Two questions pop to mind, after dinner:

1) There are many 12-volt water pumps at reasonable prices from the RV suppliers. Why not use one of them?

2) I have done a fair bit of TIG welding with my Miller from 3/8" steel to 0.016 aluminum and have simply used an air-cooled torch. I can see water cooling maybe for heavy aluminum, but then is your 150 A welder up to that? In other words, why do you need water cooling?

John

 

Centrifugal pumps and even flexible impeller pumps are really not a good idea for tig torch cooling. More than enough volume, but inadequate pressure. They minimally do the job, as many will attest, but actually aren't up to it on a 25ft cable run (with 1/8 to 1/4 in id water line!!) or if the cable gets kinked or pinched even a little bit. And it gets even tighter at the torch head. It has to maintain throughput at 15psi to 30psi but possibly higher if needed. That's why all the professional coolers use a vane or gear pump. Both have great pressure capability. Gears are supposedly louder though longer lasting. For a home shop it really doesn't matter between the two.

Just about every pro cooler I've seen is WAAY overrated for use with one torch. 1/2 or more hp coupled to a midsized Procon brass bodied pump. That motor alone already weighs as much as my whole cooler. These will pump ten times what is needed for one torch at three times the pressure. Good for any pro shop with multiple users. The problem is that AFFORDABLE compact pumps of this type are extraordiarily difficult to locate. Electric fuel pumps are often gear pumps, and in the range of usefulness, but are very noisy, usually poorly constructed unless, again, very costly, and not really suitable for water. An 'oscillating piston', or
'vibratory' pump was an idea that I was interested in. Extremely compact and right in the range I needed. I would have gone there if the MicroPump I finally found hadn't turned up on ebay. Another good bet for a very small cooler would be the smallest version of Procons brass body series coupled to a small 1/15hp motor.

The coolest (so to speak) version of this would actually be one of those vibe pumps plumbed into some thermoelectric/Peltier type component and tucked into something the size of... heck, you could probably put that right in the welder itself. As far as I was able to tell tho, that technology just isn't quite up to the task yet. But soon, no doubt.

Why water cooled? I learned to tig weld at a factory when I once worked on the assembly line. There was a 'special projects' shop tucked into the back of the building that had all sort of cool toys to play with for building prototype stuff in house. I would hang around after my shift quite often and get as much time as I wanted on the Miller welders they had. All they used were water cooled torches. Granted, the machines were much higher amperage, and were often used for heavy gauge metals. But the sad fact is that I learned on a water cooled torch.

Few years later I decided to take an intermediate tig welding class at the local college and all of the Miller 250 syncrowaves for student use had gas cooled torches. Quite fine of course. But I'd learned on power steering, so to speak, and this manual stuff was a drag. The difference in heat to your fingertips even at medium amperages is considerable, and the gas cooled torch itself is heavier, bulkier, and the cable much less flexible. The Aerowave at the college had a water cooled torch and it just felt like home to me.

So eventually I am able to spend 2200 dollars on my own tig welder after finding the Thermadyne ArcMaster 285 AC/DC on sale online. I've been using it for a year now and am happy enough but yearned for the water cooled luxury and lightweight, esp since my hands are smaller.

Interesting that welders are increasingly, especially now that the technology is mass produced enough to bring costs down to the consumer, going inverter style ... yet the only water cooling available to the welder is still the relatively 'old school' Bernard cooler that weighs three times the welder itself. Miller and Lincoln go to great lengths to tout the lightweight and portability of their inverter welders. They've got suitcase handles on top in place of hookeyes for god's sake. I realize that you're always going to be rolling around a cylinder anyway, but eventually it does come down to rack space, total dimensions/weight, and (sorry but) aesthetics. There are a few european companies that make coolers the size I've built, but no interest in them thus far here in the states.

So I got bored, and by now a little obsessed perhaps, and decided to build my own.

I do mostly artwork although occasionally will build/repair what needs building and repairing around here.

 

What are the flow and pressure ratings of the gear pump you will be using? Is the motor separate? What type of motor is it (e.g., brushed, shaded pole, etc.)? Some motors may actually be able to work off of the wall converter you described earlier. For example, hair drier motors will often work; although, they are lower power.

John

 

Here's a smaller one: http://www.allelectronics.com/cgi-bin/item/TC-500/790970/500W_UP_DOWN_TRANSFORMER_.html

Might look cute as a "tail" atop the cooler & behind the suitcase.

 

And here's a 12V/2A gear pump for only $40. John

http://www.crazypc.com/products/93340.html

Edit: Was listed as a gear pump, but on re-reading its specs., apparently it is not. Another inexpensive option would be an automotive fuel pump.

 

I'm not that good with the math for matching wattage headroom to amperage requirements at mixed voltages (whew!). Is 500watts adequate to run a 120vac 3.5A motor along with a 120vac/12vdc smps feeding approx 2 more amps of load?

 

The impeller housing on a centrifugal pump is characteristic. Usually entering from the front and exiting from the side as that one is. PSI specs on these are notoriously misleading. Kind of like the hp ratings a Shop Vac. Sure it will produce 6.0 horsepower. I think they call that brake hp or something equivalent - you'd realize it for about as long as it takes a good sized screwdriver jammed into the impeller to stop it's momentum. The marketing guys apparently didn't get the memo that I'm not likely to use it this way.

At 50psi (claimed in its specs) that dangerden pump might actually squeeze a drop or two of volume out of a pinhole. The only way to read psi on a pump is to see the curve on a graph. I'm guessing that the reason overclocking suppliers don't offer gear pumps (they'd be perfect solutions otherwise) is because of the very high premium that buyers put on noise level. Centrifugals can be almost silent.

About 1gpm at a reliable 30 to 60 psi is not a popular range apparently in circulation pumps. The inexpensive line of small gear pumps for lab use are usually very small fractions of this. The Micropump that I'm using sells for almost 700 dollars new (sans motor!).
There are a handful of this type
http://www.clarksol.com/html/prodspecsMonoOscPump120.htm
out there that look really intruiging on spec. They just edge into the right territory and are as compact and simple as it gets.

Anyway. Getting too off-topic here. But I though someone might be interested in some of this stuff. By the time I'm done with this little project I'll wish for some way to rid most of this useless knowledge from my head. I'll never (with any luck) use any of it again.

 

I'm not that good with the math for matching wattage headroom to amperage requirements at mixed voltages (whew!). Is 500watts adequate to run a 120vac 3.5A motor along with a 120vac/12vdc smps feeding approx 2 more amps of load?

120V @ 3.5A
P = EI
P = 120 x 3.5
P = 420 Watts
Ok, let's figure out the DC supply. SMPS's vary in their efficiency. Some are over 90%. Some are in the mid-70% range. Let's try the conservative end.
You say you have a 120V to 12VDC supply that is capable of 2 Amps.
2/.7= 2.86 (rounded up) - let's figure out the power
P = EI = 12*2.86 = 34.3 Watts
So, you need a total of 455.3 Watts.

 

Is the last word going to be that there is no means available to get 500w worth of 120vac out of 240vac short of an eight pound metal laminated brick?

If so I need to rethink things entirely.

 

Last word, first word, only word.

The power a transformer can handle is limited by the cross sectional area of the transformer core. Weight increases by the third power of the square root of the cross sectional area. Translated into English: twice the power needs almost three times the mass, three times the power needs more than five times the mass.

 

What Thingmaker3's referring to is if one is forced to deal strictly with 60Hz. Then yes, it's the first, last and only word.

That is why SMPS's have become so popular. The fact that they are using such high switching frequencies allows them to use much smaller transformers. I have a 400W power inverter in my car that is very lightweight. I haven't taken it apart, but it's likely mostly comprised of some MOSFETs driving a relatively small inductor to generate a 120V 60Hz output.

It's also highly likely how that 500W power conditioner module I posted earlier works.

The 8-lb laminated brick is likely to be your most immediate interim solution.

I don't see why it would be an insurmountable task to build a 240 to 120 step-down inverter, that would be much lighter in weight. It's getting it safely referenced to ground without loading the ground, and providing for circuit failures that would be problematic.

 

One further little oddity. Probably easily explained but it's thrown me once again.

I called a few distributors of these travel voltage 'adapters' to ask about running approx 300watts of motor load (my fan motor) on the 1600watt version of adapter. The instructions all state clearly that they are not applicable for use with 'electronic devices' including computers and such. They're used for small heaters, shavers, hair dryers, coffee makers, etc.

Two 'technicians' told me that it would work just fine, and two told me that the device would not handle a 300watt motor load for more than twenty minutes at a time unless very well ventilated. Might be that since it's in the airstream of my 200cfm muffin fans I'd be fine. I bench tested the unit to be certain of it's voltage before trying it on my fan motor and it only measured 70vac. Suspiciously close to half of what I want. I called back the 1-800 tech line and was informed that these devices are only designed for European current. Can't be used here at all. He explained that the U.S. utilizes two lines of 120 for 240 current and overseas it is 240 on one line against a neutral. I've figured that out by now but still didn't understand.

He went on to explain that these 'adapters' only take current from one plug, so it was effectively splitting 120vac from only one of the lines. Huh? Does that mean that you cannot use a dedicated 240vac device designed to work only in Italy here in the states if you wish to connect it to our two line outlets with a simple plug adapter? So 240vac on a multimeter may actually NOT be 240vac as seen by some devices? How does this apply to a transformer? Are some designed to work only with 240vac applied to one leg, neutral to the other, and others designed to work with 120vac applied to both?

Is this finally just getting beyond the realm of electricity 101 and should I back up and look for another way forward entirely?

 

I think we are all shooting in the dark here, as we know very little about the adapter you propose to use. Earlier you stated with reference to the converter:

A quick peek inside reveals a rather nice aluminum heatsink body around a Q383 transistor and a couple of other components with fuse.

To which I asked whether you are sure it was a transistor in the conventional sense or triac-like device. I suspect your voltage converter is simply a triac-based light dimmer (e.g., phase control), and it actually might work, depending on the type of motor in your pump. Do you know what type of motor it is?

I still think that a 12V fuel pump may be a viable alternative.

John

 

OK, I have a stupid question for you.

Did you connect the prongs across L1 and L2?
Or between L1 or L2 and neutral?

I find your readings very odd, also.
What was the voltage you were measuring at the input?

It MAY be that the adapter is simply defective.

I think whoever told you about the U.S. two 120 lines vs foreign one 240 line is full of camel excrement. A difference of potential is a difference of potential, no matter how you cut it.

What he MAY have been referring to is using US 240V on the adapter may be unsafe, because when used in Europe, the neutral/hot connections have different sized connectors, to make certain that one side is connected somewhere near ground potential, for example on an ordinary table lamp. Table lamps have the neutral line on the outside of the bulb socket. This is normally not a problem, because of the very limited current that the lamp may draw. This is not the case with items that have larger motors in them; once past a certain size the motors have to be either isolated from the case, or have the case grounded.

 

I did connect across L1 and L2. My meter read 244vac across them. Perhaps the adapter is defective after all. The person I talked with sounded more sales rep than technician, perhaps that's why I half consciously put quotes around technician in my post.

If I go the 12v motor route I can get a 12v motor of almost exactly the same dimensions as my current motor from Surplus Center (6.99) to drive my pump head. It would be a pretty easy swap. The psi i'm needing turns out to be relatively small on the range of this head (capable of 80psi and I only need 15 to deliver the flow I need) so I'm confident that the 12v motor would handle it. I noticed (for the first time) that most of my collected drawer of wall wart smps units are 120-240 rated input. yay.

Only catch at all is the timer relay that I've got (another story altogether, but part of the rube goldbergian inspiration behind this) has a 120v coil and 120 input to its little circuit board. This timer relay is the only thing I really can't swap out easily (without another big investment).

I still have a hard time understanding just how 120v and 120v makes 240v (seemingly) without a neutral. I think I even saw it referred to as +120vac and -120vac. Really? I must back up a bit at this point and get the books out.

Oh well. I'm going to step away from this for a while and get on with other things I've been leaving fallow. I can weld... just without my new water cooled torch for now. Thank you all, most sincerely, for the assistance. This thread is probably taking up too much space here as it is. I'll check back later this summer and let you know what finally came together.