Maximum Force of Compressed Air

[bob012345]

What's the maximum force that air from a typical garage air compressor tank, the kind that's used to inflate tires assuming the pressure is around 150 psi.? Can the force be changed by nozzle design? Thanks.

 

[russ_watters]

What's the maximum force that air from a typical garage air compressor tank, the kind that's used to inflate tires assuming the pressure is around 150 psi.? Can the force be changed by nozzle design? Thanks.

Nozzle? What nozzle? Could you explain in more detail what you are asking?

 

[jackwhirl]

@bob012345, it sounds like you're talking about the force produced by a jet of air. Is that right? Are you interested in peak, or sustained force?

 

[bob012345]

@bob012345, it sounds like you're talking about the force produced by a jet of air. Is that right? Are you interested in peak, or sustained force?

Sustained force releasing air at standard psi from the kinds of tanks that fill car tires.

 

[bob012345]

Nozzle? What nozzle? Could you explain in more detail what you are asking?

The air nozzle you would normally insert into your tire valve. How much force can one get from that?

 

[russ_watters]

Sustained force releasing air at standard psi from the kinds of tanks that fill car tires.

The air nozzle you would normally insert into your tire valve. How much force can one get from that?

Again, do you mean the force from the jet of air from an open nozzle? The nozzle you attach to your tire valve only allows air to flow when the valve is attached to the tire valve...

Anyway, if that's what you mean though, it is probably something you can estimate by feel; a few pounds of force. A first swag would be to multiply the pressure (maybe 100 psi) by the area (maybe a tenth or 20th of a square inch), but the flow would probably be choked and supersonic, so it would end up being somewhat less.

 

[jackwhirl]

The air nozzle you would normally insert into your tire valve. How much force can one get from that?

There are two answers to this, depending on what you mean:

From context it sounds like you're talking about a jet of air, in which case you should read about rocket engine nozzles, because the shape of the nozzle most definitely does impact the force output.

The other is the idea that you could use this air to pressurize a bladder of some sort, to lift a large load. (Think something like an air mattress.) In this situation, the force you could apply would be equal to the surface area times the pressure. Thus, 60 inches * 80 inches * 150 pounds per square inch gives you 720,000 pounds.

There's a really big difference between these scenarios. That's why were asking you what you're trying to accomplish. We don't fully understand your question.

 

[bob012345]

There are two answers to this, depending on what you mean:

From context it sounds like you're talking about a jet of air, in which case you should read about rocket engine nozzles, because the shape of the nozzle most definitely does impact the force output.

The other is the idea that you could use this air to pressurize a bladder of some sort, to lift a large load. (Think something like an air mattress.) In this situation, the force you could apply would be equal to the surface area times the pressure. Thus, 60 inches * 80 inches * 150 pounds per square inch gives you 720,000 pounds.

There's a really big difference between these scenarios. That's why were asking you what you're trying to accomplish. We don't fully understand your question.

Thanks. It's more the first case, letting the compressed air expand through a nozzle or device like a rocket. Remember when we were kids and we would take a garden hose with water flowing and by constructing the flow it had a lot more force and the hose would lift itself up. Like a water bottle rocket. I want to play with the way compressed air is released to maximize the force.

 

[bob012345]

Again, do you mean the force from the jet of air from an open nozzle? The nozzle you attach to your tire valve only allows air to flow when the valve is attached to the tire valve...

Anyway, if that's what you mean though, it is probably something you can estimate by feel; a few pounds of force. A first swag would be to multiply the pressure (maybe 100 psi) by the area (maybe a tenth or 20th of a square inch), but the flow would probably be choked and supersonic, so it would end up being somewhat less.

Thanks. By your estimate, I'd get 5-10 pounds.

 

[russ_watters]

Thanks. By your estimate, I'd get 5-10 pounds.

Right, that is what I was intending.

 

[bob012345]

Now that we are on the same wavelength, is there any way by clever design I can increase that force for the same air flow? Thanks.

 

[jackwhirl]

Now that we are on the same wavelength, is there any way by clever design I can increase that force for the same air flow? Thanks.

A nozzle that expands the flow to ambient pressure will be most efficient. Read that rocket nozzle link I placed above.

 

[russ_watters]

Now that we are on the same wavelength, is there any way by clever design I can increase that force for the same air flow? Thanks.

Right, what @jackwhirl said: rockets generate force by giving the reaction mass momentum, so the faster the exit velocity the greater the force. I bet you could get several times the force with a well designed nozzle vs a poor one. But I also expect my estimate is already generous.

 

[bob012345]

Right, what @jackwhirl said: rockets generate force by giving the reaction mass momentum, so the faster the exit velocity the greater the force. I bet you could get several times the force with a well designed nozzle vs a poor one. But I also expect my estimate is already generous.

Okay, thanks.

 

[bob012345]

A nozzle that expands the flow to ambient pressure will be most efficient. Read that rocket nozzle link I placed above.

Thanks, I will.

 

[Tom.G]

What's the maximum force that air from a typical garage air compressor tank, the kind that's used to inflate tires assuming the pressure is around 150 psi.? Can the force be changed by nozzle design?

Just to get empirical here, grab a kitchen platform scale and aim the air stream at it.
p.s. will vary with distance

 

[bob012345]

Just to get empirical here, grab a kitchen platform scale and aim the air stream at it.
p.s. will vary with distance

Thanks. Not a bad idea. That's basically what Sir Christopher Cockerell did when he invented the modern hovercraft. Big things can come from little experiments.

https://en.m.wikipedia.org/wiki/Christopher_Cockerell

 

[some bloke]

Depending on the length of time you need the force for, you may wish to explore alternative avenues.

Are you referring to a compressor tank, with an air reservoir, or a compact tyre inflator pump?

If you are using the latter, storing the air in a reservoir will allow you to produce a greater force for a short period of time. for example, a pump might only put out a small amount of force, but once my potato gun I had as a kid was pumped up to 180psi, it could fire a chunk of potato half a kilometre (approx.).

If you are looking to achieve some sort of thrust, something like a leaf blower will likely be able to deliver a higher volume of air per second than a compressor. if you were to fit a nozzle to a leaf blower, you'll probably get more thrust than from a compressor, and it will also be lighter due to the lack of a reservoir.

Are you trying to move objects with the compressed air, or move the compressor itself? (IE are you making the launcher or the rocket?)

 

[bob012345]

Depending on the length of time you need the force for, you may wish to explore alternative avenues.

Are you referring to a compressor tank, with an air reservoir, or a compact tyre inflator pump?

If you are using the latter, storing the air in a reservoir will allow you to produce a greater force for a short period of time. for example, a pump might only put out a small amount of force, but once my potato gun I had as a kid was pumped up to 180psi, it could fire a chunk of potato half a kilometre (approx.).

If you are looking to achieve some sort of thrust, something like a leaf blower will likely be able to deliver a higher volume of air per second than a compressor. if you were to fit a nozzle to a leaf blower, you'll probably get more thrust than from a compressor, and it will also be lighter due to the lack of a reservoir.

Are you trying to move objects with the compressed air, or move the compressor itself? (IE are you making the launcher or the rocket?)

Ultimately, I want to use a thin layer of fast moving air to contain a volume of air at higher pressure. That's what early hovercraft did but I want to apply it to a small personal device rather than a large scale multi-ton machine. The compressed air is only for the boundary layer. I hope to lift something like 50 pounds per square foot but only a few inches off the ground.

 

[russ_watters]

Ultimately, I want to use a thin layer of fast moving air to contain a volume of air at higher pressure. That's what early hovercraft did but I want to apply it to a small personal device rather than a large scale multi-ton machine. The compressed air is only for the boundary layer. I hope to lift something like 50 pounds per square foot but only a few inches off the ground.

This appears to me to be completely different from your original question. Is that what you intended or were you thinking one informs to the other or...?

 

[bob012345]

This appears to me to be completely different from your original question. Is that what you intended or were you thinking one informs to the other or...?

One informs the other but I was just answering some bloke. We can stick to the original question on this thread which was basically answered as 5-10 pounds unless someone can suggest how to increase that range. Thanks.