by Tom Gaylord
Writing as B.B. Pelletier
This report covers:
- AirForce Extra Air Tank
- Time test
- Two tests
- Test one
- Filling the tank
- Dumped the air
- Fill from a car battery
- Thank you — battery makers
- Second fill
Today I will test the Air Venturi Nomad II air compressor for you. In Part 1 I filled a BSA R10 Black Wrap rifle from empty in about 8 minutes. That gun takes a 232 bar fill, which is 3,365 psi. Today I will do something different.
AirForce Extra Air Tank
I chose an AirForce Extra Air Tank as my test tank for today’s work. The current tanks on AirForce airguns do not have to be taken off the guns to be filled, but the older-style tanks did. I’m doing this for the convenience of not needing to find a place to rest a whole airgun.
I used the tank from my 2001 AirForce TalonSS. That tank had been holding 3,000 psi for at least the past 5 years and was still completely full, so I had to attach an old-style refill adaptor to exhaust all the air. To do that I put three pennies into the adaptor before attaching the tank. The pennies push the valve cap down as the tank and adaptor are screwed together, to release the air in the same way the gun’s striker does it, only the pennies hold the valve open as long as you desire. In this case it was until the tank was empty.
The AirForce tank has an internal volume of 490cc. It is filled to 3,000 psi. Emptying a full tank this way takes about 4-5 minutes. The tank becomes very cold as it empties. After you think it is empty and you have removed the refill adaptor, you have to press in on the valve several more times to get all the air out. If you can’t depress the “top hat” then the reservoir is not empty, because the valve return spring has less than about 20 lbs. of force. It should push in easily.
Today I am filling this 490 cc tank from empty to 3000 psi. Pyramyd Air says to expect the compressor to fill the tank in about 17 minutes this way. But each compressor will be a little different, plus the shutoff settings I set may differ slightly from those set by Pyramyd Air. This isn’t a light switch with an on-off reaction. This compressor is like a garden hose, and you have to decide when enough is enough.
That being said, I am about to conduct two tests and I will use the same tank for both of them. So that part won’t change. The place I set the compressor to shut off (it shuts off automatically when it gets to the place that has been set) will also stay the same.
What will change is how I power the compressor. In the first test the compressor will be plugged into a 110 volt AC wall socket. In test 2 the compressor will be connected to my truck’s battery. I will time both fills so we can make a comparison.
In the first test I used the compressor in my garage, where the temperature was 18 degrees, Celsius, according to my Air Venturi HPA air compressor that has a thermometer built in and is always operational (the unit has been unplugged for about a month). That temperature converts to 64.4 degrees, Fahrenheit.
I connected the tank, closed the compressor’s hose bleed valve and checked its water bleed valve underneath the unit, and then switched the compressor on. I would like to tell you how loud this compressor is, but decibels mean very little to most people, plus I don’t have a calibrated sound meter. So, what common thing is there to compare it with? Washing machines, dishwashers and microwave ovens used to be good for noise comparisons, but in the past several years they have all become extremely silent. The closest thing I can think of is one of the electric paint can shakers you see at hardware stores. The Nomad II makes a repetitive sound like them, but it is much slower and quieter.
Filling the tank
It took 4 minutes 10 seconds for the tank’s pressure to build to 1,000 psi. It took 9 minutes 35 seconds for the pressure to build to 2,000 psi and it took 14 minutes 34 seconds for the compressor to shut off at 3,000 psi. When the compressor stopped, the cooling air that was still blowing out of the metal cabinet was not warm.
Dumped the air
The air tank was full again, so I dumped it in the same way as at the beginning. Once again it took 4-5 minutes to completely empty.
Fill from a car battery
The next test was to fill the same tank to the same pressure using a car battery to power the compressor. For this I had to break out the battery cables that came with the compressor. I showed you all the accessories that came with the Nomad II in Part 1, but let’s take a better look at the battery cables now.
Here are the battery cables that came with the compressor. There are two clamps — one red the other black. These cables end in an electrical fitting that plugs into the base of the compressor on the same side as the AC power cord. The electrical plug only fits one way, to keep the current flowing in the right direction.
Thank you — battery makers
Okay, guys, here is a little rant from a dinosaur. When I was young and starting to drive we had to check the water in our car battery every week. Right now some of you young pups are saying, “Water? Since when does water go into a car battery?” Yeah, yeah, yeah…
Okay, batteries don’t get filled with water anymore. I know that. I get it. I haven’t actually LOOKED at my truck’s battery in — ever!
But here is the point. Back when the internet ran on kerosene and car batteries actually needed water, the batteries were also marked clearly as to which terminal was positive. We needed that because we were always connecting something to them — jumper cables, a trickle charger… Guess what? They aren’t marked on the top anymore! At least the one in my truck isn’t. And the terminals are the same size, so don’t lecture me on how car batteries are supposed to be made with different-sized terminals and you can tell from that.
The thing is — you have to connect the color-coded compressor clamps to the correct terminals or — oh, oh! Now, some of you are about to tell me that my car battery is supposed to be color-coded as to which is the positive terminal. Well, guess what? It is. It’s the RED one!!!!!!!!! Now, see if you can remember what kind of color-blindness I have. Oh, that’s right. BB is red-green colorblind! And, guess what shade of red the engineer with perfect color vision who designed the rubber cover for the positive battery terminal in my truck chose? Heck, it doesn’t matter. One red is as good as another, right?
So I’m standing there, looking at the BLACK rubber cover on my truck’s battery terminal, wondering whether it is really black or actually dark red. Why couldn’t the battery maker have just put a plus sign somewhere on that battery, so I would have known which terminal it was? “Oh, BB, they did. They put it on the side of the battery, not on the top.” Well, great. Too bad I didn’t buy the truck with the mirrors on the inside of the engine compartment, so I could see the back of my battery!
Fortunately, I reasoned that if “they” (“they” are everyone who is not “us”) were going to mark a battery terminal, it would be the positive one, so what I was seeing as a black rubber terminal cover was/is probably red. With that logic as my guide I connected both clamps to the battery terminals, then the other end of the cable was plugged into the compressor, powering it on. It was already connected to the air tank and all the exhaust valves were closed, so when I pushed the buttons to start it working, everything was fine.
The temperature outside was 64 degrees, Fahrenheit. The pressure in the tank reached 1000 psi in 4 minutes and 10 seconds. It reached 2000 psi in 9 minutes and 24 seconds and the compressor shut off at 14 minutes and 14 seconds. So this fill went slightly faster than the first one on house current. In other words, the Nomad II works as advertised when powered by a car battery. When the compressor stopped, the cooling air that was still blowing out was slightly warm.
I forgot to bring my notepad out with the compressor, and I didn’t want to leave the compressor running unattended, so I wrote the times on the back of my hand. Ah — the good old days!
Okay, guys, I have now used the Nomad II three times. The total run time on this unit is on the order of 38 minutes. There is no way I will be able to give you any data about the longevity, but are there other things I need to test? And, please don’t tell me you want me to test it on a Triumph Spitfire that’s parked on a 60 percent slope, or in a condemned warehouse whose electrical power I first must restore.
Aww — BB. You are spoiling the fun!