# Compressor load times



## Hukshawn (Apr 2, 2017)

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.



And that's a tallboy beer. Lol. Huge motor.


----------



## darkzero (Apr 2, 2017)

Not sure if this will help you but I have a modern compressor. It's an older Harbor Freight 60 gal, US General model, made in USA, same unit as the BelAir 6061V, made by ABAC. It's not a slow putter though, 3450 RPM, 220V single phase, single stage twin cylinder, oil lubricated. Tag says 12.85 CFM @ 90 psi, 15 amps ("3.5 HP")

From just under 100 psi, when the pressure switch kicks on, takes 1min 57sec to get to 135psi when it kicks off. I have a Solberg air filter on it & a oem IMC aftercooler on it that it originally does not come with.

I just timed it today as it was about to kick on. No idea how long it takes from empty, I never fully drain the air, I just purge it to release any moisture which is minimal for me.

EDIT: I forgot, I also have a 17 gal tank piggy backed to it, I always forget cause that tank is sitting behind my lathe out of sight.


----------



## den-den (Apr 2, 2017)

I would not worry about cycle time, just set up the pulleys so that the motor is at rated amps just before it kicks off with the tank pressured up.  This way you are getting the max available without overloading the motor.  You may be able to push the rated current a little if you are willing to risk it.


----------



## Hukshawn (Apr 2, 2017)

Well, there's a balance for me with speed, time, and NOISE. It's a big unit. It vibrates through the house. My sons bedroom is right above the garage. Running at the 1200rpm, it shakes the floor. Lol. 
I switched back to the big R&M but a smaller pulley. Running at 740rpm. It's nice and quiet but took 15 mins from dry, and 5.5 mins from kick on. Little slow. That pulley was 2" smaller than the other one. I'll try the middle size next time I get to the hardware store. 




darkzero said:


> It's not a slow putter though, 3450 RPM, 220V single phase, single stage twin cylinder, oil lubricated



What's the pump rpm with the 3450 motor?


----------



## darkzero (Apr 2, 2017)

Hukshawn said:


> What's the pump rpm with the 3450 motor?



Unfortunately I have no idea. I don't know the sizes of the pulleys & I'd have to move the air compressor out from it's corner to access the rear belt cover.


----------



## tq60 (Apr 3, 2017)

You are thinking WRONG...

Do your homework and look at the data sheets and build to spec...period.

First get an unloader valve and control switch so the motor starts on an unloaded compressor.

Magnetic starter makes for better switching so the contacts on pressure switch last and low voltage control allows for easy power control via small switch or a relay connected to lights so lights out compressor off.

Now design...

Look up the specifications on your pump.

If it is any kind of known unit it should have a table showing motor rpm and pulley size for the suggested motor hp rating.

It will state a 2 hp 3450 rpm as pulley size X.

If you have a compressor rated 2 hp motor then get the correct size pulley and done.

Higher motor rpm is smaller pulley and lower rpm is larger so the actual torque of the motor could determine if high or low rpm would be better but it should not matter as long as you are using good quality motor. 

Sent from my SAMSUNG-SGH-I337Z using Tapatalk


----------



## Hukshawn (Apr 3, 2017)

tq60 said:


> You are thinking WRONG...
> 
> Do your homework and look at the data sheets and build to spec...period.
> 
> ...



...okay, take it easy with the offensive comment right out of the gate... I do actually know what I'm doing. There already is a dump valve and a high quality pressure switch. You don't use a princess auto switch on a 13a 2HP motor, it won't last long. I could do a contactor but I haven't seen the need, nor is it three phase.
There is zero markings on the pump. I have no idea what make it is. Nor did the professional compressor repair guy I traded it from (and 20 years as a full time repair shop dictates to me he's a professional). We had extensive talks regarding all of this over a year ago. But it turned out to be a situation of "wish I knew then what's know now" cause I was asking the wrong questions and I've since lost his contact. (Almost an hour away and found through kijiji). He had me running the pump fast for lots of cfm, said it was fine as these pumps are built for 3450rpm motors. Modern pump, old motor. You can play with the settings on newer pumps. The old big piston ones are designed to be run sloooww and push a lot of air, everything modern is go go go!

So, I was merely asking what everyone's pumps run at to collect data and decide the window I'd like to be in.


----------



## tq60 (Apr 3, 2017)

Not meant to be offensive but rather to get your thinking straight so to speak...sorry if you took it wrong.

Your op was a story of what we see when some are guessing instead of thinking so the post was reaction to that.

That being stated and with new information then some other suggestions to try.

You have an unknown pump that you are trying to get optimal output from a given motor...been there done that and after 20 years of home builds bought a 7.5 hp champion but respect the process.

Mag starter is good on single phase and can be built for a song with "found parts" or common relays so keep an open eye for parts.

For the pump brands do not matter as does bore and stroke so determine that by pulling the head or valves which likely need serviced anyway and use that as a reference.

Google is your friend here as you can use "compressor" and your measurements and locate a current manufacturer with something very close to what you have and from that you can learn the suggested motor pulley ratios as with a 2 hp motor you are power limited meaning the motor can only turn the pump X rpm regardless of the rpm limit of the pump.

So consider the pump rpm limit based on bearing or design a little but the pump may have been designed for multiple size motors.

Slow for low hp and fast for higher hp...Our compressor has a 7.5 hp single phase with a huge pulley that spins the pump fast and the 5 hp unit was identical but smaller pulley.

This allows one pump instead of many which works well for easy upgrade later.

If pump is real old then it may be a "service station pump" and designed for small Hp motor of 2 hp and slow rpm for noise along with high pressure for lifting cars and busting lug nuts but not high volume.

Had one of those...supercharged it with a vacuum cleaner motor but that is another story...

Good luck with your project as you have some homework to do to make the build more successful. 

Sent from my SAMSUNG-SGH-I337Z using Tapatalk


----------



## Tony Wells (Apr 3, 2017)

http://www.egnergy.com/calculator.html

http://www.about-air-compressors.com/fill-an-air-tank.html

http://www.compressorwale.com/calcu...o-check-the-efficiency-of-air-compressor.html


----------



## Hukshawn (Apr 3, 2017)

tq60 said:


> Mag starter is good on single phase and can be built for a song with "found parts" or common relays so keep an open eye for parts.


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.



tq60 said:


> For the pump brands do not matter as does bore and stroke so determine that by pulling the head or valves which likely need serviced anyway and use that as a reference.


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...



tq60 said:


> If pump is real old then it may be a "service station pump" and designed for small Hp motor of 2 hp and slow rpm for noise along with high pressure for lifting cars and busting lug nuts but not high volume.


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. 



tq60 said:


> Had one of those...supercharged it with a vacuum cleaner motor but that is another story...


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....


----------



## tq60 (Apr 4, 2017)

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


----------



## tq60 (Apr 4, 2017)

Hukshawn said:


> 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...
> ...


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.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk


----------



## Hukshawn (Apr 4, 2017)

tq60 said:


> 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.
> 
> ...


That's a very interesting idea.


----------



## tq60 (Apr 4, 2017)

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.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk


----------



## aliva (Apr 4, 2017)

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


----------



## Joncooey (Apr 4, 2017)

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.


----------



## Silverbullet (Apr 5, 2017)

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


----------



## Downunder Bob (Apr 9, 2017)

Hukshawn said:


> 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.
> 
> ...


----------



## Hukshawn (Apr 10, 2017)

Joncooey said:


> 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.


----------



## Hukshawn (Apr 10, 2017)

I said above already, there is a dump valve in the setup. Otherwise the motor wouldn't turn the pump at all.


----------



## Hukshawn (Apr 10, 2017)

I brought the machine down to about 800 rpm. Runs nice. Quieter, that old motor starts right up, and it doesn't actually take all that much longer to load from kick on. But from empty it takes 15 mins. Lol. 
The pump is a single stage and I feel it is probably too small for the tank for what I'm asking. I believe the pump is likely from a cheapy Chinese machine. Probably still from a 60 gallon. But it still seems to be of decent quality, reasonably well made, it just has no markings. I just would never guess a good quality pump would have zero data or name markings on it. But a pump, is a pump, is a pump... 
if I do another big furniture job, I'll probably speed it up again. 
Frankencompressor


----------



## KBeitz (Nov 6, 2018)

Quote...." But it's tired. "....  

How does an electric motor get tired... You said it need rewinding... Why...
You only rewind when you have burnt or shorted or open windings...


----------

