WOW ! This is great. I'll have to check out these sites. I'm having some concerns with a pressure tank and a solenoid controlled value. It seems I need an analog control value so I don't apply 100psi to the down stream cylinder. Pulsing solenoid would somewhat achieve an analog control .
I have a really quiet workshop compressor using a household refrigerator type compressor, and a steel tank buffer. Chopping up a (still cooling) fridge, any old refrigerator compressor may still work well, they work for decades - but please note these compressors may need a little oil lubrication in the air stream if not running in a closed circuit. I don´t know if the pump flow is sufficient for direct use, but a buffer tank may solve that. re safety, you know what to do to save yout neck...
The auto compressors are way too loud to use indoors. we used one in the First Robotics competition that were fairly quiet. you could go to the first robotics site and see all of the resources they have on valving, controls and the gardner-denver mini compressors they sell. a first team in your area would probably help set it up, we would do practice projects off season...
a reasonably inexpensive solution which I have used a number of times consists of an old refrigerator or air conditioner compressor, pressure tank, a regulator and pressure switch (the compressor is capable of up to 250psi so don't let it free-run into the tank). The whole works can be had for about $50 at surplus dealers. The only thing to add is the 3 way solenoid valve which could be made up from 2 humidifier water valves. They're good up to 150PSI and run from 24VAC. The compressor will be quiet, just the pressure switch will swish when it shuts off and relieves the pump.
And yet another email from a reader who says:
Here is a web site that has new and used pneumatic items at reasonable prices.
Examples: a new 24 VDC 3 way solenoid valve for $4.99, a new 24 VDC valve with outlet vented when unenergized for $6.95.
Surplus Center Home Page
I just received another email that read as follows:
Regarding the gentleman who wishes to automate his traction machine (aka ‘rack’), here is one possible way to do this:
Use an Air pump such as the McMaster 4251K31 (http://www.mcmaster.com/#pneumatic-compressors/=hdhz3z). If the pressurization rate is too slow, add an ullage tank and a solenoid valve, cycle the solenoid valve briefly to pressurize downstream. He should add an orifice to regulate flow for slower and more accurate pressurization if using a higher pressure ullage tank and solenoid valve. And BY ALL MEANS ENSURE HE USES A RELIEF VALVE! Without proper physical safety measures in place, overpressurization may equate to injury.
I just received an email from a reader saying "I wondered if you may have considered using an automotive emergency compressor, which is a small 12 Vdc device for pumping up your tyres when you'd rather not have to :-)
You should be able to pick one of these up a your local automotive spares warehouse or outlet for way less than $50."
Not a bad idea...
I'd say this was a rather odd channel to solve "garage" problems like that. I bet there are giga's(*) of nntp groups (remember nntp?) with lots of people owning up to several spanners just waiting for a challenge like this.
(*) computer engineer equivalent of the cliché "ton's"
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