On Fri, 14 Apr 2017 17:29:21 -0400, Neon John wrote:

On Wed, 12 Apr 2017 09:11:45 -0700, wrote:

On 12 Apr 2017 04:01:56 GMT, "DoN. Nichols"
wrote:

I thought about that but dismissed it because I really don't know how
I would go about doing it.

You should dismiss it because it is complication you don't need. My
contact in Ford Engineering tells me that the burst test speed for
"standard" alternators (the traditional ones before they started
designing a custom alternator for every engine) is 15,000 RPM and that
they will run up to around 10,000 RPM with the engine wound out.

So you have no problem getting the power to the solenoid. The problem
will be the solenoid itself.

The only way the solenoid could work is for the plunger to be exactly
axially aligned with the shaft. If it is off-center by even a tiny
amount, the whole assembly will be out of balance. Worse, the
centrifugal force will act to bind the plunger against the wall of the
solenoid tube.

Even if you work that out the fluid (air in this case) will be
affected by the same centrifugal force. The force will either work
against or with the valve. If it work against the valve, the valve
might not open. If it works with the valve, it might not shut.

I don't fully know what you're trying to achieve but it seems to me
that a stationary solenoid, a rotary coupling such as one of these.

https://www.mcmaster.com/#rotating-couplings/=17755fj

to get the air inside the tube. If you need to flow to be abruptly
started and stopped, my approach would be capillary tubing from the
valve to the outlet, the bore of which is chosen to provide the
desired air volume when full shop air is applied from the solenoid.
Here is an example of several bore sizes.

https://www.johnstonesupply.com/sear...pillary+tubing

If your solenoid is DC it will either require a snubber or use a
switching device capable of withstanding the flyback. A pure diode
will greatly slow the closing time because the current will continue
to flow until it is dissipated in the solenoid's resistance.

If you need it to close rapidly, the usual technique is to connect a
resistor in series with the solenoid and adjust its value until the
flyback voltage is as high as tolerable. For example if your
actuating device uses a 200 volt max rating transistor, I'll allow the
voltage to rise to no more than 100 volts.

You'll need an oscilloscope to observe this. I anticipate your not
having one but you probably have a friend that does.

If you need the valve to close very rapidly, I can describe a very
simple peak/hold circuit that supplies full voltage until the solenoid
is actuated and then drops the current to the much lower holding
value. Much less current to dissipate in the snubber.

John
SNIP
Greetings John,
I alread thought about the solenoid sticking. It will be concentric
with the lathe spindle centerline. I'm not sure but I think the valves
I have are piloted because they use so little current to change the
valve position. And it changes fast. Anyway, I already use these
valves with this closer as well as other air clamping devices. As to
the two passage rotary union you linked to if you read the specs you
will see they cannot be spun anywhere near as fast as I need to spin
it. That's why I'm going through all this falderal (izzat how it's
spelled?). As I have posted I would love a two passage rotary union
that can handle 4000 RPM and 120 PSI air. But they are about 10 times
more than the single passage types with the same air and speed rating.
Like $3000.00. I have even checked eBay. I did find a good deal on a
coolant rotary union and I bought it. But it is for coolant. And is a
single passage union. And it's going into the mill for through spindle
coolant.
Eric