JohnM

I notice that many of you carry compressed air tanks to air up or reseat beads or what-have-you. So this is my question...why not carry an actual air compressor?

For the same cost as a Powertank and accessories (approx $400), I can get a Dc to AC power inverter($40), a portable air compressor (6psi @90 CFM, ($250), and a complete set of basic air tools and accessories (extra hose, couplers, tire pressure gauage, etc) ($100).

Forgive me if this is a ignorant question, but I'm new. It just seems like, for spending this amount of money, you would want the most capability you could get. The downsides I can see are the weight and space issues. Are these big factors off-road?

Corey

iTrader: (1)

You would have to find a way to tie all that stuff down, plus the room factor you mentioned.

A lot use an air compressor, and have have an under the frame air tank mounted so they have a high power air source.
Something like that can provide you with the minimum 90 PSI that is required to run an air tool such as an impact wrench.

I like the ease of my Power Tank setup.

It's bolted in very tight as you can see by my write-up.

The only inconvenience with a setup like this is to resupply the CO2 once in awhile, but it's not hard at all.
Take the regulator off, and have a local welding shop fill the tank, and it's done in a few minutes.

If I did not have the PT setup, I'd probably try that one air compressor called the Extreme.
I think that is the name of it.
I think it puts out enough PSI without using an external tank to run air tools.

But I really dig the PT.
It's come in handy many a time.

One more thing about air tools.
You get what you pay for too.
Adam got an impact wrench, but found out it did not have the oomph to remove lug nuts.
You need one that goes upto 300 to 400 ft lbs of torque for that.

JohnM

I guess it comes down to individual choice, huh?

400 ft/lbs? Seems high for a light truck wheel lug. Stock toyota wheels require only 80 ft/lbs.

Mytyota

i use the stock a/c compressor, put an air tank under the flat bed, and ran an electrical switchto turn the a/c compressor on at 80 psi and shutting it down at 120 psi. Plus i got an on off switch in the cab.

Robinhood150

I don't think a $40 inverter will provide enough watts to power an air compressor, but I could be wrong though, never looked at how much power an AC compressor uses (especially at the higher pressures). My 350watt inverter was around $60 ( I think) and I doubt it provides enough power.

But yeah, the other concern is space. Just for a day trip, the back of the runner is fairly full. Plus everything has to be strapped down for safety.

Steve

JohnM

Well, I suppose thats a good question. A quality air compressors that are capable of supplying the needed level of air, the power requirement is 115V and 10-15 amps. The heavy duty power inverters supply 800 watts at 30 amps. More than enough power. Your right though, it's $70 not 40. But we are talking approximates here.

Where do you wire such a large power consumer into a truck anyway? I would look at the battery bus, I suppose.

Robinhood150

Hmm...where are you getting your numbers? Lets assume the 10 amps at 115V is correct. P=IV so P=10A x 115V=1150 watts minimum. Cabelas has a 1200W inverter for $200. At the higher air pressures, let's say it draws 15 amps, that's 1725 watts.

An 800 watt inverter can only supply 7 amps on the AC side (I=P/V=800/115=7). To supply 30 amps you would need a 3450 watt inverter. The 2000 watt inverter from Cabelas is $300. Of course, at 2000 watts, you'll be pulling 166 amps out of the DC side.

Oh, and this is not taking inefficencies into account. My inverter is 90% efficient so you can add another 10% to these numbers.

I've got my inverter under my seat and I think a lot of other people also have theirs mounted there too. I'm using 4 gauge wire running directly to the battery with a 70ish amp fuse thrown in.

Steve

seafarinman

Well said Robinhood150.

JohnM

See, this is why I ask these questions.

Do you think the inverter would have to supply the peak power requirements of the compressor at a continuous level?

The inverters I was looking at are all rated like, 800W continous 1600 peak. I would assume that compressor motors are like most other motors and only reach thier peak power output at startup and loaded shutdown.

Providing a continuous 2000W power source would be rather expensive. Prices run $300-500. (even at discount/wholesale places)

I guess that explains my original question. It costs more to set up a portable compressor than getting a powertank. At least at retail prices.

Thanks for helping me work this out guys

Corey

iTrader: (1)

John, also check into that one compressor I mentioned.
It's either the Extreme Air, or another one.

Adam F on the forum here knows the one I am talking about.
It is the most powerfull of the 12 v ones on the market, and may run air tools without a sperate tank.

Pretty easy to hook up, all you need to do is run power to it, and mount it in the back.

JohnM

are you talking about this?

Corey

iTrader: (1)

Yes, Adam just gave me the URL.
http://www.extremeoutback.com/Compressors.htm

If I did not already have my Power Tank, I would strongly be considering this unit.

Continues cycle which means it's meant to run a long time without having to cool off, and it can run air tools without a separate tank.

This is one of the best 12 v ones on the market.
More than a Power Tank, but you never have to fill it.
I am just wondering though about their claims of 150 PSI.
If so, it means it could fill up a tire as fast as my PT.
I run mine at 150 PSI for airing back up, and it is very quick, but much quicker than their claims on their site.
Corey

JohnM

It wouldn't fill a tire as fast. The mass airflow from the compressor is much lower than from the powertank. At least if I understand my compressable fluids stuff from my fluid dynamics studies.

Corey

iTrader: (1)

Ahh, no wonder.

It seems like it only takes a few seconds to air back up each tire on my rig, and seems faster than a gas station too.

Robinhood150

Well, it kinda depends on what inverter you get.

You're right, the current draw goes up as the load goes up.

Steve

Arnold

Their compressor is almost identical to this one, http://www.justairbagit-store.com/pr...t.asp&ID=18172
It's a lot cheaper too.

crash

Ran an arb pump for years, sucked... Ran my toy a/c comp for a few years, did a good job, but the york is the ticket, love it, can run air tools, and easily bead a 38.5. And I have a 2 gallon tank under my bed and its controlled by an arb pressure switch since the system is also for my ARB's...

Arnold

crash, where did you get your 2 gallon tank? I know www.onboardair.com and www.sunperformance carry 'em but would prefer to buy locally.

crash

I bought a bunch of empty freon bottles and converted it...

Robinhood150

Well it looks like this guy uses his 400W inverter to run his AC air compressor. http://forums.delphiforums.com/n/mb/...ry&msg=77618.1

My guess is that our assumed current requirements were incorrect. The compressor probably draws much less current than we had originally thought.

Steve

Edit: he said it takes 3-4 minutes to fill up a tire so it must be a pretty small compressor. That's why he can get away with a 400w inverter. So I guess it's feasible, but if you want a fast compressor then you still need a pretty big inverter.