Compressor load times

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Hukshawn

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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.

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


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?
 
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.
 
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
 
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

...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.
 
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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
 
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.

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...

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.

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....
 
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