What limits the speed of an air compressor?

matthewsx said:
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To answer the actual question about what limits things it's physics. It might be possible to modify an existing compressor pump as you've suggested but the fact of asking about it probably means the engineering required isn't available in-house.

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Thank you John. You said it so well. I hope to remember that phrasing.
I learned something really useful today.
 
I see you have clearly made u your mind to go ahead with this mod, Be my guest, but don't say you weren't warned. With that said. Good luck.
 
extropic said:
I quit reading after reply #6.
I hope the OP is the result of acute cabin fever due to the stress of the current shelter-in-place restrictions.

In reply to your initial question. First of all, you have not specified what particular compressor pump you have in mind or the environmental factors where it would operate. All "5 HP" compressor pumps are NOT created equal, therefore your question is unanswerable.
A compressor pump is a SYSTEM. All components are intended to operate within their specified limits, if it's well engineered, designed and manufactured. Exceeding a design limit by a factor of FOUR would probably induce high risk of premature pump failure. The exact mode of failure could be studied (by you?) but I decline to venture a WAG.

I can not agree with your #1 listed result: "a much better utilization of the motor".
I don't know exactly what you mean by the statement. If you want to consume more watts (at low pressure) so the motor always runs under 100% capacity (a foolish goal IMHO) there may be a more durable way. It would be relatively large, mechanically and electrically complex, as well as expensive (compared to a conventional compressor package). You might be able to create a system consisting of multiple compressor pumps which are individually clutched in and out depending on available HP (current draw). Knock yourself out.
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Your skipping ahead is understandable. This started in a rabbit hole and went even deeper. But I think you would have benefited from reading reply #27. If you go back and read that post I think you might see that I'm less stupid than I might have sounded. I was using hyperbolic numbers to illustrate the concept. And you might also see my point about better utilization of the motor.

I've always been this way. The cabin fever is admittedly bringing it to the surface though.
 
extropic said:
Thank you John. You said it so well. I hope to remember that phrasing.
I learned something really useful today.
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Not to diminish the abilities of the OP, it's just I've spent a lot of time modifying small engines and know how much effort goes into coming up with the right "recipe" for a reliable mod. If you had a half dozen of those HF pumps you could probably figure it out but you would break most of them. It sounds like he's on his way though :)

John
 
Mini Cooper S said:
Interesting question. Air is free at least until you compress it so I would have to ask "Why don't industrial piston type compressors do this?" At least I've never experienced any that do, but maybe some do. Of course, screw compressors may be a different story.
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I've touched on that a couple times but I don't think I've really explained myself fully.

I don't think there's a market for what I'm building, and I didn't set out on this voyage for the purpose of bringing something to market. The result of this will be a consumer grade compressor built with some industrial parts that make it expensive. Probably so expensive that it would have to be marketed to industrial customers who would rather spend their money on a screw compressor which will run 100s of thousands of hours. This won't do that, and I don't need it to. I need it to be ready to go quickly when I want to use it, and cheap. It's cheap for me to build because I already have the industrial stuff.

An analogy: if it's possible for a pickup truck to have 800hp, 50" tires, and 2ft of ground clearance, then why isn't Ford or anyone else making trucks like that? Since no commercial enterprises market such a truck, does that imply it can't be built? Heck no! Guys do it every day.

I just have strange priorities.
 
Well, I think you're on the right track for a rabbithole project. It's clear that you intend to modify the shape of the tank pressure-time graph by adding power to the system using a VFD while the system is under low-pressure load, then returning to stockish power levels at the top. You are exploiting an efficiency by changing how the motor is putting out it's power that isn't done in an analog scenario. You've got a complete idea, and kudos for breaking out the parts and trying it out. I won't judge if the juice isn't worth the squeeze, as long as you learn something.
 
strantor said:
I've touched on that a couple times but I don't think I've really explained myself fully.

I don't think there's a market for what I'm building, and I didn't set out on this voyage for the purpose of bringing something to market. The result of this will be a consumer grade compressor built with some industrial parts that make it expensive. Probably so expensive that it would have to be marketed to industrial customers who would rather spend their money on a screw compressor which will run 100s of thousands of hours. This won't do that, and I don't need it to. I need it to be ready to go quickly when I want to use it, and cheap. It's cheap for me to build because I already have the industrial stuff.

An analogy: if it's possible for a pickup truck to have 800hp, 50" tires, and 2ft of ground clearance, then why isn't Ford or anyone else making trucks like that? Since no commercial enterprises market such a truck, does that imply it can't be built? Heck no! Guys do it every day.

I just have strange priorities.
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I wasn't trying to say that it couldn't or shouldn't be done, I was thinking that there must be a down side that would make it impractical. With that said, new innovations can come from projects like this, Go for it!
Richard
 
I think we are all guilty of over engineering projects. This one sounds like the better uses of a a 3 phase variable speed motor in a home shop.
 
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