80gal. Air compressor build: pulley help

[joe.mama]

I’m building an air compress and need help with pulley sizing.

Building on an 80gal Campbell hausfeild tank I have a Weg 5hp 1750rpm motor and a HF 175psi pump rated for 1180rpms (850-1180). The pumps pulley is 16.5” OD, I’ve done the calculations and by the math I need a 11.125” pulley. However the dilemma is that there is no such thing as a 11.125” pulley unless it’s custom made.

There is an 11.25” (bk115) and an 10.75” (bk110), no In-betweens. The bk115 will push the pump to 1193rpm. While the bk110 pushes it at 1140rpm.

I’ve went with the bk115 pulley already. Thinking that 13rpms may not hurt it, while taking a 40 rpm is a major loss if i would have gone with the bk110.

Will it be able to handle the 13 extra rpms? What’s your guys thoughts?
Thanks

 

[The Cobbler]

I don't think 13 RPM over is going to hurt, but really, do you need that much air that running the pump a bit slower wouldn't provide?
higher RPM = more heat, noise , wear, etc .

 

[no704]

Probably better than too slow?

 

[joe.mama]

I don't think 13 RPM over is going to hurt, but really, do you need that much air that running the pump a bit slower wouldn't provide?
higher RPM = more heat, noise , wear, etc .

In all honesty I’m not a commercial shop so no it’s not going to be needed none stop. However the reason I’m building such a huge compressor, is that I’m repainting my car. Possibly more in the future.

Also I spent a pretty penny on the motor so I want to get the most out of it and the system and why not get the most out of it.

 

[no704]

It will likely slow more than 13rpm as the pressure load increases.

 

[The Cobbler]

I want to get the most out of it and the system and why not get the most out of it

that's your choice, but running things at the max often doesn't give you the most life either. just saying.

 

[joe.mama]

that's your choice, but running things at the max often doesn't give you the most life either. just saying.

Yeah I get that. Hopefully it doesn’t blow.

 

[Cruzan80]

If you are using it for painting, I would run it slower. Less heat, start with a full tank, and the CFM will still cover it. Hot air means moist air, which is bad for paint.

 

[joe.mama]

If you are using it for painting, I would run it slower. Less heat, start with a full tank, and the CFM will still cover it. Hot air means moist air, which is bad for paint.

I’m building an after cooler and will have an inline water filter.

 

[isb cornbinder]

I bought all of the components for my IR T30/80, over a few years. I cheated and went to KM Tools to measure the pulley sizes. I bought a 5hp compressor motor rated US Motor at Armature Electric. I doubt that have $900 dollars in this project. Is it loud OH YES!!! The filter is from a Cummins 4bta.
Armature Electric re&re so very large electric motors. There were two motors in the shop that were big enough to drive a 911 through.

 

[no704]

For painting there’s no reason to be running any where near 175psi.

 

[Cruzan80]

I’m building an after cooler and will have an inline water filter.

I guess my point is why make the after-cooler and water filter work harder, if the lower RPM can still supply your full CFM needs.

 

[micromind]

I've found it best to go a bit slower than faster.

If you choose to go faster, read the motor current at max pressure and make sure the overload protector is set correctly.

 

[The Cobbler]

seems the original poster is set that he wants maximum and not taking advice. I wonder if he's actually calculated the CFMs he is going to need, or just wants a bad *** compressor and that's that?

 

[Cruzan80]

In fairness, lots of posters here already know what they want the answer to be, and are just looking for confirmation via the forum. If he wants the biggest, baddest compressor, more power to him. But it would help if people say that up front...

 

[joe.mama]

In fairness, lots of posters here already know what they want the answer to be, and are just looking for confirmation via the forum. If he wants the biggest, baddest compressor, more power to him. But it would help if people say that up front...

Okay in all fairness you both are right! I’m not going to deny. I’m checking for validation and also do want the biggest and best compressor but who can blame me for all the work I’m doing building it from nothing. I already have the pulley and bushing. I was set in with going with going that extra 13rpms faster because I already have the pulley and bushing bought. The pulley can’t be returned but it was only $20 from eBay. The can bushing can be returned though.

If it means saving my pump I’ll take the lose on $20 and get the right one. But is 13rpms really that significant?

 

[Cruzan80]

Will it run hotter and not last as long as if you were running it slower? Yes. Will it be significant enough to matter for a home shop? Probably not. Just was pointing out for your use cases, you don't NEED the max CFM running the pump at that RPM gives.

Btw, thanks for owning your reasons!

 

[joe.mama]

I guess my point is why make the after-cooler and water filter work harder, if the lower RPM can still supply your full CFM needs.

15.0 CFM @ 90 PSI, 14.8 CFM @ 120 PSI.

This is the flow rate at 1180rpms. I’m not sure how much I need on the gun. However, less rpms will cut it.

Also ignore the replays to myself. Not sure why it’s happening lol

 

[dnschmidt]

A SATA X5500 will consume 17 SCFM at 29 PSIG. Believe me if you're painting a complete car you NEED THAT BIG OF A COMPRESSOR. The reason is that once you start you can't stop to wait for the compressor. You have to follow the wet edge and that means each coat has to be done complete before you can stop and let the compressor catch up. I have a 5HP Quincy 80 gallon two stage and wish I had a 7 1/2 HP instead.

 

[joe.mama]

A SATA X5500 will consume 17 SCFM at 29 PSIG. Believe me if you're painting a complete car you NEED THAT BIG OF A COMPRESSOR. The reason is that once you start you can't stop to wait for the compressor. You have to follow the wet edge and that means each coat has to be done complete before you can stop and let the compressor catch up. I have a 5HP Quincy 80 gallon two stage and wish I had a 7 1/2 HP instead.

I’m not sure what the gun is rated at. Im borrowing it from a friend. However I do see that some guns do require at least 15. This is what makes me think i should rather make it go that extra rpms to make sure im getting all of the cfm. As it even states on the sticker on the motor 15 cfm at 1180. Then lose rpms and lose cfms.

I plan to only paint the hood and roof. The clear coat is shot and I’m not scared to try repainting it. So probably won’t be completely maxing it out and will wait for it to completely fill before shooting each time if need be.

I will admit I am a beginner to all of this a painting. So enlighten me about scfms and what is recommended/ needed.

 

[dnschmidt]

Do the roof and then do the hood. The proper way to do either is to start on one side of the car and spray toward the middle. Switch over to the other side and pick up the wet edge in the center and finish at the other edge of the roof or hood. You never want the paint to dry before you complete whatever it is you're painting. THAT'S WHAT CAUSES ORANGE PEEL. If you keep the paint wet it will flow out. If you don't it doesn't.

 

[joe.mama]

Do the roof and then do the hood. The proper way to do either is to start on one side of the car and spray toward the middle. Switch over to the other side and pick up the wet edge in the center and finish at the other edge of the roof or hood. You never want the paint to dry before you complete whatever it is you're painting. THAT'S WHAT CAUSES ORANGE PEEL. If you keep the paint wet it will flow out. If you don't it doesn't.

You are saying work from edge to middle, swtich sides, continue middle, until i reach other side?

I plan to take off the hood from the car make it easier to deal with

 

[dnschmidt]

Right, In this case "the other side" as you finish would now be the one closest to you. The idea is to always have a wet edge. You can't (unless you're an NBA center) reach across the entire width of the hood to spray it all from one side. You come from one side as far as you can (normally somewhere close to or a little past the middle of the hood) then continue on immediately from the other side until the entire hood is covered. With basecoat it's less of an issue but with clearcoat you need to do this or you end with a rough finish where you first left off.

 

[isb cornbinder]

I've found it best to go a bit slower than faster.

If you choose to go faster, read the motor current at max pressure and make sure the overload protector is set correctly.

I used a SPEEDAIR twin, single stage for decades. I ran the compressor at twice the suggested max RPM. The compressor got very hot from heavy use, like painting or blasting. I wired in a switch to control a separate cooling fan. It worked but it drew a few criticisms. The person I gave the Speedair to is using it

 

[micromind]

If you need more CFM at low pressure and you don't need 175 PSI, you can turn the pump faster and lower the pressure switch setting.

A piston pump takes more HP with higher pressure so if you lower the max pressure, you'll lower the load on the motor and thus, turn it faster.

 

[marinusdees]

I’m building an air compress and need help with pulley sizing.

Building on an 80gal Campbell hausfeild tank I have a Weg 5hp 1750rpm motor and a HF 175psi pump rated for 1180rpms (850-1180). The pumps pulley is 16.5” OD, I’ve done the calculations and by the math I need a 11.125” pulley. However the dilemma is that there is no such thing as a 11.125” pulley unless it’s custom made.

There is an 11.25” (bk115) and an 10.75” (bk110), no In-betweens. The bk115 will push the pump to 1193rpm. While the bk110 pushes it at 1140rpm.

I’ve went with the bk115 pulley already. Thinking that 13rpms may not hurt it, while taking a 40 rpm is a major loss if i would have gone with the bk110.

Will it be able to handle the 13 extra rpms? What’s your guys thoughts?
Thanks

I'd recheck your math. Check Machinery's Hand Book?? I'm working on a similar set up, Curtis D 96 compressor. Factory recommends 6" motor pulley, compressor is 16". Preliminary test shows 5 hp motor using 25 amps. 5 hp is nominally 27, wasn't up to 175 psi yet.

 

[marinusdees]

If you need more CFM at low pressure and you don't need 175 PSI, you can turn the pump faster and lower the pressure switch setting.

A piston pump takes more HP with higher pressure so if you lower the max pressure, you'll lower the load on the motor and thus, turn it faster.

An AC motor speed is determined by the frequency (60 cps), will vary little with load until it dynamites the motor (overheating).

 

[micromind]

An AC motor speed is determined by the frequency (60 cps), will vary little with load until it dynamites the motor (overheating).

I was referring to the pump RPM.

As you can se, I'm not a very good writer......lol.

 

[middleclassmods]

Do you have any updates? I’m considering my own build at the moment and would be very similar to yours. I’d love to see more on where you’re at with this!