grumpyvette

Gaswelder.html

Mobile DC Welding Equipment Designed for Use in Remote Locations

TIG Welder

Classic Broncos .com - Home Made TIG Welder * 66-77 Early Ford Broncos

http://www.green-trust.org/junkyardp...oArcWelder.pdf

Sonix

iTrader: (1)

extremely cool!

grumpyvette

more stuff the wifes not likely to approve of

http://www.diyporting.com/flowbench.html

Flow Bench, by Michael Doty

EZ Flow System (affordable cylinder head flow bench kit, electronics, and
software program)

Flowbench Parts

Standard Abrasives - DIY Cylinder Head Porting Guide

FAQ

http://www.tractorsport.com/cgi-bin/...5b1;act=SF;f=1


MORE STILL

DIY Air / Fuel Ratio Meter

Pelican Technical Article: Building an In-Dash Air-Fuel Monitor

D.I.Y. air/fuel ratio meter

Celica All Trac and Gt-Four Air Fuel Meter Tuning

fuel injection and carburetion performance tools

Jaycar DIY Air

Dummy's Guide to Building the DIY-WB

https://micro-craft.com/Merchant2/me...egory_Code=AFM

406TPI

iTrader: (1)

Sonix

iTrader: (1)

Alright, i'm making the lawnmower powered arc welder on sunday, as per the link in the first post on classic broncos.

AlkyIROC

http://www.blindchickenracing.com/to...bingbender.htm

http://www.ag.auburn.edu/users/parme...les/flowbench2

www.autospeed.com/cms/article.html?&A=0798

www.autospeed.com/cms/article.html?&A=0348

www.majorleagueduning.com/tech/Brake/Brake.htm

dr1

sweet brake, sure beats my vise and a hammer :P

Sonix

iTrader: (1)

Alright, so I goofed. I have a CS105 or something like that, with a serp pulley on it. I measured the shaft at .675" or so, and bought a 5/8"bore v-belt pulley <-- 5/8" = .625"
So it seems like the typical alternator shaft is 17mm. It's not easy to find a V-belt pulley with a 17mm bore, from an industrial supplier. Doesn't look like parts stores sell just the pulley Damn, looks like i'll be JY diving now...

ryan91rs

iTrader: (1)

i want to build one but i have not found a site that gives me a step by step yet. know one?

Sonix

iTrader: (1)

Did you read the first post? The one from the bronco's website is pretty self explanatory, i'm using that one. No wiring required.

ryan91rs

iTrader: (1)

ya but i don't want TIG. I want to use arc or rods. But maybe just don't use the gas and it will work?

AlkyIROC

TIG and MIG need the shielding gas.

Sonix

iTrader: (1)

Yea, exactly. ARC welding uses rods.
The one from the broncos one, just without the gas valve and gas bottle = TIG.
They've show it wired up as DCEN, but you can swap ground and torch and have it DCEP. Your choice.

83 Crossfire TA

iTrader: (2)

The Bronco’s site is a rip off of the original thread that I think was on the Hobart weld forums, which after some arguing finally gave credit for at least the pictures to Craig who originally started the thread, took the pics and made the drawings.

Craig is local to me and I was over playing with the setup originally, and also made my own, both of us used 135A ford 3g alternators, which are easy to get at the JY off of a Taurus or similar car (they had versions o f that alternator with at least 3 different outputs, the high amp version has a different size pulley then the others).

His was a simple bracket hanging the alternator off his upright compressor, pop the belt off the compressor and put it over the alternator pulley. If I remember right I think he just swapped the orginal serpentine pulley off for an older v-grove.

Mine was a set of mounts attached to a 2x8 or 10, and I modified a serpentine power steering pulley to fit the shaft/key of the motor that I used to power it. I have pictures of it but my web server has been down for a bit.

The original setup was done using a battery to power the field coils through _I think_ a mopar light dimmer switch. I dug around for a while and couldn’t find one that had the right range of resistances, so I ended up using a battery charger and an assortment of things to knock down the power from high amp wire wound resistors (running It almost wide open and just moving fast, a 20A/240VAC motor will not power this thing wide open, it will stall). I also used a wire wound rheostat, and finally ended up using a dimmer out of my ’83 TA. Later I used a computer power supply to power the field coil and set it up with 2 ranges, a high and low using the 12 and 5V circuits and the dimmer in each range to fine tune.

Sonix

iTrader: (1)

THANK YOU!!!!
I desperately needed some help here.

-Can I just use a dimmer switch, ie the style for a home ceiling fan? I have that for my die grinder, I figured I could just move it over for this application? Or do I need a DC dimmer, like for the dash lights of the car?

- Anything special about the Ford alt? Any way to identify it? Year of Taurus perhaps? I've got the GM CS style one, and i'm not sure which wire is which on it... (other than the big one being the power output...)

- I'm going to use V-belts, so I need to hit up the JY for the pulley anyway.

- I've got a 6.5HP gas engine, think that's got enough jam?

- What kind of welding range do you think I can get with a dimmer switch, and a car battery setup? The battery is just to power the field coil, so it'll control how much output I get? Give the field max battery power (no "dimming") to get max power, or regulate it down (dim) to get less power right?

- I figured i'd just rev the engine up to ~3000RPM, which is say 5000RPM at the alt, then use the dimmer switch to control how much i'm loading the gas engine. Think this'll work?

83 Crossfire TA

iTrader: (2)

Both the AC applications are probably SCRs (they take and chop off part of the AC wave, so the load still sees full AC voltage, but only sees it part of the time so it doesn’t generate the same power/go as fast, want a fun toy, hook one to an ignition coil, the coil will see it as an on/off firing signal, of course, at 120V). Induction motors are speed controlled by changing frequency usually using something called a VFD (variable frequency drive).

You really need a high amp, variable resistor like a wire wound rheostat, and a fairly small value to make it useful, I don’t remember exactly, but I think something in the 15ohm range was optimum, more than that and as far as the circuit is concerned it acts more like an on/off switch rather than a variable source.

Cheap, easy to get, high output, internal cooling fan, and easy to bypass the internal regulator (you hook up your 12V source/pot to the field coil directly, the welding terminals to the output directly). You can use anything, but I wouldn’t waste my time with anything rated less t hen 95A. Craig (the guy that the info posted on the bronco’s forum was ripped off from) was working on a portable, gas powered one using a lawn tractor engine with 2 high output Chrysler alternators. Identifying… see my first post.

Probably, everyone that I’ve seen do it with a gas engine has used a 10hp one. I used a “5hp” electric motor rated at 15 or 20A @240VAC (to be a real 5hp motor I think it has to draw somewhere in the 23A continuous range), so although an electric motor has more torque, that gas motor should make quite a bit more power. I know that I was able to stall my electric motor with the 135A alternator wide open.

Power out will be limited to input power (as in how fast it’s spinning AND voltage to the field coil) till you run out of input power or burn out the field coils.

Yep to the rest of the question.

Sounds about right, I worked out at what rpm this thing would have maximum output with that alternator, and if I remember it was more than 5000rpm (don’t remember exactly right now), but it didn’t matter because my motor wasn’t able to spin it with the full output of the battery charger across the field coil terminals.

Mathius

There was a guy working on building a TIG pedal that would work with the HF $200 Tig. I wonder if that setup could work with your alternator driven setup? Would be better than the dimmer I think. Or you could actually probably put a tab on the dimmer switch and rig it to a pedal setup.

Problem is, I can't remember where I was reading about it. Might have been usenet, and I never bothered to figure out how to setup newsgroups under Time Warner Cable.

Mathius

Sonix

iTrader: (1)

Awesome, thanks for the info!
You lost me on your first paragraph, so i'll just smile and nod there.

I won't take any chances then, i'll just grab the Ford Alt, and dimmer switch.

Yea, I read the one with the TIG pedal, I think it was a reworked sewing machine pedal perhaps. I'll do the upgrade to TIG with a pedal later on down the line. Stick with a **** for now is fine.

83 Crossfire TA

iTrader: (2)

Heh, I totally forgot about that… just before I picked up my miller synchrowave I got a sewing machine pedal working with mine. I found an old school one with a carbon pile in it, like I mentioned before, the resistance was too high making it more of an on/off switch, so I took it apart, removed most of the carbon and replaced it with a chunk of aluminum rod that I cut as a spacer to take the removed carbon’s place, that worked great.

I also figured out how to do the gas thing with a N2O solenoid that I had sitting around. Basically I used the field coil side of the circuit to trigger a relay that switched the N2O solenoid, and then put a capacitor across the relay terminals to keep it closed slightly longer then it has a signal to give me some post flow (I’d have to go looking for a value, I just tried a few that I had sitting around till I got beteen 5 and 10 seconds).

Sonix

iTrader: (1)

Ah, N2O solenoid, that would work....

I've read part of the thread from turbomustangs, and the miller forums now. It looks like the dimmer switch works, but isn't ideal. There are some electronics specialty stores nearby, what would be the *ideal* resistor there? A 1 turn pot going from 0-20ohms?
It only needs to handle the power going to the field, so not a whole whack of current right? 130VDC, <1amp?

83 Crossfire TA

iTrader: (2)

You don't even need 20ohms, i think i was using one that was right around 12 or 15, and I think I was probably the one that suggested that the dimmer isn't perfect on turbomustangs (I'm Silverback just about everywhere else on the 'net).

The field coil is just seeing the power from the battery or charger or whatever you’re using, so something like 13.8VDC but 2 or 3A if I remember right, a rheostat that can deal with that many amps _will_ get warm.

Sonix

iTrader: (1)

Yea, I figured that was you, same sig and pic as here

Ok, so a 0-15 ohm rheostat/pot/variable resistor that can handle 50W ? I'll see if I can find such a thing...
Thanks!

ghettocruiser

iTrader: (4)

Man I want to try this. I want to use a GAS motor though. I dont have the electrical capacity at my house to run 220 to power a motor right now. House/wiring is too old. Maybe some day when I can upgrade the house's wiring. But I guess by then I can just buy a good TIG. haha.

Im going to track down a nice gas motor, and an alt. and start playing I guess.

J.

Sonix

iTrader: (1)

Thats exactly my motivations ghetto cruiser. I rent a house, so I can't rewire the garage, and even if I could.... $$$$$$$.
So instead I used the 6.5hp gas lawn mower engine from a Sears mower with the self drive function.

I purchased a 0-25ohm 50W rheostat from digikey, along with brackets for it. I should get that tomorrow afternoon. I'm going by the JY tonight for the Taurus alt, and i'll scavenge a V-belt pulley off another alternator somewhere. I found a press-fit 6" V-belt pulley at an industrial shop, which will go on the 7/8" mower shaft. I'll probably do this up on sunday.

ghettocruiser

iTrader: (4)

Definetly put up your results! Ide be curious to see how you make out.

J.

Sonix

iTrader: (1)

Sure enough, I always leave ONE tool behind... 7mm socket.
So I'll try tomorrow to get the alt.
I checked 94-94 taurus' (those are very common). The alt didn't have the fan on the outside, but the pulleys were the same between a few cars. I assume this is the right alt?

Mathius

Hm. Not the same one I'm thinking of then. This guy actually fabricated a pedal setup from raw steel. I never understood why he went through all the trouble. If it were me, I'd try to get a real TIG pedal to work. It would be worth the extra cost. But if I could remember where I read it, the technical details were very good. I'm thinking it was usenet, and the information is probably long gone.

I suppose if I have extra time this weekend, I can Yahoo for HF Tig pedal and see what comes up.

Never would have thought to use a sewing machine pedal.

Mathius

ghettocruiser

iTrader: (4)

SWEET!!! I just got my hands one two gas generators. Both have 10hp motors. One has a hole in the block, but the other should be ok. They are already mounted in a frame, have a fuel tank, and plenty of room to mount the alt and electronics!

Im gonna take them both home next week and try to get one running. They are side shafts too. So that should make mounting and hooking up the alt a breeze.

J.

Sonix

iTrader: (1)

Ok, I got an alt from a 1995 Taurus. I checked a bunch of them, they all had the same alt, roughly a 2.3" OD serp pulley...?
It's got the main power wire on a stud on the back, a 3 wire plug, and a one wire plug. Which is which there?

Sonix

iTrader: (1)

Apparently the 130A version of the 3G is different in that it's mounting holes are 180* apart. The 95/105A versions are not. I'm going to go look and see what I have...

Mark - I found this wiring diagram online, showing how to retrofit this into a mustang. Do I wire it up like this, but connect the 12V battery (or actually in my case a 12V computer power supply), to the "I" wire? With my resistor inline there? Then ground of the computer power supply in parallel to the ground of the alternator ?

Then I just hook up my welder cables to power and ground, and I can swap depending on if I want to do DCEN or DCEP eh?

Thanks

83 Crossfire TA

iTrader: (2)

I found a few in progress pics...

83 Crossfire TA

iTrader: (2)

a few more... the last one was the first bead, before I had a anything to really control power output or the correct sheilding gas.

83 Crossfire TA

iTrader: (2)

They made them with different case tabs, so that’s not a reliable way, the regulators bolted to the back of them are some indication, but you could have had a heavy duty one on a smaller alternator. Like I said before, the 130’s have larger pulleys, they measure roughly 2-5/8” and the others are somewhere just under 2-3/8”

Again, you don’t use the regulator, there should be a good wiring diagram in the bronco’s thread. Nutshell: field coil circuit uses the regulator mounting screw closer to the plug as a positive and the screw farthest from that one, shorted to the case as a negative (there’s a big threaded boss on the back o f the case that makes a nice place to screw a lug to). The welding leads: the “ground” lead connects to the positive lug and the torch to the case, I used the same case lug (tig welding, for that matter most stick welding will be DCEN with this thing).

Sonix

iTrader: (1)

I couldn't find any wiring diagram on the Bronco's thread, just that one on the page at
http://classicbroncos.com/homemade-welder.shtml

It's a little unclear, only shows 2 connections. I've wired it up like this (see attachment). Is that right? Based on that "how to wire up a 3G" it seemed like the right idea...? But it seems opposite of what was done on the Bronco's page... Will this work or...?

Sonix

iTrader: (1)

Ok, found another diagram online;

From this source it makes me think:


Center "S" terminal, still connected to lone other plug, "Stator"
Far terminal away, "I", should be left blank - no connection (right?)
Closest terminal "A" should be wired to 12V (through rheostat).

How's that, am I getting closer? This info is all I need before I can test it out.

Sonix

iTrader: (1)

Ok, I wired it up the way I think Crossfire was trying to tell me:

Center S terminal to "Stator"

far terminal "I" to ground
closest "A" terminal through rheostat to power.

Nothing happened...? I revved it up good, but no spark. No voltage across power and ground of the alt. There was 12ohms across rheo, then I tried it with 5ohms - no dice.

12V is coming out of the computer power supply though.

Mark, you got any suggestions?

83 Crossfire TA

iTrader: (2)

Reread what I wrote before, YOU DO NOT USE THE REGULATOR. You can see it in this picture, not only is the regulator partially disassembled but the harness bit that is left is tied in a knot:

http://classicbroncos.com/img/tigwelder3.jpg

In that pic the green wire goes to the screw, the case and your power supply (and you can connect your torch to that if you use the big lug that I mentioned), and the blue wire is the positive and goes to the first screw holding the regulator down.

There’s 2 wiring diagrams at the top of the page on the bronco’s site showing this also, they were all done by Craig, who’s the guy that originally did this and posted it on the welding forum.
----------
Oh, the Classicbronco's site has ***** bitching about linking to a picture that they stole from another site... at least it looks like it's working now.

Sonix

iTrader: (1)

Ok, you were serious about using the screws holding the regulator down...

So I can simply unplug the plug going into the regulator? Those wires tied in a knot made me think it needs to be jumpered across two wires? Also, do I do anything with the stator wire in that seperate plug?

Then i'll just run the power from my power supply, through the rheostat, and into that first screw holding the regulator down, (blue wire in that picture).

If that sounds good, i'll give it a shot tonight then. I'm itching to test this out again.

83 Crossfire TA

iTrader: (2)

None of the other connections do anything, doesn’t make a difference what you do with them, just don’t use them in your circuit… you could ditch the regulator if you wanted to but I was warned that it’s mounting bolts hold some of the inside terminals together and that the alternator would fall apart if you did that so I didn’t try.

Sonix

iTrader: (1)

Ok, I see where I was screwing up. Those two screws on the regulator? One had a little plastic cap on it, I was about to post and say "what other screw?!?" But I figured I should probably look closer first. I removed the regulator and saw how it worked (it's the brush holder, like in a power window motor). Then I realized there's a plastic cap on it.

Well it works, sorta. It's a bit underpowered, I keep stalling it out. If I bring in more resistance, I can make a nice short arc, (similar to 50A on my other stick welder) but I was using 3/32" 6013 rods, so I wanted to try bigger. With more power it kept stalling it out, so I need to fiddle with the resistor, and then try to "soup up" the motor.
It's pretty old and tired, a new air filter and spark plug ought to wake it up (hooboy, I make fun of people for hot rodding 4cyl engines, and now i'm doing that to a 1cyl... sad). Also my alt isn't square to the engine, not even close. I just wanted to see if it worked, then i'll put more time into making it work well.

Thank you very much for your time, patience and expertise Mark, I couldn'ta done it without you.

Now to satisfy everyone on this forum (all, 2 people?), turbomustangs, hobart, etc, I'll supply some PICTURES, and even a movie of me using. Once I learn how to do some video editing. I left my belt off and my highly intelligent roommate managed to get a stellar shot of my *** while I bent over to adjust something....

Mathius

My buddy is a computer programmer, currently working at a trucking company. He's rewriting all their internal software. It's a pretty big company..

Anyways, they had a power outage like the 2nd week he stared there, and so he went out with the maintenance guy to check out the generator. He's a handy guy, and he said there's a lot of pretty dense people working there.

He said the generator for the building is powered by a SBC.

That'd make a hell of a motor for this project, eh?

Mathius

Sonix

iTrader: (1)

Alright, as promised:

Right click and save as, then open the video's

This was done on thursday, Oct 18th, night. I finally got it together and got it running, but it would run out of power if I ran it with low resistance (high power), and would stall out.

http://shotgunsurgery.com/jayknopp/welder%20test1.avi

This is from tonight, friday oct 19. I reinforced the area that the alt hangs from, to try to get it more stable. It now has enough jam to keep up an arc at ~6ohms resistance.

http://shotgunsurgery.com/jayknopp/welder%20test2.avi


And heres a picture of the weld I did in the second video. I desperately need this welder to practice welding.
http://shotgunsurgery.com/jayknopp/w...tor%20weld.jpg

I've only used it for a short period of time, two nights in a row. I want to tinker with it during DAYLIGHT, so I can try it out more thoroughly. I'm also going to change the plug and remove the air filter probably.

As much as 8ohms makes the thing make pretty tiny welds, so I think a 0->10ohm rheostat would work best. I'm going to order one from digikey. The one i'm using now tends to drift a bit.

Also, that weird "squeeeeeek" that was mentioned on other forums - that only happens when you first strike the arc. Someone at work mentioned that may be the belt slipping when it's first loaded heavily. I think that makes more sense than "high frequency DC welding"

I still need to finish it up. The table has 2 other shelves that i'll install, then put on the wheels. Add in a nice user-friendly rotary dial pot and i'm laughing.

83 Crossfire TA

iTrader: (2)

I hope whoever was shooting that video had some sort of UV protection or after all that he’s going to be doing the “arc eye” thing…

A couple of things come to mind reading your comments and watching the videos:

You need to play with pulley ratios and/or the engine governor… as long as you’re not trying to push more then what the engine is capable of (did you say it was like a 6.5 or 8hp, at 100% efficiency it takes 3.1hp to push 130A at 18welding volts, this thing should be a bit more efficient then a transformer driven welder so I doubt it would take more than a real 4hp). That should be enough), the governor on the engine should keep the RPM fairly steady. I suspect that you might have too much of a pulley ratio there and you’re just trying to turn the alternator at more of an RPM then that engine has the power to (maybe the engine is just worn out… a little N2O might help). When you get it right, this thing will easily do the rated output of the alternator at 100% duty cycle. I suspect with enough HP driving it you could push the big ford alternator to around 175A or so without cooking anything.

The squeeeeek I’m sure is the belt… I tried all sorts of tensioner assemblies on that setup that I posted pictures of and finally found that with a full load almost all of them got tweaked or moved, I finally figured out where the tension was when I thought it was right and cut a solid board to use as a spacer between the 2 so it couldn’t move and that finally controlled my belt slipping, and a 6 rib serpentine belt will transfer a lot more power then any 2 v-belts at any reasonable tension. Honestly, you’re probably about at the limit of the belts unless you’re using something industrial. They make rotary welding power supplies that use v-belts and come with 4 and 5 rib v-belt pulleys.

Rheostat… I could have sworn that somewhere in this thread I suggested going with something in the 10-15ohm range but don’t see it now. With the tig torch you can weld at a much lower power than with a stick electrode (unless you’ve found some very small stick electrodes somewhere) and I found that between 12 and 14 ohms gave me the full useable range with a tig torch.

“high frequency DC…” heh… you’re welding with DC, there is no “frequency,” BUT, if you were using a motor to drive it rather than an engine there is a very cool high frequency “whistle” to the thing. It seems that the rectifiers that these things use are not full wave/perfect and there is a bit of a high frequency AC voltage escaping from it that has a kind of cool stabilizing effect. It’s a bit like welding with a TIG welder with an HF arc starter/stabilizer. I believe that it’s the reason why you can get a steady arc without the choke in the output leads that a traditional welder would have, I also think it makes it easier to start and maintain an arc with the thing.

Finally, looking at the bead you made, not picking on you but it looks like the welder is working fine, and looks/sounds like you have a pretty good, steady output from it, but you’re not keeping your hands steady. Usually it helps if you steady your hand with your free hand but it looks like you’re doing that, I would strongly suggest that you try setting up something table like that you can lean your arms against that doesn’t move like your body/legs that you’re using in the position that you’re welding in now. Once you get a hang of that welding in other, more uncomfortable positions comes naturally.

Did you mention what kind of rod you’re using?

Sonix

iTrader: (1)

Holy cow crossfire, you're good!

I had bought a 3.5", 5/8" bore pulley for the alt (which obviously didn't fit, it's 17mm, not 5/8"), and a 6" pulley for the engine. After getting a pulley for the alt from the JY, which was a 2.68" pulley IIRC (the stock alt pulley size) I ended up with a 2.3 ratio speed increase.
I used an optical tach on the engine, and found it was 3200RPM when running full tilt - so about 7300RPM on the alt. aha! So I got a 4" pulley now, so I'll be running the alt at 4800RPM, which I believe is about perfect to get max power, and not bog down the engine.

I told him not to look at the arc, but through the filter of the camera, who knows... He never mentioned itchy eyes...

Rheostat - yes, you did mention 10-15 ohms, I just couldn't for the life of me find a 15ohm rheostat. I assumed i'd need the 10-15ohm range, so I got the closest one above, 0-25ohm. Now, even with the pulley setup on there, 0-10ohms is what I want, so I can have some adjustability. $27 for a 25W one from digikey, or maybe i'll make something with a lower power handling one, and a pair of transistors. Someone at work was explaining how to do this circuit, maybe i'll pick his brain again.

In the videos I was using 3/32" 6013E rods. I have some (edit)-> 5/64" 6013E, and some 3/32" 6011 and 6010 rods at home. A decent selection.

You're certainly right about the bead, I only gave myself 10' of wire for pos and neg cables, so if I want to run the engine outside (and not in my garage) I can't reach my work bench, and vice. That leaves me trying to lean over something on the ground (and in the dark in the videos). I'm not in the best position, that's for sure. I also don't have much practice stick welding, that's the main purpose for building this welder - log some practice time. I'm going to get some scrap metal from work this week, and burn some rods playing with it.

83 Crossfire TA

iTrader: (2)

I wasn’t able to fine a rheostat cheap either from a normal source, I did a few things:
- I did finally find one at a Hamfest, 2 bucks admission, an hour worth of digging through old crap, $.25 for 2 rheostats (I also brought home $30 worth of the old crap, oh well)
- I mentioned that I took the carbon pile apart in a sewing machine pedal and removed carbon disks till I got the range that I wanted
- If you run a resistor in parallel to your rheostat you will lower it’s value ( 1/RT = 1/R1 + 1/R2 +…, where RT is total resistance, R1 is resistance 1, R2 resistance 2...
- If you look hard enough you will eventually find a car light dimmer that will work. I think that Craig used one from a bronco or some similar ford product, I found that the weird ceramic one used in the 3rd gen firebirds worked OK, I don’t remember if I used any other resistors in the circuit.
- For a little bit I used a big wire wound resistor that I cut through some of the insulation and got access to the winding and just clipped an alligator clip to some part of the middle of the winding which gave me part of the total resistance

Power supply… easiest way is to use one voltage regulator transistor that has a value just under the smallest value that you might want (say a 1.5V voltage regulator), then hook it up and a potentiometer as a voltage divider to add the additional voltage back to the output. Basically you end up with your power supply, the voltage regulator, potentiometer and usually a few capacitors to filter out any noise in the output, it’s the most basic variable DC power supply design, you should be able to find a good schematic for it anywhere, worst case, the old radio shack project handbook. Figure out how many amps you’re drawing before you waste your time on this so you get appropriate transistors. You might find that this ends up more expensive then ordering a proper rheostat if the current draw is too high.

5/16” rod… that’s some manly rod, not sure that this thing will be able to burn that well… the 3/32” should work great and is small enough that when you get it down you could even do a good job on relatively thin exhaust with it.

Sonix

iTrader: (1)

Ah, I might just find a 50W resistor and run it in parallel with my existing rheostat, that'd be simpler. I know how parallel resistance works, why can't I think of these things on my own?!?
Yea, I typo'd there, 3/32" and a bit of 5/64".

When I eventually upgrade this to TIG capability i'll make up a foot pedal for it. For now, I think the **** is ok. Also, I can just slow down the engine, rather than needing higher resistance... 6 of 1 half a dozen of the other eh?

83 Crossfire TA

iTrader: (2)

you said you're using a computer power supply... use the 5V leads rather then the 12V...

Sonix

iTrader: (1)

Yea, 5V leads would give me really fine control on a low heat setting, but i'm looking for more fine adjustment on the higher end of the spectrum.
Higher voltage at the field coil is more power right? I'm thinking about finding a 20-25ohm resistor that can hold 30W, and put that in parallel with the rheostat. A co-worker suggested a 12V automotive lightbulb, maybe a tail light bulb or something. I'm going to measure the resistance on that later tonight.

83 Crossfire TA

iTrader: (2)

radio shack has become such ****, but I had a few of these sitting around in a few different values and used them, they used to come in 2 packs for under $3:
http://www.radioshack.com/product/in...entPage=search
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remember that light bulbs will change resistance as their temperature changes.

Sonix

iTrader: (1)

Hmm, I didn't realize that about the lightbulbs. I'll drop by radioshack/the source/whatever on the way home and see if they've got any of those current ones.