrated strobe light is one way to measure the rotational speed of
> things. For the case of the table saw, you would gradually adjust the
> strobe rate until you got the blade to "freeze". What is really
> happening is that the blade moved in integer number of teeth from one
> flash to the next. The problem is that you don't know if it moved one
> tooth or two teeth, or whatever. You then change the strobe light
> frequency until you get the blade to "freeze" again. There is some
> procedure and calculations that are used to determine the rotational
> speed of the saw based on the strobe frequencies that froze the blade,
> but it's been too long since I have done that and I'd have to think too
> hard right now to remember how that part works.
>
> So there's today's science lesson.
>
> Ken
>
So then if a saw blade is rotating at a speed which is a multiple of 120
(such as 4800 rpm) then it could appear to be stopped, right?
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