Discussion in 'Shop Talk' started by DrippingSprings, Jan 4, 2005.

1. ### DrippingSpringsIn Remembrance

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Ok I have finally accomplished two goals.

1 I made a onboard air compressor to run impacts, inflate tires etc and have it mounted under the hood of my ford p/u using an old York ac compressor and a air can from a semi rig to hold the compresed air. I ran a impact for thrity minutes and it never bogged down. I can get 200 psi out it in about 15 seconds.

2 I just finished making a homemade welder out of an old 100 amp gm alternator and also have it mounted under the hood. (of course separate from the alternator that actually runs the truck)

So I can weld and use air tools off what I have under the hood of my truck for a total cost of about 120 dollars. Now I am reading 90 amps on the welder at the rod. How can I or can I somehow convert this to a generator as well? Like to run regular stuff IE lights electrical items etc? Also how much could 90 amps be in wattage? How would I hook it and to what to make it useful as a generator?

2. ### John HillGrand Master

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Hi.

Wattage is amps times volts, so you need to know the voltage across the arc. I assume this is quite low, so for say 10 volts that is 900 watts, a bit over a horsepower allowing something for conversion losses.

Are you useing a rectifier with that alternator? Maybe the alternator has an internal rectifier? If there is no rectifier in the picture then you could use a suitable transformer to convert the output of the alternator to a useable voltage for you tools and lights. Problem is though that the alternator is almost certainly multi phase, maybe three phase, and the frequence of the alternator will be way about the normal 60Hz. This means a special transformer. Maybe something from a ship or aircraft system would do the trick which I think are 400Hz. But you still have the issue of multi phase.

I think the easiest way would be to use an inverter on your battery and allow the trucks normal charging system to keep the battery charged up, inverters are expensive though. Of course you could use another battery and your big alternator to avoid that 'cant start the truck because I left the inverter running' syndrome.

I believe the alternator can be rewound for higher volts and single phase but the frequency is high, high frequency is not a problem for loads like lights and heaters and provided not too high is okay for 'universal' motors, such motors are in drills and saws etc and can be recognised if they have brushes and a commutator.

Lights and tools like that are happy on DC too but of course the voltage has to be high enough. Maybe you could use three cheap 12/115 transformers to convert your low voltage 3 phase alternator output to higher voltage 3 phase, then rectify it (using high voltage diodes) and you have something that might work.

Realistically though, I think the inverter is the most practical method.

3. ### Critter183Well-Known Member

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I really don't know how to make the alternator work as a power generator, but I do have question about air conditioning compressor. What is lubricating the compressor? In an AC system, the lubricant is carried in the refrigerant. It sounds as if yours will be running dry, and eventually sieze up.

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5. ### DrippingSpringsIn Remembrance

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The compressor I chose was a York compressor, which I got out of an AMC Eagle or Concord at a junkyard. York compressors are better for on-board air since they have their own oil reservoir, and don't let any of the oil get into the air you're trying to compress. They also put out more than most others as well

Thanks for the heads up and excellent information guys

6. ### CountrybumpkinWell-Known Member

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You got that rigged up to a pressure switch somehow? Was wondering how you regulated the tank pressure...

7. ### fordyWell-Known Member

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.............For a York A\C compressor.....simply take the 12vdc power lead that engages the electric clutch on the York and hook it to a standard pressure switch that you use for a 120\240 vac air compressor . then run a 12vdc to the same side of the pressure switch where you would connect the 120vac lead(s) . When the contacts Close the clutch will engage and the york will pump air to your tank . Assuming the pressure tank is grounded to the vehicle you will only NEED a single wire instead of two like the 120vac requires . You'll have an UNused set of contacts . If the pressure tank is mounted on a trailer or such you might want to run a ground wire to the UNused side of the pressure switch . The frame of the vehicle is acting as a Common ground which enables you to just run a Single wire IF the pressure tank is mounted to the same vehicle as the compressor .

8. ### Blu3dukWell-Known Member

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For converting the 12 volt into 110 you nned to build an invertor, buying one is about \$75 +/- , and building one can be done for under \$20..... big thing is a heat sink which can be scrounged from various places.

Parts and plans are available in varius places too.

William

9. ### staceyfbWell-Known Member

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can anyone tell me how you go about making an invertor. haven't been able to find anything to explain it.

10. ### John HillGrand Master

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Making an inverter IMHO requires skills, tools, materials and knowledge that are not found in every homsteader's workshop. Inverters are much cheaper than they used to be and I suggest they are one of those items tham are more easily bought that home built. As a parallel, I am sure you could build your own refrigerator if you tried but most folks choose to buy theirs.

11. ### staceyfbWell-Known Member

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I realize that they are fairly cheap nowadays. I am however one that believes that it is not what you buy its what you build.
I am not a homesteader persay. I live in the city but try to do all the stuff I can to live simple. I have a fully stocked shop. So any help would be appreciated.

12. ### John HillGrand Master

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I understand entirely, in fact I have made a number of things that in hindsight would have been cheaper and possibly better if I had just bought them.

With respect to inverters I can only advise a web search for an inverter kit, I know there are companies in Australia produce such things but you likely want something more local.

I understand simple inverters just chop up the DC to feed the primary of a transformer but when they do that the resultant output is not a sine wave. The importance of this depends on what you want the AC for and for many tools and appliances it is not a concern. However 115V of this almost square wave contains a lot more power than a true sine wave of the same peak voltage which may or may not cause you problems. Then there are 'modifided square wave' inverters which are sort of intermediate to the true sine wave types.

I have a small inverter that runs some electronic stuff in my vehicle, I bought that one but I did consider other possibilities. One thing I noticed is that PC UPS systems are pretty much an inverter, battery charger, charger combination. Unfortunately most are not rated for continuous operation but if you got one cheap enough you could bolt more metal to the heat sink and maybe experiment. The UPS I found has 24v battery pack which is what most of them seen to require.

The link provided by agmantoo was of great interest to me as I did not realise it was so easy to get 110volts from the automotive alternator, maybe no use to me though as the standard voltage here is 230.

I hope this is of some use to you.

John