Altaros Compressor

Ok, took a little longer for this one, I apologize, but the weather was too good here, I was out sending some lead downrange (down-backyard). Sorry, but needed that. It’s getting dark outside and before going to see Michael Jackson, I promised to continue the series.

OK today let’s see why we need both pressure and airflow for the Altaros unit.

While we now understand from the last writeup, what is airflow and why we need it for the Altaros unit, there still is the question why we need pressure, and maybe what it really is. From the last writeup, we also understood that an airflow which is blocked and can not escape somewhere builds up pressure.
This continues until the air can not flow in with enough power, so that the flow stops, no more air can be stacked, the pressure stops building up.
In the case of our workshop compressors, though, if we do not connect a consumer, it is pumping up it’s tank until it it stopped by an electromechanical switch, not because of the fact that it can’t stack more. And that’s better like that as otherwise it would continue to stack and it’s tank would burst.

So what is pressurized air? I said before, it is „stacked“ air. And that’s the part where I will get into trouble with the units you use over the pond. I’ll do the exercise in metric units and hope my conversions will be the right ones.
Normally, at sea level and 20°C, we have an ambient pressure of 1013 mbar or 1,013 bar (14.6885 psi). Well, let’s round that to 1 bar (14.5 psi). As said, in order to obtain air under pressure, we need to stack it in a container where it can not escape. Let’s say, we have a container of 50 liters (1.77 cu.ft). If we let 50 liters of air flow in (which we actually don’t have to do, as it does so by itself, as the pressure on the outside and on the inside always strive to be equal), the pressure is at 1 bar (14.5 psi). If we stack another 50 liters (1.77 cu.ft) in there, we have the equal volume of 100 liters (3.53 cu.ft) of air in the tank. As the tank of 50 liters (1.77 cu.ft) doesn’t get any bigger when we stack more air in, the pressure rises. In our case to 2 bar (29 psi).
To summarize: we now have 100 liters (1.77 cu.ft) of air under 2 bar (29 psi) pressure in a container of 50 liter (1.77 cu.ft) physical volume.
Now let’s stack another 50 liters (1.77 cu.ft) into our tank. As it still doesn’t get bigger, the pressure rises instead. It rises to 3 bar (43.5 psi). We now have 150 liters (5.30 cu.ft) of „stacked“ air in our tank. And so on. At 8 bars (116 psi), we (or rather our compressor) has „stacked“ 400 liters (14.13 cu.ft) of air in its tank of the physical size of only 50 liters (1.77 cu.ft).

Now let’s imagine a moment, the tank would burst at 2 bars (29 psi). 100 liters of air that exit during only a fraction of a second. It’s easier to imagine a family car tyre, which contains a bit less volume than that, let’s say 35 liters (1.24 cu.ft) but at the same pressure. From what we learned, this would be the equivalent of 70 liters (2.48 cu.ft). If it burst, this already makes a big Booom … impressive thing, we all would jump up (down, left, right) to find cover, I guess.
Let’s imagine the same thing at 8 bars (116 psi). KA-BOOOOOOOOOOOOOM. We wouldn’t want to stand (sit, lie, dance or anything else) next to this event. And jump even further to get cover.

I think, we all agree to make the analogy between pressure and power. In our case, it is stored, compressed air, we put energy in to „stack“/stock this air, the energy remains there, as long as there is pressure. More pressure, more energy, more power to release.

Hoot, I guess from your scuba diving career, you already know all of that, so apologies, if I annoyed you…

Back to our Altaros unit. The manufacturer writes that the minimum required pressure is 5 bar (72,5 psi) to make the unit work. This is the „power“ required to make the driving piston (and the attached mid-pressure piston and high-pressure piston) move and in addition compress the air in the first and in the second stage. The air in the two stages needs a minimum power to be compressed further, as it opposes resistance towards it’s compression.

But that’s not all there is to it. As we now know, the input air under pressure is a certain compressed volume of air. At 8 (116 psi) bar, it is 8 times more than it would be at the ambient pressure of 1 bar (14.5 psi).
So, the airflow defines how FAST the air gets into the Altaros unit and how fast the unit will work,, the pressure defines how MUCH air gets in there during this same time and that there is enough power for the unit to do it’s job and compress further.

Let’s say (and I don’t know the exact values, so this is only an example) the mid-pressure cylinder has a volume (at 1 bar – 14,5 psi) of 10 ccm or 0.01 liters (0.00035 cu.ft). At 8 bar, there is 8 times this volume of air in there, i.e. 80 ccm or 0.08 liters (0.0028 cu.ft), so more air equals faster filling.

I think, we now can understand, why both factors, pressure and airflow, determine the time the Altaros unit requires to fill our air guns or cylinders, as it depends on both. We increase one of the two factors or both, it goes faster, we decrease one or both factors, it’s slower. The unit entirely depends on how much it finds at it’s inlet.

In order to ensure that there is enough pressure available to the Altaros unit, you would want to connect it to the unregulated output of your workshop compressor (if available) or to screw in the limiter screw of your workshop compressor to maximize output (screwing in maximizes output pressure, as opposed to the Altaros’ unit’s „13. Air flow setting screw“, where screwing in limits – in this case – air flow, though).

This makes your workshop compressor’s output behave like a unregulated output. Unregulated means that it varies with the workshop compressor’s pressure, usually between 6 and 8 bar (87 and 116 psi).

I will not go through further compression in first and second stages of the Altaros unit, that would take too long to explain, I think we get the principle now.

On a last word for today and to explain a bit the fill times, let’s say, we fill a scuba tank of 6 liters from ambient pressure (1 bar – 14.5 psi) to 200 bar (2900 psi). Once full, it will contain 1200 liters (42.38 cu.in) of compressed air. If we filled it to 310 bar (4496 psi), it would contain 1860 liters (65.69 cu.in) of compressed air.

I think, we all understand now, why it takes the Altaros unit some time to stack this amount of air, as it is working on a slower cadence than a full-blown Bauer, Coltri or other scuba compressor. On the other hand, and that’s what Hoot stressed earlier, the positive side effect is that it is not heating up as much during it’s working cycle which brings other advantages.

That’s it for today, thanks for reading.

:hoot:

Pops….

Best wishes on the forthcoming alterations to your machinery!

I’ve had a prostate removed, a knee replacement, shoulder, hands and elbow, and stomach operated on. It’s good that you get to sleep while the mechanics have you up on the lift. Generally speaking it turns out well, and we need to be thankful that wonders in surgery can keep us on the road.

When I was young, the doctors still used leeches and bloodletting. If that wasn’t bad enough…the damn drums were beating all through the surgical procedures…they assured me the noise would help mask the pain! What nonsense. I paid extra for the rolled up cloth to bite down on when they started cutting. Several years later, they discovered ether… My goodness, how times have changed!

Since they will likely use propofol to seduce you…you might get to see Michael Jackson!!!

Keep us informed on your status…

Hoot:

Dear Uncle,

that’s not the whole truth, I fear, you have a wide variety of choices here, with or without fur, different colors and so on.
For what they say though, that might be the case of Portuguese women, though I am not in a position to confirm this… For the German ladies on the other hand…

Dear Knife,
sorry to hear that you had to pass there, as well. Get well soon. As for the scalpel edges, that’s not cool, especially having seen some of your creations, it’s obvious that they messed with a specialist concerning the topic. On the other hand, a little drag can be a wonderful feeling 😛 . As for the cramps, yes, they are starting to show up, but don’t worry, I’ll get over them. They’re not the reason for surgery though.

Pressure side of the story is under construction already, had a lot of time today, not being at work but in hospital for the preliminaries :whistle:

Stay tuned (oh yes, I always wanted to say that…)

Kindly yours

I had Day Surgery yesterday, and Doctor did a fine Job of it!

I sure wish they had Scalpels as sharp as a KnifeMaker prepared edge. Not impressive at all. I could feel the scalpel edge drag. Grrrrr! 8-(

Knife

:hoot:

Dear Pop’s…

Before you go under the knife…seriously…is it true that French women don’t shave their armpits???

Regards,

Kindly ‘Ol Uncle Hoot:

I agree completely Uncle!

And yes my Winged Wonder, the onward and aggressive push to change our Country from a Democracy to Communism ( Being hidden under the acronym of Progressivism), has for the time at least, been halted dead in its tracks). And I could care less who puts the brakes on, as long as they are full on! Political Correctness be Damned!

A Very Anti-Progressive/Communist/Progressive;

KnifeMaker

Okay Gentlemen, another one, thanks for your comments. I agree, I keep it way too short every time. :rofl:

Let’s get into understanding airflow, pressure and why we need both for the Altaros booster.

A simple example, I have two workshop compressors. The first is smaller, rather silent, with a 0,75hp electric motor and 6 liter (0.211 cu.ft) pressure container (I’d say comparable to Hoot’s … compressor … from what I could see). The second is way bigger, way less silent, with a 2hp electric motor and 50 liter (1.77 cu.ft) pressure container.
Both deliver up to 8 bar (116 psi), both switch on when falling below 6 bar (87 psi) and off again when reaching 8 bar (116 psi).
Except for the noise level (which makes no difference for what we want to look at) and the container volume (which makes a bit of a difference, more later) they deliver the same pressures. What is the difference?
You guessed it – Airflow. This is the famous number describing how much air is delivered in liters/min or cfm for all the good people over the pond.
Here, from what I have found out while shopping for mine (and what I have found out after, guess why I have 2… :whistle: ) there is no real standard as how to advertise this airflow value.
Some manufacturers advertise air intake values. In my eyes, this value alone is useless, as we are interested in stable output and this depends on the compressor itself, it’s power, potential leakage, efficiency of the machine and so on.
Some others advertise air outlet values. This is already better, but in my eyes still useless, as this value depends still hugely on the compressor’s power and efficiency and the airflow varies with the pressure. At 1 bar (14.5 psi) it is way higher than at 8 bar (116 psi).
As an example, my bigger compressor is advertised as follows:
– intake air flow: 220 l/min (7.8 cfm)
– outlet air flow at 1 bar (14.5 psi): 118 l/min (4.2 cfm)
– outlet air flow at 5 bar (72.5 psi): 79 l/min (2.8 cfm)
– outlet air flow at 6 bar (87 psi): 71 l/min (2.5 cfm)
– outlet air flow at 7 bar (101.5 psi): 63 l/min (2.22 cfm)
– outlet air flow at 8 bar (116 psi): 58 l/min (2.05 cfm)

For the smaller one I only have the following data:
– intake air flow: 100 l/min (3.5 cfm)
– outlet air flow at 7 bar (102 psi): 61 l/min (2.15 cfm)

From the above, we clearly see that there is a relationship between airflow and pressure.

The manufacturer of the smaller one gives less details, nevertheless at 7 bars, on paper, they seem quite similar in airflow. Still, I don’t believe in this value, as when using it with the Altaros booster unit in a 60/40 cycle, I easily double the time to fill my TalonSS, compared to the bigger one, so it would be realistic to say that the real value turns around 30 l/min (1.06 cfm) or less, given that the values for the bigger compressor are realistic.

Airflow is therefore related to pressure and the power of the machine. Even more so, it also depends on the design: one cylinder, two cylinders, the more air can be displaced, the better, as our friend Knife has already stated.

On a side note, I still like the small one due to it’s silent operation and low maintenance (it’s oilless).

Let’s try to understand the difference between pressure and air flow. Pressure builds up, when air meets an obstacle, hindering it to flow freely. The more air hits the obstacle and the more air is flowing towards this obstacle, without being able to escape, the more it is „stacked“, the pressure builds up.
An analogy would be: being the first to arrive in front of a big department store’s door (still closed) on black Friday. As more and more people arrive (air flow), while the store’s door is still closed, the less space you have for yourself, you get more and more „compressed“ between them and the store’s (closed) door (pressure).

So our compressor, while the motor is running, stacks air in the compressor’s tank. As long as we’re not letting any air out, pressure builds up until the workshop compressor shuts off (in my case at 8 bar – 116 psi). Now when we connect it to a device which consumes air (in our case the Altaros booster unit) and open the valves, air can flow out. We can see the pressure in our workshop compressor’s tank diminish due to the fact that the workshop compressor is still shut off, and not „stacking“ new air to replace the one which is flowing out towards the Altaros unit. At around 6 bar (87 psi) in the case of my compressor, the motor switches back on and starts to pump air back in the tank, trying to „stack“ it up again and trying to reach the shut-off pressure of 8 bar (116psi). At the same time, our Altaros booster unit is still consuming outflowing air.
And here’s where the crucial part comes: if our Altaros booster is consuming more air than our workshop compressor is able to deliver, the pressure in the tank diminishes more and more, falling below the 5 bar minimum requirement for the Altaros unit to work properly.

Well, the good folks over at Altaros have foreseen the most unlikely case :rofl: where none of us probably does have the same workshop compressor, nor can buy exactly the same, and therefore built in a valve which „tells“ the Altaros unit to work faster or slower, and therefore consuming more or less air.
You’ve guessed it, I’m talking about the famous „13. Air flow setting screw“.

In analogy with the black Friday store, we’re talking about the doors. The personnel opens the door, so people can rush in.
If the door is open wide enough, then the store will fill up with people and the outside will empty, no more stacking, no more pressure.
If the door is not open wide enough, people on the outside continue stacking up even though some manage to enter but not relieving any „pressure“ on the outside, as more people still stack up in front than people can get in.
If the door is open in a balanced way, the stack of people on the outside remains the same, trying to push in (pressure) while a certain number of people get into the store (flow). This is the analogy to flow rate at a certain pressure. With the screw on the Altaros unit, we decide how far we open the door for the air to pass.

Turn it in (clockwise when seen from the front), the Altaros booster works slower, consuming less air than your workshop compressor delivers, allowing your workshop compressor to stack enough air again to reach 8 bar (116 psi) and switch off for as long as the pressure does not fall below 6 bar (87 psi). This is the famous ratio of run time/pause, ideally at 60/40 to avoid overheating of your workshop compressor.

How to find a setting for the „13. Air flow setting screw“?
1) fire up your workshop compressor and let it run until it switches off by itself. Do not yet connect the output hose.
2) plug in the Altaros booster power supply (both ends, each end in the plug where it belongs)
3) connect an (empty or to be topped-up) air gun or cylinder to the high pressure output hose, close the bleed screw(s) and open up the cylinder valve if required for filling. I am not 100% sure, but I think that you do not necessarily connect anything to the output of the booster unit for what we want to do
4) Now connect the worksop compressor output to the Altaros booster’s input
5) Let the Altaros unit do it’s thing until your workshop compressor fires up again
6) Watch the workshop compressor’s gauge. If the pressure still decreases, then turn in the Altaros unit’s „13. Air flow setting screw“ (clockwise, seen from the front side of the unit) until you note that the pressure in your workshop compressor slowly, but steadily increases.

Basically, the system is now set in a way that the workshop compressor will be able to turn off at a certain point in time.
7) In order to get to the 60/40 cycle, you need to use a stopwatch, taking the time of the running cycle and the time during which the workshop compressor doesn’t run, e.g. 3 minutes running, 2 minutes not running would be just right.

If the running time is more than 60%, e.g. 4 minutes running for 1 minute stop time, you would want to slow down the Altaros unit a bit more by turning the „13. Air flow setting screw“ in a tad more.
8) Adjust until you reach the desired ratio.

On the opposite, turning this „13. Air flow setting screw“ anti-clockwise or out, increases the Altaros unit’s working speed and therefore the air consumption, your workshop compressor will need to deliver more air (higher airflow).

Next will be why we still would want the highest possible pressure from our workshop compressor and airflow alone is not enough.

But did you? really?