Compressor load times

Supercharging is basically a pump that forces additional air into intake to overcome low atmospheric pressure or to supply additional air that would not be there due to other limitations...

We had a champion service station compressor from the 60 ' s and it was quiet and was 175 psi but would not keep up with much as it was old and somewhat worn and designed for above stated service station use.

Polish valves improved but still sucked.

Went to a surplus supply and found what looked like a vacuum cleaner pump which is a motor with a stack of turbines to increase pressure and it had a flange on both ends so we made some adaptors for adding hoses to plumb it to the intake and add a better filter to the intake side of the pump as well as a relay on the motor lines to control the 120 volt motor.

It sounded like a quiet Lear jet when running and compensated for filter losses and put a slight boost pressure on the intake so the piston did not suck in air but allowed it to fill up with a slight pressure instead of slight vacuum at bottom dead center.

It made a great improvement in air volume and not that much increase in motor load since it was 2 stage.

It was now 3 stage...

Been thinking about using the pump on the champion just as an experiment but too many other chores.

Most any discarded shop vac could be used to do same.

Just measure your motor amps to be sure it stays in the happy place.

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I have the parts. I built one a while back for my 2hp dust collector downstairs. I'll ponder it next time I'm rummaging through the electrical parts bin.


I had one of the cylinder heads off to clean the reeds cause that side has a bum filter. I should have measured the bore but I didn't think about it. Which was stupid... I should have...


It's not old. It's less than 20 years. The pump I traded for this was an old brunner two stage, but it needed rebuilding... I should have kept it and rebuilt it. It was wicked quiet. But I needed big air quickly as I had a job to do.


I would like to hear this story...

Moral of the story, yes, I realize I have some homework to do. I was looking for some specific info with this post but it seems to have gone in a different direction. I can appreciate that. I think I'm going to try to get this pump to 900-1000 rpm. From my experience with this setup, and the info I have, I think that will serve me well. Itll pump fast enough for my hobby shop, and be quiet enough that the wife won't complain when if it runs when I'm not home. She usually calls me a work when it runs once a week to tell me there's a terrible noise coming from the garage....
That speed sounds good but the pump may require more hp than your motor has to get there.

Pull that head and measure or swap pulleys and measure amps and pressure.

Also note if 2 stage they often run on at 150 and off at 175 to insure constant availability of air but most tools top out at 90 so reducing operating pressure to cut in at 110 and off at say 135 or lowest while cut in at 110 greatly reduces the hp need thus the need for smaller pulley on the motor.

Lower operating pressure allows for faster motor speed with same hp.

If using a mag starter then plum in 2 pressure switches with an a/b switch that is spring loaded to low pressure side do you can force it to pump 175 if needed to blast something and the motor will not like it but being spring loaded it will not stay in high pressure mode.

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Supercharging is basically a pump that forces additional air into intake to overcome low atmospheric pressure or to supply additional air that would not be there due to other limitations...

We had a champion service station compressor from the 60 ' s and it was quiet and was 175 psi but would not keep up with much as it was old and somewhat worn and designed for above stated service station use.

Polish valves improved but still sucked.

Went to a surplus supply and found what looked like a vacuum cleaner pump which is a motor with a stack of turbines to increase pressure and it had a flange on both ends so we made some adaptors for adding hoses to plumb it to the intake and add a better filter to the intake side of the pump as well as a relay on the motor lines to control the 120 volt motor.

It sounded like a quiet Lear jet when running and compensated for filter losses and put a slight boost pressure on the intake so the piston did not suck in air but allowed it to fill up with a slight pressure instead of slight vacuum at bottom dead center.

It made a great improvement in air volume and not that much increase in motor load since it was 2 stage.

It was now 3 stage...

Been thinking about using the pump on the champion just as an experiment but too many other chores.

Most any discarded shop vac could be used to do same.

Just measure your motor amps to be sure it stays in the happy place.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
That's a very interesting idea.
 
You add a pressure gage to the line between stages and you can see the pressure rise there indicating more volume into stage 2.

Only will show increase when tank pressure is above that point as it will pump straight to tank through stage 2 until that time.

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Presently I have a Gardner Denver inter cooled 2 stage 25 CFM compressor.with a 80 gallon receiver.
5 HP 220v motor @ 900 RPM
Fill time is roughly 4 minutes @ 125 PSI
 
I have an old Devilbliss 5Hp 60 gallon oil-less; takes about 10 minutes from empty. Probably needs a rebuild. And an old tank like your talking about; 2 HP, 60 gallon, 2 stage; takes a little more to charge from empty. Way quieter though and I think that I can get the time down with a pulley swap.(1750 rpm motor). That's my benchmark as you asked. Not sure about the recharge from 80-120 psi; usually using it at the same time as it's trying to keep up. On a side note; I've been told that the Oil-less are better for paint applications as the oil lubricated types can mist some oil unless filtered. I like to collect all types for versatility. (Welding/Millwright Contractor). Also have a twin cylinder 5 hp Briggs and Stratton wheel barrel type, a 5 hp Campell Hausfeld 13 gallon 110v wheeled unit and I'm toying with building a large mobile using a 3 cylinder Duetz Diesel that I just picked up. I figure that if you live long enough, you should have one of everything. Gonna leave my kids with a bunch of stuff that they don't know how to use, I think, unfortunately. Maybe Grampa's tool gene will skip a generation and some little kid won't have to start from scratch like I did.

Jon.
 
Sounds to me your motor isn't big enough or strong enough for what you expect from it. The old saying , go big or go home works . Dual stage will fill quicker , but screw compressors will maintain the pressure better. More thoughts to ponder
 
This for the folk with 60 gal compressors.
What's your average run time from dry to full? And from kick on to kick off. (List the psi's)
And for reference list your compressor HP and cfm's if you have them.

Reason.
I'm a bit of a Victor Frankenstein with compressors. I've built my way from a home made 8 gal up to my current 2 HP 60 gal.
Originally this was a Brunner 2 HP two stage. The head was shot so I traded it for a single stage 2 cylinder. The original 2 HP Robbin's & Myers from 1964, is a TANK of a motor. It's 1740 rpm. Amperage rates it a true 2HP. But it's tired. Short of rewinding it, its had it's day.
Since I swapped the head to the two cylinder I've been playing around with rpms. I use this unit for general shop air and lacquer spraying/pneumatic sanding. So I need high cfm output.
The head runs about 1200 rpm. That's quick... I needed it to be able to keep up to me. But I finished the big furniture refinishing job I needed this brute for, so I can slow things down.
Due to the pulley size to get those speeds, it put that big ol motor under some stress. It would cough and spit before it jumped into second stage then it was fine. But sometimes it would cough and spit for 30 seconds or so before the centrifugal switch had enough speed to kick over. I replaced the caps and over gauged the wire and breaker to give it some more amps but that had limited success. It's a nice old motor and I don't want to kill it.

So, currently, I obtained a Franklyn electric 2HP motor. Seriously smaller than the R&M as modern motors are. Rated for the proper amperage, so it's a true 2HP. But it's a 3450rpm. But starts right up immediately under the compressor load. Again, playing with pulley sizes, with various pulleys I have in the shop the pump is running 1400rpm. Wayyyy too fast. Motor is pulling 20amps running (supposed to be 12a @ 240v) it started to let the smoke out, so I killed it. Gonna reduce the rpms, gonna try to do down to 770rpm, which is pretty slow for this pump, but I gotta get those amps down.

So, since I have zero reference to average fill times, I'm having a hard time finding that butter zone. The rpm won't dictate the butter zone, but it'll give me an idea if I'm running too fast or too slow based on your input with stock compressors.

I realise modern compressors are **** and I'm going to have to sift through the information and pick what I think is best.
Modern compressors do not list the true HP. They list pipe dreams and complete lies. But let's hear what you got.

View attachment 230366
And that's a tallboy beer. Lol. Huge motor.[

You don't mention an unloader valve, so I'm guessing you don't have one, or it's not working. Do you compressor a favour and fix or fit an unloader valve. Faulty or non existent unloader valves are the main cause of compressor motor problems. Your compressor should always run up to full speed before it loads up. Also if you have to run it faster than the maker recommends it is simply not big enough for the demand.

Also check the compressor head valves, a very slight leak in the suction valve will make you machine work overtime, it will also cause it to overheat and possibly carbonise the oil around the valves A slight leak in the outlet valve will cause it run longer to get to pressure. Compressor valves are the cause of most problems with performance and usually the most overlooked part of the system.
 
I have an old Devilbliss 5Hp 60 gallon oil-less; takes about 10 minutes from empty. Probably needs a rebuild. And an old tank like your talking about; 2 HP, 60 gallon, 2 stage; takes a little more to charge from empty. Way quieter though and I think that I can get the time down with a pulley swap.(1750 rpm motor). That's my benchmark as you asked. Not sure about the recharge from 80-120 psi; usually using it at the same time as it's trying to keep up. On a side note; I've been told that the Oil-less are better for paint applications as the oil lubricated types can mist some oil unless filtered. I like to collect all types for versatility. (Welding/Millwright Contractor). Also have a twin cylinder 5 hp Briggs and Stratton wheel barrel type, a 5 hp Campell Hausfeld 13 gallon 110v wheeled unit and I'm toying with building a large mobile using a 3 cylinder Duetz Diesel that I just picked up. I figure that if you live long enough, you should have one of everything. Gonna leave my kids with a bunch of stuff that they don't know how to use, I think, unfortunately. Maybe Grampa's tool gene will skip a generation and some little kid won't have to start from scratch like I did.

Jon.

I had an oiless when I started. Terrible machine. LOUUUD, and the filter was subquality. I eventually decommissioned it as it took longer and longer to load up. I assume it got gummed up. I never took the head apart to find out, didn't care. Machine was junk. Says it's 1 hp with a motor the size of my fist...

I have two filtration units. One on the machine that has a regulator oil/water/particulate separator and an air desiccant dryer, then at the gun point I have another regulator with an inline desiccant filter.
That's for paint and sanding.
For air tools I have another leg coming out of that setup between the separator and desiccant with an oiler, and a separate air hose to reduce contaminates. Oil or water and lacquer do NOT mix. A painters worst nightmare is a silicone contaminate.

How can you ruin a painters hopes and dreams? Go spray a bunch of WD-40 around his shop.
 
I said above already, there is a dump valve in the setup. Otherwise the motor wouldn't turn the pump at all.
 
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