Without the on-board welder this truck would be stuck on the trail!

How To Build An On-board Welder

By, Jeff Fretwell

You have several options when it comes to buying a welder for you're off road vehicle. One is to spend around $825 for a Link Arc mobile unit. Very trick set up, but not everyone has that much money to spend on a welder. There's also the Premier Power Welder which starts at around $399 (not including the alternator). Then theirs the two cheap home built welders I'm about to tell you how to build.

Home Built Welder Using NAPA Parts.

Parts needed for welder:

1. 110-volt power supply---NAPA Part # 782-1757 $90, or there are cheaper ones to choose from.
2. Adjustable hand throttle---$53.49 NAPA Part# 731-1132
3. Welding cable quick connects (male and female). You can get these from your local welding supply shop for around $20.
4. You will need a moisture resistant DC voltmeter that reads 0-200 or 0-250 volts.
5. Some 4 gauge cable (power unit to alternator)
6. welding cables- this can be very costly depending on where you buy it from and what type of cable you use. You could build a cheap set out of jumper cables, or buy it by the foot at the welding supply store.

7. You will need a "stinger" and a ground clamp. Stingers are expensive for the good ones, but Harbor Freight Tools and Post Tools sells cheap ones for around $10. Also cheap ground clamps for around $2.

8. You can also pick up cheap #10 lens welding hoods and goggles at a variety of tool stores.
9. Welding rod: The best all around rod to carry is 3/32 6010 or 6011. With this rod you can weld just about any trail repair up. It is a good rod for penetrating through paint, grease and dirt. You may also want to carry a few sticks of Nickel rod for cast irons such as steering boxes, differential housings, transfer cases, etc. Keep in mind that you should pre heat these items before welding. A propane torch will work just fine.

10. An external regulated Ford type alternator of at least 70 amps. When you purchase the power converter box it will come with instructions to wire it up to your alternator. This will not work with GM internal regulated alternators. It is ideal for Ford type alternators. (note: if you have a GM alternator read "welder option two")

 

Below are some pictures of the homemade welder

Notice the NAPA part # 782-1757 is only the upper left part of the welder. The rest of the welder is a flat piece of 12 gauge steel with all the other components in the list added on.
Here is a picture of the welder showing the cable connecters plugged into the fittings.
And here is a pic of the connecters:

The hand throttle, voltage meter, and welding cable connecters are all mounted as a unit just for convienance. You can mount them wherever you want. Keep in mind though, that there will be wires all over the place if they are mounted apart from each other.

How it works: When the power converter is hooked up properly all you need to do is flip the switch from 12 volts to 110 volts. That will bypass the regulator and allow your alternator to produce whatever it is capable of (at least 70 amps), and up to 150 volts! Then you're ready to weld! Just plug in the cables and get to it! This is also where the adjustable throttle comes in handy. 2500rpm is a good RPM to start at. Also, the smaller the pulley on the alternator the faster it will turn, which means less RPM needed. When the converter is set at 110 volts you can use the 110v outlets to run tools such as: drop lights, drills, grinders, etc. Keep in mind that all of these power supplies deliver only D.C. power! Some electric motors will not operate (induction motors). And fluorescent lights also will not work. Here are a few other shots of the welder, notice the one with the light on and the grinder, that grinder is turning!

Welder "option two": If you have a GM alternator and don't want to change over to a Ford, here's what you can do. You can mount the Ford alternator separately and not even hassle with wiring into your charging system. If you do not have an extra pully to run the belt off of, you can weld another pulley to your primary alternators pully and run off of that. I suggest that you mount the alternator, but leave the belt disconnected when not in use. If you do not have room for a second alternator you can simply mount it to your fender well or something. It's not like it will be hooked up all the time, so it should be just fine. With this system you do not need the power converter box, but may want it for the convenience of the power outlets and such. You only need a power wire from the battery to the field post of the alternator to energize it. I suggest you put a on/off switch in between the alternator and battery. Then run a heavy 4 gauge cable off the output terminal of the alternator for your stinger. That's the very simple way to use a alternator as a welder, it's simple, plain, but works as well as the other type I explained.

Battery Welding: here are some brief instructions on welding with batteries. First of all, you need at least two car batteries, but three is better. The reason for this is that you need about 36 volts to get a decent arc from the weld rod. You must wire the batteries in a series fashion. You can use a few sets of jumper cables to do so. The batteries must be as far away from the welding as possible! Also cover them with a blanket or tarp incase of an explosion.

Three batteries: From the first battery, attach a cable from positive to negative of the second battery. Then from the second battery, connect a cable from the positive to the negative of the third battery. Now, your welding rod cable will go from your positive side on your third battery, and the ground cable will come off the negative side of the first battery. Your ready to weld now! Be real careful!!!!!!

This will produce 36 volts and about 250 amps. .

 

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