Homegrown On-Board Welder

Damon Gentile

So you want the ultimate trail tool ?

This is an amazingly easy conversion that can give you serious fixability on the trail for much less than the commercial setups. For comparison, my setup ran under $200 for everything, including helmet, cables, clamps, rebuilt alternator, etc. Premier Power Welder, MobiWeld and Link-Arc start at about $600 or so.

I started with an alternator that I grabbed from the boneyard with my York air compressor for my CJ. It was 66A, low power judging by what other folks are running, but it was free and if I toasted a 25 year old Delco alternator I wouldn't exactly shed a tear.

 Some folks ask what I can weld with only 66 Amps. Well it does sound like a small number, but the rating was for 12V operation and we're going to bypass the regulator and that will bump up the rating. Also the DC current this produces will usually work better than AC, and require less current than a similar weld using AC current. It's not glamorous. It does however work very well.

 Well the first joy was to get the case apart. There are 4 small screws on the outside that hold the two halves together. I suggest unbolting them, but in my case they all were nice enough to snap off. At this point I took the photo and monkeyed around a bit.


Since I had no easy way to reassemble it, I got a rebuilt 66A alternator for about $25. I selected this as it was a drop in to my CJ and pretty easily available. At $25 it was pretty cheap considering a brush and holder set alone was about $15. Okay not having 25 years of New England winter let this one come apart.

 The photo shows all that's in the alternator. I did disassemble it before the photo and put the guts back in. It's all you need to know, though.


So what's what in alternatorville?

Looking at the photo above you can readily find the few components inside.

 - On the left, the cylindrical part is the capacitor.
- Upper Right : Brush holder is on top -broken in photo (brushes ride on the base of the shaft.)
- Also Upper Right : Regulator is below brush holder (you can see the electrical connections at 2 o'clock exiting the case.)
- Bottom : Large finned aluminum unit : diode pack.
- Also Bottom : Exciter Diode - mounted to the diode pack is a small black unit that connects the diode pack to the brush holder.
- Not shown is the Rotor. It's the part that spins around.

Yeah that's great. Now what ?

The basic plan of action is to give you control of how much the welder puts out. You'll end up controlling that with the engine's throttle. It takes only a brief modification to get the alternator into a weldernator.

0) open the alternator.
1) remove the capacitor.
2) remove the exciter diode.
3) remove the plastic insulation from the LEFT (in photo above) bolt securing the regulator & brush holder.
4) reassemble the alternator. Put a paper clip into the hole through the brush holder to keep them held back during assembly.

Note : You may want to keep the capacitor, diode, and insulator in the jeep to use as trail spares. Replace them and it's a completely usable alternator.


What did that do?

In normal (alternator) operation, the regulator adjusts the current out of the alternator to keep the voltage around 13-14V. It does this by adjusting how much current goes through the rotor.

 This modification connects terminal 1 on the regulator directly to the rotor. So when you put 12V onto that terminal, the alternator will go to 100% and you will have available the alternator's full potential. Keep in mind that the alternator can provide more current at higher RPMs, so you get more current for welding at higher RPMs.

What's next?

Well you need to be able to spin the alternator so find someway to mount it to the engine's V-belt or serpentine belt. I ordered a combo pulley from Brad Kilby of onboardair.com that let me replace my alternator's serpentine pulley with a serpentine/v-belt pulley. This let me keep the factory serpentine belt routing, and I just had to fit the welder where it could run from the V-belt side of the combo pulley.


In my case I ended up mounting the welder to a stock alternator mount in a non-stock location. This let me move the welder to adjust tension on the belt. The final location on my 4.0 was beside my on-board air compressor. I made an error in my mounting bracket such that the pivot mechanism doesn't really adjust the tension. What I should have done is rotate it 90 degrees so the 'pivot slot' is up and down, not side to side. (As it is, when the welder pivots, it doesn't get closer or further to the pulley so it doesn't affect tension.)

At this point, head on down to your local parts store and find a V-belt that fits. Just grab one and play bigger/smaller until you get one that you can work with.


There are two distinct sections to wiring, so let's look at the low power side first.

 You need a master on/off switch for the welder. Since the rotor can draw 4 or 5 Amps easily, a relay is in order. The system I came up with used an 'accessory' supply through a switch. That switch activated a relay that let 12V from the battery go directly to the rotor.

Now for the business end... Get two lengths of welding cable with ring terminals at one end. Bolt on one ring terminal to the + output of the welder. On the back of the new welder, there is a threaded hole. Use this to bolt on the other ring terminal.

 If you want to save some money you can probably get a deal on 'odd lengths' of cable at your welding supply shop. I wanted 50' of #4 cable. I got 49'8" of #1 at the price of #4!

At this point you can go ahead and connect your ground clamp and electrode holder to the welding cables. You will probably want a set of cable disconnects in line. I have mine about one foot from the weldernator. Get two pair of the same connectors so your leads can be interchangeable as to where they plug into. There are times when you'll need to change polarity.


What's left ?

Try it out!

I started with some old 3/32" E6013. I had relatively bad luck with it. It spattered all over the place and I could not hold a bead with it. I ended up getting a fresh box of 3/32" E6011 and right after I opened the package I put the remainder into a sealed storage tube. This stuff worked pretty well! I've since picked up some 1/8" E6013. It works nicely, too. Also, I have tried some 1/8" E7018. It was a challenge to get an arc to start and not stick, but aside from the learning curve, it's a great rod. Pretty easy to use once you get the knack.

After about 3 or 4 rods I was feeling pretty comfortable with the welder. It was not too tough for me to get the hang of it. One thing I did wrong was the angle of the rod. The proper position for the rod is to point slightly backwards, along the line that you have just welded. (I was pointing it forwards, a habit from Oxy/Acetylene welding.)

So after puttering around with it, I figured I'd give it a little exercise. Keep in mind that I'm a true rookie at Arc welding ! I can weld 1/8" plate beautifully. 1/4" plate took me 2 passes but I had it set up like I was going to weld with Oxy/Acetylene. I took a sample pass with 3/32 E6011 on rusted 3/8" and it stuck pretty well. I don't know that I would want to rely on one pass to hold something structural this thick together, but to hold my mailbox together it's more than adequate. (Yes I have a 3/8" thick steel mailbox!)

Since then I've gone through a few more rods and really have it down. Welds on 1/4" plate with 3/32" rod at 2000 RPM look great and hold well.

I was able to easily weld on some spring perches to an axle housing and also set a small stud onto the housing for a brake line fitting. Those were two operations that were pretty difficult with Oxy/Acetylene. Spring perches were difficult because the tube needs to get hot and it takes a lot of heat. And the weldor tries not to let it get hot enough to warp. The stud was challenging with O/A because you heat the tube and before the tube is ready to melt, the stud is starting to dissolve! Both welds were easy as pie with the Arc welder. I had the throttle set at about 3000 RPM with a 66A alternator throughout. It seems to work pretty well for me. Faster should get more output but a hotter arc could give problems with undercutting the bead and burning through the work.

In the past few weeks, I've really been using the Weldernator for just about everything that I could think of. My main goal was to get a feel for its capacity and capability. At this point I have gathered an assortment of rods, 3/32"  (6011, 6013, 7018) and 1/8" (6013, 7018).  3/32" rods are perfect for use on 1/4" plate with the engine at 2000 RPM.  1/8" rods work better up in the 3000 RPM area.  Given the choice, the 3/32" rod at 2000 would be my selection. It will weld a V-joint on 1/4" plate in one pass. 1/8" rods are pushing it with this setup. They are a little harder to work with and penetration seems shallower and the beads are much more protruding. Also I don't believe that there is anything thicker than 1/4" on my vehicle so I should be in good shape. Besides if you need to tackle a thicker piece of steel, just take a couple of passes.  Using the 6011 base and 7018 filler works very well.

Note: Some typical recommendations for welding rod:

E6013 : Great for visible welds. Quite easy to work / learn with. Medium penetration, medium slag. Best on flat welds. (rod +) Will help you build confidence.

E6011 : Not as "pretty" as 6013 but more penetration. Also good on metals that aren't so clean, like those rusted or oily. Works well in welds on angles/overhead and for filling gaps. Very light slag formation. Easy to strike an arc with and great for tack welds, too. (AC or DC) Excellent penetration but damn ugly with a lot of spatter.

E6010 : Very similar to 6011 but will only work on DC only. Supposedly better than 6011. (DC)

E7018 : Not as easy to start an arc as 6011 or 6013, but it works well. Strong and leaves a very clean weld area with no spatter and a distinctly ridged bead. Once you get the knack of this it will handle 95% of your jobs. Heavy slag formation. This rod depends on the molten slag for shielding and as such, it requires a very small arc, 1/16" or less. Larger arcs can cause slag to be trapped in the weld bead. If you whip or weave, don't remove the rod from the puddle. Required on hard to weld steels like those high in Phosphorus or Sulfur because this rod traps minimal Hydrogen in the bead, so there is much less chance of the Hydrogen reacting with the trace metals and popping the bead free.  (rod +)

As a side note, In the pipefitting industry, code specifies the first pass to be done with 6011 to fill the gaps between pieces, then come back and finish the bead with 7018. Try it, it works
very well.

All in all, it's a nice weekend project. Especially for someone like myself without an Arc welder in the shop. It adds a lot of flexibility. I have not needed to use it on the trail. Yet! But I always carry the cables, rod, and helmet. (If you want to splurge, get a self-darkening helmet, much easier to deal with!)

One other parting note : Sometimes you will want to have the rod connected to the + side, other times to the - side depending on what you are welding and what you are using for rod and your welding position. If you are welding on your own vehicle, you must connect the rod to the + side. If not, you will essentially short out your vehicle's charging system and battery. Needless to say, this would cause serious damage!

A couple of useful links:

What does the rod number mean?
Lincoln Electric
Text and photos copyright 2001 Damon Gentile. All rights reserved.