Mild steel, or hardened? Mild would be better.
> Inside this tube will be the
> solenoid actuated valve and counterweights so that the tube is
> balanced. And the plumbing that will bring the air from the valve to
> the collet closer mounted in the spindle. Into the end of this tube
> will be screwed a rotary union that passes air.
Hmm ... any reason why you can't put the valve on the outside
end of the union? That looks like it (the union) might wear faster than
the slip rings anyway.
> If I have a coil
> wrapped around the steel tube won't that be a problem? What if a
> plastic sleeve were to be pressed over the O.D. of the tube and the
> coil wrapped on it. Would that be better?
Hmm ... let's make the part which contains the coil fairly
short, and put a plastic spacer say 1/4" thick or a bit more between it
and the main tube. Let me sketch how I would make it for reasonable
magnetic coupling.. (I'm sure that there are many ways.)
BBBBBBBBBB
XXXXXXXXXXXXXXX XXXXXXXXXXXXXXBBBBBBBBBB
XXX:::::::::::: :::::::::::XXXBB
XXX:::::::::::: :::::::::::XXXBB
XXX:::::::::::: :::::::::::XXXBB
XXX:::::::::::: :::::::::::XXXBB
XXX:::::::::::: :::::::::::XXXBB
XXX:::::::::::: :::::::::::XXXBB
XXXXXXXXXXXXXXX XXXXXXXXXXXXXXBB
PPPPPPPPPPPPPPP
PPPPPPPPPPPPPPP
PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP
PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP
SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
This image is only above the centerline of the tube.
If your newsreader is using a proportional space font, the image
will be distorted -- unless you can send it to a printer which has a
fixed-space font like Courier available. Proportional space fonts will
squeeze the ':'s closer together than the 'P', 'S' and 'X' characters.
The second and third row of Ps should end just below the
right-most '|'s
The parts made of ||| are mild steel cups. The one to the left
fits onto a plastic sleeve PPP over the steel sleeve SSS.
The ::: are the ends of wires in the coil wound and glued into
the cup. (With the wire ends brought out though a hole or two drilled in
the bottom wall of each cup.
BBB is a bracket -- steel, aluminum, or perhaps a strong plastic. The
two cups will concentrate the magnetic field fairly well from one coil
to the other. Whether it goes up, or down depends on where you have
something to bolt it to.
> voltage to the stationary coil it seems tome that a 1:1 ratio between
> the coils would be easiest to do. Does this mean that I can also get
> away with just about any number of turns provided the wire can handle
> the minute current?
Too few turns will make the inductance too low for the 60 Hz
voltage, even with the steel cups, and will draw too much current from
the supply. At a guess, I would go for perhaps 100-200 turns on each
coil.
> The valve only needs .2 amps to operate so the
> wire can be pretty fine.
Probably 24 to 30 ga magnet wire. Measure it and calculate how
much area would be taken up by 200 turns to decide how deep to make the
cups. You can use mild steel pipe and bore it out truly round (since
most pipes have an internal weld bead) and then turn a mild steel plate
to press into the pipe. Or -- machine the whole thing out of a mild
steel. If you want it to look nice, and have some, 12L14 machines
nicely. Pipe is usually ugly to machine. :-)
> The valve operates on DC but a rectifier can
> be stuffed into the tube along with everything else. Will the tube
> coil need a snubber diode too? Any advice?
A snubber diode will short half of the AC voltage. Bad news
here. Maybe put one on the DC coil of a relay from whatever is
generating the pulses, and use that to switch the AC into the coil.
On the output coil (between it and the solenoid valve) you'll
want a small bridge rectifier. If you use a plain single diode, you
will only get power for half of each cycle (1/120 second on, 1/120th
second off) which will likely buzz, and you may need to boost the
voltage a bit (maybe 20-50% to get sufficient current into the solenoid
valve.
> Thanks,
> Eric
You have my thoughts above -- including putting the solenoid
valve outside the union so it does not need to rotate. :-)