Vehicle mounted air compressors.

[CommonHighrise]

I got my hands on a fairly decent little 1.5 gallon air compressor. While it's too small to be put into use in the shop, and a little too big for airbrushing, it has just been sitting around.

Was thinking it would be a neat little addition to mount it in the trunk of my car, as I'm often found stopping to help cars on the side of the road with flats. It'll fit, and bolting it down shouldn't be too tough.

Now, it is wired to run off of 110AC. I need to double check on the amperage draw of the motor. I'm wondering, what is a good way to invert my car's 12DC to run the compressor? I've looked at some inverters online, and they seem to run a wide price range. Anyone have recommendations of a reliable inverter, that is budget friendly (<$40)?

Also, while I need to look at the amperage draw, anyone know at what point I would have to install a second battery in parallel? I have been considering doing so anyway, but didn't know how much a standard car battery could take before needing backup.

[nepawolf]

Running a second battery is a good idea (while not normally being necessary) for almost every vehicle. If you replace your standard battery with a high quality deep cycle battery, it can provide the same performance as a dual battery set up with standard batteries. Now if you were to run dual deep cycles, you would get awesome performance (it would also be about $260 every time you needed to replace your batteries, though). As far as when it's necessary, there was some math equation that I forgot years ago for that.

I've never found a reliable DC to AC inverter, no matter the price. Even if the inverter itself manages to continue working, almost every inverter that I've ever used has burned out power sockets and/or lines. Be careful where you mount the inverter, they can overheat pretty quickly and the cheap ones can catch fire from overheating. If someone else can point you in a good direction for one, I would definitely say to run the power lines for it into the fuse box or run it straight to the battery with an in-line fuse. If you go for the directly to the battery route, you're like to need an in-line limiter to keep from sending too much power down the line. That can be done either by choosing your wire by it's resistance level or by installing a box or homemade board. You're likely to be best off that way, it should help out with most of the problems.

If anyone else is thinking about mounting an air compressor in their vehicle and they have a self-oiled AC compressor, the compressor can be converted rather easily into a standard air compressor. If you're interested, the plans are available here: http://www.offroaders.com/info/tech-corn...rd-air.htm

[CommonHighrise]

Actually, I may be going another route. A friend of mine pointed out that on early 90s Cadillac cars, they had air shocks in back that are supplied by a small compressor under the hood, which is easy to get out and remove.

I'm not sure of the pressures it can reach, but if it can hit 35psi, that would be all I need (not planning on running air tools or anything). It's already set up to run off of 12dc, on a 30A fuse.

I'd have to fabricate lines between the compressor and a small storage tank, but it might be an easier setup than messing with inverters and dual batteries.

[nepawolf]

The old caddy shock air compressors probably put out about the same amount of PSI as an air horn air compressor off of a big rig. If you have a big rig scrap yard near you, you could pull either that compressor or the one for the air brakes. Taking the tanks, fittings and chunks of the lines might not be a bad idea either. The caddy compressor would probably be an easier job, but the compressor for the air brakes on a big rig is likely to have a longer life.

[CommonHighrise]

(11-17-2009 05:01 AM)nepawolf Wrote:  The old caddy shock air compressors probably put out about the same amount of PSI as an air horn air compressor off of a big rig.

Got any idea what that PSI is? I know it's nothing massive, like I said, if it can run every once in a while, and keep 35psi in, say, a 2 gallon tank, I'll be happy. Since they are fairly quiet, I would probably wire it in hot whenever the key is on, so it'll keep the tank at pressure at all times.

[nepawolf]

I couldn't find anything that specifically said what the PSI or CFM is, but it was apparently sufficient for filling tires. Apparently, some of the models had a service plug to fill your tires from. I managed to find a page that gives a step-by-step manual for doing a project like the one you're planning on. http://www.robinhood4x4.com/compressors.htm. As far as linking it straight into the hot, I would put a toggle switch in and have a pressure gauge. By just linking it straight to the hot, the compressor will be on the whole time you're driving unless you can locate where the cut-off sensor is, it might be built-in I don't know.

[Drewid]

Umm train horns are illegal in PA but check out http://www.hornblasters.com/ for fun as I was ticketed for blowing my horn at a State Trouper that cut me off in my Miata without using a turn signal.

[nepawolf]

It depends on the decibel level, but yes most train horns are illegal as are most yacht horns (at least for on road use).