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Let's talk about pneumatics / on-board air hose size

Wildman

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So in redoing my TJ this coming year and I need to update some things in my onboard air system. So right now I have 3/8" hose going down to me air tank and then 3/8" hose going to a front and rear air chuck for filling the tires. But I'd like to redo some of this so I am wondering if changing this hose size down to 1/4" air line will reduce the capacity/capability of the system. I learned this stuff years ago but I'll be danged if I can remember it now.

Basic Onboard air system.

87880


Part of what is confusing me is say you buy a 3/8" air hose it has 1/4" NPT fittings. Most of the stuff I found online about this subject was discussing 100' of piping and what the size change would do to your air pressure. I doubt you would have 50' total of air line totally on a TJ. If there is going to be a decrease in PSI or air flow by going to a smaller size I won't do it. I was just looking for ways to save space if possible. So for all of you guys who are smarter and the math whiz break it down for those of us that aren't.

Thanks and I figure this might help those who are looking at installing some type of on board air on their TJ.
 

mrblaine

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I would reduce most of the extra by getting rid of the tank unless you are using it as an air/oil separator. The tank isn't doing anything for you except adding complexity, taking up space, and adding expense. The test to see what it is doing is simple. With the system operational and the tank full, start to air up a tire from 8 psi to street pressure. From the time you click on the chuck to when the compressor kicks in and starts refilling the tank is all the good it is doing and that is typically what, 10 seconds max worth of air?
 
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Brianj5600

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Wildman, you are living up to your description,
Over Analizer Extraordinaire..............

Basic on board air system? I have trouble over thinking thinking things to the point I freeze up and projects stall. I think you are over thinking pressure loss unless you are using air tools. Then a 3/8 hose with a short run will help. Every fitting will cost efficiency/flow too. When the area changes the air is either accelerated through a smaller cross section or slowed through a larger cross section. When it's all said and done I doubt it would make much of a difference. There is a lot to be said for simplicity.

My theory is to taking air from close to the compressor would be most efficient. Right after the separator, put a tee and put the hose you are attaching to do work in the straight though port and the 90* port to the rest of the system. The tank could be at a dead end. It would still accumulate excess and flow back if pressure drops. No bigger than the tank is it is probably acting more like a damper than a reservoir. Or ditch the tank. Taking air from before the maze should have a slight advantage, but probably not enough to matter.
 

Mr. Bills

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I would stick with 3/8" air line and 1/4" NPT fittings. Why change what's working?

And I agree with @mrblaine - If all you are doing with your compressor is airing up tires you don't need a tank. Tanks are only necessary if you need to store compressed air to operate air lockers, air horns, etc., and no tank that will fit in or under a jeep will have enough capacity to operate air tools.
 

mrblaine

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Wildman, you are living up to your description,
Over Analizer Extraordinaire..............

Basic on board air system? I have trouble over thinking thinking things to the point I freeze up and projects stall. I think you are over thinking pressure loss unless you are using air tools. Then a 3/8 hose with a short run will help. Every fitting will cost efficiency/flow too. When the area changes the air is either accelerated through a smaller cross section or slowed through a larger cross section. When it's all said and done I doubt it would make much of a difference. There is a lot to be said for simplicity.

My theory is to taking air from close to the compressor would be most efficient. Right after the separator, put a tee and put the hose you are attaching to do work in the straight though port and the 90* port to the rest of the system. The tank could be at a dead end. It would still accumulate excess and flow back if pressure drops. No bigger than the tank is it is probably acting more like a damper than a reservoir. Or ditch the tank. Taking air from before the maze should have a slight advantage, but probably not enough to matter.
Getting folks to understand that one or two restriction points in a fluid system is not going to affect the overall output much is always a challenge. We use high performance steering fluid pumps from PSC that put out 5 gpm at 1850 psi. All of that goes through a fitting at the output on the pump that is .170 in diameter. We bump up the return side (all 6 feet of it) to -8 with an internal diameter of .500 just to keep the flow up.
 
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Wildman

Wildman

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Thanks folks.
Blaine, I have to keep the tank for the AiRock system.
Brian, yes I tend to over think things too many times but it does work to my advantage now and then. The diagram I posted is the recommended setup if you are using a York compressor. I can't speak for any of the electric compressors. But I have only been using a York since I installed OBA. The York does expel some oil & moisture into the air. Just like on my shop compressor I have a metal line running from my York to the coalescing filter.
Mr. Bill, yes most likely better to just keep it all one size.

Off-Road Only has came out with a new York style compressor that is suppose to help with not putting as much oil into the air.
 
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Wildman

Wildman

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Let me try and show what my air system looks like. First off for the AiRock kit it has to have as clean of air as possible.
IMG00684.jpg


My air tank stuffed in between the lower control arm and stinger.
IMG00696.jpg


IMG00701.jpg


IMG00700.jpg


See the steel line coming off the back of the York compressor? Just like on a shop compressor it is suppose to help cool the air charge so that the filter can stop the oil and moisture from going any further.

IMG00694.jpg


Then a air line off a regulator/filter to the ARB solenoids

IMG00881.jpg


And part of the AiRock system is the SwayLoc which uses an air cylinder to lock & unlock that is controled by a solenoid.

IMG00270.jpg


IMG00271.jpg


The two regulator/filters- 1 for the ARB and 1 for the AiRock. You can see the distribution block with the blow off valve, pressure switch & a chuck to get air for whatever.

IMG00278.jpg


IMG00280.jpg


And to start it all the coalescing filter, bulkhead fitting then check valve and then distribution block.

IMG00685.jpg


So my air system is not simple nor is it basic.

But isn't these forums where we are suppose to share ideas and experiance? My air system is probably the extreme edge of what someone would have but it is what it is.
 

toximus

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Tanks are only necessary if you need to store compressed air to operate air lockers
Actually, you don't need much volume of air to actuate an air locker. The mini reservoirs that ARB compressors come with can last a few cycles of the air lockers without a recharge.
 

jjvw

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The tank on my OBA lets me use my framing nail gun whenever and wherever I want.
So. yeah.


I'll just show myself out
When I first installed the York, I had a job where I needed to run a big roofing stapler. There wasn't a tank and the stapler ran just fine.
 
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mrblaine

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When I first installed the York, I had a job where I needed to run a big roofing stapler. There wasn't a tank and the stapler ran just fine.
Depending on diameter and length of it, the air hose to the stapler makes a jim dandy tank.
 
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Wildman

Wildman

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All of the plumbing is a "tank" as well.
Well then if you use that analogy wouldn't it make more sense to use the largest hose/plumbing possible?
Again not being a math whiz I can't sit down without a lot of chicken scratching and hours of headache to come up with the volume of a 25' 1/4" house and let's say 25' of 3/8" hose as a air tank.
 

mrblaine

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Well then if you use that analogy wouldn't it make more sense to use the largest hose/plumbing possible?
Again not being a math whiz I can't sit down without a lot of chicken scratching and hours of headache to come up with the volume of a 25' 1/4" house and let's say 25' of 3/8" hose as a air tank.
One sentence answer, 15 words or less. What are you trying to accomplish?
 
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Wildman

Wildman

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One sentence answer, 15 words or less. What are you trying to accomplish?
Not trying to accomplish anything Blaine was just commenting in JJVW's comment.

If you are asking what am I trying to accomplish with my air system? I need to replaces a hose that has a leak and run some new lines for things I screwed up the first time.
 

kmas0n

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I would reduce most of the extra by getting rid of the tank unless you are using it as an air/oil separator. The tank isn't doing anything for you except adding complexity, taking up space, and adding expense. The test to see what it is doing is simple. With the system operational and the tank full, start to air up a tire from 8 psi to street pressure. From the time you click on the chuck to when the compressor kicks in and starts refilling the tank is all the good it is doing and that is typically what, 10 seconds max worth of air?
So, this is a question, not an argument. Last year I ran my OBA briefly without its tank, The switch on the dash would activate the relay which would activate the pressure switch. The pressure was below 90psi so it would activate the clutch on my compressor. When engaged the compressor would almost instantly surpass max pressure of 120psi and then trip the blowoff valve. I believe the valve is set at 140 or 160psi. When the blowoff valve released pressure, the volume of air is so small, it would drop below 90 PSI and the pressure switch would again activate the compressor. There is less than 3 feet of 3/8 line between the compressor and switches. It would just cycle like this a few times a second. In my case, the tank acts as a buffer and keeps the system from excessive cycling. Is there something I could change to prevent these short cycles? I can't just use a really long air hose, because the system runs my air lockers too
 

mrblaine

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So, this is a question, not an argument. Last year I ran my OBA briefly without its tank, The switch on the dash would activate the relay which would activate the pressure switch. The pressure was below 90psi so it would activate the clutch on my compressor. When engaged the compressor would almost instantly surpass max pressure of 120psi and then trip the blowoff valve. I believe the valve is set at 140 or 160psi. When the blowoff valve released pressure, the volume of air is so small, it would drop below 90 PSI and the pressure switch would again activate the compressor. There is less than 3 feet of 3/8 line between the compressor and switches. It would just cycle like this a few times a second. In my case, the tank acts as a buffer and keeps the system from excessive cycling. Is there something I could change to prevent these short cycles? I can't just use a really long air hose, because the system runs my air lockers too
What is your pressure switch that disengages the clutch set at?