On Board Air

[rusty_tlc]

I'm a CO2 guy right now. But I'm considering an electric for the new rig.

I'm doing a tote sheet to compare. What am I missing?

CO2;
Plus-
Cost, around $100 to get started.
Easy installation, just a bracket to mount the tank.
Portable, I can take my current set-up from rig to rig.
High CFM possiable, fast fillup, re-seatting tires etc.
Quite, no compressor running.

Minus-
Size, tanks are bulky.
Consumable, tanks need to be re-filled, ongoing $.
Finite supply, I could get stranded with an empty tank.

Electric;
Plus-
Infinate supply, as long as the batteries/gas hold out.
Size, much more compact.

Minus-
Cost, good units are $$$
Current requirments, might need aux battery.
Duty cycle limits CFM.
Installation, wiring, mounting, plumbing.

Mechanical (not an option for me but worthy of discussion);
Plus-
Unlimited supply, as long as you have gas.
Relaible
Cost, probably somewhere between CO2 and Electric if you use a junk yard AC Comp.

Minus-
Not possiable on all rigs
Instalation, bracket, pully, pressure tank, manifold, pressure switch, reliefe valve guage, etc. etc.
Limited CFM.

 

[xcmountain80]

Your list sounds fairly accurate, when I was shopping for a compressors I got a good deal on a ViAir 450c very nice model. I have it mounted under the hood and it weathers just fine. I thinks parks offroad did a comparison at some point in time that was in 4WD Toyota Owner. http://parksoffroad.com/prodreview/inflatortest/inflatormain.htm


• 12-Volt
• Permanent Magnetic Motor
• Duty Cycle: 100% @ 100 PSI
• Max. Working Pressure: 150 PSI
• Amp Draw: 19 Amps
• Min. Ambient Temp: -40° F
• Max. Ambient Temp: 158° F
• Dimensions: 12.75” L x 4.00” W x 7.00” H
• Net Weight: 9.75 lbs.
2.5 Gallon Tank Fill Rate
0 To 105 PSI 1 Min. 55 Sec.
0 To 145 PSI 3 Min. 02 Sec
85 To 105 PSI 28 Seconds
110 To 145 PSI 59 Seconds

5 Gallon Tank Fill Rate
0 To 105 PSI 4 Min. 20 Sec.
0 To 145 PSI 6 Min. 40 Sec.
85 To 105 PSI 58 Seconds
110 To 145 PSI 2 Min. 11 Sec.


Aaron

 

[Robthebrit]

One thing to remember is if you are only filling tires you don't need a tank, but if you go tankless with a home grown system you do have to be careful of how you connect things. For example running the compressor output straight to a quick connector would be a bad idea as the pipe would act as a tiny tank and you would quickly build a dangerous pressure.

The best tank less approach is to connect the output of the compressor to the quick connect via an electric pressure switch that controls the clutch on the compressor. In this model once the air in the pipe gets to pressure the switch will shut the compressor off and you will not be building a dangerous pressure or wasting engine power. As soon as you connect something to the quick connect the pressure will drop and the compressor clutch will reactivate.

Really all you need for this system is the engine mount for the compressor and a way to drive it, the plumbing is simple. You also need a back flow valve stopping the pressure in the pipe leaking back past the piston rings of the compressor while its off. If you do not have the value the pressure leaks out about as quickly as it builds up and the end result is the compressor switching on and off quite rapidly and an upset compressor clutch.

If you really wanted a tank system you do exactly the same but the tank is between the pressure switch and the quick connect, the back flow value is not as important but still a nice thing to have. In both both cases there the back flow value is before the pressure switch!

The only reason a truck would want an air tank is to run air brakes, trailer brakes or power tools. My mog has a quite big air tank at 120psi but it does not speed up tire inflation. My inflation speed is limited by how fast air can get down the fill hose, even at idle I can hear the compressors switching on and off while I fill a tire, at this point other than acting as a buffer the tank is having no effect as I am filling slower than the compressors can make air.

Rob

EDIT: I have a spare belt driven mog compressor that will out perform any electric unit, its nearly 10CFM@100 psi (its actually a aux compressor on the mog as the primary is built into the engine block and crank driven). Actually this compressor would be great for a none mog vehicle as the compressors crank also drives a hydraulic pump for a REAL hydraulic winch (not a mile marker) without tapping your power steering circuit.

 

[rusty_tlc]

I wish a mechanical compressor were a possiablity for me. That MOG unit sounds like the kitties titties. How does it compare to a York for size? Got a picture of it?

 

[devinsixtyseven]

Personally I really like the idea of redundancy, mainly because I've had various SPVs in the past and one of them has always failed, leaving me to seek other solutions or limp home. The Mog setup sounds great...plenty of reliability there.

CO2 is a great thing to have. However, its reliability is limited by the regulator and threads...if something isn't sealing properly, you'll lose the charge (or just lose too much pressure through the leak) and probably won't be able to fill the tires (both of these happened to me recently, now I have a new regulator). Carry a backup regulator...just the simple fixed pressure kind is all you need. Knowing how much volume a given weight of liquid CO2 will expand to at the pressure you run will also help, just like your fuel guage. Unfortunately I don't have that information yet, but it's on the to-do list.

Same goes for the compressor. You don't need two compressors (or do you?), but definately make sure you have a backup plan if the motor burns out or seals are leaking.

Personally I think the CO2 tank can be more reliable (provided all your !@%$ is together regarding the regulator) due to the simplicity of it, but you also have to consider icing around the regulator and on the hose--I've had the hose almost solid filling in falling snow--do you run in a humid climate or is the air dry?

I'll be carrying a spare regulator from now on. Spare compressors are more expensive .

Soon the truck will be equipped with CO2 and a small compressor, with the CO2 for tires and the compressor driving the locker(s), and interchangability if one system fails.

-Sean

 

[DaveInDenver]

Same goes for the compressor. You don't need two compressors (or do you?), but definately make sure you have a backup plan if the motor burns out or seals are leaking.

Spare compressors are more expensive .

I actually have two compressors, the ARB and a MV-50. I use the the ARB for the lockers and the MV-50 for tires, but either could be substituted for the other in a pinch. Now if I sell the lockers (which is looking sort of unlikely right now) I'll have to rethink the redundancy aspect. I paid $25 for my MV-50 when Checker was clearing them out, but even at the regular price of like $50 or $60, they are a good buy.

 

[Robthebrit]

I don't think you need two compressors and I don't think I get any additional reliability from the two I have.

On heavy duty diesel engines its common to have a crank powered compressor attached to the engine, mainly because most applications that uses these engines also need air. This is the primary compressor and it really cannot fail independently of the engine. If the engine is running it is running. If I only had a single compressor this would be the one. Obviously this is not an option for most people.

My mog happens to have a second belt driven compressor, its not quite stand alone as it has an oil feed from the engine. This aux compressor makes more air than the block compressor but its more likely to fail due to the belt breaking. Because the primary compressor cannot break I don't see this aux compressor adding any backup capability it simply adds capacity.

Both compressors use the same plumbing so any problem in that area will take out both compressors, likewise if one of them blows a piston ring the air from the other compressor would leak past and not go to the tank.

The reason the truck has two compressors is because it has trailer air brakes and while the block compressor is enough for its own air brakes its not enough for its own plus an unknown trailer.

Rob

 

[rusty_tlc]

I actually have two compressors, the ARB and a MV-50. I use the the ARB for the lockers and the MV-50 for tires, but either could be substituted for the other in a pinch. Now if I sell the lockers (which is looking sort of unlikely right now) I'll have to rethink the redundancy aspect. I paid $25 for my MV-50 when Checker was clearing them out, but even at the regular price of like $50 or $60, they are a good buy.

Setting my lockers up to use CO2 in the event that the ARB compressor fails is on my TO DO list. I'd rather do it at home with my shop at hand than in the field. I do however carry extra o-rings etc for the pump as well as a 9mm air line splicing kit and extra airline.