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DIY: OnBoard Welder (OBW)

32K views 41 replies 23 participants last post by  L4CX 
#1 · (Edited)
Looking to be able to weld on the trail? No looking to spend $1200 on a Mobiarc or preimer welder? Here is the answer. A homebrewed stand alone OnBoard welder.

You want to use an alternator that is 80amps or larger. I used a 100amp Ford Large Case Alternator. You want the alternator to be Externally regulated so that you don't have to modify the alternator to make it a weldernator.

The Alt I used was from like a mid 70's ford. The part number is GNC 7705-12. It cost about $90 new from a our local parts joint.


On my motor, I have a York compressor already mounted. I was able to use the other side of the york for the bottom mount:


This the upper mount that I made:


I ended up slotting the top hole to all for some more adjustment. I might end up remaking it to have some more adjustment.

Now, I really wanted a nice clean Control Panel/ Control box for this welder and could not find much online that I liked. I found the plastic box at Radio Shack. It was like $8 for it.





I used 2 toggles; 1 to turn on the welder, the other to turn on the outlets. The light is to signal when the welder is on. The two fuse holders on top are holding 30a fuses. The top one is for the outlets and the lower one is for the welder trigger.

I purchased the Panel Meter from China. Found it on ebay. You can get them for about $25. The guage reads from 0-200v's. You can find ones that will ready 0-150v's as well.

The last two things on the box are the + and - plug in's for the welding leads. I need to mark them better, but currently I have the right one for + and the left for -.

I purchased all the welding stuff from our local welding supply shop. It cost about $200 for the wire, rod, rod holder, ect.

Wiring Diagram:


Positive lead, 20 feet:


Negative lead, 20 feet:


3/32" rod 6011 and holder:


The welder is not strong enough to burn 1/8" rod, so you must use 3/32".

Purchased this bag from Youngs Army Navy for $9.


Did not like the idea of working under the hood without a guard on the alternator fins:


The inside wiring of the box:


System hooked up and on:






Cleaned weld:


On the trail use:




The entire cost of the project was about $375 + about 2 days of my time. I could probably build this setup for others installed for about $700. I could also build the control panels for those that need just that made.
I will put together a wiring diagram tomarrow and I will also get some pics of the hand throttle and some other things.
 
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#5 · (Edited)
I'd love to see the hookup of the wires on the back of the alternator. Field, + and -. I have had a weldernator project on my back burner for a year now and already have an externally regulated alternator from a '76 Ford motorhome (I think...got specs at home and am at work now). I made an adjustable bracket to mount it in the same spot you have. Need a combo serp/v-belt alternator pulley to spin it tho. That control box you have is totally awesome. You mentioned making just the box...I'd be interested in that for sure. Then all I'd need is the cables and manual throttle. You got me fired up on my project again. Thanks! :thumb:

Let us know how much you'd like for the box so I can get it together and send you some $.
 
#21 ·
You mentioned making just the box...I'd be interested in that for sure. Then all I'd need is the cables and manual throttle. You got me fired up on my project again. Thanks! :thumb:

Let us know how much you'd like for the box so I can get it together and send you some $.
To build a control panel, fully wired (you would just need to run the trigger to 12v and to the alt and hook up the cables from the alternator) it would be $125.
 
#7 ·
I understand that if you use the hand throttle to dial in 115 volts DC on your guage that you can use those outlets to power any type of electrical device with brushes...like grinders and drills and such. Is this correct?
 
#10 ·
Yah you can run only brush type AC motors. The Voltage output from this is actually high frequency DC not AC.

Let me crunch some numbers on the control box and get back to you on that.

If you were to use crappier welding leads you could probably do this project cheaper. However you will lose voltage to the arc with crappy stringer or ground.
 
#24 ·
have you tested out the outlets yet? or is it an ac alternator.

my understanding would be that a normal alt. is a/c current but is rectified to dc using the six diodes in the alternator. so your outlets would have power, but only dc power and not a/c current and 60 hz that any standard electrical device uses.

maybe i am overlooking something
 
#26 ·
I also thought that the Alt would put out AC voltage, but once I tested it with a voltmeter it would not ready any AC voltage. It will only read DC voltage. So you actually are geting 110v of DC voltage. This is the reason why you can only run Brush driven type AC motors. Ie: Drills, and Grinders.
 
#35 ·
well it would put out 3 phase a/c voltage if you removed the diode pack form it, but then the frequency of it would vary with rpm, and would be useless

i see only brush type motors now. thanks for the reply back
There is No diode pack in this alternator. It is an Externally regulated alternator, so if you don't have the regulator hooked up you can get max voltage out of the alternator. No alternator puts out any form of AC voltage, because in order to get AC voltage you would need a motor with two windings.
 
#27 ·
Could you please PM me your address and name so I can send you $125 for that control box? That is really worth it to me. It looks fantastic! Will a money order be okay?
 
#29 ·
Just to help explain a few of the weird posts:

Don't do this:


I was having a hard time getting the voltage, it was mostly because I was using the voltmeter to look for AC voltage. I thought maybe that there was an internal regulartor screwing me. I pulled it apart to find nothing.

While re-assembling this alternator, I must have not got the back brush in correctly. It took a crap at flat nasty and would no longer put out any voltage. We stole a brush from kart racers grinder and made a spring out of mechanics wire. It worked for about 5 minutes and then died :( I went and picked up a new alternator today and installed it. Everything works great.

So, don't tear it apart! lol. If it is a Big case Ford Alternator. It will not be internally regularted at all.
 
#31 ·
So, don't tear it apart! lol. If it is a Big case Ford Alternator. It will not be internally regularted at all.
Yep. The 70's Chryslers used mostly externally regulated alternators also. The housing looks like a cage. Mounting options can suck with these though.

Great write up.

I can see the paper clip, how could you not put it back together properly???:tonka:
 
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