I need lots and lots of compressed air for sandblasting, but I'm on a tight budget and only have residential power. Let me show you how to create a rig with four compressors in parallel!
Transcript:
OK, Hi Kids! Welcome back to Hannah’s Bug!
To remove the paint and rust from my bug, I’m going to use a lot of sand blasting. Now, sandblasting requires a lot of air volume, not so much air pressure. Air pressure is measured in PSI while air volume is measured in SCFM, or Sustained Cubic Feet per Minute. You might think that I can buy, just, an air compressor with a really large tank, however, that will not work because the air tank will only supply me enough air for about 25 to 30 seconds of sandblasting and then the air compressor will need to refill the air and it’ll never be able to catch up.
For me to feel confident that I’m getting enough compressed air, I need to have 25 SCFM at 80 PSI. There aren’t many air compressors on the market today that can give me that on standard household 240 voltage. There are many on the market that can give me that on three phase power, however, on the street that I live on here in Teddyland, I can’t get three phase power off the poles.
One affordable solution would be to rent a diesel screw-type compressor. Those would really only cost my producer and camera-dog under 200 dollars a week. However, I don’t want to do all my sandblasting in one week, and to rent this over the entire course of the project would become extremely expensive, and I do not want to do that. So let me ask you a question. What would Chris Hemsworth do?
Chris Hemsworth would use multiple inexpensive compressors in parallel. Bernoulli got me these four compressors at about $140.00 each. Good boy Bernoulli! [Off-screen bark]
To run them in parallel, the air connection is actually very simple. You can see how I did them here, with more tube than 25 me’s. Yup, more. The final one. And now for the real problem: the electricity!
First, obviously, you need to make it so that each compressor is on an individual circuit because each household circuit only supplies 15 amps, while each compressor takes around nine. In simpler words, no 2 compressors in socket or else house go boom-boom!
So you’ll need to run a lot of extension cords. You need to plan this beforehand that way you get as short a run of extension cord as possible, because each foot of extension cord adds resistance to the circuit.
There are many problems to face ahead. The first problem is that reciprocating compressors have what’s called a duty cycle, which means that they’ll turn on so that they can fill their tank then take a break until it’s time to fill their tank again. Since these individual compressors are not in coordination, one of them may decide to be the hero and stay on all the time so that it burns itself out.
So I have to figure out a way to turn them all on in unison, but that will create another problem. It will create a power sag, which means there won’t even be enough current to turn them on, and they would all stall.
Each compressor has a pneumatic switch, which means the compressor will turn on when the tank is low, then turn off when the tank is full. You might just think that I can adjust these points so that the compressors are in coordination, but this won’t work, because the on and off points will change depending on the load. So I’m going to need to use electrical relays.
If these are my compressors, this will be my control, and these four will be my slaves. What would happen is, I would turn this one on, then there would be a 2 second delay before this one turns on, then another 2 seconds before this one, then another 2 seconds before this one, then another 2 seconds before the fourth slave. If I could see into the future, I would...
